Construction method for short-distance underneath passing of operating subway tunnel through shield in water-rich soft stratum

Abstract

The invention relates to the technical field of subway tunnel construction, and discloses a water-rich soft stratum shield short-distance underpass operation subway tunnel construction method which comprises the following steps: S1, stratum advanced pre-reinforcement; s2, optimizing tunneling parameters; s3, posture deviation correction control is carried out; s4, synchronous grouting reinforcement is conducted; s5, a secondary slurry supplementing process; s6, monitoring the existing tunnel; and S7, stratum response monitoring. According to the water-rich soft stratum shield short-distance underneath passing operation subway tunnel construction method, superfine cement-water glass double-liquid slurry and macromolecule nanometer polymers are adopted for alternate grouting, a gradient permeation reinforcing layer is formed, and the problem that traditional water-rich soft stratum single-liquid slurry is prone to dilution is solved; formation resistance, cutterhead torque and soil bin pressure are analyzed in real time based on a BP neural network algorithm, thrust, propelling speed and cutterhead rotating speed are dynamically adjusted, the stability of an excavation face is ensured, the shield axis is controlled to be cheap through pressure feedback of a laser guiding system and a hydraulic oil cylinder, and disturbance to an existing tunnel is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of subway tunnel construction, and in particular to a construction method for a shield tunnel passing closely under an operating subway tunnel in a water-rich soft stratum. Background Art

[0002] In recent years, urbanization has accelerated, and the scale of urban rail transit construction has continued to expand. As the backbone of urban transportation, subways, with their large capacity, high efficiency, and strong punctuality, have effectively alleviated urban traffic congestion. However, with the increasing development and utilization of urban underground space, the overlap of new subway lines with existing ones has become increasingly frequent. In particular, shield tunneling operations are increasingly underpassing existing subway tunnels in water-rich, soft strata. Water-rich, soft strata, such as silty soils and saturated fine sand, have complex engineering properties. These strata have high water content, low effective stress between soil particles, and are characterized by high compressibility, low strength, and low rheological properties. During shield tunneling, the tunneling of the shield machine can easily disrupt the existing stress equilibrium in the stratum, causing significant deformation. Due to the poor self-stabilization capacity of water-rich, soft strata, improper shield machine control during passage can easily cause accidents such as ground collapse and water and sand inrush. At the same time, when passing under an operating subway tunnel at close range, the ground deformation caused by shield construction will have an adverse effect on the existing tunnel structure, which may cause settlement, horizontal displacement, cracks, water leakage and other defects in the tunnel structure, seriously threatening the driving safety and structural stability of the operating subway.

[0003] At present, there are three major technical difficulties in carrying out such construction in water-rich soft strata: 1. Grouting materials in high permeability formations are easily diluted by groundwater, resulting in poor reinforcement effect; 2. Shield tunneling disturbance causes settlement of existing structures; 3. Traditional construction relies on manual experience, and parameter adjustment lags behind. Summary of the Invention

[0004] The present invention provides the following technical solution: a construction method for a shield tunnel in water-rich soft strata passing under an operating subway tunnel at close range, comprising the following steps: S1. Advance pre-reinforcement of strata Ultrafine cement-water glass double slurry and high molecular nano-polymer are alternately grouted with a grouting pressure of 0.3-0.5 MPa to form a gradient reinforcement layer with a penetration radius of 1.5-2.0 m; S2. Optimization of tunneling parameters A BP neural network algorithm with 6 nodes in the input layer, 12 nodes in the hidden layer, and 3 nodes in the output layer analyzes the formation resistance, cutterhead torque, and soil bin pressure in real time, dynamically adjusting the thrust control range to 30,000-40,000 kN, the propulsion speed to 10-20 mm / min, and the cutterhead speed to 0.8-1.2 rpm. S3, attitude correction control Using the Leica TS60 total station, a laser guidance system with an accuracy of ±1 and a hydraulic cylinder pressure sensor with a range of 0-50MPa and an accuracy of 0.1%FS, the shield axis offset is controlled to ≤3‰D; S4, synchronous grouting reinforcement Use a fast-setting sulphoaluminate cement-based slurry with a water-cement ratio of 0.45:1 and an initial setting time of ≤4h, add 8%-12% bentonite-silica fume composite additive, and the grouting volume should be ≥200% of the theoretical void volume; S5. Secondary grouting process After the segment is out of the shield tail 5 rings, inject ultrafine cement with a specific surface area of ​​≥800m² / kg and epoxy resin composite slurry with a 28-day strength of ≥3MPa through the reserved grouting holes with a diameter of 10mm and an annular spacing of 1.2m; S6. Existing tunnel monitoring Fiber Bragg grating sensors with a wavelength resolution of 1pm and inclinometers with an accuracy of 0.001° are deployed in the operating tunnel, with early warning values ​​of 2mm and alarm values ​​of 3mm set to monitor settlement and track geometric deformation; S7. Formation response monitoring A distributed optical fiber temperature measurement system with a temperature measurement accuracy of ±0.5°C and a pore water pressure sensor with a measuring range of 0-1 MPa are used to trigger grouting pressure compensation in real time, with a compensation rate of 0.05 MPa / min.

