CN109707388B - Method for preventing ground collapse when shield tunneling machine starts to pass through existing shield tunnel - Google Patents
Method for preventing ground collapse when shield tunneling machine starts to pass through existing shield tunnel Download PDFInfo
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- CN109707388B CN109707388B CN201910011562.9A CN201910011562A CN109707388B CN 109707388 B CN109707388 B CN 109707388B CN 201910011562 A CN201910011562 A CN 201910011562A CN 109707388 B CN109707388 B CN 109707388B
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/20—Hydro energy
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Abstract
The invention provides a method for preventing ground collapse when a shield tunneling machine starts to downwards pass through an existing shield tunnel. The method specifically comprises the following steps: firstly, a multilayer pipe shed is arranged between a shield tunnel portal contour line and an existing tunnel, then an extension steel ring is added at a shield tunnel portal, the steel ring is reinforced by adopting a steel ring supporting structure, the extension steel ring is connected with a tunnel portal embedded annular plate, at least two steel brushes are arranged in the middle of the extension steel ring, a curtain cloth rubber plate is arranged at the tail of the extension steel ring to form a plurality of cavities, a circle of ball valves are arranged at positions, corresponding to each cavity, of the extension steel ring, a head planting preventing structure is constructed at the bottom of the extension steel ring, finally, a reinforcing net is arranged at the opening part of a cutter disc of a shield machine for improving the cutter disc of the shield machine before the shield machine goes down in the well, and torsion preventing blocks are arranged at the shield body. The method can ensure that the existing line is not influenced in the process of starting and downwards penetrating the existing line, ensure that shield construction can be completed within the planned time and not delay the whole subway construction.
Description
Technical Field
The invention belongs to the field of shield construction, and particularly relates to a construction method for preventing ground collapse when a shield machine starts to downwards pass through an existing shield tunnel.
Background
Along with the rapid development of the economy in China, the life rhythm of people is gradually accelerated, more and more people start to rush to cities, so that pressure is brought to urban traffic, and in order to relieve the traffic pressure of the cities, subways are taken as important traffic means for relieving the traffic pressure in all large cities. For subway tunnel construction, the tunneling of the shield tunnel by the shield machine is started more and more, so that the construction period can be shortened as much as possible. The manpower input is reduced, so that the subway line is put into use as soon as possible, and the problem of traffic jam is solved as soon as possible. Meanwhile, in order to enable urban subways to form a four-way underground traffic network, the subway lines are always penetrated downwards in the subway construction process, and the shield tunneling machine is started to be penetrated downwards.
When the shield tunneling machine starts to run down the existing line, the existing line has very strict requirements on settlement, if the shield tunneling process is performed due to the fact that the cutter head can cause disturbance to surrounding soil during tunneling, the shield is out of square, some parts can even form partial collapse, ground settlement is easy to cause, and if displacement settlement is too large, subway operation of the existing line can be influenced, so that a great difficulty is brought to the shield running down. In the existing shield tunneling process, most of the shield machines are earth pressure balance shield machines. In the tunneling process of the earth pressure balance shield machine, the earth bin pressure is an important parameter for maintaining the stability of a tunneling face, so that the stability of the face is ensured, the face collapse can be prevented, the earth over-excavation is reduced, the ground collapse is prevented, and the earth pressure balance shield machine is an important factor for ensuring normal tunneling. In the tunneling process of the shield tunneling machine, soil around the tunnel face is influenced by disturbance of the cutter head, if the pressure of the soil bin is insufficient, the tunnel face is often caused to collapse, local cavities are formed, and finally the bottom layer is caused to collapse. At present, most of conventional methods for establishing accurate soil bin pressure are gradually established in the tunneling process, but in the process of penetrating an existing line when the shield tunneling machine starts tunneling, the soil bin pressure is not completely established, and at the moment, a tunnel face is easy to collapse, so that the ground is collapsed, and the operation of the existing line is influenced.
In addition, because the diameter of the cutter head of the shield tunneling machine is larger than that of the pipe piece, and the cutter head has larger disturbance to surrounding soil in the rotating process, larger gaps exist around the pipe piece and the tunnel, and in order to prevent the surrounding soil from collapsing, grouting is carried out on the pipe piece, the stability of the pipe piece and the surrounding soil is ensured through grouting, and the ground collapse is prevented. Whether the soil bin pressure is established in advance or the duct piece grouting is carried out, the requirements on the construction period, the working environment and the construction space are relatively high, and construction difficulties and even construction incapability exist for construction projects with short construction period and limited space in the working environment.
Disclosure of Invention
The invention provides a construction method capable of preventing ground collapse when a shield machine starts to downwards pass through an existing shield tunnel under the conditions of urgent construction period, limited operation environment and limited space according to the defects of the prior art.
