CN110924967B

CN110924967B - Fine control construction method for shield proximity sensitive building in water-rich sandy gravel stratum

Info

Publication number: CN110924967B
Application number: CN201911177411.7A
Authority: CN
Inventors: 肖洪波; 杨果林; 陈亚军; 张沛然; 吕涛; 戴志浩; 龙彪
Original assignee: CCFEB Civil Engineering Co Ltd
Current assignee: CCFEB Civil Engineering Co Ltd
Priority date: 2019-11-27
Filing date: 2019-11-27
Publication date: 2021-09-28
Anticipated expiration: 2039-11-27
Also published as: CN110924967A

Abstract

The invention discloses a fine control construction method for a shield proximity sensitive building in a water-rich sandy cobble stratum, which comprises the following steps: step S101, setting construction parameters of a shield machine to control the soil output amount, so that the pressure of a soil bin of the shield machine is equal to the pressure of the soil water on a driving surface, and the shield machine is in a soil pressure balance state for construction; calculating the injection amount of the grouting body: calculating the target injection amount of the shield mud according to the gap of the shield body, and calculating the target injection amount of the cement paste according to the gap of the pipe shell; step S102, in the tunneling process of the shield tunneling machine, shield mud is synchronously injected through radial holes in the front shield to fill gaps of the shield body, and cement slurry is synchronously injected into the outer side of a pipe sheet ring out of the rear shield through grouting holes in the rear shield to fill gaps of pipe shells. The water-rich sandy cobble stratum shield proximity sensitive building fine control construction method realizes millimeter-level control construction of disturbance ground surface settlement of water-rich sandy cobble stratum shield construction.

Description

Fine control construction method for shield proximity sensitive building in water-rich sandy gravel stratum

Technical Field

The invention relates to the technical field of building construction, in particular to a fine control construction method for a shield proximity sensitive building in a water-rich sandy gravel stratum.

Background

In recent years, with the rapid advance of urbanization, basic traffic and facility construction activities have rapidly progressed. In urban rail transit and municipal pipe gallery construction, shield tunnels are widely used due to their outstanding characteristics. However, due to the complexity of the underground environment and the ground conditions, a number of problems of shield tunneling are emerging. The disturbance influence of shield construction on the earth surface and the adjacent building is difficult to avoid, and the problems of earth surface collapse, underground pipeline breakage, building inclination damage and the like are easily caused under the condition of instability control of shield construction of a special stratum, so that shield tunnel construction and normal urban production activities are seriously influenced.

The water-rich sandy gravel stratum is widely distributed in China and is one of the main stratum conditions faced by shield construction, and the engineering problems caused by the shield construction in the water-rich sandy gravel stratum are more frequent. The main reasons are the particularity of the water-rich sandy gravel stratum: firstly, the grading of most sandy gravel stratums is poor, the content of fine particles is low, the permeability coefficient is high, and the permeability water pressure is high under the water-rich condition; secondly, the connection of sand gravel stratum particles is mostly point-to-point contact, the structure is strong, under the construction disturbance, the pore size is increased after the relative movement of the particles, and the stable state of the original stratum is difficult to recover.

The main problems of the existing shield method in the construction of water-rich sandy gravel stratum are as follows: firstly, in a stratum with low disturbance sensitivity, the prior art can basically meet the engineering safety control requirement, but the prior art is difficult to meet the requirement of a water-rich sandy gravel stratum with higher sensitivity coefficient; secondly, the problems of dilutability, seepage and early low strength of the cement grouting body in the water-rich sandy gravel stratum in the existing shield construction period are still serious, and the problems are not effectively solved, so that the cement grouting body is the main reason for causing a large amount of disturbance deformation. The urban underground shield tunnel engineering with the water-rich sandy gravel stratum has great potential safety hazard, great influence on sensitive buildings in the construction process and poor construction effect.

Disclosure of Invention

The invention provides a fine control construction method for a shield proximity sensitive building of a water-rich sandy gravel stratum, which aims to solve the technical problems of large influence on the sensitive building and poor construction effect caused by construction disturbance in the construction process of the shield proximity sensitive building of the water-rich sandy gravel stratum.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: the utility model provides a sensitive building fine control construction method of rich water sand cobble stratum shield hugging closely, the shield body of shield constructs the machine includes the anterior shield of arranging and connecting in proper order along the direction of tunnelling, well shield and rear shield, and the anterior shield, the diameter of well shield and rear shield reduces in proper order, be equipped with the blade disc that is used for excavating on the anterior shield front end, the excavation diameter of blade disc is greater than the diameter of anterior shield, in the shield constructs the machine excavation propulsion process, form the shield body clearance between blade disc excavation section and the surface of shield body, and after the section of jurisdiction ring of installation breaks away from the rear shield in the rear shield, constitute the tube shell clearance between section of jurisdiction ring and the shield body clearance, including following step: step S101, setting construction parameters of a shield machine to control the soil output amount, so that the pressure of a soil bin of the shield machine is equal to the pressure of soil water on a driving surface, and the shield machine is in construction in a soil pressure balance state, wherein the construction parameters of the shield machine comprise the pressure of the soil bin, the propelling speed, the rotating speed of a cutter head, the rotating speed of a screw conveyor and the soil output amount; calculating the injection amount of the grouting body: calculating the target injection amount of the shield mud according to the gap of the shield body, and calculating the target injection amount of the cement paste according to the gap of the pipe shell; step S102, in the tunneling process of the shield tunneling machine, shield mud is synchronously injected through radial holes in the front shield to fill gaps of the shield body, and cement slurry is synchronously injected into the outer side of a pipe sheet ring out of the rear shield through grouting holes in the rear shield to fill gaps of pipe shells.

Further, before entering a water-rich sandy gravel stratum from other strata, the shield machine sprays shield mud to the shield gap in a grading pressure manner through radial holes of a front shield in a shutdown state: step S1041, injecting shield mud into the gap of the shield body under the pressure of 0.4Mpa to 0.5Mpa according to 40% to 50% of the target injection amount of the shield mud; step S1042, stopping injecting shield mud, and injecting 0.3Mpa pressure air into the gap of the shield for 10-15 minutes; step S1043, under the pressure of 0.3Mpa to 0.4Mpa, the shield mud is additionally injected into the gap of the shield body according to 50 percent to 60 percent of the target injection amount of the shield mud; step S1044, stopping injecting shield mud, and injecting air with pressure of 0.2Mpa into the gap of the shield body for 15 to 20 minutes; and S1045, under the pressure of 0.2MPa to 0.3MPa, injecting the shield mud into the gap of the shield body in a reinforcing way according to 30 percent to 60 percent of the target injection quantity of the shield mud.

Further, according to formula V₁=π/4×[(D²-R₁ ²)×L₁+(D²-R₂ ²)×L₂+(D²-R₃ ²)×L₃]Calculating the gap of shield body according to formula V₂=π/4×(R₃ ²-d²) Xl calculates the case gap, where: d is the cutter excavation diameter, R₁Is anterior shield diameter, L₁Is anterior shield length, R₂Is the diameter of the middle shield, L₂Is the length of the middle shield, R₃Is the diameter of the posterior shield, L₃Is the length of the rear shield, d is the diameter of the segment ring, and L is the length of the segment ring.

