CN116837831A

CN116837831A - Pile foundation perturbation construction method adjacent to subway facilities

Info

Publication number: CN116837831A
Application number: CN202311022927.0A
Authority: CN
Inventors: 林刚; 操海滨; 赵毅; 吴周杰; 潘一奇; 王凯; 郭帅帅; 陈朋
Original assignee: Zhejiang Geological And Mineral Construction Co ltd
Current assignee: Zhejiang Geological And Mineral Construction Co ltd
Priority date: 2023-08-15
Filing date: 2023-08-15
Publication date: 2023-10-03

Abstract

The invention discloses a pile foundation perturbation construction method adjacent to subway facilities, which comprises the following steps: determining a construction point, positioning a full-sleeve full-circle drilling machine, hoisting and placing a plurality of sections of steel casings, and connecting the two sections of steel casings by electric welding; adopting punching and grabbing to assist in soil taking, wherein the bottom of the first-section steel casing is kept for 3m and not taken, and the bottom is kept for more than 6-8m after the rest steel casings sink; hoisting and placing the last section of steel pile casing, and welding with the previous section of steel pile casing by adopting electric welding connection; drilling by a full-casing full-gyratory drilling machine, punching and grabbing to assist in grabbing soil to a depth of 18-25m, and directly sinking the casing; cutting off the last section of steel casing by 0.4m, withdrawing the full sleeve full rotary drilling machine, performing upper construction on a GPS-25 type drilling machine, and drilling to the target depth; and (5) cleaning holes, lifting drills, placing a reinforcement cage, pouring concrete, and completing construction. The invention can effectively control soil disturbance, can not influence the subway shield structure in pile foundation engineering construction, and has the advantages of higher construction speed and strong risk resistance.

Description

Pile foundation perturbation construction method adjacent to subway facilities

Technical Field

The invention relates to the technical field of pile foundation engineering, in particular to a pile foundation perturbation construction method adjacent to subway facilities.

Background

Hangzhou storing a No. 1 land block project pile foundation and enclosing engineering, wherein the Hangzhou city lower urban area Fengjiu road and the southeast corner of the knife and cogongrass road intersection, the south side is provided with Bidi, and the east side is provided with an urban east road. The total area of the project is: north plot is 20380m ² The south land block is 14035m ² The project comprises a row house, a high-rise residence, a matched property, a skirt house, a road, greening and the like. The pile foundation engineering of this project adopts bored pile with diameter of phi 600-phi 1000mm, the total pile number of this engineering is about 1799, pile length is about 39-75 m, and the post grouting process of pile bottom is partly adopted. The Hangzhou subway No. 2 line traverses the engineering north block, so that 2 subway shield tunnels are penetrated at present, and the No. 2 line is formally in traffic. Because the subway shield tunnel is extremely sensitive to deformation, the deformation control index is millimeter-sized, and once the deformation exceeds the control index, the operation safety is affected. Therefore, the subway group is used for protecting the subway structure, ensuring the safety of the shield structure, and providing very strict control requirements for the construction of the engineering, wherein the floating and sinking amounts of the shield tunnel are less than or equal to 15mm, the horizontal displacement amount of the shield tunnel is less than or equal to 10mm, and the transverse deformation of the shield tunnel segment is less than or equal to 5mm. Based on the factors, how to adopt an effective construction method to control soil disturbance, each construction processThe influence of various factors on the subway shield structure is reduced to the minimum, and the aim of achieving the pile foundation perturbation of the adjacent subway facilities is achieved.

Disclosure of Invention

The invention aims to provide a pile foundation perturbation construction method adjacent to subway facilities. The invention can effectively control soil disturbance, can not influence the subway shield structure in pile foundation engineering construction, and has the advantages of higher construction speed and strong risk resistance.

The technical scheme of the invention is as follows: a pile foundation perturbation construction method adjacent to subway facilities is applied to the middle and periphery construction of a subway shield tunnel and comprises the following steps:

step 1, determining a construction point, positioning a full-sleeve full-circle drilling machine, hoisting and placing a plurality of sections of steel casings, and connecting the two sections of steel casings by adopting electric welding;

step 2, adopting punching and grabbing to assist in soil taking, wherein 3m undisturbed soil is reserved at the bottom of the first-section steel pile casing and is not taken, and more than 6-8m undisturbed soil is reserved at the bottom of the rest standard-section steel pile casings after sinking;

step 3, hoisting and placing the final-section steel pile casing, and welding the final-section steel pile casing with the previous standard-section steel pile casing by adopting electric welding connection;

step 4, drilling by a full-casing full-rotary drilling machine, punching and grabbing to assist in grabbing soil to a depth of 16-25m, and directly sinking the casing, so that undisturbed soil is not grabbed;

step 5, exposing the final-node steel pile casing to 0.3m above the terrace, withdrawing the field by a full-sleeve full-convolution drilling machine, performing upper construction by a rotary drilling machine, and continuously drilling to the target depth;

and 6, clearing holes, lifting drills, placing a reinforcement cage, pouring concrete, and completing construction.

