WO2020224233A1

WO2020224233A1 - Construction method for shield tunnels passing underneath viaduct in multi-interval, small-clear-distance and overlapping manner

Info

Publication number: WO2020224233A1
Application number: PCT/CN2019/120380
Authority: WO
Inventors: 孙捷城; 路林海; 刘瑞琪; 胡永利; 韩帅
Original assignee: 济南轨道交通集团有限公司
Priority date: 2019-05-05
Filing date: 2019-11-22
Publication date: 2020-11-12
Also published as: CN110080781A; AU2019444087B2; AU2019444087A1; CN110080781B

Abstract

Disclosed is a construction method for shield tunnels passing underneath a viaduct in a multi-interval, small-clear-distance and overlapping manner. The construction method comprises the following steps: according to a principle of having the minimal deformation effect on pile foundations of a viaduct and the surrounding environment, formulating an optimal construction sequence for constructing shield tunnels passing underneath the viaduct in a multi-interval and overlapping manner; before a tunnel passes underneath the viaduct, carrying out active isolation reinforcement for construction in which a shield passes underneath for a short distance; constructing the shield tunnel passing underneath the viaduct; in an area where a plurality of shield tunnel sections pass underneath the viaduct in an overlapping manner, reinforcing a segment structure of the shield tunnel and reinforcing the interior of a tunnel hole; and carrying out track vibration reduction and isolation control in a section where the shield tunnel passes underneath the viaduct.

Description

Construction method for shield tunnels with multiple intervals, small clear distances, and overlapping underpass viaducts

Technical field

The invention relates to the technical field of subway shield tunnel construction, in particular to a construction method for shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts.

Background technique

The statements here only provide background art related to the present invention, and do not necessarily constitute prior art.

With the continuous expansion of the scale of cities in my country, the construction of urban three-dimensional transportation has become the main trend in the development of transportation in the new era. Urban subways and viaducts are the main channels to achieve three-dimensional transportation. The parallel development of the two will inevitably lead to multiple sections of subway tunnels. There are more and more cases of small clear distances and overlapping underpasses. In particular, the two have relatively strict requirements for their respective operating environment and deformation control. They are affected by factors such as the dynamic load of the viaduct, the ground loss during the shield tunneling construction, and the superimposed ground disturbance of the multi-section subway operation. It is easy to cause adjacent viaduct piles. Safety risks such as uneven settlement, surface subsidence and deformation, and irregular subway tracks. Therefore, formulating corresponding construction methods and prevention and control measures to ensure the safety of shield tunnels with small clear distances, stacking and falling through viaducts, and avoiding uneven settlement and deformation of viaduct piles and shield tunnels, has become a key problem to be solved in design and construction. .

The existing technology is mainly aimed at the isolation and reinforcement control of shield tunnels passing through viaducts orthogonally. The isolation and reinforcement usually use bored piles, mixing piles, jet-grouted piles, and even underground continuous walls to block shield tunnels and elevated bridges. The continuous deformation of the pile foundation has limited deformation control effects. It is difficult to meet the construction safety control requirements under multiple complex conditions such as water-bearing strata, multi-interval shield tunnels, and small-clear overlap crossing construction, and there is no combination of multiple control technologies. Comprehensive control system and construction methods.

Summary of the invention

In order to solve the shortcomings of the prior art, the present invention provides a construction method for shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts.

In order to achieve the above objective, the present invention adopts the following technical solutions:

A construction method for shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts. The specific steps are as follows:

Step 1: According to the principle of the least impact on the deformation of the viaduct pile foundation and the surrounding environment, formulate the optimal construction sequence for the construction of the shield tunnel with multiple sections and stacked under the viaduct;

Step 2: Before the tunnel underpasses the viaduct, conduct active isolation and reinforcement of the short-distance underpass construction of the shield;

Step 3: Carry out the construction of the shield tunnel under the viaduct;

Step 4: Reinforce the segment structure of the shield tunnel in the area where the multi-shield tunnel overlaps and pass through the viaduct, and strengthen the tunnel cavity;

Step 5: The track vibration reduction and isolation control is carried out in the section of the shield tunnel passing through the viaduct.

As a further technical solution, the specific working method of step one is to establish a high-precision three-dimensional numerical model, simulate and analyze the deformation of the viaduct structure and surrounding stratum caused by the construction of multiple shield tunnels in different sequences, and determine the correctness of the viaduct pile foundation and surrounding environment The underpass construction sequence with the least deformation effect is the optimal construction sequence.

Furthermore, the formation parameters, tunnel direction and size, viaduct load and pile foundation parameters, shield tunneling process and other information in the high-precision three-dimensional numerical model must be consistent with the actual construction situation to improve the accuracy of the numerical simulation.

As a further technical solution, the specific working method of the second step is:

Step 2.1 Construct bored piles as isolation piles;

The isolation pile construction is completed some time before the shield passes through the viaduct, and bored piles are built between the shield tunnel and the viaduct pile foundation. The protection range of the cast-in-place pile extends beyond the pier cap, and the bottom of the cast-in-place pile reaches the shield segment. Below the structure bottom, in order to limit the horizontal deformation of bridge piles caused by shield tunneling, and try to block the stress transmission and deformation expansion of shield construction;

Step 2.2 Carry out sleeve valve pipe grouting to stop water between piles;

Sleeve valve tube grouting is adopted for the middle, fine sand layer and pebble layer between the isolated piles.