Further, step S102 specifically includes: step S1021, starting and tunneling according to initial parameters, synchronously injecting shield mud through radial holes in the front shield to fill the gap between the shield bodies, synchronously injecting cement slurry into the outer sides of the pipe sheet rings out of the rear shield through grouting holes in the rear shield to fill the gap between the pipe shells, and step S1022, tunneling according to construction parameters, synchronously injecting shield mud through the radial holes in the front shield to fill the gap between the shield bodies, and synchronously injecting cement slurry into the outer sides of the pipe sheet rings out of the rear shield through grouting holes in the rear shield to fill the gap between the pipe shells.

Further, step S103 is included, after the pipe shell gap is filled, the ground surface settlement is continuously monitored, whether the ground surface settlement value is within a preset range or not is judged, and when the ground surface settlement value is not within the preset range, secondary grouting is carried out through the grouting channel of the pipe sheet ring.

Further, step S101 further includes: and calculating the component mixing ratio of the shield mud according to the performance of the grouting equipment of the shield machine and the geological conditions of the stratum.

Further, the injection rate of the target injection amount of the shield mud is not lower than 130% of the gap of the shield body, and the grouting speed of the shield mud is matched with the tunneling speed.

Further, the raw materials of the shield mud are two-component preparation materials, including a material A and a material B, wherein the material A is shield mud powder, the material B is a diluted solution, and the mass ratio of the material A to water is 1: 1.5-1: 2.5, wherein the mass ratio of the material B to the water is 1: 0.5-1: 1.5, the mass ratio of the mixture of the material A and the water to the mixed liquid of the material B and the water is 10: 1-20: 1, and the specific gravity range is 1.16-1.28.

Further, the cement slurry ratio is calculated according to each cubic cement slurry as follows: cement: fly ash: bentonite: sand: water 125:370:40:575:375 in kilograms and gel time from 3 to 6 hours.

Furthermore, the secondary grouting pressure is 0.2MPa to 0.4 MPa.

The invention has the following beneficial effects: according to the fine control construction method for the shield-proximity sensitive building of the water-rich sandy gravel stratum, when the shield-proximity sensitive building is constructed, the shield mud is synchronously injected through the radial hole of the front shield to fill the gap of the shield body, the settlement of the water-rich sandy gravel stratum of the shield body part in the shield excavation stage is controlled, and the shield mud grouting ring with a certain thickness is formed around the shield body to form a double-ring structure, so that cement slurry is prevented from seeping into larger pores of the stratum or being diluted by underground water when grouting is carried out in the water-rich sandy gravel stratum, the effective grouting filler is formed by the cement slurry, and the problem of grouting series flow and slurry leakage of the water-rich sandy gravel equal-strength water-permeable stratum is solved; in the process of injecting the shield mud, a part of shield mud permeates into the soil layer around the shield body to form a mud film, so that the permeation of cement paste for subsequent synchronous grouting into the soil layer is effectively reduced, the vault deformation of the tunnel is effectively controlled, and the multistage step-by-step filling of excavation gaps is realized; the disturbance control concept of the whole process is realized by filling and earth pressure balance control from synchronous grouting of an excavation gap, the construction disturbance of the water-rich sandy gravel stratum is controlled in a targeted manner, the pressure difference between the earth pressure of a driving working face and the earth pressure of an earth cabin plate of the shield tunneling machine is fully considered, the construction parameters of the shield tunneling machine are controlled in a refined manner, the earth pressure balance control is realized, the strong disturbance of overexcavation and abnormal excavation on the water-rich sandy gravel stratum is avoided, and the millimeter-level control construction of the disturbance earth surface settlement of the shield tunneling construction of the water-rich sandy gravel stratum is realized. In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.

Description of the drawings:

the accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a flow chart of a shield approach sensitive building fine control construction method for a water-rich sandy gravel stratum according to a preferred embodiment of the invention;

FIG. 2 is a schematic diagram of a shield excavation according to a preferred embodiment of the present invention;

fig. 3 is a schematic view of a water-rich sandy gravel formation of the present invention.

Illustration of the drawings: 10. a shield body; 11. anterior shield; 12. middle shield; 13. a posterior shield; 20. a cutter head; 30. a shield body clearance; 40. a tube shell gap; 50. a tube sheet ring; 60. a water-rich sandy pebble formation.

Detailed Description

The embodiments of the invention will be described in detail below with reference to the accompanying drawings, but the invention can be embodied in many different forms, which are defined and covered by the following description.

FIG. 1 is a flow chart of a shield approach sensitive building fine control construction method for a water-rich sandy gravel stratum according to a preferred embodiment of the invention; FIG. 2 is a schematic diagram of a shield excavation according to a preferred embodiment of the present invention; fig. 3 is a schematic view of a water-rich sandy gravel formation of the present invention.

As shown in fig. 1 and fig. 2, in the fine control construction method for the shield proximity sensitive building in the water-rich sandy gravel stratum according to the embodiment of the present invention, a shield body 10 of a shield machine includes a front shield 11, a middle shield 12 and a rear shield 13 which are sequentially arranged and connected in a tunneling direction, diameters of the front shield 11, the middle shield 12 and the rear shield 13 are sequentially reduced, a cutter head 20 for excavation is provided at a front end of the front shield 11, an excavation diameter of the cutter head 20 is larger than that of the front shield 11, a shield body gap 30 is formed between a section of the cutter head 20 and an outer surface of the shield body 10 during an excavation propulsion process of the shield machine, and after a segment ring 50 installed in the rear shield 13 is separated from the rear shield 13, a segment gap 40 is formed between the segment ring 50 and the shield body gap 30, including the following steps: step S101, setting construction parameters of a shield machine to control the soil discharge amount, so that the pressure of a soil bin of the shield machine is equal to the pressure of soil water on a driving surface, and the shield machine is in construction in a soil pressure balance state, wherein the construction parameters of the shield machine comprise the pressure of the soil bin, the propelling speed, the rotating speed of a cutter head 20, the rotating speed of a screw conveyor and the soil discharge amount; calculating the injection amount of the grouting body: calculating the target injection amount of shield mud according to the shield body gap 30, and calculating the target injection amount of cement paste according to the shell gap 40; step S102, in the tunneling process of the shield tunneling machine, shield mud is synchronously injected through radial holes in the anterior shield 11 to fill the shield body gap 30, and cement slurry is synchronously injected through grouting holes in the posterior shield 13 to the outer side of the pipe sheet ring 50 out of the posterior shield 13 to fill the pipe shell gap 40.