In order to solve the technical problems, the technical scheme provided by the invention is as follows: the method for preventing the ground collapse when the shield tunneling machine starts to downwards pass through the existing shield tunnel is characterized by comprising the following specific steps:
(1) Before the shield starts, the pipe shed advanced support is constructed for the shield tunnel: a multi-layer pipe shed is arranged between the outline of the tunnel portal of the shield tunnel and the existing tunnel, all pipe shed steel pipes adopt flower pipes with grouting holes on the pipe walls, and grouting is carried out through each pipe shed steel pipe after the pipe shed is arranged;
(2) The method comprises the steps of constructing an extension steel ring structure for pre-establishing shield soil bin pressure when a shield is started at a shield tunnel entrance:
a. positioning and mounting of a portal extension steel ring: the extension steel ring is arranged at a shield tunnel gate, extends from a pre-buried steel ring of the tunnel gate to a large mileage end of a station for 2-3 m, is divided into an upper half extension steel ring and a lower half extension steel ring, and is respectively arranged after a steel ring base is arranged, and the upper half extension steel ring and the lower half extension steel ring are connected into a whole;
b. reinforcing the steel ring by adopting a steel ring supporting structure: the steel ring supporting structure comprises a base support arranged on a steel ring base, a split heads support arranged at the groove part at the bottom of the extension steel ring and profile steel supports arranged at two sides of the extension steel ring, wherein the extension steel ring is arranged at a shield starting hole through the steel ring base, a steel ring body of the extension steel ring is connected with an embedded steel ring of the shield hole, and is fixedly supported with a main body side wall and a structural beam of the shield starting hole through the steel ring supporting structure;
c. sealing of the portal extension steel ring: connecting the extension steel ring with an embedded ring plate at the hole, adopting a connecting plate transitional connection mode, connecting the connecting plate with the steel ring in a full-welded mode, and connecting the connecting plate with an embedded steel ring groove in a full-welded mode; at least two steel wire brushes are arranged in the middle of the inside of the extension steel ring, a cord fabric rubber plate is arranged at the tail of the extension steel ring to form a plurality of cavities, and a circle of ball valve is arranged at the position, corresponding to each cavity, outside the extension steel ring;
d. constructing a head planting preventing structure at the bottom of the extension steel ring: firstly, installing a guide rail, wherein the height of the top surface of the guide rail is 1.5-3 cm lower than that of the top surface of a bracket rail, the front end of the guide rail is 60-80 cm away from a structural wall, and the rear end of the guide rail is 1.5-3 m away from the front end of the bracket; fine stones are filled between the two guide rails, and the filling height of the fine stones is equal to that of the guide rail tracks;
(3) Aiming at improvement of a cutter head of a shield machine: selecting a panel cutter with an aperture ratio of 33% -40%, wherein a reinforcing net is arranged at the aperture position of the cutter;
(4) The shield body anti-torsion measure: when the cutter head is ready for rotary pile grinding, a plurality of anti-torsion blocks are respectively arranged on two sides of the middle shield and the shield tail at equal intervals, the distance between the adjacent anti-torsion blocks is 30-50 cm, the torque of the shield machine is controlled to be below 2500KN.M in the propelling process, the thrust is controlled to be about 500T, the rolling angle is controlled to be within +/-5 mm/m, and a method of high thrust and small torque is adopted.
The invention has the preferable technical scheme that: the method further comprises the step of improving a foam injection system and a bentonite injection system of the shield tunneling machine; wherein, the foam injection system is provided with 5 groups of single-pipe single-pump single-nozzle foam injection systems in the shield machine, the system adopts single-pipe single-pump, and each path of foaming agent can work independently; the bentonite injection system is improved by configuring two bentonite pumps, wherein the two pumps can be injected into the front of the cutter head through separate pipelines, and can also be injected outside the shield shell in a single way; the grouting mode is as follows:
a. in the tunneling process of the shield machine, high-concentration bentonite slurry is adopted to fill and press a soil bin, so that the stability of a tunnel face is ensured;
b. in the middle shield pushing process, the middle shield radial holes of the shield machine are utilized to synchronously perform middle shield grouting in the shield machine downward penetrating process, and a construction gap between the excavation surface and the shield body is filled;
c. and synchronously injecting mortar into the shield tail.
d. And (3) carrying out grouting supplement in the region with hidden danger after synchronous grouting and secondary grouting in the shield process, wherein the grouting supplement position is 6-9 rings at the tail of the shield.
The invention has the preferable technical scheme that: the pipe shed advanced support in the step (1) comprises a four-layer pipe shed, wherein the lower two layers are arc-shaped, are arranged along the outer edge of the upper part of the shield tunnel portal, have the length of 30 meters and are formed by arranging hot-rolled seamless steel pipes with the diameter of 194mm and the pipe wall thickness of 10 mm; the two layers on the upper part are arranged in a straight shape, are arranged on the upper part of the arc-shaped pipe shed, are arranged with a length of 33 meters, and are formed by arranging hot-rolled seamless steel pipes with a diameter of 146mm and a pipe wall thickness of 10 mm; the pipe wall of each hot-rolled seamless steel pipe is provided with two rows of grouting holes which are staggered.
The invention has the preferable technical scheme that: in the step (2), when the steel ring base is reinforced, a base support is adopted to reinforce the steel ring base, three 20H-shaped steel supports are welded on two sides of the steel ring base respectively, three steel supports on one side are fixedly supported on an upturned beam, and the other group of steel supports are fixedly supported on a main body side wall; then carry out reinforcement support to extension steel loop, adopt two 20H shaped steel split heads to support extension steel loop bottom, weld three 20H shaped steel supports on each side upper portion of extension steel loop, the lower part welds three 20H shaped steel supports, wherein the three steel supports in upper portion of one side are fixed to be supported on the main part longeron, the three steel supports other end fixed support of lower part is on the upturning roof beam, the three steel supports other end fixed support in upper portion of opposite side is on the ring frame roof beam, the three steel supports other end fixed support of lower part is in main part side wall bottom.
The invention has the preferable technical scheme that: in the step (2), in the step c, the connecting plate is connected with the embedded steel ring through full welding with a 45-degree groove; the connecting plate, the embedded steel ring plate and the extension steel ring are welded into an inner part and an outer part, the inner ring is welded after the steel ring is positioned, and the outer ring is welded after the shield body enters the steel ring and the pile grinding is completed; the middle part of the steel ring is provided with two steel wire brushes, the tail part is provided with a curtain cloth rubber plate seal to form three cavities, a circle of ball valve is arranged on the outer side of the steel ring along each cavity, the two steel wires are brushed with tail oil of a shield, after pile grinding is completed, before tunneling is resumed, the cavity is filled with oil through the ball valve for sealing.
The invention has the preferable technical scheme that: the length of the guide rail in the step (2) in the step d is 35-50 cm, one half of the guide rail is arranged on the end wall of the main structure, the other half of the guide rail is in a steel ring), the height of the top surface of the guide rail is 1.5-2.5 cm lower than that of the top surface of the bracket rail, and the rear end surface of the guide rail is provided with 45-degree slope feet.
The invention has the preferable technical scheme that: the shield cutter head in the step (3) adopts a wear-resistant panel, 10 double-edge cutters are arranged on the periphery of the shield cutter head, 4 duplex cutters are arranged in the center of the cutter head, 20 single-edge cutters are arranged on the front of the shield cutter head, the cutter head track spacing of the cutter head is ensured to be 95-105mm, the cutter head is symmetrically arranged, and the cutter ring of the front single-edge cutters is 448mm; the edge scrapers are arc split type edge scrapers, the number of the edge scrapers is 8, the height of the edge scrapers is 130mm, and E5 type materials are adopted as cutter head materials; and a wear detection device is arranged on the cutterhead.
