Dynamic anti-seepage construction method for preliminary bracing layer of underground excavation subway station

Abstract

The invention relates to the technical field of underground engineering waterproofing, and discloses a dynamic anti-seepage construction method for a primary support layer of an underground excavation subway station, grouting is dynamically triggered by monitoring the total displacement (the threshold value is 0.2 m / m.d) of a water collecting well, and a process of partition and block isolation by water swelling strips and hole separation grouting from low to high is adopted. The construction method has the advantages that the drainage blind pipe and the repeatable grouting pipe are buried between the primary support layer and the waterproof layer after primary support construction of the underground excavation station is completed to serve as a channel for later drainage, grouting and water stopping, then secondary lining construction is conducted, operability is high, and construction efficiency is high. Active control over hydrostatic pressure between the primary support and the waterproof layer is achieved, and damage to the structure caused by follow-up water leakage grouting is avoided.

Description

Technical Field

[0001] This invention relates to the field of waterproofing technology for underground engineering, and in particular to a dynamic seepage prevention construction method for the initial support layer of a tunnel-excavated subway station. Background Technology

[0002] Controlling leakage in the initial support layer of underground railway stations using the cut-and-cover method has been a long-standing technical challenge in the industry. In traditional initial support arch construction, gaps often form between the initial support layer and the waterproof layer due to geological disturbance and concrete shrinkage, allowing groundwater to seep in and accumulate, creating hydrostatic pressure.

[0003] Existing seepage prevention technologies have the following drawbacks: Passive Drainage: Water accumulation between the initial support and the waterproofing layer relies solely on natural drainage through blind drains, lacking active pressure relief. Water trapped in gaps cannot be drained promptly, creating continuous hydrostatic pressure and causing the waterproofing layer to bulge and crack. Delayed Grouting: Existing grouting systems mostly provide reactive repair after leakage occurs, lacking real-time seepage monitoring and early warning mechanisms. Grouting timing relies on manual experience, often missing the optimal intervention window. System Fragmentation: Drainage and grouting systems operate independently, leading to a disconnect between drainage and grouting. Repeated remediation increases costs and can easily damage the existing structure.

[0004] Therefore, there is an urgent need to develop a collaborative seepage prevention construction method that dynamically monitors drainage volume, isolates areas and blocks, and performs precise grouting as needed, so as to solve the problem of hydrostatic pressure damage from the source. Summary of the Invention

[0005] One of the objectives of this invention is to solve the above-mentioned technical problems and provide a dynamic seepage prevention construction method for the initial support layer of a tunneled subway station.

[0006] A dynamic seepage prevention construction method for the initial support layer of a cut-and-cover subway station includes the following steps: Step S1: After the initial support construction of the station is completed and before the waterproof layer construction, drainage blind pipes are installed along the circumferential and longitudinal directions on the side walls of the station platform level and station hall level. Drainage pipes are pre-embedded in the structural side walls. The drainage pipes penetrate the waterproof layer of the side wall on the water-facing side and are connected to the drainage blind pipe system installed between the initial support layer and the waterproof layer. The back surface of the pre-embedded drainage pipes is flush with the inner surface of the side wall concrete. After the initial support construction of the station is completed and before the waterproof layer construction, repeatable grouting pipes are installed along the circumferential direction on the side walls of the station platform level and station hall level. Grouting pipes are pre-embedded in the structural side walls. The grouting pipes penetrate the waterproof layer of the side wall on the water-facing side and are connected to the tee of the repeatable grouting pipes at their ends. The back surface of the pre-embedded grouting pipes and the grouting pipes is flush with the inner surface of the side wall concrete. Step S2: Divide and block the structure and perform isolation grouting. Divide the structure into sections according to the principle of vertical zoning and longitudinal slab division. The bottom slab and side walls of each vertical layer are considered as one section, and several construction sections are considered as one block in the longitudinal direction. Step S3: The leakage water from the initial support layer is discharged to the station wall ditch or drainage ditch through the drainage blind pipe, and then collected in the station end water collection well. The total drainage volume flowing into the station water collection pit is monitored. Based on the monitoring data and the leakage situation on the side wall surface, it is determined whether to use the grouting system to grout to fill the gap between the initial support layer and the waterproof layer to strengthen the waterproofing. Step S4: Grouting. During grouting, monitoring is performed. The grouting sequence is from low to high in the vertical direction, and grouting is performed from one side to the other along the station direction.

[0007] Step S5: Grouting is terminated when thick slurry overflows from the vent hole.