According to the pile foundation perturbation construction method for the adjacent subway facilities, the inner diameter of the steel pile casing is the diameter of the foundation pile to be constructed plus 40mm, the wall thickness is 16mm, and the steel pile casing is made of Q345B material.

According to the pile foundation perturbation construction method for the adjacent subway facilities, the length of the first section of the steel pile casing is 10m, the length of the standard section is 10m, the length of the final section is calculated according to the total length of the steel pile casing, the first section and the standard section multiplied by n, the steel pile casings are welded, groove welding is adopted, the height of a welding line is 8mm, the connection reliability is improved by adopting a male opening and a female opening at the joint of the steel pile casings, and after the steel pile casings sink to a specified depth, the final section of the steel pile casings is exposed out of a terrace by 0.3m.

According to the pile foundation perturbation construction method for the adjacent subway facilities, the steel pile casing is sunk to 30m for 8.5 hours, the steel pile casing welding time is 4.5 hours, and when the soil sampling depth reaches 20 meters, the steel pile casing is sunk completely.

In the aforementioned construction method for the perturbation of pile foundations adjacent to the subway facilities, in step 4, if the resistance is too large to sink, soil is continuously grabbed; during construction, the grab bucket is firstly slowly lowered to the bottom of the hole, then lifted for 2m, and then freely lowered, so that impact force is reduced, and the bottom of the hole at least retains 6-8m of undisturbed soil.

In the step 5, after the steel casing is sunk, the upper construction is performed by the rotary drilling rig, the drilling is performed to 76 meters, the mud siltstone is converted into 4 meters, and the construction time is 9.5 hours.

According to the pile foundation perturbation construction method adjacent to the subway facility, the slurry protection wall is used for preventing the collapse holes when the soil is punched and gripped and the rotary drilling rig is used for drilling; the slurry performance parameters comprise specific gravity of 1.10-1.15, viscosity of 20-22 s and sand content of less than 5%.

According to the pile foundation perturbation construction method for the adjacent subway facilities, the slurry is prepared by the following steps: the preparation method comprises the steps of preparing raw materials including bentonite, CMC and sodium carbonate, adding water into bentonite, stirring for 5 minutes, adding water into CMC and sodium carbonate, stirring for 5 minutes, mixing and stirring for 3 minutes to set slurry performance parameters, and finally swelling for 24 hours for later use.

In the above construction method for the micro disturbance of the pile foundation adjacent to the subway facility, in the step 6, the time for cleaning the hole, lifting the drill and lowering the reinforcement cage is 10 hours.

In the aforementioned construction method for the perturbation of pile foundation adjacent to the subway facility, in step 6, the time for pouring concrete is 3 hours.

Compared with the prior art, the method and the device have the advantages that the optimized construction is carried out on pile foundation engineering adjacent to the subway facilities, the influence on the subway shield tunnel can be weakened in the construction process, and the safety requirements of the subway shield tunnel can be met. The construction method can reduce soil disturbance, prevent accidents in holes such as hole collapse and necking, and ensure the perpendicularity of the pile body. In each monitoring project, the final data of the invention is in the effective early warning value, so the construction method of the invention can provide reliable reference and basis for the subsequent mass construction of the type of pile foundations in the area.

Drawings

FIG. 1 is a schematic view of the full casing full rotary drill of step 1 of the present invention in place;

FIG. 2 is a schematic view of the hoisting head section steel casing of the full casing full rotary drill in step 1 of the present invention;

FIG. 3 is a schematic illustration of the first section of steel casing of the present invention;

FIG. 4 is a schematic view of the hoisting of the first section steel casing and the second section steel casing in step 1 of the present invention;

FIG. 5 is a schematic illustration of the connection between the steel casings of the present invention;

FIG. 6 is a schematic view of hoisting a multi-section steel casing in step 1 of the present invention;

FIG. 7 is a schematic view of the hoisting of the last section of steel casing in step 3 of the present invention;

FIG. 8 is a schematic diagram of the construction of the rotary drilling rig in step 5 of the present invention;