The invention has the preferable technical scheme that: the anti-torsion block in the step (4) adopts a steel plate with the thickness of 1.5-2.5 cm as a stop block, 1 track is arranged every 40cm, and 12-16 blocks are arranged on one side.
The invention has the preferable technical scheme that: in the construction of the pipe shedThe concrete steps of the back grouting adopted in the steel pipe of the pipe shed are as follows:
(1) After the construction of the pipe shed is completed, the pipe orifice of the steel pipe is sealed, and grouting holes and exhaust holes are reserved;
(2) Feeding a back grouting drill rod to a position of 20m in the pipe according to the requirement, and reserving 1m outside the pipe orifice of the drill rod;
(3, a sealing structure is arranged and fixed at a reserved grouting hole position of the pipe orifice of the pipe shed along the axis of the back grouting drill pipe;
(4) Connecting grouting pipelines and stirring cement slurry according to design requirement parameters;
(5) Filling the steel pipes of the pipe shed according to the theoretical grouting amount;
(6) After filling the steel pipe, pulling back the grouting drill pipe for 2-5 m, compacting the sealing structure, and continuing to fill grouting by the pressing force;
(7) Circularly backing grouting drill pipes according to the interval of 1m, and circularly grouting and supplementing until the drill pipes reach the orifice;
(8) Pulling out the back grouting drill rod, closing the orifice valve, and completing back grouting of the single pipe shed steel pipe;
(9) And (3) moving the drilling machine to position the next pipe-shed steel pipe, positioning according to parameters, continuing construction operation, and stopping grouting of all the pipe-shed steel pipes.
The invention has the preferable technical scheme that: in the construction of the pipe shedThe pipe shed adopts a mode of firstly placing a reinforcement cage and then injecting mortar, and the mortar injection steps are as follows:
(1) Inside general length installation of part reinforcement cage that processing was accomplishedThe mortar guide pipe is fixed with the reinforcement cage;
(2) The pipe shed steel pipe is sent into a steel reinforcement cage to seal the pipe orifice of the steel pipe, a mortar conduit penetrates through the hole sealing plate and is welded and fixed with the hole sealing plate, and an exhaust port is reserved on the steel pipe;
(3) Installing and debugging a mortar pump, connecting a pump pipe, filling 90-95% of theoretical mortar filling amount into a steel pipe of a pipe shed, sealing a filling hole after filling the mortar in the steel pipe by using 1:1:1 mortar, and supplementing cement paste according to filling degree;
(4) And (3) moving the pouring facility to position the next one, positioning according to parameters, and continuing the construction operation until grouting of all the pipe-shed steel pipes is completed.
The invention has the beneficial effects that:
(1) The pipe shed is used for reinforcing the shield tunnel before the shield, and plays a role in protecting and isolating the shield tunnel in the shield tunneling construction process, so that the corresponding existing tunnel can be effectively protected, and the subsidence of the earth surface and surrounding building (construction) can be effectively controlled;
(2) The pipe shed construction process realizes the synchronous construction of broken impact pebbles, guiding, deslagging and steel pipe jacking, solves the problems of short supporting distance and low construction precision of pebble floor pipe sheds, and reduces sedimentation deformation caused by overlarge construction disturbance;
(3) In the pipe shed construction process, guiding deviation correction and reaming deviation correction are utilized to ensure the construction precision of the pipe shed, the construction quality of the pipe shed and the maximum effect of the pipe shed during the period of underpass;
(4) The method can ensure that the existing line is not influenced in the process of starting and downwards penetrating the existing line, ensure that shield construction can be completed within the planned time, and not delay the whole subway construction;
(5) According to the invention, by modifying equipment and modifying the cutterhead, the cutterhead is more wear-resistant, the service cycle is prolonged, and the edge scraper is modified, so that the edge scraper is mounted and dismounted, and compared with an integral type cutterhead, the cutterhead has the characteristics of light weight, convenience in replacement and economy; through the transformation of the grouting system of the shield machine, the requirement of multiple grouting during and after the shield machine is in the downward wearing process can be met.
(6) According to the invention, high-concentration bentonite is injected before the downward penetration, the soil bin pressure is established, the tunnel face is stabilized, normal tunneling is ensured, synchronous grouting is carried out through the middle shield and the shield tail in the downward penetration process, and gaps of the segment to excavate the face are filled in time, so that surrounding soil body collapse is prevented; after the segment is separated from the shield tail by a certain distance, in order to prevent the tail clearance from settling and subsequent settling, secondary double-liquid grouting and even tertiary double-liquid grouting are required to be carried out on the segment. The method has obvious advantages in construction of the existing line which is penetrated downwards when the shield machine starts under the complex geological condition.
Drawings
FIG. 1 is a schematic view of a pipe shed support structure in an embodiment;
FIG. 2 is a cross-sectional view of AA in FIG. 1;
FIG. 3 is a schematic diagram of the connection of a plurality of sections of steel pipes of a pipe shed;
FIG. 4 is a schematic structural view of a pipe shed steel pipe;
FIG. 5 is a schematic front view of an embodiment of an elongated steel ring seal;
FIG. 6 is a cross-sectional view of AA in FIG. 5;
FIG. 7 is a cross-sectional view of BB in FIG. 5;
FIG. 8 is a schematic diagram of the distribution of an extended steel ring seal junction ball valve in an embodiment;
FIG. 9 is a top view of an elongated steel ring seal structure in an embodiment;
FIG. 10 is a schematic view of the mounting of the shield block according to the embodiment;
FIG. 11 is a schematic structural view of an improved shield cutterhead in an embodiment;
FIG. 12 is a schematic illustration of grouting flow during the shield tunneling machine pull-down phase in an example;
fig. 13 to 17 are schematic views of shield tunneling in the embodiment.