[0008] After the initial support construction of the tunnel station is completed, drainage blind pipes and reusable grouting pipes are buried between the initial support layer and the waterproof layer to serve as channels for subsequent drainage and grouting to stop water. Then, secondary lining construction is carried out. This method is highly operable and enables active control of hydrostatic pressure between the initial support and the waterproof layer. Drainage and grouting simultaneously prevent seepage, avoiding damage to the structure caused by subsequent leakage grouting.

[0009] Furthermore, in step S1, the repeatable grouting pipes are arranged circumferentially between the initial support layer and the waterproof layer, with a circumferential spacing of 7-15m, and have the function of multiple grouting. The pipes are 20-40mm in diameter and made of PVC.

[0010] Furthermore, in step S1, the grouting pipes pre-embedded in the structural side wall are galvanized steel pipes with an inner diameter of not less than 30mm and a wall thickness of not less than 3mm. The water-facing side penetrates the waterproof layer of the side wall, and the end of the galvanized steel pipe is connected to a tee for repeated grouting. The back water surface is flush with the inner surface of the side wall concrete and has 7-12cm internal threads.

[0011] Furthermore, in step S1, the top of the grouting pipe embedded in the side wall of the concourse level is 80-120mm higher than the structural surface of the middle slab, and the bottom elevation of the grouting pipe embedded in the side wall of the platform level is higher than the track drainage ditch.

[0012] Furthermore, in step S1, drainage blind pipes are arranged in the circumferential and longitudinal directions between the initial support layer and the waterproof layer, with a circumferential spacing of 7-15m. One pipe is installed in the longitudinal direction on the side walls of the station platform level and the station hall level. The drainage blind pipes are DN30 double-wall corrugated pipes, which are perforated and wrapped with non-woven fabric.

[0013] Furthermore, in step S1, the circumferential repeatable grouting pipes and the circumferential drainage blind pipes are evenly spaced along the longitudinal direction. Furthermore, in step S1, pre-embedded drainage pipes are installed on the side walls of the station concourse and platform levels. The pre-embedded drainage pipes are galvanized steel pipes with an inner diameter of not less than 30mm and a wall thickness of not less than 3mm, with 7-12cm internal threads. The water-facing side penetrates the waterproof layer of the side wall and connects to the drainage blind pipe system installed between the initial support layer and the waterproof layer.

[0014] Furthermore, in step S1, the top of the pre-embedded drainage pipe in the side wall of the station hall is 80-120mm higher than the structural surface of the middle slab, and the drainage pipe is connected to the drainage blind pipe five-way connector; the bottom elevation of the pre-embedded drainage pipe in the side wall of the platform is higher than the track drainage ditch, and the drainage pipe is connected to the drainage blind pipe four-way connector. Furthermore, in step S1, a water-stop flange is installed in the middle of the pre-embedded grouting pipe and drainage pipe. The water-stop flange is made of steel plate with a thickness t≥8mm, coated with anti-rust paint, and the exposed width of the water-stop steel plate is 7-12cm. The pre-embedded grouting pipe and drainage pipe are set at a spacing of 7-15m along the longitudinal direction of the station, and the installation position does not conflict with the construction joint.

[0015] Furthermore, in step S2, the three construction sections are divided into a single block.

[0016] Furthermore, in step S2, water-swellable waterstops are used to isolate sections in blocks. They are installed in the circumferential construction joints at the ends of each section. The waterstops are placed between the initial support layer and the waterproof layer. Before installation, the base surface must be flat. During installation, the waterstops must be horizontal and vertical, without any hollow areas. The overlap of the waterstops should be 200-350mm. No isolation measures are set for the longitudinal construction joints.

[0017] Furthermore, in step S3, after the main structure and auxiliary structures have been completed and reached the design strength, the total drainage volume flowing into the station sump is monitored. If the drainage volume detection value (m³ / m·d) is ≥0.2 for three consecutive days, the pre-embedded grouting system is started regardless of whether there is leakage on the structural surface. If the drainage volume detection value (m³ / m·d) is <0.2, and there is local leakage or wet leakage, grouting is performed in the grouting pipe within ±10m of the leakage point. If there is no leakage and there is no continuous water flow in the pre-embedded grouting pipe, no grouting is performed.

[0018] Furthermore, in step S4, ordinary cement grout is used for grouting, with a water-cement ratio of (1:1) to (0.5:1), and the grouting pressure is controlled at 0.8-1.2 MPa. The grouting process is monitored. The grouting sequence is from low to high in the vertical direction, and grouting is carried out from one side to the other along the station direction. The pre-embedded grouting pipes are grouted every other one, and the middle hole is used as an air vent. Furthermore, step S6 is included: after grouting is completed, continue to inject an appropriate amount of clean water to keep the grouting pipe unobstructed and reserve conditions for subsequent grouting. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the cross-section of the pre-embedded grouting pipe and the pre-embedded drainage pipe.