According to the fine control construction method for the shield-driven proximity sensitive building of the water-rich sandy gravel stratum, when the shield-driven proximity sensitive building is constructed, the shield mud is synchronously injected through the radial hole of the anterior shield 11 to fill the shield gap 30, the settlement of the water-rich sandy gravel stratum of the shield 10 in the shield excavation stage is controlled, and the shield mud grouting ring with a certain thickness is formed around the shield 10 to form a double-ring structure, so that cement slurry is prevented from seeping into larger holes of the stratum or being diluted by underground water when grouting is carried out in the water-rich sandy gravel stratum, an effective grouting filler is formed, and the problem of grouting streaming and slurry leakage of the water-rich sandy gravel and other strong water-permeable strata is solved; in the process of injecting the shield mud, a part of shield mud permeates into the soil layer around the shield body 10 to form a mud film, so that the permeation of subsequent cement slurry synchronously injected into the soil layer is effectively reduced, the vault deformation of the tunnel is effectively controlled, and the multistage step-by-step filling of excavation gaps is realized; the disturbance control concept of the whole process is realized by filling and earth pressure balance control from synchronous grouting of an excavation gap, the construction disturbance of the water-rich sandy gravel stratum is controlled in a targeted manner, the pressure difference between the earth pressure of a driving working face and the earth pressure of an earth cabin plate of the shield tunneling machine is fully considered, the construction parameters of the shield tunneling machine are controlled in a refined manner, the earth pressure balance control is realized, the strong disturbance of overexcavation and abnormal excavation on the water-rich sandy gravel stratum is avoided, and the millimeter-level control construction of the disturbance earth surface settlement of the shield tunneling construction of the water-rich sandy gravel stratum is realized.

It can be understood that the shell gap 40 is a gap including the thickness of the rear shield 13, namely, a region from the region of the shield gap 30 to the region between the segment rings 50 after the segment ring 50 installed in the rear shield 13 is separated from the rear shield 13, during grouting, the shield machine advances, the shield gap 30 is poured through shield mud, then the segment rings 50 are laid, and during continuous advancing of the shield machine, the shell gap 40 is poured through cement paste to form a double-ring structure, so that a composite grouting body is formed between the segment rings 50 and the water-rich sandy gravel stratum.

Understandably, the construction parameters of the shield machine are set mainly including the fine control of excavation construction parameters: and (3) setting the pressure of the soil bin: since the shield machine's capsule earth pressure is generally less than the ripper face earth pressure as a result of the cutter head 20 openness ratio, the construction parameter control range is deviated, the precise control of the water-rich sandy gravel stratum is difficult to meet, the invention takes the classical soil pressure calculation method as the standard in the soil pressure setting control aspect of the soil warehouse in the soil pressure balance shield construction period, and the mapping relation between the earth pressure value of the earth cabin sealed cabin and the earth pressure of the tunneling working face is considered, before shield construction of the water-rich sandy gravel stratum, the corresponding soil pressure setting range of the driving face is calculated, then the soil pressure value of the sealing cabin plate of the soil cabin is corrected according to the formula a of 0.0106 eta +0.1248, namely, the earth pressure value Pt of the earth cabin sealing cabin plate is equal to the product aP of the earth pressure value P of the driving working face and the pressure transmission coefficient a, wherein the soil pressure value P of the driving working face satisfies a formula Pa not less than P not more than Pp, wherein the corresponding lower limit active soil pressure Pa passes through the formula: pa = π D²γ(H+D)tan²(45-phi/2), and the corresponding upper limit passive soil pressure value Pp is obtained through the formula: pp = π D²γ(H+D)tan²(45 degrees + phi/2), the soil pressure value Pt of the soil bin sealing plate is controlled to meet a formula of aPa-aPp; wherein phi is a friction angle; eta is the opening rate of the cutter head 20; h is the buried depth of the tunnel, and the depth from the vault of the tunnel to the ground; gamma is the soil gravity; setting the propelling speed: due to the sensitivity of the water-rich sandy gravel stratum, shield construction should pass as soon as possible, but the too fast speed is unfavorable for controlling the pressure balance of the soil bin, the precise control value of the propelling speed is 30-40 mm/min, and the corresponding total thrust is controlled according to the set target propelling speed; setting the rotating speed of the screw conveyer: the rotating speed of the screw conveyer is adjusted according to the condition of soil bin pressure balance, the rotating speed of the screw conveyer is correspondingly adjusted according to the basically constant propelling speed within the range of the pressure value of the soil bin sealing cabin plate meeting the regulation, when the soil pressure value of the soil bin sealing cabin plate is greater than aPp, the rotating speed of the screw conveyer is increased, and when the soil pressure value of the soil bin sealing cabin plate is less than aPa, the rotating speed of the screw conveyer is decreased, whereinObserving the change condition of the soil pressure value of the soil cabin sealing cabin plate by delaying for 10-15 seconds when the rotating speed of the screw conveyor is adjusted each time so as to eliminate the time lag phenomenon; controlling the soil output: in order to realize the settlement control target, the actual soil output of each ring is calculated and controlled according to 95-98% of the theoretical soil output, so that the soil body above the shield cut can have a trace amount of uplift not more than 1 mm, and the later settlement amount of a fourth-stage settlement deformation period of a part of soil body can be offset, thereby controlling the total settlement amount in a minimum range. Wherein, the theoretical soil output of each ring is equal to the excavation volume multiplied by the loosening coefficient, and the loosening coefficient of the water-rich sandy gravel stratum takes a value of 1.2-1.4.

In the invention, the grouting body comprises shield mud and cement slurry, wherein the shield mud mainly fills a shield gap 30 between the excavation surface and a shield shell of the shield machine, the cement slurry mainly fills a shell gap 40 between the shield shell and a segment ring 50, and the corresponding grouting body volumes are respectively calculated.

Understandably, in the excavation process of the shield machine, the shield mud is synchronously injected through the radial holes on the anterior shield 11 to fill the shield body gap 30, wherein the shield mud is injected firstly before the shield machine is started, and the shield mud is continuously and synchronously injected when the shield machine is started for excavation; or synchronously injecting shield mud when the shield machine is started.

The invention adopts a method of filling and controlling deformation step by step in the whole shield excavation gap, controls the stratum deformation of the shield body 10 part in the excavation period, namely effectively fills the shield body gap 30 in time, and adopts impervious water retention grouting body and construction parameters for fine control, so as to solve the problem of settlement deformation of the water-rich sandy gravel stratum.