[0005] Preferably, in step S1, the water-cement ratio of the ultrafine cement-water glass double liquid slurry is 0.8:1-1:1, the water glass modulus is 2.4-3, and the double liquid slurry grouting includes three stages: the first stage grouting pressure is 0.3 MPa, the injection volume is 0.5 m³ / m, the second stage pressure is 0.4 MPa, the injection volume is 0.3 m³ / m; the third stage pressure is 0.5 MPa, the injection volume is 0.2 m³ / m, the high molecular nano polymer is polyurethane, and the solid content is ≥30%, and the gel time of the high molecular nano polymer grouting is controlled at 30-60 s, and the permeability coefficient is reduced to 1×10 -9 cm / s or less.

[0006] Preferably, in step S2, the BP neural network training sample includes 200 sets of historical excavation data, the learning rate is 0.01, the number of iterations is ≥1000 times, and when the soil bin pressure fluctuation exceeds ±0.02MPa, the system automatically triggers thrust adjustment with a step size of ±500kN.

[0007] Preferably, in step S3, D is the tunnel diameter.

[0008] Preferably, in step S4, the mass ratio of the slurry is cement: fly ash: bentonite: silica fume = 1:0.5:0.1:0.05, and grouting adopts 4 synchronous grouting pumps with a flow rate of 30L / min, and the grouting holes are opened in the order of spandrel first and then back arch.

[0009] Preferably, in step S5, the mass ratio of the composite slurry is ultrafine cement: epoxy resin: curing agent = 100:15:2, and the grouting is carried out three times, with the first grouting pressure being 0.3 MPa, the second grouting pressure being 0.4 MPa, and the third grouting pressure being 0.5 MPa, with an interval of 2 hours between each grouting.

[0010] Preferably, in step S6, the fiber Bragg grating sensors are arranged at a spacing of 3 m, the monitoring frequency is 1 time / min, and the data is transmitted wirelessly via LoRa. When the settlement rate is greater than 0.5 mm / d for three consecutive times, the emergency grouting program is automatically started.

[0011] Preferably, in step S7, temperature measuring units are arranged every 5 m along the axis of the tunnel using distributed optical fibers, and pore water pressure sensors are arranged in a 3 m × 3 m grid. When the ground temperature rises by 2°C or the pore water pressure changes by more than 0.05 MPa, an early warning is triggered and excavation parameters are adjusted.

[0012] Preferably, in steps S1-S7, the cutterhead opening rate of the shield machine is 35%-40%, and it is equipped with a central flushing system with a flow rate of 50m³ / h. The shield tail seal adopts 3 wire brushes plus 1 emergency airbag, and the pressure resistance is ≥0.6MPa.

[0013] Preferably, in steps S1-S7, deep hole grouting reinforcement is carried out simultaneously during construction, grouting is carried out within a 135° range of the tunnel top, the reinforcement radius is 3m, the unconfined compressive strength is ≥1MPa, and an automated monitoring system is carried out, including a three-dimensional monitoring network consisting of a static level with an accuracy of 0.01mm and an inclinometer tube with an accuracy of 0.02mm / m.

[0014] Compared with the existing technology, the present invention provides a construction method for shield tunneling in water-rich soft strata at close range through an operating subway tunnel, which has the following beneficial effects: This construction method of shield tunneling under an operating subway tunnel at close range in water-rich soft strata adopts alternating grouting of ultrafine cement-water glass double slurry and high molecular nano-polymer to form a gradient permeability reinforcement layer, solving the problem of easy dilution of traditional single-liquid slurry in water-rich soft strata.

[0015] This construction method of a shield tunnel passing under an operating subway tunnel at close range in water-rich soft strata uses a BP neural network algorithm to analyze stratum resistance, cutterhead torque, and soil bin pressure in real time, and dynamically adjust the thrust, propulsion speed, and cutterhead speed to ensure a stable excavation surface.

[0016] This construction method for a shield machine to pass closely beneath an operating subway tunnel in water-rich soft strata controls the displacement of the shield machine axis through a laser guidance system and hydraulic cylinder pressure feedback, thereby reducing disturbance to the existing tunnel.