Further, the bored pile is formed by a positive circulation drilling machine with a grinding disc. When drilling, it is drilled with light pressure, low rotation speed and slow drilling. After entering the normal state, the rotation speed and the drilling speed are gradually increased; the drilling parameters and drilling speed are controlled throughout the process. Speed; when changing layers, appropriately slow down the speed and reduce the weight on bit to prevent the borehole from tilting.

Furthermore, the construction of bored piles adopts steel casing and mud water wall protection. The mud wall protection effect is good and it is suitable for the construction of pebble stratum. If there is a hole collapse, the surrounding drilling should be stopped immediately, the cause of the hole collapse should be found out, and the monitoring of the bridge structure should be strengthened; when the pile is repaired, the original pile should be drilled and poured.

Furthermore, the construction of bored piles adopts jumping pile construction, and guarantees "drill one hole, inject one hole" and guarantee symmetrical drilling to reduce the impact of isolation pile construction on viaduct piles.

Furthermore, due to the height restriction of the viaduct in the construction site, the steel cage is made in sections, and the hoisting equipment of the millstone drill is used for hoisting the steel cage to meet the construction space under the viaduct.

Further, the sleeve valve tube is drilled with a pilot hole drill, and the hole depth needs to meet the design requirements. The area where the working space of grouting is restricted can be adjusted by adjusting the angle of the grouting pipe and the arrangement of dense grouting holes.

Furthermore, the sleeve valve pipe construction adopts the grouting construction method of interval skipping holes, gradual restraint, and first down and then up. Drilling sequence: drill the peripheral holes first, and gradually drill from the outside to the inside. Grouting sequence: from the outside to the inside, first grouting the holes on the reinforcement range line, blocking the slurry leakage channel, and then gradually densifying the grouting holes to perform grouting and compaction in the middle of the area.

Further, special field experiments should be done for the grouting reinforcement of sleeve valve tube in the pebble layer with high water richness and strong permeability. Various measures should be taken to solve the problem that traditional sleeve valve tube grouting is easy to collapse in such formations, the slurry is easy to lose, and the grouting is dense. Insufficient performance and other issues; measures include: strengthening the plugging of the grouting port, injecting cement-water glass double-liquid slurry, adding AB chemical slurry, adding polyurethane slurry, etc.

As a further technical solution, the shield tunnel segment structure strengthening is performed in the step 4, which mainly includes:

1. Reinforce the main reinforcement and distribution reinforcement of the tunnel segment;

2. Improve the longitudinal bolt grade of the segment and increase the longitudinal rigidity of the tunnel.

3. Improve the waterproofness of the tube structure; a porous EPDM elastic gasket is set at the joints of the tube sections, a nitrile cork rubber pad is set at the circumferential and longitudinal seams of the tube sections, and the full loops of the tube sections are caulked with flexible polyurethane sealant; Water-wet stains in the invert range are made of polymer waterproof mortar, all bolt holes are sealed with water-swellable rubber rings, and the lifting holes are sealed with plastic protective covers.

As a further technical solution, the reinforcement in the tunnel in the overlap zone is carried out in the fourth step, which mainly includes:

1. Add a reserved grouting hole in the segment structure, and use the grouting hole to reinforce the soil in the overlapping area to reduce the additional stress and stress on the first formed tunnel structure after the construction of the multi-section overlapping area. Degradation effects such as superimposed deformation;

2. During the ascending shield tunneling, a support trolley is erected in the descending tunnel to support and strengthen the overall longitudinal rigidity of the previously formed tunnel to prevent longitudinal uneven settlement of the tunnel segments.

Furthermore, each ring tunnel segment is generally divided into 6 blocks, which are 3 standard blocks, 2 adjacent blocks, and 1 capping block. The additional reserved grouting holes for the segment are added to each standard block and adjacent blocks. 2 reserved grouting holes, so that after the segment is assembled and stabilized, the interlayer soil in the overlapping area is reinforced by grouting twice or more through the reserved grouting holes.

As a further technical solution, in the fifth step, the track vibration reduction and isolation control is performed in the subway tunnel underpassing the viaduct section, which mainly includes:

Vibration reduction and isolation measures are adopted for the subway track within the 50m tunnel range on both sides of the pier cap of the subway tunnel under the viaduct section to reduce the impact of rail transit operations on the vibration of the elevated bridge.

Furthermore, the subway track uses an improved rubber (polyurethane) floating slab damping track (the first-order natural vibration frequency is 10-20 Hz) to avoid resonance with the railway train running on the viaduct and reduce the vibration energy of the subway train itself.

The positive effects of the present invention are embodied as:

1. The present invention forms an active control system of shield tunnel underpassing viaduct through a combination of control technologies in five aspects: construction sequence optimization, active isolation and reinforcement, segment structure reinforcement, tunnel grouting reinforcement, and track vibration reduction and isolation, and the construction stability and deformation The control effect is excellent. It overcomes the disadvantages of single control method of traditional isolation piles, limited control effect, and failure to actively prevent risks. It can meet the safety control of water-bearing strata, multiple intervals, small clear distance, and overlapping shield tunnels under the viaduct construction Claim.

2. The present invention formulates the optimal construction sequence for the multi-section and stacked-down underpass construction of the shield tunnel, and determines the sequence of the multi-section underpass construction according to scientific and informatized means, avoiding the subjectivity and blindness of empirical decision-making, and effectively reducing Crossing construction risks.