Further, before entering a water-rich sandy gravel stratum from other strata, the shield machine sprays shield mud to the shield gap 30 in a grading pressure mode through radial holes of the anterior shield 11 in a shutdown state: step S1041, injecting shield mud into the shield gap 30 according to 40% to 50% of the target injection amount of the shield mud under the pressure of 0.4MPa to 0.5 MPa; step S1042, stopping injecting shield mud, and injecting 0.3Mpa pressure air into the shield gap 30 for 10-15 minutes; step S1043, under the pressure of 0.3Mpa to 0.4Mpa, the shield mud is additionally injected into the shield body gap 30 according to 50 percent to 60 percent of the target injection amount of the shield mud; step S1044, stopping injecting shield mud, and injecting 0.2Mpa pressure air into the gap 30 of the shield body for 15 to 20 minutes; and S1045, reinforcing the shield mud to be injected into the gap 30 of the shield body according to 30-60% of the target injection amount of the shield mud under the pressure of 0.2-0.3 Mpa. It can be understood that before entering the water-rich sandy gravel stratum from other stratum, in a shutdown state, the shield mud is subjected to graded pressure injection in stages through the radial holes of the anterior shield 11 to the excavation gap in the full-length range of the shield body 10, namely, through the radial holes of the anterior shield 11 to the gap between the shield body 10 and other stratum: injecting the shield mud into the excavation gap within the full length range of the shield body 10 according to 40 to 50 percent of the target injection amount of the shield mud under the pressure of 0.4 to 0.5 Mpa; stopping injecting shield mud, and injecting 0.3Mpa pressure air outside the shield body 10 for 10-15 minutes; under the pressure of 0.3 to 0.4Mpa, the excavation gap within the full length range of the injection shield body 10 is supplemented according to 50 to 60 percent of the target injection amount of the shield mud; stopping injecting shield mud, and injecting 0.2Mpa pressure air to the outside of the shield body 10 for 15-20 minutes; under the pressure of 0.2MPa to 0.3MPa, the excavation gap in the whole length range of the injection shield body 10 is strengthened by 30 percent to 60 percent of the target injection amount of shield mud. Preferably, as the diameters of the anterior shield 11, the middle shield 12 and the posterior shield 13 are sequentially reduced, and the diameter of the cutter head 20 is larger than that of the anterior shield 11, a gap exists between the outer surface of the full-length range of the shield body 10 and the soil body, and the shield mud is injected into the full-length gap of the shield body 10 according to 50% of the target injection amount of the shield mud under the pressure of 0.4 Mpa; stopping injecting shield mud, and injecting 0.3Mpa pressure air outside the shield body 10 for S10-15 minutes; supplementing the full-length gap of the injection shield body 10 by 50% of the target injection amount of shield mud under the pressure of 0.3-0.4 Mpa; stopping injecting shield mud, and injecting 0.2Mpa pressure air to the outside of the shield body 10 for 15-20 minutes; step S1045, under the pressure of 0.2 to 0.3Mpa, the full-length gap of the injection shield body 10 is strengthened according to 30 to 60 percent of the target injection quantity of the shield mud, finally, a plastic waterproof shield mud ring is formed at the interface of other stratum and the water-rich sandy gravel stratum, and the plastic waterproof shield mud ring is used as an anti-seepage ring of the cement slurry of the first ring of the water-rich sandy gravel stratum, so that the effect of effective injection of the cement slurry is realized when each segment ring 50 is in a continuous shield mud ring closed state in the subsequent excavation process.

Further, the air conditioner is provided with a fan,according to formula V₁=π/4×[(D²-R₁ ²)×L₁+(D²-R₂ ²)×L₂+(D²-R₃ ²)×L₃]Calculating the shield clearance 30 according to the formula V₂=π/4×(R₃ ²-d²) Xl calculates the case gap 40, where: d is the excavation diameter of the cutter head 20, R₁Is anterior shield 11 diameter, L₁Is the length of anterior shield 11, R₂Is the diameter of the middle shield 12, L₂Is the length of the middle shield 12, R₃Is the diameter of the posterior shield 13, L₃Is the length of the rear shield 13, d is the diameter of the segment ring 50, and L is the length of the segment ring 50.

Further, step S102 specifically includes: step S1021, starting and tunneling according to initial parameters, synchronously injecting shield mud through radial holes in the anterior shield 11 to fill the shield gap 30, synchronously injecting cement slurry into the outer side of the pipe sheet ring 50 out of the posterior shield 13 through grouting holes in the posterior shield 13 to fill the pipe shell gap 40, step S1022, tunneling according to construction parameters, synchronously injecting shield mud through the radial holes in the anterior shield 11 to fill the shield gap 30, and synchronously injecting cement slurry into the outer side of the pipe sheet ring 50 out of the posterior shield 13 through grouting holes in the posterior shield 13 to fill the pipe shell gap 40. It can be understood that the injection manner and process of the slurry body can be as follows: in the advancing process of shield excavation, injecting shield mud synchronously through a radial hole of a front shield 11 of a shield machine, filling a shield body gap 30, controlling the settlement of a water-rich sandy gravel stratum of a shield body 10 part in a shield excavation stage, and forming a shield mud grouting ring with a certain thickness around the shield body 10; in addition, cement paste is injected outside the tube sheet ring 50 of the trailing shield 13 through the injection hole of the trailing shield 13 of the shield machine to fill the tube shell gap 40. The shield mud has good fluidity, so that the small shield only needs to inject single-point injection, the large shield needs to alternately inject two points, 2 radial holes at the top of the front shield 11 can be selected, namely radial holes ranging from 11 points to 1 point, and in the injection process of the shield mud, a part of the shield mud can permeate into the soil layer around the shield body 10, so that a mud film is formed, the permeation of cement paste for subsequent synchronous grouting into the soil layer is effectively reduced, and the deformation of the arch top of the tunnel is effectively controlled.

Further, step S103 is included, after the tube shell gap 40 is filled, the ground subsidence is continuously monitored, whether the ground subsidence value is within the preset range is judged, and when the ground subsidence value is not within the preset range, secondary grouting is performed through the grouting channel of the tube sheet ring 50. It can be understood that, in order to further avoid the settlement of the ground after the shield excavation, after the segment ring 50 is separated from the rear shield 13, the settlement of the surface of the ground can be controlled by secondary grouting if the settlement exceeds the early warning value.

Further, step S101 further includes calculating the component mixing ratio of the shield mud according to the performance of the grouting equipment of the shield machine and the geological condition of the stratum. Specifically, for water-rich sandy gravel stratum, certain flow plasticity and impermeability requirements need to be met, and as the shield mud formed in different proportions has different viscosity and flow state and the grouting equipment performance of different shield machines is different, the adaptive shield mud material mixing proportion of a shield 12 machine in a specific project needs to be determined through tests, and the appropriate proportion of the shield mud can be determined through testing the specific weight and viscosity of the shield mud in different proportions by three slurry sets.

Specifically, the construction method is explained by the length L of the segment ring 50 in the shield tunnel excavation process as follows: the shield grouting pipe is conveyed to a grouting device, namely a shield mud tank, of a shield machine, cement slurry prepared in proportion is conveyed to the grouting device, namely the cement slurry tank, and pipe pieces are conveyed to the lower part of an assembling machine of the shield machine; pressing and conveying the shield mud to a radial hole of a front shield 11 through a grouting pumping pipeline, and starting injection; starting the shield machine according to the propelling speed, the rotating speed of the cutter head 20 and the rotating speed of the spiral conveyor set by the initial parameters, starting excavation, gradually increasing the propelling speed, the rotating speed of the cutter head 20 and the rotating speed of the spiral conveyor to the range value of the construction parameters required by the invention, wherein the rotating speed of the spiral conveyor is set according to the calculated pressure range value of the soil bin of the water-rich sandy gravel stratum, the cement slurry injection pump of the rear shield 13 is started simultaneously after the excavation of the shield machine is started, and the outer side of the segment ring 50 is injected according to the set pressure; in the excavation process, continuously injecting grouting bodies through a shield mud injection pipeline and a cement slurry injection pipeline respectively to finally form a composite grouting ring body consisting of shield mud and cement slurry outside the segment ring 50; stopping excavation after the excavation reaches the width of a circular pipe piece, stopping the injection of cement liquid of the rear shield 13 and shield mud of the shield body 10 in sequence, and installing the circular pipe piece to form a circular pipe piece ring 50; and (3) continuously monitoring the surface settlement, and if the surface settlement 1 day after the segment ring 50 is separated from the rear shield 13 exceeds the early warning value, controlling the surface settlement through secondary grouting.