[0020] Figure 2 This is a node diagram for pre-embedded grouting pipes and pre-embedded drainage pipes.

[0021] Figure 3A schematic longitudinal section of the system for pre-embedded grouting pipes and pre-embedded drainage pipes.

[0022] 1-Reusable grouting pipe, 2-Pre-embedded grouting pipe, 3-Drainage blind pipe, 4-Pre-embedded drainage pipe, 5-T-connection, 6-Four-way connection, 7-Five-way connection, 8-Longitudinal construction joint, 9-Waterproof layer, 10-Initial support, 11-Secondary lining, 12-Waterproof reinforcement layer, 13-Water-swellable sealing strip, 14-Waterproof flange, 15-Metal hoop, 16-Ditch separating from wall, 17-Arch, 18-Intermediate slab, 19-Bottom slab. Detailed Implementation

[0023] The present invention, in conjunction with the accompanying drawings, describes a dynamic seepage prevention construction method for the initial support layer of a mined subway station, comprising the following steps: Step S1: After the initial support construction of the station is completed and before the construction of the waterproof layer 9, repeatable grouting pipes 1 are installed circumferentially on the side walls of the station platform level and station hall level. Step S2: Pre-embed grouting pipe 2 in the structural side wall, penetrate the side wall waterproof layer 9 on the water-facing side, and connect the end to the repeatable grouting pipe 1 tee. The back water surface is flush with the inner surface of the side wall concrete. Step S3: After the initial support construction of the station is completed and before the waterproof layer 9 is constructed, drainage blind pipes 3 are installed along the circumferential and longitudinal directions on the side walls of the station platform level and station hall level. Step S4: A drainage pipe 4 is pre-embedded in the structural side wall. The water-facing side penetrates the side wall waterproof layer 9 and is connected to the drainage blind pipe 3 system set between the initial support and the waterproof layer 9. The back water surface is flush with the inner surface of the side wall concrete. Step S5: Divide and block the structure and perform isolation grouting. Divide the structure into sections according to the principle of vertical zoning and longitudinal slab division. The bottom slab and side walls of each vertical structure are considered as one section, and the three longitudinal construction sections are considered as one block.

[0024] In step S6, the leakage water from the initial support is discharged through the drainage blind pipe 3 to the station wall ditch 16 or drainage ditch, and then collected by the wall ditch 16 or drainage ditch to the station end sump. The total drainage volume flowing into the station sump is monitored. Based on the monitoring data and the leakage situation on the side wall surface, it is determined whether to use the grouting system to grout to fill the gap between the initial support and the waterproof layer 9 to strengthen the waterproofing.

[0025] Step S7: Ordinary cement grout is used for grouting, and the grouting process is closely monitored; the grouting sequence is from low to high in the vertical direction, and grouting is carried out from one side to the other along the direction of the station.

[0026] Step S8: Grouting ends when thick grout overflows from the vent hole. After grouting is complete, continue to inject an appropriate amount of clean water to keep the grouting pipe unobstructed, reserving conditions for subsequent grouting.

[0027] In step S1, the repeatable grouting pipe 1 is arranged circumferentially between the primary support and the waterproof layer 9, with a circumferential spacing of 10m. It has the function of multiple grouting, a diameter of about 30mm, and is made of PVC.

[0028] In step S2, the grouting pipe 2 embedded in the side wall is a galvanized steel pipe with an inner diameter of not less than 30 mm and a wall thickness of not less than 3 mm. The water-facing side penetrates the waterproof layer 9 of the side wall, and the end is connected to the tee of the repeatable grouting pipe 1. The back water surface is flush with the inner surface of the side wall concrete and has a 10 cm inner thread.

[0029] In step S2, the top of the grouting pipe 2 embedded in the side wall of the station hall is 100mm higher than the structural surface of the middle slab, and the bottom elevation of the grouting pipe 2 embedded in the side wall of the platform is slightly higher than the track drainage ditch.

[0030] In step S3, the drainage blind pipes 3 are arranged in the circumferential and longitudinal directions between the initial support and the waterproof layer 9, with a circumferential spacing of 10m. One is set in the longitudinal direction on the side wall of the station platform level and the station hall level. All drainage blind pipes 3 are DN30 double-wall corrugated pipes, which are wrapped with non-woven fabric after being perforated.