In the figure: 1-extension steel rings, 2-steel ring bases, 3-embedded steel rings, 3-1-connecting ribs, 3-2-anchoring ribs, 4-base supports, 5-split heads supports, 6-section steel supports, 7-main body side walls, 8-upturning beams, 9-main body longitudinal beams, 10-ring frame beams, 11-shield tail brushes, 12-curtain rubber sheets, 13-ball valves, 14-filling layers, 15-steel plate support pads, 16-end walls, 17-connecting plates, 18-guide rails, 19-shield machines, 20-shield starting brackets, 21-6-line shield tunnels, 22-arc-shaped leading greenhouse, 23-line leading greenhouse, 24-pipe greenhouse steel pipes, 24-1-grouting holes, 24-2-reinforced steel plates, 25-existing 3-line tunnels, 26-anti-torsion blocks, 27-cutter disc main bodies, 28-reinforced nets, 30-arc-edge scrapers, 31-duplex hob, 32-single-edge hob, 29-double-edge hob.
Detailed Description
The invention is further described below with reference to examples and figures.
In the embodiment, a certain section of a subway line 6 of a certain project is used as a specific construction site by shielding to downwards pass through the existing line 3, and the section has a left line length 823.842 and a right line length 821.940m. The distance between the starting station and the outer end wall of the existing No. 3 line main body is 8m, the forward penetration length is 20m, 1-28 are the lower penetration and high risk intervals, the buried depth of the shield tunnel at the lower penetration position is 20.39m, and the vertical distance between the starting station and the No. 3 line shield tunnel is 4.065m. The underground water in the underpass zone is rich, the zone is in the first-order land of the plain of the Min river system, the surface water is river water, and the underground water mainly comprises upper layer stagnant water, fourth series sand, pore diving of a pebble soil layer and bedrock fissure water which are reserved in a clay layer upper filling layer. The shield tunnel is positioned on the saturated medium dense pebble layer in the penetrating stratum, the underground water is rich, and the geological condition is poor in self-stability. The ground is a main road, and the risk of the shield penetrating under a short distance is high.
Because the shield starting point is only 8 meters away from the existing line 3, the vertical distance between the underpass tunnel and the existing line 3 is only 4.065m, because the existing line has higher requirements on sedimentation and the starting point in the existing line is nearer, the shield machine cannot establish stable soil bin pressure to maintain the stability of the tunneling face, meanwhile, because the shield cutterhead self-shields the segment and the adult stratum are sand eggs, disturbance of soil mass around the cutterhead is easily caused in the cutterhead tunneling process, meanwhile, collapse of soil mass around the cutterhead is easily caused due to abundant groundwater, and earthwork supersquare is formed, so that ground sedimentation is caused. Therefore, the construction method is needed to reinforce the tunnel of the shield, the soil bin pressure is built in advance by adopting a welded portal extension steel ring sealing structure, the normal tunneling of the shield machine in the extension steel ring is ensured, and meanwhile, the shield machine is needed to be modified in a targeted manner to ensure the normal tunneling of the shield machine and the multiple grouting in the tunneling process in order to ensure that the shield machine can rapidly pass through the existing tunnel. Aiming at the requirements, the method for preventing the ground collapse when the shield tunneling machine starts to downwards pass through the existing shield tunnel is adopted for construction, and the specific steps are as follows:
1. the construction steps of the pipe shed between the sixth-line tunnel hole and the existing third-line tunnel hole by adopting the pipe shed advanced support specifically comprise:
(1) Intersecting the construction drawings, and setting out on site to determine the specific positions of all the pipe sheds;
(2) Processing steel pipes of a pipe shed, and selecting the steel pipes of the pipe shedAnd->Two types of hot rolled seamless steel pipes are processed into a pipe shed steel pipe, and as shown in figure 4, the pipe walls are symmetrical and staggered to form 2 rows of +.>Grouting holes; the connection between the steel pipes is shown in fig. 5, the pipe orifice is processed into a 45-degree groove, a reinforced steel plate is longitudinally welded along the steel pipe joint after circumferential welding, the width of the reinforced steel plate is not less than 1/3D, and the length is not less than 1.5D (D is the diameter of the construction steel pipe);
(2) As shown in fig. 1 and 2, two rings are arranged within the range of 180 degrees of the circumferential direction of 650mm of the outer side of the contour line of the No. 6 line shield tunnel 21Arc-distributed advanced greenhouse, two rows of +.>The pipe shed is arranged around according to an inclination angle of 1.5 degrees; 29 outer rings of left and right sections of the shield tunnel are respectively provided with 28 inner rings, and 57 shield tunnels are provided; the length of the pipe shed is 33m by the single side of the end well, and the total construction amount of the pipe shed is 3762m; after the pipe shed is arranged, grouting filling is completed in time, a steel reinforcement cage is inserted into a pipe shed steel pipe, and filling mortar is poured; grouting is carried out once according to every two holes; the deviation of the hole position of the steel pipe inlet is controlled to be +/-20 mm; the construction of the tunnel pipe shed of the shield tunnel adopts a guiding reaming pipe-jacking construction process, namely, an impact crushing guiding impactor is arranged in a pipe shed steel pipe, a measuring water pipe is arranged through a drilling tool, the pipe shed steel pipe is impacted and crushed pebbles are impacted at the same time of jacking, and the pipe shed steel pipe is drilled forwards through the impactor;
(3) As shown in fig. 1 and 2, two rows are arranged in a straight line at 2210mm and 2980mm positions on the upper side of the arch top of the 6 # line shield tunnel 21Advance big-arch shelter, two rows->Setting an inclination angle of 1.5 degrees or horizontally setting the pipe shed according to the experimental deviation of the pipe shed setting in the step (2); the center distance of the steel pipes of the pipe shed is 1000mm, and the pipe shed is distributed in a quincuncial shape; 17 right lines and 15 left lines of the shield tunnel are distributed, and 32 right lines are distributed in total; the length of the pipe shed is 30m from one side of the shaft pit enclosure surface, and the total construction amount of the pipe shed is 960m; filling cement paste by adopting a backward process after the pipe shed is arranged, wherein the proportion of the cement paste is 0.8-1:1; grouting is carried out once according to every two holes, and the deviation of the hole positions of the steel pipe inlet holes is controlled to be +/-20 mm; the construction of the tunnel pipe shed of the shield tunnel adopts a guiding reaming pipe-jacking construction process, namely, an impact crushing guiding impactor is arranged in a pipe shed steel pipe, a measuring water pipe is arranged through a drilling tool, the pipe shed steel pipe is impacted and crushed pebbles are impacted at the same time of jacking, and the pipe shed steel pipe is drilled forwards through the impactor.