Further, the injection rate of the target injection amount of the shield mud is not lower than 130% of the shield body gap 30, and the grouting speed of the shield mud is matched with the tunneling speed. It can be understood that in the actual construction, in order to ensure the grouting filling effect, the injection rate should not be lower than 130%, the grouting speed of the shield mud and the cement paste of the invention should be matched with the advancing speed of the tunneling, the average grouting speed is determined according to the ring grouting amount completed within the time of completing one ring tunneling of the shield, so as to achieve the purpose of uniform grouting, and the double-index control standard of grouting pressure and grouting amount is adopted, namely when the grouting pressure reaches the set value, the grouting amount reaches more than 95% of the designed value, the quality requirement can be considered to be reached. The injection pressure of the shield mud is 0.2-0.4 MPa; the cement slurry injection pressure is determined according to performance parameters, stratum characteristics and design parameters of a lining ring of the shield machine, is generally 0.5-1.5 bar higher than the water and soil pressure of a shield cut and is not larger than 3.0bar, and shield 13 sealing or duct piece displacement caused by too high grouting pressure breakdown is avoided.

Further, the raw materials of the shield mud are two-component preparation materials, including a material A and a material B, wherein the material A is shield mud powder, the material B is a diluted solution, and the mass ratio of the material A to water is 1: 1.5-1: 2.5, wherein the mass ratio of the material B to the water is 1: 0.5-1: 1.5, the mass ratio of the mixture of the material A and the water to the mixed liquid of the material B and the water is 10: 1-20: 1, and the specific gravity range is 1.16-1.28. The material of the shield mud used in the invention is a two-component preparation material, and comprises a component A and a component B, wherein the component A is shield mud powder, namely a material A, and the component B is a diluted solution, namely a material B. Specifically, the shield mud is prepared by adopting shield mud powder, plasticizer and diluent according to construction requirements, the flow plasticity and viscosity of the shield mud are directly related to the proportion of each component in the shield mud, and the production proportion of the shield mud meeting engineering requirements is determined through tests before construction. The mass ratio of the shield mud powder to the diluted solution (water) is 1: 1.5-1: 2.5; the mass ratio of the plasticizer to the water is 1: 0.5-1: 1.5; the mass ratio of the shield mud mixture to the plasticizer mixed liquid is 10: 1-20: 1, the specific gravity range is 1.16-1.28. The recommended proportion is as follows: the mass ratio of the shield mud powder to the water is 1: 1.5; the mass ratio of the plasticizer to the water is 1: 0.75; the mass ratio of the mixed solution of the shield mud mixture and the plasticizer is 17.5:1, corresponding specific gravity of 1.255. The viscosity of the prepared shield mud is 350-600 dpa.s, the load capacity is not lower than 1.5 kg/square centimeter, the water loss rate is 39.4-47% (constant temperature 30 degrees), and the adhesive force is 1-7 (constant temperature 40 degrees).

Further, the cement slurry ratio is calculated according to each cubic cement slurry as follows: cement: fly ash: bentonite: sand: water 125:370:40:575:375 in kilograms and gel time from 3 to 6 hours. Optionally, the cement slurry ratio of the invention is calculated by per cubic meter of slurry as: cement: fly ash: bentonite: sand: water in kilograms 125:370:40:575: 375. The gelling time is generally 3-6 h, the gelling time can be adjusted by adding a coagulant and changing the mixture ratio through field tests according to the formation conditions and the tunneling speed, and the mixture ratio can be further adjusted or an additive can be added through the field tests for the highly permeable sandy gravel formation and the section with higher disturbance resistance level, so that the gelling time is further shortened.

Furthermore, the secondary grouting pressure is 0.2MPa to 0.4 MPa. Understandably, the secondary grouting adopts cement-water glass double-slurry, and the proportion of the double-slurry is as follows: the concentration of the water glass is 35 Baume degrees, the water-cement ratio is 0.8-1.0, the stabilizing agent is 2-6%, the water reducing agent is 0-1.5%, and the mixing volume ratio of the mixed liquid is 1: 1-1: 0.3. Optionally, the secondary grouting of the invention adopts cement-water glass double-slurry, and the proportion of the double-slurry is as follows: 35 baume degrees of water glass, 0.8-1.0 of water-cement ratio, 2-6% of stabilizer, 0-1.5% of water reducing agent and 1: 1-1: 0.3 of mixing volume ratio. The secondary grouting pressure is controlled to be 0.2 MPa-0.4 MPa, and the actual pressure is finally determined according to the field grouting effect. The reinforcing grouting is generally controlled by pressure, the grouting is finished when the designed grouting pressure is reached, and the supplementary grouting can be performed again according to the grouting effect.

Preferably, the invention improves the dregs: the improved scheme is that the foam volume fraction is 3%, the injection volume ratio is 15-40%, the bentonite mass ratio is 150-300 g/L, and the volume injection ratio is 15-50%. Wherein, the foam volume fraction is to the volume ratio of the foam agent stock solution to water, the bentonite mass ratio is the mass ratio of the dry bentonite powder to water, and the volume injection ratio is the volume ratio of foam or bentonite slurry to excavation slag soil, so as to effectively reduce pollution.

Referring to fig. 3, during the shield construction of the water-rich sandy gravel stratum 60, the present invention provides a specific embodiment as follows: the total length of a certain 220kV electric power tunnel project is 5957.012m, the shield method is adopted for construction, the inner diameter of the tunnel is 3.6m, the outer diameter is 4.1m, the minimum curve radius is 150m, the maximum gradient is 18 per mill, and 4-circuit 220kV cables and 8-circuit 110kV cables are planned to be led out. The length of a 2# shield machine-1 # shield well section of the standard section tunnel is 3050m, and the length of a 2# shield well-3 # shield section is 2841.8m, and the shield construction method is adopted. The tunnel engineering adopts 2 shield machines to undertake the interval tunnel construction task, and the driving directions of the two shield machines are started from the 2# shield well to the 1# and 3# shield wells. The shield machine excavation diameter is 4.35m, the rotation speed of the cutter head 20 is 0-3 rpm, the opening rate of the cutter head 20 is 38%, the maximum propelling speed is 80 mm/min, the maximum propelling force is 1862T, the total length of the whole machine is 115m, and the length of the shield body 10 is 7.813 m. The stratum condition in this shield tunnel section is complicated, and ground environment along the line is complicated, and the sensitivity is built the structure and is more, and disturbance safety risk is high. In the interval of the 2# shield well to the 2# outlet well, the surrounding conditions are complex, and important buildings (structures) along the line mainly comprise bridge piles along the line, newly-built pedestrian overpasses, residential districts, street-approaching commercial houses, high-voltage iron tower foundations, important underground pipelines along the line and the like for building subway entrances and exits and urban main road rapid reconstruction viaducts. Particularly, the subway in construction is parallel to the electric power tunnel of the shield segment; the house close to the street is a commercial house, is 3.6m closest to the space of the electric power tunnel, and is a brick-concrete-shallow foundation structure. And evaluating the II-level high risk of the related proximity building according to the urban rail transit underground engineering construction risk management standard, the urban rail transit engineering risk evaluation guide, the subway squeezing underground engineering construction risk management guide and the like.