3. The invention actively changes the stress field state of the stratum surrounding the viaduct by pre-implementing measures such as isolation and reinforcement of bored piles and sleeve valve pipe grouting piles before the underpass construction, thereby improving the mechanical properties of the soil and blocking the original The continuous deformation and stress development trend of the stratum play a role in active isolation and risk control.

4. In the present invention, by adding reserved grouting holes to the tunnel segments, grouting reinforcement is carried out in the overlapping area of multiple sections, and the weak disturbing soil between the overlapping tunnels is cemented into a whole, which improves the rigidity, strength and self-control of the ground. Stability, so as to reduce the impact of additional stress and superimposed deformation on the structure of the first formed tunnel.

In summary, the present invention has successfully realized the construction safety of shield tunnels with multiple intervals, small clear distances, and overlapping underpasses in water-bearing soft formations, effectively controlling the structural damage and settlement deformation of the viaducts and subway tunnels, and can be widely used. It is suitable for shield crossing construction projects under the conditions of water-bearing and weak geology, shield tunneling with small clear spacing, multiple interval tunnels under the same bridge span, and under the conditions of strict control of the deformation of the viaduct.

Description of the drawings

The drawings of the specification forming a part of the application are used to provide a further understanding of the application, and the exemplary embodiments and descriptions of the application are used to explain the application, and do not constitute an improper limitation of the application.

Fig. 1 is a cross-section view of the reinforcement control of the shield tunnel of the present invention with multiple sections, small clear distances, and overlapping underpass viaducts;

Figure 2 is a plan view of the reinforcement control of the shield tunnel with multiple sections, small clear distances, and overlapping underpass viaducts;

Figure 3 is a schematic diagram of the section of the shield tunnel segment with additional reserved grouting holes;

Figure 4 is a schematic diagram showing the structure of additional reserved grouting holes for shield tunnel segments;

Figure 5 is a schematic diagram of grouting pre-reinforcement in shield tunnels with small clearance and overlapping areas;

Figure 6 is a schematic diagram of the layout of the supporting trolley in the shield tunnel;

Figure 7 is a flow chart of the construction process of bored piles.

Legend: 1-down section of shield tunnel; 2-up section of shield tunnel; 3-high-speed railway bridge; 4-pile foundation; 5-isolated pile; 6-pier cap; 7-sleeve valve tube; 8-segment Structure; 9-hoisting hole; 10-prepared grouting hole; 11-connecting bolt; 12-grouting pipe; 13-grouting area; 14-support trolley; 15-wheeled support arm.

Detailed ways

It should be pointed out that the following detailed descriptions are all illustrative and are intended to provide further explanations for the application. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

It should be noted that the terms used here are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and/or "including" are used in this specification, they indicate There are features, steps, operations, devices, components, and/or combinations thereof;

As described in the background technology section, the existing technology is mainly aimed at the isolation and reinforcement control of shield tunnels crossing the viaduct orthogonally. The isolation and reinforcement mostly use bored piles, mixing piles, jet grouting piles, and even underground continuous walls and other retaining structures , Blocking the continuous deformation of the shield tunnel and the elevated pile foundation, its deformation control effect is limited. It is difficult to meet the construction safety control requirements under multiple complex conditions such as water-bearing strata, multi-interval shield tunnels, and small-clear overlap crossing construction. , A comprehensive control system and construction method that does not form a combination of multiple control technologies; the present invention provides a construction method for shield tunnels with multiple sections, small clear distances, and overlapped underpass viaducts, in order to enable the objectives, technical solutions and The effect is clearer and clearer, and the present invention will be described in further detail below. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention.

The shield tunnel multi-interval, small clear distance, and overlapped underpass construction method proposed by the present invention mainly includes shield tunnel multi-interval, overlapped underpass construction sequence determination technology; shield tunnel close underpass construction active isolation control technology; shield Tunnel segment structure strengthening technology; tunnel reinforcement control technology in the overlap zone; vibration reduction and isolation control technology for subway tunnels under the viaduct; the combination of the above 5 technologies forms a shield tunnel with multiple sections, small clear distances, and overlap Actively control construction methods across viaducts.

The invention provides a construction method for shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts, which specifically includes the following steps:

Step 1: Before multiple shield tunnels, small clear distances, and overlapping underpass viaducts, first formulate the optimal construction sequence for multi-section underpass viaduct construction. Through the establishment of a high-precision three-dimensional numerical model, simulation and analysis of the viaduct structural deformation and surrounding ground deformation caused by the construction of multiple shield tunnels in different sequences, the optimal construction sequence is determined by the construction sequence that has the least impact on the viaduct pile foundation and surrounding environment deformation.

Step 2: Complete the isolation pile construction one month before the shield tunnel goes under the viaduct, and drill cast-in-place piles between the shield tunnel and the viaduct pile foundation as isolation piles to limit the horizontal deformation of the viaduct pile foundation caused by shield tunneling , Try to block the stress transmission and deformation expansion of shield construction.

Preferably, the size of the isolation pile is selected as Φ800@1000; and it is generally required that the protection range is 15m beyond the pier cap, and the bottom of the isolation pile reaches 4.0m below the bottom of the shield segment; but the specific size is not limited to this size, and can be based on specific The construction environment shall be adjusted accordingly.