2. After the pipe shed support is finished, constructing an extension steel ring sealing structure at the tunnel portal of the six-wire shield tunnel, wherein the steel ring sealing structure is shown in fig. 5 to 9 in detail, and the construction steps of the extension steel ring sealing structure specifically comprise:
(1) Positioning of the portal extension steel ring: the embedded steel ring of the tunnel portal extends to the large mileage end of the station for 2m, and the central axis of the steel ring horizontally deviates to the left by 3cm along the tunneling direction according to the designed central axis according to the actual measurement tunnel portal deviation. The steel ring is positioned at the height position according to the designed height and the corresponding gradient of 2 per mill and 2cm too high;
(2) Installing a portal extension steel ring: before the steel ring is installed, measuring and rechecking the position of the steel ring, and rechecking the position, elevation and ellipticity of the transverse plane and the longitudinal plane of the steel ring; the steel ring installation sequence comprises the steps of descending a shield machine trolley, descending a steel ring base, descending a semi-circular steel ring, descending a shield body and installing a cutter head, positioning and temporarily reinforcing the lower semi-circular steel ring by a measuring shift according to set coordinates, connecting the semi-circular descending well with the lower semi-circular steel ring, positioning and rechecking the position of the steel ring by the measuring shift, and integrally reinforcing the steel ring by a special person;
(3) Supporting structure installation of the portal extension steel ring: as shown in fig. 6 and 7, the portal steel ring support mainly comprises a base support 4, a split heads support 5 and a section steel support 6, wherein the base support 4 comprises three 20H section steel supports respectively arranged on two sides of the steel ring base 2, and the split heads support 5 comprises 2 20H section steel split heads supports arranged in grooves at the bottom of the steel ring 1 of a tobacco plant; the section steel support 6 comprises three welded 20H section steel supports arranged at the upper part of each side of the extension steel ring 1 and three welded 20H section steel supports arranged at the lower part of each side of the extension steel ring; when the steel ring base 2 is reinforced, six I-beams with the length of 1440mm are specifically adopted for supporting, three I-beams are symmetrically arranged on two sides of the steel ring base 2, one end of each of the six I-beams is welded on the steel ring base 2, the other end of each of the six I-beams on the left side is supported on an upturned beam 8, and the other ends of the three I-beams on the right side are supported at the bottom of a side wall 7 of the main body; then reinforcing the steel ring, wherein the steel ring support comprises an upper group of second I-shaped steel support rods and a lower group of second I-shaped steel support rods which are arranged on each side of the extended steel ring 2, each group comprises three 20H-shaped steel bars which are arranged side by side, wherein the length of the left three I-shaped steel bars is 2713mm, one end of each of the three I-shaped steel bars is welded on the extended steel ring 2, the other end of each of the three I-shaped steel bars is supported on the main body longitudinal beam 9, the length of the right three I-shaped steel bars is 2460mm, one end of each of the three I-shaped steel bars is welded on the extended steel ring 2, and the other end of each of the three I-shaped steel bars is supported on the ring frame beam 10; six 20H-shaped I-shaped steels arranged at the lower part of the extension steel ring 2 are 3232m in length, one ends of the six I-shaped steels are respectively welded at the lower part of the extension steel ring 2, wherein the other ends of the three I-shaped steels at the left side are fixedly supported on the upturned beam 8, and the three I-shaped steels at the other side are fixedly supported at the bottom of the side wall 7 of the main body;
(4) Sealing the door extension steel ring: as shown in fig. 5 and 9, the extension steel ring 1 and the embedded steel ring 3 are in transitional connection by adopting a connecting plate 17, the connecting plate 17 and the extension steel ring 1 are in full-welded connection, and the connecting plate 17 and the embedded steel ring 3 are in full-welded connection by adopting a 45-degree groove; the welding seam is prevented from deforming after the shield body enters the steel ring, the connecting plate 17 of the welding seam is welded with the embedded steel ring 3 and the extension steel ring 1 in an inner part and an outer part, the inner ring is welded after the steel ring is positioned, and the outer ring is welded after the shield body enters the steel ring and the pile grinding is completed; after the steel ring 1 is well reinforced, a first shield tail brush is welded at 650mm distance from the tail of the steel ring on the inner side of the steel ring 1, a second shield tail brush is welded at 1350mm distance from the tail of the first shield, finally a sealing curtain cloth rubber plate 12 is welded at the tail of the steel ring to form three cavities, a plurality of ball valves 13 are arranged on the outer side of the steel ring along each cavity, the ball valves are distributed as shown in 8, shield tail grease is smeared on the two steel wire brushes 11, after pile grinding is completed, grease is fully filled into the cavities through the ball valves for sealing before tunneling is resumed;
(5) Construction in the extended steel ring of the tunnel portal prevents planting the head structure: as shown in fig. 5 and 7, the guide rail 18 is installed first, the length of the guide rail 17 is 40cm (20 cm is arranged on the end wall of the main structure, 20cm is arranged in the steel ring), the front end of the guide rail 18 is 70cm away from the end wall 16 of the structure, the rear end of the guide rail 18 is 2m away from the front end of the shield starting bracket 20, the top surface of the guide rail 17 is 2cm lower than the top surface of the bracket track, and 45-degree slope feet are applied to the rear end surface of the guide rail 17 (namely, the shield body is contacted with the guide rail surface for the first time) so that the shield body can be smoothly pushed into the upper guide rail; after the guide rail is installed, fine stones are adopted to fill the non-track range of the tunnel portal, and the filling height is equal to that of the track.
4. The shield body anti-torsion measure: when the cutter head is ready for rotary pile grinding, as shown in fig. 10, the anti-torsion blocks 26 are arranged at the middle shield and the tail of the shield, the anti-torsion blocks 26 are made of steel plates with the thickness of 2cm, 1 track is arranged every 40cm, 14 blocks are arranged on one side, two sides of the shield body are all arranged, the torque of the shield machine is controlled to be below 2500KN.M according to the shield tunneling parameters in the propelling process, the rolling angle is controlled to be +/-5 mm/m, and the cutter head is reversed in time.