FIG. 9 is a data diagram of the soil inclinometer CX-01 for the soil inclinometer at CX1 point in example 1 of the present invention;

FIG. 10 is a data diagram of the soil inclinometer CX-01 for the soil inclinometer at CX2 point in example 1 of the present invention;

FIG. 11 is a data diagram of the soil inclinometer CX-01 for the soil inclinometer at CX3 point in example 1 of the present invention;

FIG. 12 is a data diagram of the soil inclinometer CX-01 for the CX4 point in example 1 of the present invention;

FIG. 13 is a data diagram of soil inclinometry performed at CX2-1 by inclinometer CX-01 in example 2 of the present invention;

FIG. 14 is a data diagram of soil inclinometry performed at CX2-2 by inclinometer CX-01 in example 2 of the present invention;

FIG. 15 is a data diagram showing soil inclinometry performed at CX2-3 by inclinometer CX-01 in example 2 of the present invention;

FIG. 16 is a data diagram showing soil inclinometry performed at CX2-4 by the inclinometer CX-01 in example 2 of the present invention.

Detailed Description

The invention is further illustrated by the following figures and examples, which are not intended to be limiting.

Example 1: a pile foundation perturbation construction method adjacent to subway facilities is applied to the middle and periphery of a subway shield tunnel to construct ultra-deep engineering piles, the construction project of the embodiment is Hangzhou province to store a No. 1 land project pile foundation and enclosure engineering, the construction project is located at the southeast corner of an intersection of a Fengzhu road and a Jiangang roadway in a city below Hangzhou, and the southeast side is an urban east road. The total area of the project is: north plot is 20380m ² The south land block is 14035m ² The project comprises a row house, a high-rise residence, a matched property, a skirt house, a road, greening and the like. The pile foundation engineering of this project adopts bored pile with diameter of phi 600-phi 1000mm, the total pile number of this engineering is about 1799, pile length is about 39-75 m, and the post grouting process of pile bottom is partly adopted.

1. Engineering geological conditions

Drilling results show that the thickness of the fourth series of the field is larger. According to the stratum structure, lithology characteristics, burial conditions and physical and mechanical properties revealed by the drilling, a plurality of engineering geological layers are divided within the range of 92.0m of exploration depth.

The following is from top to bottom:

0-1. Filling soil: the concrete foundation is characterized by being mottled and gray brown, loose, compact and slightly wet, mainly comprising concrete blocks, bricks, stones, broken stones and the like, wherein the concrete foundation is partially an old building concrete foundation, the soil is extremely uneven, and the content of hard impurities is more than 90%. Only the boundary bands of the south and north regions are missing.

0-2. Plain filling soil: gray, loose-slightly dense, wet, mainly composed of silt and crushed gravel, containing a small amount of tiles and humus locally, uneven soil texture, and the content of hard impurities is generally about 10% -20%. The crushed stone foundation of the old house is backfilled occasionally. Local deletions.

1-1, clay silt: grey yellow, slightly wet-wet, slightly dense. Contains a small amount of ferro-manganese, is uneven in soil quality, is locally sandy silty soil, has rapid shaking reaction, is matt, has low dry strength and low toughness. The physical and mechanical properties of the layer are general, and the layer has medium compressibility. Locally.

1-2, sandy silt: grey, greyish yellow, yellowish green, very wet, slightly dense-medium dense, lamellar, containing mica and shell fragments, and higher local silt content. The shaking reaction is rapid, matt, low in dry strength and low in toughness. The physical and mechanical properties of the layer are still good, and the layer has medium compressibility. Full field distribution.

2-1, silt is used for sandwiching silt: light grey, huang Huise, very wet, medium density, lamellar, uneven soil quality, mainly silty sand, local sandy silty soil, moderate-rapid shaking reaction, no luster, low dry strength and low toughness. The layer has good physical and mechanical properties and medium compressibility. The south block is partially missing.

2-2, sandy silt: dark grey, very wet, slightly dense-medium dense, lamellar, impure soil, and local entrapment of small amounts of clay. The shaking reaction is rapid, matt, low in dry strength and low in toughness. The physical and mechanical properties of the layer are general, and the layer has medium compressibility. Locally.

3. Muddy silty clay: grey and flow molding. Thick layer structure, containing a small amount of humus, partially sandwiching thin layer silt, sandwiching shell fragments. No shaking reaction, smoother section, higher dry strength and toughness; the local part is silt clay or powdery clay. The local layer has more shells. The layer has poor physical and mechanical properties and high compressibility. The whole field distribution is that the embedded depth and thickness of the north block are larger than those of the south block.