Further, the above-mentioned bored piles are formed by a positive circulation drilling machine with a grinding disc. When drilling, they are drilled with light pressure, low rotation speed and slow drilling. After entering the normal state, the rotation speed and the drilling speed are gradually increased, and the drilling parameters are controlled throughout the process. Drilling speed; when changing layers of drilling, appropriately slow down the speed and reduce the drilling pressure to prevent the borehole from tilting; the time interval from the completion of the hole to the start of the concrete pouring is generally controlled within 16 hours, and the pouring time of each pile is generally controlled Within 4-6 hours; of course it is not difficult to understand that the time interval from the completion of the hole formation to the start of the concrete pouring is generally controlled and the pouring time of each pile can also be set to another time, depending on the actual construction needs.

The construction of bored piles adopts steel casing and mud water protection. The construction adopts jumping pile construction, jumping 2 holes and drilling 1 hole, and ensuring "drill one hole, inject one hole", symmetrical drilling, adjacent piles should not be poured in less than time 24 hours to avoid the impact of isolation pile collapse on the horizontal deformation of the viaduct pile foundation.

Due to the height restriction of the viaduct on the construction site, the drill rig is 6m high, and the steel cage is made in 8 sections, and the length of a single section is about 5m. The hoisting equipment of the millstone drill rig is used to hoist the steel cage to meet the construction space under the viaduct.

Step 3: Consider the influence of groundwater on the settlement of the viaduct pile foundation and reduce the difficulty of shield construction, and adopt sleeve valve tube grouting treatment for the isolation between the piles, the fine sand layer and the pebble layer to stop the water between the piles.

Preferably, a 40mm diameter rigid sleeve valve tube retreat type segmented grouting can be used, the outlet hole diameter is about 6mm, the quincunx pattern hole, the hole spacing is 20cm, and the outer tube is sealed with rubber. The pipe diameter grouting spacing is 1.2m, and the filling influence radius is 0.8m.

Further, the above-mentioned sleeve valve tube is drilled by a pilot hole drill, the diameter of the hole is about 90mm, and the hole depth needs to meet the design requirements. The sleeve valve pipe construction adopts the grouting construction method of interval skipping holes, gradual restraint, and first down and then up. Drilling sequence: drill the peripheral holes first, and gradually drill from the outside to the inside. Grouting sequence: from the outside to the inside, first grouting the holes on the reinforcement range line, blocking the slurry leakage channel, and then gradually densifying the grouting holes to grouting and compacting in the middle of the area; the grouting local reinforcement work space is affected The limit can be adjusted by adjusting the angle of the grouting pipe and the arrangement of dense grouting holes.

The grouting reinforcement of the sleeve valve tube in the pebble layer with high water-rich and strong permeability should be conducted on-site special experiments, and the solution should be solved by strengthening the grouting port plugging, injecting cement-water glass double-liquid slurry, adding AB chemical slurry, and adding polyurethane slurry. Traditional sleeve valve pipe grouting is easy to collapse, easy to lose grout, and insufficient grouting compactness in such formations. For example: the grouting material can be cement and water glass two-liquid grout, the volume ratio can be 1:1, the water glass concentration can be 35Be, and the grouting pressure can be controlled at 0.5 to 1.0 MPa; but the specific ratio and final grouting The pressure shall be determined by field test.

Step 4: Carry out the excavation construction of the downward section of the shield tunnel. The downward section of the shield tunnel underpasses the first 100m of the viaduct as the shield tunneling test section, and optimizes, adjusts, and determines the reasonable control range of the tunneling parameters according to the measured data. The downward sections of the shield tunnel go under the viaduct in the order of left and right, and the distance between the two sections is at least 100m. After the downward section of the shield tunnel is traversed, at least a month later, the shield tunnel traversal and excavation construction in the upward section of the shield tunnel shall be carried out. The upward section of the shield tunnel goes under the viaduct in the order from right to left, and the distance between the two sections is at least 100m.

Step 5: Cross the viaduct area under the overlap of multi-shield tunnels, and adopt strengthening measures for the segment structure of the shield tunnel to meet the requirements of strength, durability and waterproofing. The specific measures are as follows:

To strengthen the main reinforcement and distribution reinforcement of the tunnel segment, the reinforced segment with HRB400 steel bar diameter of 25mm is generally used.

To improve the longitudinal bolt grade of the segment, the connecting bolts generally adopt B grade M27 and performance 8.8 bolts to increase the longitudinal rigidity of the tunnel.

To improve the waterproof of the pipe segment structure, the impermeability grade is P12 concrete, the pipe segment joints are equipped with a porous EPDM elastic gasket, the pipe segment circumferential and longitudinal joints are equipped with nitrile cork rubber pads, and the pipe segments are full of flexible rings. Polyurethane sealant is used for caulking, water stains appearing in the invert range are made of polymer waterproof mortar, all bolt holes are sealed with water-swellable rubber rings, and the lifting holes are sealed with plastic protective covers.

Step 6: In the overlap area of multiple shield tunnels, add reserved grouting holes in the segment structure, and carry out secondary or multiple grouting reinforcements for the interlayer soil in the overlap area through lifting holes and grouting holes. In order to reduce the deteriorating effects of additional stress and superimposed deformation on the structure of the first formed tunnel after construction of the tunnel in the overlapping area.