5. The construction of the shield machine before the well is closed: in order to meet the transformation requirement, the project selects middle iron equipment 327 and 177 shield machine, and the concrete transformation is as follows:
(1) Cutter head: a panel, wherein the opening ratio is about 36%, the opening is provided with grids, and a wear-resistant plate which is denser and more wear-resistant is welded on the panel;
(2) Hob configuration: the periphery of the cutter head is provided with 10 double-edge hob; the front surface adopts a single-blade hob with the configuration form of a hob tip track as a basis, so that the distance between the hob tip tracks is ensured to be about 100mm, and symmetrical configuration is ensured; 4 double-linked hobs are arranged in the cutter disc center 1-8 # of the cutter disc; in order to improve the limit abrasion of the front single-blade hob, the cutter ring is enlarged to 448mm from the previous 432 mm;
(3) Edge scraper: the cutter head edge scraper is of an arc-shaped structure, the number of the cutter head edge scrapers is 8, the height of the cutter head edge scraper is 130mm, and the cutter head is made of E5 type materials, so that the cutter head has good wear resistance and shock resistance;
(4) Abrasion detection: the cutter head is provided with 4 abrasion detection devices, so that the abrasion condition of the cutter head cutter is judged in time, and the cutter head body of the cutter head is prevented from being abraded and damaged;
(5) Foaming agent injection system: the shield is provided with 5 groups of single-pipe single-pump single-nozzle foam injection systems; the foam system adopts a single-pipe single-pump mode, each path of foam can independently work, a premixing mode is adopted, the foaming effect is enhanced, the foam consumption is reduced, the nozzle assembly can be completely extracted from the back of the cutter head, and the maintenance or the replacement is convenient;
(6) Bentonite system: 2 bentonite pumps are configured for improving the dregs; the two pumps can be injected into the front of the cutterhead through separate pipelines, and can also be injected outside the hole shell in one way.
6. And (3) a shield grouting process: because the shield tunneling machine underpass has an influence range of-2 rings to 28 rings, the grouting process in the shield tunneling machine underpass is specifically as follows:
(1) As shown in fig. 13, inert slurry material is injected from the middle shield radial bore as the negative 1 ring begins to advance; filling and prolonging a gap between the steel ring 1 and the shield shell to seal a tunnel portal, and building a soil bin for pressure pushing; filling a gap between an excavated soil body and a shield shell before synchronous grouting does not reach, preventing the excavated soil body from settling, when the +28 ring pushing and splicing are finished, at the moment, the shield tail is separated to the 10m outside the existing line, and stopping the middle shield grouting, so that the construction gap in the shield construction pushing process is effectively filled for guaranteeing the injection effect, and key time is won for synchronous grouting behind the subsequent pipe piece and soil body reinforcing grouting;
(2) Synchronous grouting: when +1 pushing and splicing are completed and +2 ring starts to push (when the cutter disc surface reaches 700mm of the outer edge of the existing line), synchronous grouting is started, grouting pressure is controlled to be 1.2-1.8bar, and special people are dispatched to observe the sealing condition, and leakage is timely blocked;
(3) And (3) secondary grouting to block the tunnel portal: when pushing and splicing of the +3 ring are completed and pushing of the +4 ring is started, at the moment, hoisting holes of the 0 ring or the negative 1 ring pipe slice are filled with cement and water glass double-liquid slurry, and sealing of the tunnel portal is carried out; the cement slurry has a water-cement ratio of 1:1, the water glass Baume degree of 22 (diluted by water glass and water in a volume ratio of 1:1), the cement slurry has a volume ratio of 1:1, and the grouting pressure is controlled within 1.0 bar; because the distance from the shield tail to the grouting position is relatively short at this moment, in order to prevent slurry from wrapping the shield tail and the shield body, grouting and tunneling are required to be carried out synchronously. The principle of multiple points, small quantity and low pressure is adopted in the plugging grouting;
(4) Grouting behind the segment wall according to different purposes, the grouting behind the wall is divided into synchronous grouting and secondary supplementary grouting:
a, synchronous grouting, in order to ensure synchronous grouting in time and in place, grouting and tunneling are synchronous, double control is carried out by grouting pressure and grouting amount, the average grouting amount per ring is not less than 7, the grouting pressure is controlled within 2bar, and the mixing ratio is as follows:
b, secondary grouting, when the +6 rings are spliced and pushed, secondary grouting is started, cement slurry and water glass dual-liquid slurry are selected, the cement slurry water cement ratio is 1:1, the water glass Baume degree is 22 (the water glass is diluted by 1:1 in volume ratio), the cement slurry is 1:1 in volume ratio, and the grouting pressure is 2-3 bar.
The shield machine is started to penetrate downwards through the existing shield tunnel, is rare in China, particularly in water-rich sand pebble areas, and has the characteristics of easy disturbance, high water content, easy collapse and the like. The accurate earth bin pressure is built in the stratum, normal tunneling difficulty is guaranteed to be high, and meanwhile, ground settlement is easily caused in the process of underpass due to the fact that the distance between an existing line tunnel and the underpass tunnel is short, and operation of an existing line is affected. The method of the invention is adopted to complete the construction settlement control of the shield penetrating the existing line under the complex high-risk stratum by completing the construction of the existing line 3 under the shield between the first-stage engineering soil station and the second-stage engineering soil station of the No. 6 line of the capital subway and the section between the first-stage engineering soil station and the beam home roadway station, thereby increasing the stability of the shield starting section, establishing the complete and effective soil bin pressure before the shield starting, ensuring the shield machine to safely, quickly and stably penetrate the existing shield tunnel when starting, and preventing the ground collapse when the shield machine starts to penetrate the existing shield tunnel when penetrating the lower shield tunnel.
The detailed description of the invention is intended to be illustrative and exemplary in nature and should not be construed as limiting the invention in its implementation and scope. In addition to the specific implementations described herein, those skilled in the art will be able to adopt other obvious solutions based on the disclosure of the claims and specification of the present application, including any obvious modifications and substitutions made by the specific implementations described herein.