4-1. Silty clay: the green and yellow layers are mostly blue gray, soft and plastic, hard and plastic locally, thick and lamellar, contain a small amount of ferro-manganese tuberculosis or speckles, have slight luster, no shake reaction, and have moderate dry strength and toughness. The local part is clay. The physical and mechanical properties of the layer are general, and the layer has medium compressibility. The south blocks are distributed in the whole area and the north blocks are distributed in the local area.

4-2, clay: gray, brown gray, soft plastic-soft plastic, thick layer, even soil, containing a small amount of organic matters, even semi-rotten plant scraps, smoother section, dark luster reaction, high dry strength and toughness. The layer has poor physical and mechanical properties and medium high compressibility. The south blocks are distributed in the whole area and the north blocks are distributed in the local area.

5. Powdery clay: light grey, blue grey, huang Huise, etc., soft plastic-hard plastic. Thick layer structure, contains kaolin and ferro-manganese, has uneven soil quality, higher local powder content, rough section, moderate gloss reaction, moderate dry strength, moderate toughness and slight shake reaction in local part. Locally.

6-1. Sandy silty clay: brown yellow, soft and plastic, powder sand of the sandy soil, thick layer structure, no layer, uneven soil quality, slight shake reaction, rough section, no luster, low dry strength and toughness. The layer has good physical and mechanical properties, medium compressibility and local distribution.

6-2, powder sand: brown yellow, medium dense-dense. The thick layer structure has impure sandy quality and poor sorting property, the cohesive soil is contained by about 10 to 30 percent, the local part is fine sand or medium sand which is clamped with the cohesive soil, and the uniformity is poor. The layer has good physical and mechanical properties, low compressibility and local loss of the field.

6-3, round gravel: gray yellow, yellow gray, medium density. The particle size is larger than 2cm, the particle content is about 10-30%, the maximum particle size is 5cm, the particle content is about 20-30%, the sand content is about 20-30%, and the powder clay content is about 10-30%; the particle size is 2-30 mm, the components are sandstone, tuff and the like, and the particle is in a sub-circular shape or flat shape. The layer has good physical and mechanical properties, low compressibility and full field distribution.

7-1, silty clay: grey, soft and plastic. Thick layers, smooth section, moderate dry strength and toughness. The physical and mechanical properties of the layer are general, medium compressibility and are in a lens shape, and are only disclosed in a drilling ZK 90.

7-2, round gravel: gray, dark gray, dense to dense, saturated. The particle content of the particles with the diameter of more than 20mm is about 20-30%, the particle content of 2-20 mm is about 30-40%, the sand content is about 20-30%, and the powder clay content is about 10-20%; the particle size is mainly 1.0-3.0 cm, the maximum size is more than 10cm, the components are quartz sandstone, tuff and the like, and the particles are in a sub-circular shape; the bottom of the local section is pebble. The layer has good physical and mechanical properties and low compressibility. Full field distribution.

8-1. Strongly weathered argillaceous siltstone: reddish brown, mauve, soft rock mass, most of the rock mass is weathered, the rock core is in a soil state or broken block shape, the rock mass is easy to knock, the original rock structure is clear, the clay or silt structure is provided, the clay is cemented, and the sand feeling is provided by hand pinching. Locally.

8-2, apoplexy argillite siltstone: brownish red, mauve, soft and medium-thick layer, the rock body is weathered into a block shape or a short column shape, and is softened after water absorption, and the original rock has a muddy or silty structure and has a thin layer structure, and a small amount of gravel is locally clamped, so that the muddy is cemented. The uniaxial natural compressive strength is 1.75-6.26 MPa, the standard value is 3.59MPa, and the uniaxial natural compressive strength belongs to extremely soft rock. Is distributed in north zone 1# building and south zone.

2. Hydrogeological conditions

According to the water-bearing medium, occurrence condition, water physical property and hydraulic characteristic of the underground water, the underground water of the investigation region can be divided into a fourth series of loose rock pore diving water, a fourth series of loose rock pore bearing water and bedrock fracture water.

1. Loose rock pore diving system

The shallow groundwater of the field region belongs to the fourth loose rock pore diving, and is distributed in the artificial filling soil and the sea-flushing laminated silt layer of the shallow region of the plain region, and the thickness is about 13.30-21.90 m. The water level is obviously changed along with the climate, and the annual amplitude of the water level is about 1.0-2.0 m. The buried depth of the groundwater level is 0.90-2.10 m during investigation, and the elevation of the water level is 4.32-5.93 m. The aquifer has close relations with foundation pit support, precipitation, anti-floating design and the like.