Furthermore, the above-mentioned shield tunnel segments are generally divided into 6 blocks, which are 3 standard blocks, 2 adjacent blocks, and 1 capping block. The additional reserved grouting holes for the segments are in each standard block and adjacent block. Two additional reserved grouting holes are added so that after the segment is assembled and stabilized, the interlayer soil in the overlapping area is reinforced by grouting twice or more through the reserved grouting holes.

The grouting pipe can be a steel pipe with a diameter of 42mm, t=3.5mm, and the setting angles are along the radial direction of the tunnel, the longitudinal spacing is 2.4m, the length of the grouting pipe is L=3.0m, and the reinforcement range is 120° at the bottom of the ascending tunnel, and the reinforcement thickness 3m. The grouting liquid adopts cement slurry with a water-cement ratio of 1:1, and grouting is drilled at intervals. The grouting pressure is controlled at 0.5～1.0MPa, and it is optimized according to the grouting test on site. After reinforcement, the soil shall have good self-support, sealing and strength, and the unconfined compressive strength shall be greater than 0.8MPa.

Step 7: During the shield tunneling of the upward tunnel, a support trolley is erected in the downward tunnel to support and strengthen the overall longitudinal rigidity of the previously constructed tunnel to prevent longitudinal uneven settlement of the tunnel segments.

The length of the support section of the support trolley should be selected according to the length of the shield machine. The support trolley can travel on the steel rail. Each support consists of 5 wheeled support arms at 9 o'clock, 11 o'clock, 12 o'clock, 1 o'clock, and 3 o'clock. , Under the thrust of external force, the supporting trolley can move forward in the longitudinal direction without releasing the force.

In the design of the trolley, the minimum stiffness of the steel support should be estimated in advance according to the maximum internal force that the support may bear and the allowable value of uneven deformation of the tunnel. The support should have the function of prestress adjustment. The supporting trolley in the downward tunnel must keep in touch with the upward shield tunneling machine at any time, and keep the two moving synchronously.

Step 8: Use vibration reduction and isolation measures on the subway track within 50m of the tunnel on both sides of the pier cap of the multi-section tunnel under the viaduct section to reduce the vibration impact of rail transit operations on the viaduct. The subway track adopts an improved rubber (polyurethane) floating slab damping track (the first-order natural vibration frequency is 10-20Hz) to avoid resonance with the railway train running on the viaduct and reduce the vibration energy of the subway train itself.

Example

In order to further describe the technical solution of the present invention, a more detailed description will be given below in conjunction with specific embodiments and accompanying drawings 1 to 7.

The project described in this embodiment is the project of 4 shield tunnels, small clear distance, and overlapped under-crossing high-speed railway bridge 3. Among them, 4 shield tunnels correspond to the two shield tunnels 1 and 2 in the figure. The upper section 2 of the shield tunnels are all driven by an active articulated earth pressure balance shield machine. The outer diameter of the cutter head is 6.68m. The shield segment 8 adopts a single-layer reinforced concrete assembly structure with an outer diameter of 6.4m and an inner diameter of 5.8. m, the thickness is 0.3m, the ring width is 1.2m, the segment ring is divided into six pieces, consisting of a capping block K, two adjacent blocks B, and three standard blocks A, assembled in staggered seams. High-speed rail bridge 3 is a 64m-span pre-stressed continuous beam bridge. The current high-speed rail operating speed is 300km/h. The low-cap pile foundation is adopted under the bridge. The size of the pier cap 6 is 11m×26.6m, and 21 diameters are arranged under the cap 6. The 1.5m round piles constitute the pile group foundation, and the lengths of the pile foundations 4 on the left and right sides are 45m and 42m respectively. The minimum distance between the left and right sections of the shield down tunnel is 4.33m, and the buried depths are 28.35m and 19.22m respectively; the shield up tunnel is 5.25m above the shield down tunnel, the left and right sections have a clear distance of 5.6m, and the buried depth is 7.57m. .

The minimum clear distances between the 4 shield tunnels and the pile foundations 4 of the high-speed railway bridge on both sides are 10.45m and 10.84m, respectively, as shown in Figure 1. The geology of the four shield tunnels with small clear distances and overlapping high-speed railway bridges is mainly loess, silty clay, fine sand and pebble layers. The water content in the fine sand and pebble layers is relatively rich. In order to effectively control the construction safety of shield tunnels in multi-sections, small clear distances, and overlapping under-crossing high-speed railway bridges 3 in water-bearing soft formations, and to avoid uneven settlement of pile foundations 4 of high-speed railway bridges and damage and deterioration of subway tunnel structures, this implementation is proposed. The technical solutions are mainly as follows:

(1) Before the four shield tunnels with small clear distances and overlap and underpass the high-speed rail bridge 3, firstly formulate two shield-driven down tunnel sections 1 and two shield-machined tunnel up sections 2 under the high-speed rail bridge 3 construction optimal construction order. By establishing a high-precision three-dimensional numerical model, and simulating and analyzing the structural deformation of the high-speed railway bridge 3 and the surrounding ground deformation caused by the construction of 4 shield tunnels in different sequences, the construction sequence of the underpassing construction with the smallest deformation of the high-speed railway bridge pile foundation 4 and the surrounding ground is obtained: Shield tunnel down section left line → shield tunnel down section right line → shield tunnel up section right line → shield tunnel up section left line. According to scientific and information methods, the construction sequence of multi-shield section is determined to avoid the subjectivity and blindness of empirical decision-making, and the risk of crossing construction is effectively reduced.