The stratum of the lower penetrating section of the shield in the region mainly comprises a plain soil filling layer, a powdery clay layer, a round gravel layer, a pebble layer, conglomerate and a clay layer. Wherein, the vegetarian fill layer (Q4jm 1): the main components are cohesive soil and sandy soil, the local part contains gravels, the bottom of the cohesive soil and sandy soil are clamped with planting soil, the thickness of the cohesive soil and sandy soil is not equal to 0.60-9.5 m when a road is built recently, and the cohesive soil and sandy soil are distributed in most areas along the line; fine clay layer (Q3bsa 1): yellow and brown yellow gray white hard plastics contain a little black iron manganese oxide, are similar to a reticulate pattern structure, have no shake reaction, have luster and medium strength, and have different thicknesses of 1.0-16.2 m; fine clay layer (Q3bsa 1): yellow and brown yellow with grey white color and soft plastic, contains a little black iron manganese oxide and fine powder sand, has no shake reaction, and has luster, medium dry strength, medium toughness and different thicknesses of 0.8-5.7 m; pebble layer (Q3bsa 1): brown yellow, saturated, slightly dense to medium dense, gravel content of more than 50 percent, particle size of 0.5-2 cm, quartz component, good roundness grinding, medium coarse sand filling, more cobbles, increasing trend downwards, and particle size of 4-6 cm. Mixing a small amount of cohesive soil, and obtaining good gradation with the thickness of 0.6-38 m; pebble layer (Q3bsa 1): brown yellow, saturated, medium-density to compact, pebble content is about 60%, the main components are quartz sandstone, sub-round, grain size is 2-4cm, maximum grain size reaches 8-10cm, sand filling, about 10% of cohesive soil is mixed, and thickness is 0.5-49.5 m; fine clay layer (Qe 1): brown yellow, brown red, hard plastic-hard, contains a little black iron manganese oxide, has no shake reaction, is slightly glossy, has moderate toughness and moderate dry strength, and has different thicknesses of 0.6-27.0 m; conglomerate (K): mauve, brown yellow, the complete morals and manners, the piece structure, thick layer form structure, it is extremely poor to consolidate, and most morals and manners are the soil form, and the hand is held between fingers and is dispersed promptly, and the gravel is mostly slate, sandstone, a small amount of mudstone, and the particle diameter is 2 ~ 30 millimeters, and thickness 1.0 ~ 48.50m is not equal, and the basic quality grade of rock mass is V level, and most regions along the line all have the distribution.

The hydrological conditions of the shield lower penetration section of the interval mainly comprise: groundwater type and water-rich. The stable water level burial depth of the underground water level of the site is 0.4-17.4 meters, and the water level elevation changes between 22.57-59.49 meters. Water retention in the upper layer: the artificial filling soil is mainly supplemented by atmospheric precipitation and surface water infiltration, and is discharged in a mode of evaporating or permeating downwards into the diving, and the seasonal change is large and discontinuous. It is related to the buried depth of the aquifer and is basically consistent with the landform slope; diving: the water-retaining agent is added into silt, fine sand, round gravel and pebbles in riverbeds, flood beaches and various terraces, the water yield is rich, the water supply and water permeability are good, the pore diving is adjacent to the water retention of the upper layer, the hydraulic power relationship is close, and the diving water-containing layer belongs to a strong water-permeable stratum; confined water: the soil layer segment and the round gravel layer which are mixed with fine sand at the bottom of the silty clay on the two banks of the river are confined water aquifers, the water-containing performance of the soil layer segment and the round gravel layer is closely related to the shape, the size, the grain size, the content of sticky particles and the like of the gravel, the main supply source is the overflow supply of subsurface runoff and upper-layer pore diving, the permeability is strong, and the water-rich property is medium; bed rock fracture water: the sandstone is applied to slate, conglomerate and argillaceous siltstone, and has better connectivity of bed rock fractures, poor water permeability and poor water-rich property. The bedrock fracture water mainly exists in strong-stroke weathered bedrock fractures, and has pressure bearing performance and uneven underground water existence. The water inflow and water permeability of the rock stratum are mainly controlled by the development degree of cracks, obvious nonuniformity exists, and the possibility of large water inflow is locally provided. Generally, the pore water in the terraces presents the property change from confined water to diving due to the rising of the river water level, and brings certain risks to the safe construction of the shield tunnel.

Analyzing the serious and difficult points of the shield construction in the section: the interval is penetrated under DK1+ 705-DK 1+772, DK1+ 881-DK 2+010 and DK2+ 130-DK 2+180, and the control of the interval ground surface settlement and the protection of buildings and pipelines along the line are the key points of the project and the important standard for measuring the quality of the project construction. The interval design is to formulate a reinforcement protection principle according to the relation between the interval tunnel and the building (structure), the mutual influence degree and possible consequences of the interval tunnel construction, and carry out classification and grading protection on the buildings (structures) along the interval. According to design drawings, the lower wearing position is reinforced by grouting through a sleeve valve pipe, the civil house monitoring settlement data reach an early warning value of 8 mm, and protective measures are taken. Because the sleeve valve pipe grouting scheme adopted by the original design cannot be implemented due to the restriction of ground traffic fluffing and construction site conditions, the ground reinforcing condition is not carried out at the underpass position; in addition, the interval is mainly the rich water sand cobble stratum, mainly faces in the shield excavation process: formation losses are more difficult to control: according to a geological survey report, the stratum has high compressibility and low strength, so that the foundation settlement is large and is mostly uneven settlement, the stratum loss caused by shield construction is difficult to control, and the controllability is difficult to accurately ensure; the houses passing through the section are relatively dense, all soil layers are not uniformly distributed, and factors such as the design and materials of the foundation of the house easily cause uneven settlement or inclination, so that the existing houses are unevenly settled to cause house deformation or cracks; the synchronous grouting effect is uncertain, for inert grout, the problems of grout bleeding and shrinkage exist, the excessive grouting pressure is easy to crack the surrounding soil, and long-term settlement is caused; stratum secondary disturbance settlement is difficult to control, the interval passes through a house group, a soil body is disturbed, if cracks with different degrees appear on the wall body of the house, secondary grouting is carried out at the position where the shield penetrates the house in the later period, secondary disturbance influence is caused on the house, and settlement control difficulty is large; according to the early-stage tunneling summary, the shield attitude change phenomenon is easy to occur when the machine is stopped for more than 24 hours because the bearing capacity of the foundation is low.