2. Fourth series loose rock pore pressure-bearing water

The loose rock pore pressure-bearing water is distributed in the flood deposit, the powder sand and the round gravel layer at the middle and lower parts of the field, the burial depth of the top plate is about 34.50-41.20 m, and the total thickness is about 25.00-32.10 m. The water rich property is good, and the water inflow of a single well is 1000-3000 m < 3 >/d. The investigation was not performed on the pressurized water. According to the observation of the bearing water of the subway No. 2 line celebration water-road station and the national road station, the measured bearing water head burial depth of the celebration water-road station is 7.80 meters, and the corresponding elevation is-0.72 meters; the actual measurement of the road station in China shows that the burial depth of the pressure-bearing water head is 7.20 meters, and the corresponding elevation is-1.32 meters. The project pressure-bearing water head elevation proposal is-1.00 meters. According to similar engineering experience in Hangzhou and site environment, the pressure-bearing water head is relatively high and the flow velocity is slow. The construction of the bored pile is affected to a certain extent, importance should be attached during construction, and corresponding wall protection measures are adopted when necessary. The aquifer has no influence on foundation anti-floating and engineering precipitation and has little influence on foundation.

2. Bedrock fracture water

The matrix fracture water mainly exists in matrix weathered and joint cracks, the water enrichment is extremely nonuniform, the matrix in the field is mud siltstone and sand conglomerate which are formed by the Chalk system facing Chuan, the layer top elevation is-53.55 to-56.60 m, mud cementation is performed, the crack closure is good, and the permeability is poor. Mainly receives lateral replenishment and upper pressure-bearing underwater infiltration replenishment, has weak water quantity and has little influence on engineering.

Based on the engineering geological conditions and the hydrogeological conditions, the construction method of the embodiment aims at carrying out pile foundation construction among 2 subway shield tunnels. The method specifically comprises the following steps:

step 1, as shown in figure 1, determining a construction point, positioning a full sleeve full rotary drilling machine, wherein the front 5 sections of steel casings are 6m long, 980mm in outer diameter, 930mm in inner diameter and 25mm in wall thickness; as shown in fig. 2-4, the first 5 sections of steel casings are hoisted and placed, wherein the first section of steel casings is provided with a bottom boot, and the bottom boot is provided with 10 alloy cutter heads. The two sections of steel casings are connected by electric welding, and the steel casings sink to 30m total time: 10 hours;

step 2, adopting punching and grabbing to assist in soil taking, wherein 3m undisturbed soil is reserved at the bottom of the first-section steel pile casing and is not taken, and more than 6-8m undisturbed soil is reserved at the bottom of the rest steel pile casings after sinking; in order to prevent the hole from collapsing when the soil is grabbed by punching, a mud is used for protecting the wall; the slurry performance parameters comprise specific gravity of 1.10-1.15, viscosity of 20-22 s and sand content of less than 5%. The slurry is prepared by the following steps: the preparation method comprises the steps of preparing raw materials including bentonite, CMC and sodium carbonate, adding water into bentonite, stirring for 5 minutes, adding water into CMC and sodium carbonate, stirring for 5 minutes, mixing and stirring for 3 minutes to set slurry performance parameters, and finally swelling for 24 hours for later use.

Step 3, as shown in fig. 5, hoisting and placing the last section of steel casing, wherein the last section is 4m long, the outer diameter is 980mm, the inner diameter is 930mm, and the wall thickness is 25mm; welding with the previous steel casing by adopting electric welding connection; the welding time of the steel casing is 14 hours;

step 4, drilling by a full-casing full-convolution drilling machine, punching and grabbing to assist in grabbing soil to a depth of 18m, and directly sinking the casing; if the resistance is too large and can not sink, the soil continues to be grabbed, in the embodiment, when the final soil sampling depth reaches 23 meters, the steel pile casing is completely sunk, the grab bucket is firstly slowly lowered to the bottom of the hole during construction, and then the grab bucket is lifted for 2m and then is freely lowered, so that the impact force is reduced. The hole bottom at least keeps the undisturbed soil body of 6-8 m.

Step 5, cutting off the final-node steel pile casing until the final-node steel pile casing is exposed to 0.3m above the terrace, so that the subsequent mechanical upper construction is facilitated; the full-casing full-rotary drilling machine is evacuated, as shown in fig. 6, the GPS-25 type drilling machine is constructed in an upper position, the drilling is carried out to a target depth of 75.1 meters (4 m for the in-process argillaceous siltstone), and the total time of drilling is as follows: and (3) drilling holes by a GPS-25 drilling machine for 96 hours, and protecting walls by using slurry for preventing holes from collapse.