(2) The isolation pile 5 construction was completed one month before the 4 shield tunnels under the high-speed railway bridge 3, actively changing the original stress field state of the formation and blocking the continuous deformation and stress development trend of the formation. Set up Φ800@1000 bored piles between the shield tunnel and the 4 pile foundations of the high-speed railway bridge. The protection range is 15m beyond the pier cap 6 and the bottom of the isolation pile 5 reaches 4.0m below the bottom of the shield segment 8 Limit the horizontal deformation of the pile foundation 4 of the high-speed railway bridge caused by shield tunneling, and try to block the stress transfer and deformation expansion of shield construction. The isolation pile 5 is arranged in a broken line shape, as shown in FIG. 2.

The construction process of bored piles is shown in Figure 7. The main points of the construction are as follows:

①The bored pile is formed by a positive circulation drilling machine with a grinding disc. When drilling, the drilling is carried out with light pressure, low speed and slow drilling. After entering the normal state, the speed and drilling speed are gradually increased, and the drilling parameters and drilling speed are controlled throughout the process; When changing layers and drilling, appropriately slow down the speed and reduce the weight on bit to prevent the borehole from tilting; the time interval from the completion of the hole formation to the start of the concrete pouring is controlled within 16 hours, and the pouring time of each pile is controlled within 4-6 hours Inside.

②In order to avoid the impact of the collapse of the isolation pile 5 on the horizontal deformation of the viaduct pile foundation 4, the construction of the bored pile adopts steel casing and mud water wall protection. The mud wall protection effect is good, and it is suitable for the construction of the pebble stratum; Immediately stop the surrounding drilling construction, find out the cause of the hole collapse, and strengthen the monitoring of the bridge structure. When refilling piles, the original pile should be drilled and poured.

③The construction of bored piles adopts jumping pile construction, jumping 2 holes and drilling 1 hole to ensure "drill one hole, pour one hole" and ensure symmetrical drilling. The pouring time of adjacent piles should not be less than 24 hours.

④Due to the height limit of the high-speed railway bridge 3 in the construction site, the drill rig is 6m high, and the steel cage is made in 8 sections, and the length of a single section is about 5m. The hoisting equipment of the grinding disc drill rig is used for the steel cage hoisting work to meet the construction space under the high-speed railway bridge. The location is 3.4m away from the bottom of the high-speed rail bridge.

(3) Considering the influence of groundwater on the settlement of the pile foundation 4 of the high-speed railway bridge and reducing the difficulty of shield construction, the sleeve valve tube 7 grouting treatment is adopted for the middle and fine sand layer and the pebble layer between the 5 isolation piles. A 40mm diameter rigid sleeve valve tube 7 is used for stepwise grouting. The outlet hole diameter is about 6mm, and the plum blossom-shaped hole is 20cm apart. The outer tube is sealed with rubber. The pipe diameter grouting spacing is 1.2m, and the filling influence radius is 0.8m.

The main points of grouting construction for sleeve valve pipe 7 are as follows:

①Sleeve valve tube 7 is drilled by a pilot hole drill with a hole diameter of 90mm, and the hole depth must meet the design requirements. The area where the working space of grouting is restricted can be adjusted by adjusting the angle of the grouting pipe and the arrangement of dense grouting holes.

②The sleeve valve pipe 7 construction adopts the grouting construction method of interval skipping holes, gradual restraint, and first down and then up. Drilling sequence: drill the peripheral holes first, and gradually drill from the outside to the inside. Grouting sequence: from the outside to the inside, first grouting the holes on the reinforcement range line, blocking the slurry leakage channel, and then gradually densifying the grouting holes to grouting and compacting in the middle of the area;

③The grouting material is cement and water glass two-liquid grout, the volume ratio is 1:1, the water glass concentration is 35Be, the grouting pressure is controlled at 0.5 to 1.0 MPa, and the ratio and final grouting pressure need to be determined by field tests.

④The grouting reinforcement of the sleeve valve tube 7 in the pebble layer with high water content and strong permeability should be carried out on-site special experiments, by strengthening the grouting port plugging, injecting cement-water glass double-liquid slurry, adding AB chemical slurry, adding polyurethane slurry, etc. Measures to solve the problems of traditional sleeve valve pipe grouting in such formations as easy collapse, easy loss of grout, and insufficient grouting compactness.

(4) Carry out the construction of 4 shield tunnels under the high-speed railway bridge 3 in turn, and each shield section goes under the high-speed railway bridge 3 before 100m as the shield tunneling test section. According to the measured data, optimize, adjust and determine the reasonable tunneling parameter control range ; Before the shield tunnel is 30m away from the high-speed rail bridge pile foundation 4, check the wear of the cutter. If there is wear, the hob should be replaced immediately to ensure the waterproof and assembly quality of the pipe segments. Use high-quality shield tail grease. The sections of the shield down tunnel go through the high-speed rail bridge 3 in the order of left and right, and the distance between the two sections is at least 100m. After the traversal of the shield tunnel section is completed, at least 3 months later, the shield tunnel boring construction of the shield tunnel section will be carried out. The sections of the shield-bored up tunnel go under the high-speed rail bridge 3 in the order from right to left, and the distance between the two sections is at least 100m.

(5) When the 4 shield tunnels overlap and pass through the high-speed railway bridge 3 area, the shield tunnel segment structure 8 shall be strengthened to meet the requirements of strength, durability and waterproofing. The main measures are as follows:

① To strengthen the main reinforcement and distribution reinforcement of the tunnel segment, the reinforced segment with HRB400 steel bar diameter of 25mm is adopted.