Claims (10)
1. A method for preventing ground collapse when a shield tunneling machine starts to downwards pass through an existing shield tunnel is characterized by comprising the following specific steps:
(1) Before the shield starts, the pipe shed advanced support is constructed for the shield tunnel: a multi-layer pipe shed is arranged between the outline of the tunnel portal of the shield tunnel and the existing tunnel, all pipe shed steel pipes adopt flower pipes with grouting holes at pipe wall openings, and grouting is carried out through each pipe shed steel pipe after the pipe shed is arranged;
(2) The method comprises the steps of constructing an extension steel ring structure for pre-establishing shield soil bin pressure when a shield is started at a shield tunnel entrance:
a. positioning and mounting of a portal extension steel ring: the extension steel ring is arranged at a shield tunnel gate, extends from a pre-buried steel ring of the tunnel gate to a large mileage end of a station for 2-3 m, is divided into an upper half extension steel ring and a lower half extension steel ring, and is respectively arranged after a steel ring base is arranged, and the upper half extension steel ring and the lower half extension steel ring are connected into a whole;
b. reinforcing the steel ring by adopting a steel ring supporting structure: the steel ring supporting structure comprises a base support arranged on a steel ring base, a split heads support arranged at the groove part at the bottom of the extension steel ring and profile steel supports arranged at two sides of the extension steel ring, wherein the extension steel ring is arranged at a shield starting hole through the steel ring base, a steel ring body of the extension steel ring is connected with an embedded steel ring of the shield hole, and is fixedly supported with a main body side wall and a structural beam of the shield starting hole through the steel ring supporting structure;
c. sealing of the portal extension steel ring: connecting the extension steel ring with an embedded ring plate at the hole, adopting a connecting plate transitional connection mode, connecting the connecting plate with the steel ring in a full-welded mode, and connecting the connecting plate with an embedded steel ring groove in a full-welded mode; at least two steel wire brushes are arranged in the middle of the inside of the extension steel ring, a cord fabric rubber plate is arranged at the tail of the extension steel ring to form a plurality of cavities, and a circle of ball valve is arranged at the position, corresponding to each cavity, outside the extension steel ring;
d. constructing a head planting preventing structure at the bottom of the extension steel ring: firstly, installing a guide rail, wherein the top surface of the guide rail is 1.5-3 cm lower than the top surface of a bracket track, the guide rail is firstly contacted with a shield body, the rear end surface of the guide rail is provided with a slope toe, the front end of the guide rail is 60-80 cm away from a structural wall, and the rear end of the guide rail is 1.5-3 m away from the front end of the bracket; fine stones or sand are filled between the two guide rails, and the filling height of the fine stones or sand is equal to that of the guide rail tracks;
(3) Aiming at improvement of a cutter head of a shield machine: selecting a panel cutter with an aperture ratio of 33% -40%, wherein a reinforcing net is arranged at the aperture position of the cutter;
(4) The shield body anti-torsion measure: when the cutter head is ready for rotary pile grinding, a plurality of anti-torsion blocks are respectively arranged at two sides of the middle shield and the shield tail at equal intervals, the distance between the adjacent anti-torsion blocks is 30-50 cm, the torque of the shield machine is controlled to be below 2500KN.M in the propelling process, the thrust is controlled to be 495-510T, and the rolling angle is controlled to be within +/-5 mm/m.
2. The method for preventing ground collapse when a shield tunneling machine originates from or descends through an existing shield tunnel according to claim 1, wherein: the method further comprises the step of improving a foam injection system and a bentonite injection system of the shield tunneling machine; wherein, the foam injection system is provided with 5 groups of single-pipe single-pump single-nozzle foam injection systems in the shield machine, the system adopts single-pipe single-pump, and each path of foaming agent can work independently; the bentonite injection system is improved by configuring two bentonite pumps, wherein the two pumps can be injected into the front of the cutter head through separate pipelines, and can also be injected outside the shield shell in a single way; the grouting mode is as follows:
a. in the tunneling process of the shield machine, high-concentration bentonite slurry is adopted to fill and press a soil bin, so that the stability of a tunnel face is ensured;
b. in the middle shield pushing process, the middle shield radial holes of the shield machine are utilized to synchronously perform middle shield grouting in the shield machine downward penetrating process, and a construction gap between the excavation surface and the shield body is filled;
c. synchronously injecting mortar into the shield tail;
d. and (3) carrying out grouting supplement in the region with hidden danger after synchronous grouting and secondary grouting in the shield process, wherein the grouting supplement position is 6-9 rings at the tail of the shield.
3. The method for preventing ground collapse when a shield tunneling machine originates from or descends through an existing shield tunnel according to claim 1, wherein: the pipe shed advanced support in the step (1) comprises a four-layer pipe shed, wherein the lower two layers are arc-shaped, are arranged along the outer edge of the upper part of the shield tunnel portal, have the length of 30 meters and are formed by arranging hot-rolled seamless steel pipes with the diameter of 194mm and the pipe wall thickness of 10 mm; the two layers on the upper part are arranged in a straight shape, are arranged on the upper part of the arc-shaped pipe shed, are arranged with a length of 33 meters, and are formed by arranging hot-rolled seamless steel pipes with a diameter of 146mm and a pipe wall thickness of 10 mm; the pipe wall of each hot-rolled seamless steel pipe is provided with two rows of grouting holes which are staggered.
4. The method for preventing ground collapse when a shield tunneling machine originates from or descends through an existing shield tunnel according to claim 1, wherein: in the step (2), when the steel ring base is reinforced, a base support is adopted to reinforce the steel ring base, three 20H-shaped steel supports are welded on two sides of the steel ring base respectively, three steel supports on one side are fixedly supported on an upturned beam, and the other group of steel supports are fixedly supported on a main body side wall; then carry out reinforcement support to extension steel loop, adopt two 20H shaped steel split heads to support extension steel loop bottom, weld three 20H shaped steel supports on each side upper portion of extension steel loop, the lower part welds three 20H shaped steel supports, wherein the three steel supports in upper portion of one side are fixed to be supported on the main part longeron, the three steel supports other end fixed support of lower part is on the upturning roof beam, the three steel supports other end fixed support in upper portion of opposite side is on the ring frame roof beam, the three steel supports other end fixed support of lower part is in main part side wall bottom.