And 6, cleaning holes, lifting drills, placing a reinforcement cage (comprising a sounding pipe, a reinforcement stress meter and a grouting pipe) for 11 hours, pouring concrete for 2.5 hours, and completing construction.

The basic construction principle is as follows:

1. the full rotary drilling machine is accurate in positioning, and the steel casing position is subjected to positioning rechecking when the first steel casing is lifted and installed, so that construction errors are reduced.

2. The two sections of steel casings are connected by electric welding, and the sealing is ensured not to leak water by welding.

3. The soil taking surface is 6-8m higher than the sinking depth of the pile casing, piping is avoided, and after the soil taking depth reaches 18m, the soil taking should be avoided in an effort unless the full rotary drilling machine cannot drill. If the soil is required to be punched and grabbed for assisting in drilling, the punching and grabbed is slowly lowered to the light touch bottom, and then lifted by about 2m and then freely lowered, so that the impact force is reduced.

4. The GPS-25 type drilling machine should try to avoid phenomena such as hole collapse, diameter shrinkage and the like in the construction process, high-quality slurry should be prepared during construction, the specific gravity of the slurry should be properly increased, and the construction speed should be slowed down at the junction of soft and hard soil layers so as to avoid steps.

5. The pore-forming speed is reasonably controlled, so that the phenomenon that large mud blocks are formed due to too fast drilling, sediment is not cleaned up, and the sediment is extruded to the periphery when concrete is poured, thereby causing exposed ribs.

6. When the steel reinforcement cage is placed, the steel reinforcement cage is straight, the upper steel reinforcement cage and the lower steel reinforcement cage are kept concentric during connection, the protection blocks are placed according to requirements, and the protection blocks are hung slowly, so that the hole wall is prevented from being scratched.

7. Because the drilling construction time is longer, the stability of the hole wall is particularly critical, and each process should be accelerated as much as possible while high-quality slurry is adopted, so that the continuity of the previous and subsequent processes is maintained.

8. And arranging a professional device for entering by a professional monitoring unit, acquiring data comprising pile body verticality, deep soil displacement and the like, and judging whether the construction is suitable for the construction between subway shield tunnels.

9. And during pile test construction, the side station is carried out in the whole course, the drilling machine footage speed, soil layer properties, concrete pile forming time, whether the steel sleeve is smoothly lowered or not, how the slurry properties are adjusted and other technical data are recorded in each stratum, the condition is found, and the guidance is provided for subsequent construction operation.

The final piling parameters were as follows:

the depth of the holes is 75.1m, and the theoretical square is 49.07m ³ The actual square quantity is 55.5m ³ Filling factor 1.13. The total construction time is 133.5 hours.

In this example, soil inclinations were measured using an inclinometer CX-01 for CX1, CX2, CX3 and CX4 during construction of the project, and the results are shown in FIGS. 7 to 10, respectively. The construction monitoring results are summarized in the following table 1:

sequence number	Monitoring point location	Important detection depth (m)	Maximum variation (mm)
				1	CX1	18～24	-1.73
2	CX2	18～24	-3.45
				3	CX3	18～24	-3.25
4	CX4	18～24	0.87

TABLE 1

From the results of FIGS. 7-10 and Table 1, the maximum variation is within the range of the shield tunnel floating and sinking amounts of 15mm or less, the shield tunnel horizontal displacement amount of 10mm or less and the shield tunnel segment transverse deformation of 5mm or less, which proves that the method of the invention can weaken the influence on the subway shield tunnel in the construction process, so that the method can meet the safety requirement of the subway shield tunnel

Example 2: a pile foundation perturbation construction method adjacent to subway facilities is applied to the middle and periphery of a subway shield tunnel to construct ultra-deep engineering piles, the construction project of the embodiment is Hangzhou province to store a No. 1 land project pile foundation and enclosure engineering, the construction project is located at the southeast corner of an intersection of a Fengzhu road and a Jiangang roadway in a city below Hangzhou, and the southeast side is an urban east road. The total area of the project is: north plot is 20380m ² The south land block is 14035m ² The project comprises a row house, a high-rise residence, a matched property, a skirt house, a road, greening and the like. The pile foundation engineering of this project adopts bored pile with diameter of phi 600-phi 1000mm, the total pile number of this engineering is about 1799, pile length is about 39-75 m, and the post grouting process of pile bottom is partly adopted. The engineering geological condition and the hydrogeological condition in the embodiment are the same as those in embodiment 1, and the construction method in the embodiment aims at performing pile foundation construction between 2 subway shield tunnels and optimizing part of parameters in embodiment 1. The method specifically comprises the following steps:

step 1, determining a construction point, positioning a full sleeve full rotary drilling machine, wherein the front 3 sections of steel casings are made of materials with the length of 10m, the outer diameter of 972mm, the inner diameter of 940mm, the wall thickness of 16mm and the quality of Q345B; the front 3 sections of steel casings are hoisted and put into, wherein the bottom of the first section of steel casing is provided with bottom boots, the bottom boots are provided with 10 alloy cutter heads, two sections of steel casings are welded, groove welding is adopted, the welding seam height is 8mm, the connection reliability of the steel casings is increased by adopting a male opening and a female opening, and the steel casings sink to 30m in total time: 8.5 hours;

Step 3, hoisting and placing the last section of steel pile casing, wherein the length of the last section is 4m, the outer diameter is 972mm, the inner diameter is 940mm, and the wall thickness is 16mm; adopting welding connection, groove welding and welding seam height of 8mm, and adopting a male port and a female port at the joint of the steel casing to increase connection reliability; the total welding time of the steel casing is 4.5 hours;

step 4, drilling by a full-casing full-convolution drilling machine, punching and grabbing to assist in grabbing soil to a depth of 18m, and directly sinking the casing; if the resistance is too large to sink, the soil continues to be grabbed, and in the embodiment, when the final soil sampling depth reaches 20 meters, the steel casing is completely sunk. During construction, the grab bucket is slowly lowered to the bottom of the hole, lifted for 2m and then freely lowered, so that impact force is reduced. The hole bottom at least keeps the undisturbed soil body of 6-8 m.

Step 5, cutting off the final-node steel pile casing until the final-node steel pile casing is exposed to 0.3m above the terrace, so that the subsequent mechanical upper construction is facilitated; the full-casing full-rotary drilling machine is withdrawn, the rotary drilling machine is constructed at the upper position, the drilling is carried out to the target depth of 76 meters (4 m for the in-process argillaceous siltstone), and the total time of drilling is as follows: 9.5 hours (because a rotary drilling machine is used), and the wall is protected by slurry for preventing the hole from collapsing when the rotary drilling machine drills.

And 6, cleaning holes, lifting drills, placing a reinforcement cage (comprising a sounding pipe, a reinforcement stress meter and a grouting pipe) for 10 hours, pouring concrete for 3 hours, and completing construction.

The optimization parameters are as follows:

1. compared with the embodiment 1, the inner diameter of the steel casing is increased, the drilling tool is smoothly lowered in construction, the wall thickness is reduced by adopting reinforced steel, the purpose of reducing the outer diameter of the steel casing is achieved, and soil disturbance is further reduced.

2. Compared with the embodiment 1, the steel casings are not connected by socket connection, the connection is adjusted to be male-female connection, the diameter of the connection is not increased, and soil disturbance is further reduced.

3. Compared with the embodiment 1, the alloy cutter head is directly welded on the reserved notch instead of being connected on the bottom boot by bolts, so that the outer diameter of the bottom boot is consistent with the outer diameter of the steel protective barrel, and soil disturbance is further reduced.

4. The subsequent pore-forming equipment is adjusted to be a rotary drilling rig, so that the construction time is greatly shortened, and the soil disturbance is further reduced.

The basic construction principle is as follows:

4. The phenomena of hole collapse, diameter shrinkage and the like should be avoided in the construction process of the rotary drilling rig, high-quality slurry should be prepared during construction, the specific gravity of the slurry should be properly increased, and the construction speed should be slowed down at the junction of soft and hard soil layers so as to avoid steps.

The final piling parameters were as follows: the depth of the holes is 76m, and the theoretical square quantity is 50.44m ³ Actual square quantity 58m ³ Filling factor 1.15. The total construction time was 35.5 hours.