②Improve the 11 grade of the longitudinal connecting bolts of the tube segments. The connecting bolts 11 of the tube segments adopt B grade M27 and performance 8.8 bolts to increase the longitudinal stiffness of the tunnel.

③Improve the waterproof of the segment structure 8, adopt P12 concrete with impermeability grade, set a porous EPDM elastic gasket at the joints of the pipe segments, and set up nitrile cork rubber pads at the circumferential and longitudinal joints of the pipe segments, and the pipe segments are fully ringed. Use flexible polyurethane sealant for caulking, use polymer waterproof mortar for water stains in the invert range, all bolt holes are sealed with water-expandable rubber rings, and lifting holes 9 are sealed with plastic protective covers.

(6) In the overlap area of the 4 shield tunnels, a reserved grouting hole 10 is added to the segment structure 8, as shown in Figures 3 and 4. Before the construction of the right line of the shield tunnel section 1, use the left tunnel The segment 8 reserved grouting hole 10 and the original hoisting hole 9 are used for secondary or multiple grouting reinforcement in the interlayer soil in the overlapping area; after the construction of the right line, the grouting hole 10 and the original The lifting hole 9 and compensation grouting to the interlayer soil, as shown in Figure 5. The additional stress and superimposed deformation of the first formed tunnel structure 8 are degraded by reducing the overlap area and then constructing the tunnel.

The control points for adding reserved grouting holes 10 to segments are as follows:

①The shield tunnel segment 8 is divided into 3 standard blocks, 2 adjacent blocks, and 1 capping block. Two reserved grouting holes 10 are added to each standard block and adjacent block, so that the segments can be assembled and stabilized. , Through the reserved grouting hole 10, the interlayer soil in the overlapping area is reinforced by grouting twice or more times.

②The grouting pipe 12 adopts a steel pipe with a diameter of 42mm and t=3.5mm. The installation angles are along the radial direction of the tunnel. The longitudinal spacing is 2.4m. The length of the grouting pipe 12 is L=3.0m. The reinforcement range is 120° at the bottom of the ascending tunnel. The reinforcement thickness is 3m.

③Cement slurry is used for grouting liquid, water cement ratio is 1:1, and grouting is drilled at intervals. The grouting pressure is controlled at 0.5-1.0MPa, and the site is optimized according to the grouting test. After reinforcement, the soil shall have good self-support, sealing and strength, and the unconfined compressive strength shall be greater than 0.8MPa.

(7) Since the construction of the left and right lines of the shield tunnel section is only 100m apart, and the two sections overlap with a small clear distance, during the construction of the right line, the soil around the lower left line tunnel is not fully consolidated, which will affect the tunnel segment structure 8 Produce longitudinal uneven settlement. Therefore, during the excavation of the right line of the shield tunnel section, a support trolley 14 is erected in the left line to support and strengthen the overall longitudinal rigidity of the existing tunnel, and prevent longitudinal uneven settlement of the tunnel segments 8.

As shown in Figure 6, the length of the support section of the support trolley 14 needs to be selected according to the length of the shield machine. The support trolley 14 can travel on the rails. Each support consists of 9 o'clock, 11 o'clock, 12 o'clock, 1 o'clock and 3 o'clock. A total of 5 wheeled support arms 15 are composed, and the support trolley 14 can move forward in the longitudinal direction without releasing the force under the thrust of external force. When designing the support trolley 14, the minimum rigidity of the wheel support arm 15 should be estimated in advance according to the maximum internal force that the wheel support arm 15 may bear and the allowable value of uneven deformation of the tunnel. The wheel support arm 15 should have the function of pre-stress adjustment . The shield machine on the right line of the shield down tunnel section must keep in touch with the supporting trolley 14 at any time to keep the two moving in sync.

(8) In order to reduce the impact of subway operation on the vibration of the high-speed rail bridge 3 and ensure the safe operation of high-speed rail trains, 4 subway tunnels pass through the pier caps of section 3 of the high-speed rail bridge within 50m on both sides of the tunnel. The track adopts vibration reduction and isolation measures. The subway track adopts an improved rubber (polyurethane) floating plate damping track (the first-order natural vibration frequency is 10-20Hz) to avoid resonance with the railway train running on the high-speed railway bridge 3, and to reduce the vibration energy of the subway train itself.

The above are only preferred embodiments of the present invention. The present invention is not limited to the above embodiments. It should be noted that any person skilled in the art can make all equivalent substitutions, Obviously deformed forms fall within the essential scope of this specification and should be protected by the present invention.