[0017] This construction method for a shield tunnel passing under an operating subway tunnel at close range in water-rich soft strata adopts a fast-setting sulphoaluminate cement-based slurry mixed with a bentonite-silica fume composite additive to improve the slurry's resistance to groundwater scouring.

[0018] This construction method of a shield tunnel passing under an operating subway tunnel at close range in water-rich soft strata is to inject ultra-fine cement-epoxy resin composite slurry through the reserved grouting holes after the segments are released from the shield tail to fill the synchronous grouting gaps.

[0019] This construction method uses a shield tunnel to pass closely under an operating subway tunnel in water-rich soft strata. Fiber Bragg grating sensors and inclinometers are deployed in the operating tunnel to monitor settlement, horizontal position, and track geometric deformation in real time.

[0020] This construction method for a shield tunnel passing closely beneath an operating subway tunnel in water-rich soft strata uses a distributed fiber optic temperature measurement system and pore water pressure sensors to dynamically feedback stratum seepage and liquefaction risks, triggering an automatic grouting pressure compensation mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the process structure of the present invention. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] See also Figure 1 The present invention provides a technical solution: a construction method for a shield tunnel in water-rich soft strata with close distance passing through an operating subway tunnel, comprising the following steps: S1. Advance pre-reinforcement of strata Ultrafine cement-water glass double slurry and high molecular nano-polymer are alternately grouted with a grouting pressure of 0.3-0.5 MPa to form a gradient reinforcement layer with a penetration radius of 1.5-2.0 m; The water-cement ratio of ultrafine cement-water glass double liquid slurry is 0.8:1-1:1, the water glass modulus is 2.4-3, and the double liquid slurry grouting includes three stages: the first stage grouting pressure is 0.3MPa, the injection volume is 0.5m³ / m, the second stage pressure is 0.4MPa, the injection volume is 0.3m³ / m; the third stage pressure is 0.5MPa, the injection volume is 0.2m³ / m, the polymer nanopolymer is polyurethane, and the solid content is ≥30%. The gel time of the polymer nanopolymer grouting is controlled at 30-60s, and the permeability coefficient is reduced to 1×10 -9 cm / s or less.

[0024] S2. Optimization of tunneling parameters A BP neural network algorithm with 6 nodes in the input layer, 12 nodes in the hidden layer, and 3 nodes in the output layer analyzes the formation resistance, cutterhead torque, and soil bin pressure in real time, dynamically adjusting the thrust control range to 30,000-40,000 kN, the propulsion speed to 10-20 mm / min, and the cutterhead speed to 0.8-1.2 rpm. The BP neural network training sample contains 200 sets of historical excavation data, with a learning rate of 0.01 and an iteration number of ≥1000 times. When the soil bin pressure fluctuation exceeds ±0.02MPa, the system automatically triggers thrust adjustment with a step size of ±500kN.

[0025] S3, attitude correction control A Leica TS60 total station, a laser guidance system with an accuracy of ±1, and a hydraulic cylinder pressure sensor with a range of 0-50MPa and an accuracy of 0.1%FS are used to control the shield axis offset to ≤3‰D, where D is the tunnel diameter. S4, synchronous grouting reinforcement Use a fast-setting sulphoaluminate cement-based slurry with a water-cement ratio of 0.45:1 and an initial setting time of ≤4h, add 8%-12% bentonite-silica fume composite additive, and the grouting volume should be ≥200% of the theoretical void volume; The mass ratio of the slurry is cement: fly ash: bentonite: silica fume = 1:0.5:0.1:0.05. Four synchronous grouting pumps with a flow rate of 30L / min are used for grouting. The grouting holes are opened in the order of arch spandrel first and then back arch.

[0026] S5. Secondary grouting process After the segment is out of the shield tail 5 rings, inject ultrafine cement with a specific surface area of ​​≥800m² / kg and epoxy resin composite slurry with a 28-day strength of ≥3MPa through the reserved grouting holes with a diameter of 10mm and an annular spacing of 1.2m; The mass ratio of the composite slurry is ultrafine cement: epoxy resin: curing agent = 100:15:2. The grouting is carried out in three times, with the first grouting pressure of 0.3MPa, the second grouting pressure of 0.4MPa, and the third grouting pressure of 0.5MPa, with an interval of 2h each time.