In this example, soil inclinations were measured using inclinometers CX-01 for CX2-1, CX2-2, CX2-3 and CX2-4 during construction of the project, and the results are shown in FIGS. 11 to 14, respectively. In FIG. 11, the displacement of the CX2-1 inclinometer pipe at the depth of 18-24 m is increased by 1.47mm compared with the displacement before concrete is poured by 1.55mm after concrete is poured, and the displacement is at the depth of-1 m. In FIG. 12, the displacement accumulated maximum variation of the CX2-2 inclinometer pipe at the depth of 18-24 meters is 0.76mm, and the displacement is unchanged before and after concrete filling. In FIG. 13, the CX2-3 inclinometer tube has a displacement cumulative maximum change of 1.76mm at a depth of 18-24 m, and the displacement after concrete pouring is increased by 0.4mm compared with that before concrete pouring, and the displacement is at a depth of-2 m. In FIG. 14, the displacement cumulative maximum variation of CX2-4 inclinometer tube at depth of 18-24 m is 0.91mm, and the displacement after concrete pouring is increased by 0.12mm compared with that before concrete pouring, at depth of-1 m. From the results of fig. 11-14, the maximum variation is within the range of the floating and sinking amounts of the shield tunnel being less than or equal to 15mm, the horizontal displacement amount of the shield tunnel being less than or equal to 10mm, and the transverse deformation of the shield tunnel segment being less than or equal to 5mm.

In summary, the invention optimizes the construction for the pile foundation engineering adjacent to the subway facilities, and can weaken the influence on the subway shield tunnel in the construction process, so that the safety requirement of the subway shield tunnel can be met. The construction method can reduce soil disturbance, prevent accidents in holes such as hole collapse and necking, and ensure the perpendicularity of the pile body. In each monitoring project, the final data of the invention is in the effective early warning value, so the construction method of the invention can provide reliable reference and basis for the subsequent mass construction of the type of pile foundations in the area.

Claims

1. A pile foundation perturbation construction method adjacent to subway facilities is applied to the middle and periphery construction of a subway shield tunnel and is characterized in that: the method comprises the following steps:

2. The pile foundation perturbation construction method of the adjacent subway facilities according to claim 1, wherein: the inner diameter of the steel pile casing is equal to the diameter of a foundation pile to be constructed plus 40mm, the wall thickness is 16mm, and the steel pile casing is made of Q345B material.

3. The pile foundation perturbation construction method of the adjacent subway facilities according to claim 2, wherein: the length of the first section of the steel pile casing is 10m, the length of the standard section is 10m, the length of the final section is calculated according to the total length of the steel pile casing, the first section and the standard section multiplied by n, the steel pile casings are welded, groove welding is adopted, the height of a welding seam is 8mm, the connection reliability is increased by adopting a male opening and a female opening at the joint of the steel pile casings, and after the steel pile casings sink to a specified depth, the final section of the steel pile casings are exposed out of a terrace for 0.3m.

4. The pile foundation perturbation construction method of the adjacent subway facilities according to claim 1, wherein: and the steel pile casing is sunk to 30m for 8.5 hours, the welding time of the steel pile casing is 4.5 hours, and the steel pile casing is sunk completely when the soil sampling depth reaches 20 meters.

5. The pile foundation perturbation construction method of the adjacent subway facilities according to claim 1, wherein: in the step 4, if the resistance is too large to sink, continuing to grab the soil; during construction, the grab bucket is firstly slowly lowered to the bottom of the hole, then lifted for 2m, and then freely lowered, so that impact force is reduced, and the bottom of the hole at least retains 6-8m of undisturbed soil.

6. The pile foundation perturbation construction method of the adjacent subway facilities according to claim 1, wherein: in the step 5, after the steel pile casing is sunk, the upper construction of the rotary drilling rig is carried out, the drilling is carried out until the depth reaches 76 meters, the mud silt sandstone is filled in the rotary drilling rig for 4m, and the construction time is 9.5 hours.

7. The pile foundation perturbation construction method of the adjacent subway facilities according to claim 1, wherein: the mud wall protection is used for preventing hole collapse when the drilling machine drills holes; the slurry performance parameters comprise specific gravity of 1.10-1.15, viscosity of 20-22 s and sand content of less than 5%.

8. The pile foundation perturbation construction method of the adjacent subway facilities according to claim 7, wherein: the slurry is prepared by the following steps: the preparation method comprises the steps of preparing raw materials including bentonite, CMC and sodium carbonate, adding water into bentonite, stirring for 5 minutes, adding water into CMC and sodium carbonate, stirring for 5 minutes, mixing and stirring for 3 minutes to set slurry performance parameters, and finally swelling for 24 hours for later use.

9. The pile foundation perturbation construction method of the adjacent subway facilities according to claim 1, wherein: in the step 6, the time for cleaning the holes, lifting the drill and lowering the reinforcement cage is 10 hours.

10. The pile foundation perturbation construction method of the adjacent subway facilities according to claim 1, wherein: in step 6, the time for pouring the concrete is 3 hours.