Claims

A construction method for shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts is characterized in that it comprises the following steps:

Step 1: According to the principle of the least impact on the deformation of the viaduct pile foundation and the surrounding environment, formulate the optimal construction sequence for the construction of the shield tunnel with multiple sections and stacked under the viaduct;

Step 2: Before the tunnel underpasses the viaduct, conduct active isolation and reinforcement of the short-distance underpass construction of the shield;

Step 3: Carry out the construction of the shield tunnel under the viaduct;

Step 4: Reinforce the segment structure of the shield tunnel in the area where the multi-shield tunnel overlaps and pass through the viaduct, and strengthen the tunnel cavity;

Step 5: The track vibration reduction and isolation control is carried out in the section of the shield tunnel passing through the viaduct.
The construction method of shield tunnels with multiple intervals, small clear distances, and overlapping underpass viaducts according to claim 1, wherein the specific working method of step one is: establishing a three-dimensional numerical model consistent with the actual construction situation, and simulating Analyze the structural deformation of the viaduct and the surrounding ground deformation caused by the construction of multiple shield tunnels in different sequences, and determine the optimal construction sequence that has the least impact on the deformation of the viaduct pile foundation and the surrounding environment.
The construction method of shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts according to claim 1, characterized in that the specific working method of step two is:

Step 2.1 Construct bored piles as isolation piles;

The isolation pile construction is completed some time before the shield passes through the viaduct, and bored piles are built between the shield tunnel and the viaduct pile foundation. The protection range of the cast-in-place pile extends beyond the pier cap, and the bottom of the cast-in-place pile reaches the shield segment. Below the structure bottom;

Step 2.2 Carry out sleeve valve pipe grouting to stop water between piles;

Sleeve valve tube grouting is adopted for the middle, fine sand layer and pebble layer between the isolated piles.
The construction method of shield tunnels with multiple intervals, small clear distances, and overlapping underpass viaducts according to claim 3, characterized in that the bored piles are formed by grinding disc positive circulation drills, which are lighter when drilling. After entering the normal state, gradually increase the rotation speed and the drilling speed; control the drilling parameters and drilling speed throughout the whole process; when changing the drilling, appropriately slow down the speed and reduce the drilling pressure to prevent Cause the borehole to tilt.
The construction method of shield tunnels with multiple sections, small clear distances, and overlapped underpass viaducts according to claim 3, characterized in that the construction of the bored piles adopts steel casing and mud water protection. If the hole collapses, the surrounding drilling should be stopped immediately, the cause of the hole collapse should be found, and the monitoring of the bridge structure should be strengthened; when the pile is repaired, the original pile should be drilled and poured;

Further, the construction of bored piles adopts jumping pile construction, and it is ensured that “one hole is drilled and one hole is injected” and symmetrical drilling is ensured.
The construction method of shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts according to claim 3, characterized in that the steel cages of the cast-in-place piles are made in sections, and the steel cages are hoisted by the hoisting equipment of the millstone drill Work to meet the construction space under the viaduct.
The construction method of shield tunnels with multiple intervals, small clear distances, and overlapping underpass viaducts according to claim 3, characterized in that the sleeve valve tube construction adopts interval skipping, gradual restraint, and grouting construction. method;

Further, the drilling sequence: drill the peripheral holes first, and gradually drill holes from the outside to the inside; the grouting sequence: proceed from the outside to the inside, first grouting the holes on the reinforcement range line, blocking the slurry leakage channel, and then gradually densifying Grouting hole, grouting and compaction in the middle of the area.
The construction method of shield tunnels with multiple sections, small clear distances, and overlapped underpass viaducts according to claim 3, characterized in that the grouting reinforcement of the sleeve valve tube in the pebble layer with high water content and strong permeability shall be subject to on-site special experiments. A variety of different measures are adopted to solve the problems of traditional sleeve valve pipe grouting in such formations.
The construction method of shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts according to claim 1, wherein said step four mainly includes:

Reinforce the main reinforcement and distribution reinforcement of the tunnel segment;

Improve the grade of longitudinal bolts of the segment and increase the longitudinal rigidity of the tunnel;

Improve the waterproof of the tube structure.
The construction method of shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts according to claim 9, characterized in that:

The segment structure adopts concrete with an impermeability grade of P12;

A porous EPDM elastic sealing gasket is provided at the joint of the tube piece,

Nitrile cork rubber pads are provided for the circumferential and longitudinal joints of the segments, and the full loops of the segments are caulked with flexible polyurethane sealant; water stains appearing in the invert range are made of polymer waterproof mortar, and all bolt holes are made of water-swellable rubber rings. Sealed, the lifting hole is blocked with a plastic protective cover.
The construction method of shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts according to claim 1, characterized in that step four mainly includes:

Additional grouting holes are reserved in the segment structure, and the soil in the overlapping area is reinforced by grouting holes and lifting holes; and during the upward shield tunneling, a support trolley is erected in the downward tunnel to support and strengthen First shape the overall longitudinal stiffness of the tunnel.
The construction method of shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts as claimed in claim 11, characterized in that:

The length of the supporting section of the supporting trolley needs to be selected according to the length of the shield machine. The supporting trolley can travel on the rails. Each support consists of 5 wheels at 9 o'clock, 11 o'clock, 12 o'clock, 1 o'clock, and 3 o'clock. The trolley can move forward in the longitudinal direction without releasing the force under the thrust of external force.
The construction method of shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts according to claim 11, characterized in that each ring tunnel segment is divided into 6 blocks, which are 3 standard blocks and 2 adjacent blocks , 1 capping block, additional reserved grouting holes for the segment is to add 2 reserved grouting holes in each standard block and adjacent blocks.
The construction method of shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts according to claim 11, characterized in that step five mainly includes:

Within the tunnel area of 50m on each side of the pier cap of the subway tunnel under the viaduct section, vibration reduction and isolation measures are adopted for the subway track.
The construction method of shield tunnels with multiple sections, small clear distances, and overlapping underpass viaducts according to claim 14, characterized in that the subway track adopts rubber floating slabs with a natural vibration frequency of 10-20Hz to absorb vibration track.