The interval shield excavation disturbance sensitive interval coping measure and reference construction process comprises the following steps: (1) according to the exploration data, geological reconnaissance is performed in a targeted mode, particularly the shield penetrates through a building section, the geological condition of the penetrating section is further clarified, a typical geological section is selected for drilling and coring, and according to the geotechnical test result, the shield penetrating construction parameters are preliminarily set in combination with the condition of the shield machine. Before the shield crossing construction, a simulated crossing construction section is arranged, analysis and summary are carried out according to actual propulsion parameters, and the propulsion parameters are continuously optimized, so that the rationalization of the shield crossing construction parameters is ensured, and the influence on the building and the construction is reduced to the minimum; (2) in order to reduce the safety risk of shield construction, the settlement of the ground and buildings (structures) is controlled, and the safety of the shield passing through the buildings (structures) such as civil houses is guaranteed. The project department respectively carries out grouting reinforcement and proportional shield mud scheme selection on the shield underpass disturbance sensitive section from the aspects of technical scheme, construction time, construction equipment, civilized construction and protection, settlement control effect and the like, and finally decides to adopt the construction method provided by the invention on the shield construction disturbance sensitive section under the condition that ground grouting reinforcement cannot be carried out according to the design scheme and the proportional shield mud is superior and has outstanding economic and technical indexes. In the tunneling process of the shield machine, balanced shield mud is synchronously injected out of the shield body 10 through radial holes of the front shield 11, and a gap between the shield body 10 and a soil body is filled, so that the water-rich sandy gravel stratum settlement deformation caused by the shield propulsion is effectively controlled, and the stratum settlement control is obtained after the shield passes through the auxiliary shield; (3) the synchronous grouting matching ratio test is carried out before shield construction, the grouting matching ratio with small bleeding rate and proper initial setting time is optimized through the test, and in the shield advancing process, the synchronous grouting speed is ensured to be matched with the advancing speed, so that the synchronous grouting slurry can effectively fill the rear shield 13 building gap, and the synchronous grouting matching ratio and the injecting amount are further optimized according to monitoring data; (4) according to the construction method, the stability of the shield excavation surface is ensured, the thrust is strictly controlled by optimizing the excavation parameters and combining the actual measurement feedback, and the disturbance of the shield propulsion to the stratum is reduced; setting a propelling speed, adjusting a soil discharge amount or setting the soil discharge amount and adjusting the propelling speed to achieve dynamic balance of the soil bin pressure and the formation pressure and effectively control ground settlement; (5) during shield tunneling, sufficient cement slurry materials are filled in the annular building gap on the back side of the lining after the shield is removed as soon as possible, and secondary grouting reinforcement is performed in time according to monitoring data so as to reduce later-stage settlement of soil after the shield passes through and control ground settlement.

The specific process method comprises the following steps: the shield machine adaptability is determined by shield mud mixing ratio: according to geological conditions and tunneling requirements of stratums, the recommended proportion of the invention is selected as follows: the proportion of the material A to the water is 1: 1.5, the ratio of the material B to the water is 1:0.75, the ratio of the mixture of the material A and the water to the mixed liquid of the material B and the water is 17.5:1, and the corresponding specific gravity is 1.255. Wherein, the configuration flow of the shield mud of the weighing apparatus: weighing the component A → adding the required water amount → fully stirring evenly → (after reacting for 30 minutes to 24 hours) → adding the component B with the matched dosage → adding the component B into the shear pump A and stirring evenly; calculating the injection amount of the grouting body: the excavation diameter of the cutter head 20 of the shield tunneling machine is 4350 mm, the outer diameter of the rear shield 13 is 4290 mm, and the injection volume of shield mud of the shield shell outer scale per meter is 0.5 cubic meter according to the calculation of the maximum clearance outside the shield body 10. The injection volume per meter is 0.75 cubic meter calculated according to the injection rate per meter of 150%; the injection pressure is set to be 0.3-0.4 MPa, and the injection process is properly adjusted according to different stratums and burial depths. 240 tons of shield mud A materials and 40 tons of shield mud B materials are used together in the interval, wherein the loss amount is 5 percent; and (3) injection process: in the shield tunneling process, shield mud is synchronously injected from a radial hole at the position of a front shield 11 of a shield machine, and injection is started ten rings ahead of time before a building of a ground disturbance sensitive community is penetrated, namely the method for treating the interface between other stratums and the water-rich sandy gravel stratum provided by the invention. In the construction process, a gap between the shield body 10 and the soil body caused by the over excavation of the cutter head 20 in the shield construction process is timely filled, and in the specific construction process, the adjustment is timely carried out according to the settlement of the ground right above the shield machine; during the shield tunneling process, according to the construction parameter calculation and value taking method, the shield tunneling parameters of the section are analyzed and summarized in time, and the fine control value of the tunneling parameters of the lower penetration section is formulated by integrating actual conditions. Wherein the pressure of the soil bin is 1.6-1.8 bar, the total shield thrust is 4000-5000 kN, the torque of the cutter head 20 is 600-800 kN.m, the rotating speed of the cutter head 20 is 1.2-1.5 r/min, the shield tunneling speed is 35-50 mm/min, and the penetration is 20-30 mm/r.

The construction method for finely controlling the shield close-proximity sensitive building in the water-rich sandy gravel stratum has the following effects: firstly, injecting shield mud in the shield tunneling process, controlling in real time in the tunneling process, and synchronously performing shield construction, so that other construction link time is not occupied, and the construction time is short; the construction in the tunnel is civilized, the construction difficulty is small, the materials are free of pollution, the environmental protection requirement is met, most importantly, the deformation of the water-rich sandy gravel stratum caused by shield tunneling is effectively controlled, the deformation of the stratum can be controlled within 7 mm, the disturbance control target of the ground sensitive building is realized, and the cost is saved compared with the traditional ground drilling grouting reinforcement.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fine control construction method for a shield approach sensitive building in a water-rich sandy gravel stratum is characterized in that,

the shield body of the shield machine comprises a front shield, a middle shield and a rear shield which are sequentially arranged and connected along a tunneling direction, the diameters of the front shield, the middle shield and the rear shield are sequentially reduced, a cutter disc for excavating is arranged at the front end of the front shield, the excavating diameter of the cutter disc is larger than the diameter of the front shield, a shield body gap is formed between an excavating section of the cutter disc and the outer surface of the shield body in the excavating propulsion process of the shield machine, and after a duct piece ring installed in the rear shield is separated from the rear shield, a duct shell gap is formed between the duct piece ring and the shield body gap, and the shield machine comprises the following steps:

step S101, setting construction parameters of the shield machine to control the soil output amount, so that the pressure of a soil bin of the shield machine is equal to the pressure of soil water on a driving surface, and the shield machine is in a soil pressure balance state for construction, wherein the construction parameters of the shield machine comprise the pressure of the soil bin, the propelling speed, the rotating speed of a cutter head, the rotating speed of a spiral conveyor and the soil output amount;