5. The method for preventing ground collapse when a shield tunneling machine originates from or descends through an existing shield tunnel according to claim 1, wherein: in the step (2), in the step c, the connecting plate is connected with the embedded steel ring through full welding with a 45-degree groove; the connecting plate, the embedded steel ring plate and the extension steel ring are welded into an inner part and an outer part, the inner ring is welded after the steel ring is positioned, and the outer ring is welded after the shield body enters the steel ring and the pile grinding is completed; the middle part of the steel ring is provided with two steel wire brushes, the tail part is provided with a curtain cloth rubber plate seal to form three cavities, a circle of ball valve is arranged on the outer side of the steel ring along each cavity, the two steel wires are brushed with tail oil of a shield, after pile grinding is completed, before tunneling is resumed, the cavity is filled with oil through the ball valve for sealing.
6. The method for preventing ground collapse when a shield tunneling machine originates from or descends through an existing shield tunnel according to claim 1, wherein: the length of the guide rail in the step (2) in the step d is 35-50 cm, one half of the guide rail is arranged on the end wall of the main structure, the other half of the guide rail is in a steel ring), the height of the top surface of the guide rail is 1.5-2.5 cm lower than that of the top surface of the bracket rail, and the rear end surface of the guide rail is provided with 45-degree slope feet.
7. The method for preventing ground collapse when a shield tunneling machine originates from or descends through an existing shield tunnel according to claim 1, wherein: the shield cutter head in the step (3) adopts a wear-resistant panel, 10 double-edge cutters are arranged on the periphery of the shield cutter head, 4 duplex cutters are arranged in the center of the cutter head, 20 single-edge cutters are arranged on the front of the shield cutter head, the cutter head track spacing of the cutter head is ensured to be 95-105mm, the cutter head is symmetrically arranged, and the cutter ring of the front single-edge cutters is 448mm; the edge scrapers are arc split type edge scrapers, the number of the edge scrapers is 8, the height of the edge scrapers is 130mm, and E5 type materials are adopted as cutter head materials; and a wear detection device is arranged on the cutterhead.
8. The method for preventing ground collapse when a shield tunneling machine originates from or descends through an existing shield tunnel according to claim 1, wherein: the torsion-proof block in the step (4) adopts a steel plate with the thickness of 1.5-2.5 cm as a stop block, 1 track is arranged every 40cm, 12-16 blocks are arranged on one side, the thrust of the shield machine is controlled to be 500T according to the shield tunneling parameters in the propelling process, and a method of high thrust and small torque is adopted.
9. The method for preventing ground collapse when a shield tunneling machine starts to pass through an existing shield tunnel downwards according to claim 3, wherein the method is characterized in that in the construction of the pipe shed, a reverse grouting is adopted in a pipe shed steel pipe with diameter of 146mm x 10mm, and the concrete steps are as follows:
(1) After the construction of the pipe shed is completed, the pipe orifice of the steel pipe is sealed, and grouting holes and exhaust holes are reserved;
(2) Feeding a back grouting drill rod to a position of 20m in the pipe according to the requirement, and reserving 1m outside the pipe orifice of the drill rod;
(3 edge-back grouting) the axis of the drill rod is arranged at the orifice of the shed a sealing structure is arranged at a reserved grouting hole position and is fixed;
(4) Connecting grouting pipelines according to design stirring cement slurry according to required parameters;
(5) Pipe shed steel pipe internal pressing theoretical grouting filling in a quantity;
(6) After filling the steel pipe, pulling back the grouting drill pipe for 2-5 m, compacting the sealing structure, and continuing to fill grouting by the pressing force;
(7) Circularly backing grouting drill pipes according to the interval of 1m, and circularly grouting and supplementing until the drill pipes reach the orifice;
(8) Pulling out the back grouting drill rod, closing the orifice valve, and completing back grouting of the single pipe shed steel pipe;
(9) And (3) moving the drilling machine to position the next pipe-shed steel pipe, positioning according to parameters, continuing construction operation, and stopping grouting of all the pipe-shed steel pipes.
10. The method for preventing ground collapse when a shield tunneling machine starts to pass through an existing shield tunnel downwards according to claim 3, wherein a reinforcement cage is placed in a pipe shed pipe with diameter of 194mm to 10mm in the pipe shed construction, mortar is poured in the pipe shed pipe, and the method comprises the following steps:
(1) A phi 45mm mortar conduit is installed in the processed part of the reinforcement cage in a through length mode, and the conduit is fixed with the reinforcement cage;
(2) The pipe shed steel pipe is sent into a steel reinforcement cage to seal the pipe orifice of the steel pipe, a mortar conduit penetrates through the hole sealing plate and is welded and fixed with the hole sealing plate, and an exhaust port is reserved on the steel pipe;
(3) Installing and debugging a mortar pump, connecting a pump pipe, filling 90-95% of theoretical mortar filling amount into a steel pipe of a pipe shed, sealing a filling hole after filling the mortar in the steel pipe by using 1:1:1 mortar, and supplementing cement paste according to filling degree;
(4) And (3) moving the pouring facility to position the next one, positioning according to parameters, and continuing the construction operation until grouting of all the pipe-shed steel pipes is completed.
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| CN111636878B (en) * | 2020-04-30 | 2021-10-22 | 广州地铁集团有限公司 | Pipe jacking construction method for double-hole door |
| CN111706337B (en) * | 2020-05-19 | 2022-07-15 | 北京城建中南土木工程集团有限公司 | Construction method for shield to penetrate high-speed rail |
| CN112647963A (en) * | 2020-12-21 | 2021-04-13 | 上海隧道工程有限公司 | Construction method for shield to obliquely penetrate existing ground wall |
| CN114293993B (en) * | 2021-12-09 | 2023-04-04 | 中国建筑第五工程局有限公司 | Vertical deformation repairing structure for construction of up-and-down overlapped tunnel and construction method |
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| CN209444350U (en) * | 2019-01-07 | 2019-09-27 | 中铁十一局集团城市轨道工程有限公司 | Shield launching wears existing shield tunnel barrel vault advanced support structure under being |
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| CN109707388A (en) | 2019-05-03 |
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