[0027] S6. Existing tunnel monitoring Fiber Bragg grating sensors with a wavelength resolution of 1pm and inclinometers with an accuracy of 0.001° are deployed in the operating tunnel, with early warning values ​​of 2mm and alarm values ​​of 3mm set to monitor settlement and track geometric deformation; The fiber grating sensors are arranged at a spacing of 3m, with a monitoring frequency of 1 time / min. The data is transmitted wirelessly via LoRa. When the settlement rate is greater than 0.5mm / d for three consecutive times, the emergency grouting program is automatically started.

[0028] S7. Formation response monitoring A distributed optical fiber temperature measurement system with a temperature measurement accuracy of ±0.5°C and a pore water pressure sensor with a measuring range of 0-1 MPa are used to trigger grouting pressure compensation in real time, with a compensation rate of 0.05 MPa / min.

[0029] Distributed optical fiber temperature measurement units are arranged every 5 meters along the tunnel axis, and pore water pressure sensors are arranged in a 3m×3m grid. When the local temperature rises by 2°C or the pore water pressure changes by more than 0.05MPa, an early warning is triggered and the excavation parameters are adjusted.

[0030] The cutterhead opening rate of the shield machine is 35%-40%, and it is equipped with a central flushing system with a flow rate of 50m³ / h. The shield tail seal uses 3 wire brushes plus 1 emergency airbag, and the pressure resistance is ≥0.6MPa.

[0031] During the construction period, deep hole grouting reinforcement was implemented simultaneously. Grouting was carried out within a 135° range at the top of the tunnel, with a reinforcement radius of 3m and an unconfined compressive strength of ≥1MPa. An automated monitoring system was also implemented, including a three-dimensional monitoring network consisting of a static level with an accuracy of 0.01mm and an inclinometer with an accuracy of 0.02mm / m.

[0032] This method for constructing a shield tunnel under an operating subway tunnel at close range in water-rich, soft strata employs alternating grouting of ultrafine cement-water glass dual-liquid slurry and high-molecular-weight nanopolymers to form a gradient permeability reinforcement layer, addressing the dilution problem of conventional single-liquid slurry in water-rich, soft strata. A BP neural network algorithm analyzes stratum resistance, cutterhead torque, and soil bin pressure in real time, dynamically adjusting thrust, propulsion speed, and cutterhead rotational speed to ensure excavation face stability. A laser guidance system and hydraulic cylinder pressure feedback are used to control the shield axis offset, minimizing disturbance to the existing tunnel. A fast-setting sulphoaluminate cement-based slurry with a bentonite-silica fume composite additive is incorporated to enhance the slurry's resistance to groundwater erosion. After the segments emerge from the shield tail, ultrafine cement-epoxy resin composite slurry is injected through pre-reserved grouting holes to fill the gaps between the simultaneous grouting injections. Fiber Bragg grating sensors and inclinometers are deployed within the operating tunnel to monitor settlement, horizontal position, and track geometric deformation in real time. A distributed fiber optic temperature measurement system and pore water pressure sensors provide dynamic feedback on stratum seepage and liquefaction risks, triggering an automatic grouting pressure compensation mechanism.

[0033] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A construction method for a shield tunnel in water-rich soft strata passing under an operating subway tunnel at close range, characterized in that: The following steps are involved: S1. Advance pre-reinforcement of strata Ultrafine cement-water glass double slurry and high molecular nano-polymer are alternately grouted with a grouting pressure of 0.3-0.5 MPa to form a gradient reinforcement layer with a penetration radius of 1.5-2.0 m; S2. Optimization of tunneling parameters A BP neural network algorithm with 6 nodes in the input layer, 12 nodes in the hidden layer, and 3 nodes in the output layer analyzes the formation resistance, cutterhead torque, and soil bin pressure in real time, dynamically adjusting the thrust control range to 30,000-40,000 kN, the propulsion speed to 10-20 mm / min, and the cutterhead speed to 0.8-1.2 rpm. S3, attitude correction control Using the Leica TS60 total station, a laser guidance system with an accuracy of ±1 and a hydraulic cylinder pressure sensor with a range of 0-50MPa and an accuracy of 0.1%FS, the shield axis offset is controlled to ≤3‰D; S4, synchronous grouting reinforcement Use a fast-setting sulphoaluminate cement-based slurry with a water-cement ratio of 0.45:1 and an initial setting time of ≤4h, add 8%-12% bentonite-silica fume composite additive, and the grouting volume should be ≥200% of the theoretical void volume; S5. Secondary grouting process After the segment is out of the shield tail 5 rings, inject ultrafine cement with a specific surface area of ​​≥800m² / kg and epoxy resin composite slurry with a 28-day strength of ≥3MPa through the reserved grouting holes with a diameter of 10mm and an annular spacing of 1.2m; S6. Existing tunnel monitoring Fiber Bragg grating sensors with a wavelength resolution of 1pm and inclinometers with an accuracy of 0.001° are deployed in the operating tunnel, with early warning values ​​of 2mm and alarm values ​​of 3mm set to monitor settlement and track geometric deformation; S7. Formation response monitoring A distributed optical fiber temperature measurement system with a temperature measurement accuracy of ±0.5°C and a pore water pressure sensor with a measuring range of 0-1 MPa are used to trigger grouting pressure compensation in real time, with a compensation rate of 0.05 MPa / min.