[0031] In step S3, the circumferential repeatable grouting pipe 1 and the circumferential drainage blind pipe 3 are evenly arranged at longitudinal intervals. In step S4, a pre-embedded drainage pipe 4 is installed on the side wall of the station concourse level and platform level. The drainage pipe is a galvanized steel pipe with an inner diameter of not less than 30mm and a wall thickness of not less than 3mm, with a 10cm internal thread. The water-facing side penetrates the waterproof layer 9 of the side wall and is connected to the drainage blind pipe 3 system installed between the initial support and the waterproof layer 9.

[0032] In step S4, the top of the pre-embedded drainage pipe 4 in the side wall of the station hall is 100mm higher than the structural surface of the middle plate, and the drainage pipe is connected to the drainage blind pipe 3 five-way connector; the bottom elevation of the pre-embedded drainage pipe 4 in the side wall of the platform is slightly higher than the track drainage ditch, and the drainage pipe is connected to the drainage blind pipe 3 four-way connector. In steps S2 and S4, a water-stop flange 14 is installed in the middle of the pre-embedded grouting pipe 2 and drainage pipe. The water-stop flange 14 is made of steel plate with a thickness t≥8mm, coated with anti-rust paint, and the exposed width of the water-stop steel plate is 10cm. The pre-embedded grouting pipe 2 and drainage pipe are set at a spacing of 10m along the longitudinal direction of the station, and the installation position does not conflict with the construction joint.

[0033] In step S5, water-swellable waterstops are used for zoned isolation, installed at the end of each section within the circumferential construction joint. The waterstops are positioned between the initial support surface and the waterproof layer 9. Before installation, ensure the base surface is flat. During installation, ensure horizontal and vertical alignment, no hollow areas, and a 300mm overlap at the joints. No isolation measures are provided for the longitudinal construction joint 8.

[0034] In step S6, after the main structure and auxiliary structures are completed and reach the design strength, monitor the total drainage volume flowing into the station sump. If necessary, use the grouting system to grout to fill the gap between the initial support and the waterproof layer 9 to reinforce the waterproofing. Table 1. Grouting Start Timing and Conditions for Pre-embedded Grouting Systems Discharge monitoring value (m³ / m·d) Structural Surface Condition Grouting area ≥0.2 for 3 consecutive days Whether or not there is leakage Full system startup <0.2 Localized leakage / wet stains Grouting pipe within ±10m of the leakage point <0.2 No leakage + no continuous water flow from the pre-buried pipe No grouting In step S7, ordinary cement grout is used for grouting, with a water-cement ratio of 1:1-0.5:1. The grouting pressure is controlled at 0.8-1.2MPa, and the grouting process is closely monitored. The grouting sequence is from low to high in the vertical direction, and grouting is carried out from one side to the other along the station direction. Grouting is carried out every other pre-embedded grouting pipe 2, and the middle hole is used as an air vent. Furthermore, in step S8, the grouting is terminated when thick grout overflows from the vent hole. After grouting is completed, continue to inject an appropriate amount of clean water to keep the grouting pipe unobstructed, reserving conditions for subsequent grouting.

[0035] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A dynamic anti-seepage construction method for an initial support layer of a subway station, comprising the following steps: Step S1: After the initial support construction of the station is completed, before the waterproof layer construction, drainage blind pipes are arranged along the ring direction and the longitudinal direction on the side walls of the station platform layer and the station hall layer; drainage pipes are pre-buried in the structure side walls, penetrate the waterproof layer of the side walls on the water side, and are connected with the drainage blind pipe system arranged between the initial support layer and the waterproof layer; the backwater surface of the pre-buried drainage pipes is flush with the inner surface of the side wall concrete; after the initial support construction of the station is completed, before the waterproof layer construction, repeatable grouting pipes are arranged along the ring direction on the side walls of the station platform layer and the station hall layer; grouting pipes are pre-buried in the structure side walls, penetrate the waterproof layer of the side walls on the water side, and are connected with the repeatable grouting pipes through a tee joint; the backwater surface of the pre-buried grouting pipes is flush with the inner surface of the side wall concrete; Step S2: partitioning, blocking and grouting, the station is partitioned and blocked according to the principle of vertical partitioning and longitudinal blocking; the bottom plate and the side wall of each vertical layer of the structure are taken as a partition, and a plurality of longitudinal construction sections are taken as a block; Step S3: the seepage water of the initial support layer is discharged to the station off-wall ditch or the drainage ditch through the drainage blind pipes, is collected to the station end head water collecting well through the station off-wall ditch or the drainage ditch, the total drainage amount of the station water collecting pit is monitored, and whether grouting is performed by using the grouting system according to the monitoring data and the side wall surface seepage condition to fill the gap between the initial support layer and the waterproof layer and to strengthen waterproof is judged; Step S4: grouting, grouting and monitoring are simultaneously performed; the grouting sequence is from low to high in the vertical direction, and the grouting is performed from one side to the other side along the station direction; Step S5: the overflow of the grouting through the exhaust hole is taken as the end condition of the grouting.