calculating the injection amount of the grouting body: calculating the target injection amount of shield mud according to the shield body gap, and calculating the target injection amount of cement paste according to the shell gap;

step S102, in the tunneling process of the shield tunneling machine, shield mud is synchronously injected through radial holes in the front shield to fill the gap between the shields, and cement slurry is synchronously injected through grouting holes in the rear shield to the outer side of the pipe sheet ring out of the rear shield to fill the gap between the pipe shells;

step S103, after the pipe shell gap is filled, continuously monitoring the surface subsidence, judging whether the surface subsidence value is in a preset range, and performing secondary grouting through the grouting channel of the pipe sheet ring when the surface subsidence value is not in the preset range;

before entering a water-rich sandy gravel stratum from other stratums, the shield machine sprays shield mud to the shield body clearance in a grading pressure mode through radial holes of the front shield in a shutdown state: step S1041, injecting shield mud into the gap of the shield body according to 40% to 50% of the target injection amount of the shield mud under the pressure of 0.4MPa to 0.5 MPa; step S1042, stopping injecting shield mud, and injecting 0.3Mpa pressure air into the gap of the shield body for 10-15 minutes; step S1043, injecting shield mud into the gap of the shield body at a pressure of 0.3Mpa to 0.4Mpa according to 50% to 60% of the target injection amount of the shield mud; step S1044, stopping injecting shield mud, and injecting air with pressure of 0.2Mpa into the gap of the shield body for 15 to 20 minutes; step S1045, injecting shield mud into the gap of the shield body in a reinforced manner according to 30 to 60 percent of the target injection amount of the shield mud under the pressure of 0.2 to 0.3 Mpa;

and (3) setting the pressure of the soil bin: before shield construction of a water-rich sandy gravel stratum, calculating a corresponding tunneling surface soil pressure setting range, and then correcting a soil pressure value of a sealing cabin plate of an earth cabin according to a formula a which is 0.0106 eta +0.1248, wherein a tunneling working surface soil pressure value P is equal to a formula Pa which is not less than P and not more than Pp, and the soil pressure value Pt of the sealing cabin plate of the earth cabin is equal to the product of the tunneling working surface soil pressure value P and a pressure transmission coefficient a; wherein:

the corresponding lower limit active soil pressure Pa is calculated by the formula: pa = π D²γ(H+D)tan²(45 ° - Φ/2) obtaining;

and (3) corresponding to the upper limit passive soil pressure value Pp through a formula: pp = π D²γ(H+D)tan²(45 ° + φ/2) acquisition;

wherein phi is a friction angle; eta is the cutter head opening rate; h is the buried depth of the tunnel, and the depth from the vault of the tunnel to the ground; gamma is the soil gravity; d is the excavation diameter of the cutter head;

when the shield construction of the proximity sensitive building is carried out, the shield mud is synchronously injected through the radial hole of the front shield to fill the gap of the shield body, the settlement of the water-rich sandy gravel stratum of the shield body part in the shield excavation stage is controlled, and a shield mud grouting ring with a certain thickness is formed around the shield body to form a double-ring structure, so that cement slurry is prevented from seeping into the larger hole of the stratum or being diluted by underground water when grouting is carried out in the water-rich sandy gravel stratum, and the cement slurry forms an effective grouting filler; and in the process of injecting the shield mud, a part of shield mud can permeate into the soil layer around the shield body to form a mud film, so that the permeation of cement paste for subsequent synchronous grouting into the soil layer is effectively reduced, the deformation of the vault of the tunnel is effectively controlled, the disturbance control concept of the whole process is realized by synchronously grouting from the excavation gap to fill and control the soil pressure balance, the construction disturbance of the water-rich sandy gravel stratum is controlled in a targeted manner, the pressure difference between the soil pressure of the tunneling working surface and the soil pressure of a sealing cabin plate of a soil bin of the shield machine is fully considered, the construction parameters of the shield machine are controlled finely, the soil pressure balance control is realized, the strong disturbance of the water-rich sandy gravel stratum caused by over-excavation and abnormal excavation is avoided, and the construction disturbance of the water-rich sandy gravel stratum shield construction is realized to control the ground surface settlement in a millimeter level.

2. The fine control construction method of the shield approach sensitive building in the water-rich sandy gravel stratum according to claim 1,

according to formula V₁=π/4×[(D²-R₁ ²)×L₁+(D²-R₂ ²)×L₂+(D²-R₃ ²)×L₃]Calculating the gap of the shield body;

according to formula V₂=π/4×(R₃ ²-d²) Calculating the tube shell gap by x L;

wherein: r₁Is anterior shield diameter, L₁Is anterior shield length, R₂Is the diameter of the middle shield, L₂Is the length of the middle shield, R₃Is the diameter of the posterior shield, L₃Is the length of the rear shield, d is the diameter of the segment ring, and L is the length of the segment ring.

3. The fine control construction method of the shield proximity sensitive building in the water-rich sandy gravel stratum according to claim 2,

step S102 specifically includes:

step S1021, starting with initial parameters and performing tunneling, injecting shield mud through radial holes on the front shield synchronously to fill the gap between the shields, injecting cement slurry through grouting holes on the rear shield synchronously to the outer side of the pipe sheet ring out of the rear shield to fill the gap between the pipe shells,

and step S1022, performing tunneling according to the construction parameters, synchronously injecting shield mud through radial holes in the front shield to fill the gap between the shields, and synchronously injecting cement slurry into the outer sides of the pipe sheet rings out of the rear shield through grouting holes in the rear shield to fill the gap between the pipe shells.

4. The fine control construction method of the shield proximity sensitive building in the water-rich sandy gravel stratum according to claim 3,

step S101 further includes: and calculating the component mixing ratio of the shield mud according to the performance of the grouting equipment of the shield machine and the geological conditions of the stratum.

5. The fine control construction method of the shield proximity sensitive building in the water-rich sandy gravel stratum according to claim 4,

the injection rate of the target injection amount of the shield mud is not lower than 130% of the gap of the shield body, and the grouting speed of the shield mud is matched with the tunneling speed.

6. The fine control construction method for the shield proximity sensitive building of the water-rich sandy gravel stratum according to claim 5, wherein the raw material of the shield mud is a two-component preparation material comprising a material A and a material B, wherein the material A is a shield mud powder, the material B is a dilution solution, and the mass ratio of the material A to water is 1: 1.5-1: 2.5, wherein the mass ratio of the material B to the water is 1: 0.5-1: 1.5, the mass ratio of the mixture of the material A and the water to the mixed liquid of the material B and the water is 10: 1-20: 1, and the specific gravity range is 1.16-1.28.

7. The fine control construction method for the shield proximity sensitive building in the water-rich sandy gravel stratum as claimed in claim 6, wherein the cement paste ratio is calculated by cement paste per cubic meter as: cement: fly ash: bentonite: sand: water 125:370:40:575:375 in kilograms and gel time from 3 to 6 hours.

8. The fine control construction method for the shield proximity sensitive building of the water-rich sandy gravel stratum as recited in claim 7, wherein the secondary grouting pressure is 0.2 MPa-0.4 MPa.