2. The method for constructing a shield tunnel in water-rich soft strata at close range through an operating subway tunnel according to claim 1, characterized in that: In step S1, the water-cement ratio of the ultrafine cement-water glass double liquid slurry is 0.8:1-1:1, the water glass modulus is 2.4-3, and the double liquid slurry grouting includes three stages: the first stage grouting pressure is 0.3 MPa, the injection volume is 0.5 m³ / m, the second stage pressure is 0.4 MPa, the injection volume is 0.3 m³ / m; the third stage pressure is 0.5 MPa, the injection volume is 0.2 m³ / m, the high molecular nano polymer is polyurethane, and the solid content is ≥30%, and the gel time of the high molecular nano polymer grouting is controlled at 30-60 s, and the permeability coefficient is reduced to 1×10 -9 cm / s or less.

3. The method for constructing a shield tunnel in water-rich soft strata at close range through an operating subway tunnel according to claim 1, characterized in that: In step S2, the BP neural network training sample includes 200 sets of historical excavation data, the learning rate is 0.01, the number of iterations is ≥1000 times, and when the soil bin pressure fluctuation exceeds ±0.02MPa, the system automatically triggers thrust adjustment with a step size of ±500kN.

4. The method for constructing a shield tunnel in water-rich soft strata at close range through an operating subway tunnel according to claim 1, characterized in that: In step S3, D is the tunnel diameter.

5. The method for constructing a shield tunnel in water-rich soft strata at close range through an operating subway tunnel according to claim 1, characterized in that: In step S4, the mass ratio of the slurry is cement: fly ash: bentonite: silica fume = 1:0.5:0.1:0.05, and grouting is performed using four synchronous grouting pumps with a flow rate of 30 L / min, and the grouting holes are opened in the order of spandrel first and back arch later.

6. The method for constructing a shield tunnel in water-rich soft strata at close range through an operating subway tunnel according to claim 1, characterized in that: In step S5, the mass ratio of the composite slurry is ultrafine cement: epoxy resin: curing agent = 100:15:2, and the grouting is carried out three times, with the first grouting pressure of 0.3 MPa, the second grouting pressure of 0.4 MPa, and the third grouting pressure of 0.5 MPa, with an interval of 2 hours between each grouting.

7. The method for constructing a shield tunnel in water-rich soft strata at close range through an operating subway tunnel according to claim 1, characterized in that: In step S6, the fiber Bragg grating sensors are arranged at a spacing of 3 m, the monitoring frequency is 1 time / min, and the data is transmitted wirelessly via LoRa. When the settlement rate is greater than 0.5 mm / d for three consecutive times, the emergency grouting program is automatically started.

8. The method for constructing a shield tunnel in water-rich soft strata at close range through an operating subway tunnel according to claim 1, characterized in that: In step S7, temperature measurement units are arranged every 5 meters along the tunnel axis using distributed optical fibers, and pore water pressure sensors are arranged in a 3m×3m grid. When the ground temperature rises by 2°C or the pore water pressure changes by more than 0.05MPa, an early warning is triggered and tunneling parameters are adjusted.

9. The method for constructing a shield tunnel in water-rich soft strata at close range through an operating subway tunnel according to claim 1, characterized in that: In steps S1-S7, the cutterhead opening rate of the shield machine is 35%-40%, and it is equipped with a central flushing system with a flow rate of 50m³ / h. The shield tail seal adopts 3 wire brushes plus 1 emergency airbag, and the pressure resistance is ≥0.6MPa.

10. The method for constructing a shield tunnel in water-rich soft strata at close range through an operating subway tunnel according to claim 1, characterized in that: In steps S1-S7, deep hole grouting reinforcement is carried out simultaneously during construction. Grouting is carried out within a 135° range of the tunnel top, with a reinforcement radius of 3m and an unconfined compressive strength of ≥1MPa. An automated monitoring system is also implemented, including a three-dimensional monitoring network consisting of a static level with an accuracy of 0.01mm and an inclinometer with an accuracy of 0.02mm / m.

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