2. The dynamic anti-seepage construction method for the initial support layer of a subway station constructed by excavation according to claim 1, characterized in that, In step S1, the repeatable grouting pipes are arranged between the initial support layer and the waterproof layer along the ring direction, the ring direction spacing is 7-15 m, the diameter is 20-40 mm, and the material is PVC.

3. The dynamic anti-seepage construction method for the initial support layer of a subway station constructed by excavation according to claim 1, characterized in that, In step S2, the pre-buried grouting pipes in the structure side walls are made of galvanized steel pipes with an inner diameter of not less than 30 mm and a wall thickness of not less than 3 mm, penetrate the waterproof layer of the side walls on the water side, and are connected with the repeatable grouting pipes through a tee joint; the backwater surface of the galvanized steel pipes is flush with the inner surface of the side wall concrete and is internally threaded by 7-12 cm.

4. The dynamic anti-seepage construction method for the initial support layer of a subway station constructed by excavation according to claim 1, characterized in that, In step S1, the top of the pre-buried grouting pipes in the station hall layer side walls is 80-120 mm higher than the structure surface of the middle plate, and the bottom of the pre-buried grouting pipes in the station platform layer side walls is higher than the track drainage ditch.

5. The dynamic anti-seepage construction method for the initial support layer of a subway station constructed by excavation according to claim 1, characterized in that, In step S1, the drainage blind pipes are arranged between the initial support layer and the waterproof layer along the ring direction and the longitudinal direction, the ring direction spacing is 7-15 m, one drainage blind pipe is arranged on the side walls of the station platform layer and the station hall layer along the longitudinal direction, the drainage blind pipes are made of DN30 double-wall corrugated pipes, and the perforated pipes are wrapped with non-woven fabric; the repeatable grouting pipes along the ring direction and the drainage blind pipes along the ring direction are arranged uniformly along the longitudinal direction.

6. The dynamic anti-seepage construction method for the initial support layer of a subway station constructed by excavation according to claim 1, characterized in that, In step S1, the pre-buried drainage pipes are arranged on the side walls of the station hall layer and the station platform layer, are made of galvanized steel pipes with an inner diameter of not less than 30 mm and a wall thickness of not less than 3 mm and are internally threaded by 7-12 cm, penetrate the waterproof layer of the side walls on the water side, and are connected with the drainage blind pipe system arranged between the initial support layer and the waterproof layer.

7. The dynamic anti-seepage construction method for the initial support layer of a subsurface metro station according to claim 1, characterized in that, In step S1, the top of the pre-buried drainage pipe in the station hall side wall is higher than the structure surface of the middle plate by 80 mm or more, and the drainage pipe is connected with the blind drain pipe five-way; the bottom of the pre-buried drainage pipe in the station platform side wall is higher than the track drainage ditch, and the drainage pipe is connected with the blind drain pipe four-way.

8. The dynamic anti-seepage construction method for the primary support layer of a subsurface excavation subway station according to any one of claims 1-7, characterized in that, In step S3, after the main structure and the auxiliary structure are implemented and reach the designed strength, the total drainage amount of the station catch basin is monitored, and when the drainage amount detection value (m³ / m·d) is greater than or equal to 0.2 for three consecutive days, whether the structure surface is leaking or not, the pre-buried grouting system is started; when the drainage amount detection value (m³ / m·d) is less than 0.2, if there is local leakage or wet leakage, the grouting pipe is grouted within ±10 m of the leakage point, and if there is no leakage and the pre-buried grouting pipe has no continuous water flow, no grouting is performed.

9. The dynamic anti-seepage construction method for the primary support layer of a subsurface excavation subway station according to any one of claims 1-7, characterized in that, In step S4, the slurry water-cement ratio of grouting is (1:1)-(0.5:1), the grouting pressure is controlled at 0.8-1.2 MPa, and the grouting process is monitored; the grouting sequence is from low to high in the vertical direction and from one side to the other side along the station direction, and the pre-buried grouting pipe is grouted every other one.

10. The dynamic anti-seepage construction method for the initial support layer of a subway station constructed by excavation according to claim 8, characterized in that, Further comprising step S6: after grouting is completed, a proper amount of water is continuously injected to keep the grouting pipe unblocked and reserve conditions for subsequent grouting.

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