A deformation control method for a double-line shield tunnel underpassing a soft soil roadbed of an existing railway

Abstract

The present application relates to underground engineering and rail transit engineering field, specifically relates to a kind of deformation control method of double-line shield tunnel underpass existing railway soft soil subgrade, comprising the following steps S1.Determine grouting reinforcement range;S2.Pile position and grouting hole position lofting is carried out in reinforced area, groove is excavated;S3.MJS pile main machine is in position after being made, and before putting drill rod, it is tried to spray;S4.Drill rod reaches specified depth after being sprayed grouting, until design elevation, MJS pile main machine is removed to next pile position lofting point;S5.After MJS pile reaches design strength, drill rig is in position, and drill into hole to design depth;S6.Perfusion is carried out, and after completion, grouting stop grouting section construction is carried out.The present application has the advantages that: the present application is combined with model to make corresponding reinforcement measures, improve the shear strength of soft soil, reduce the risk of shear failure of soft soil, realize the timely control to soft soil subgrade deformation, ensure the safety and stability in the process of shield underpass construction.

Description

Technical Field

[0001] This invention relates to the fields of underground engineering and rail transit engineering, specifically to a deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade. Background Technology

[0002] Soft soil is a unique type of soil formed in underwater sedimentary environments and is widely distributed in coastal areas of my country. Twin-track shield tunneling refers to the simultaneous excavation of two parallel tunnels using a tunnel boring machine (TBM). This construction method is particularly common in urban subway, railway, and highway tunnel construction. With the rapid development of coastal cities, existing urban infrastructure can no longer meet the ever-increasing demands of economic construction. Therefore, numerous infrastructure projects, such as rail transit, highways, docks, and airports, have been incorporated into urban planning. However, the high compressibility, high sensitivity, and low strength of soft soil present numerous challenges to engineering construction.

[0003] When conducting shield tunneling in soft soil layers, the physical and mechanical properties of the soft soil are crucial for deformation control. Because soft soil typically has low strength and high compressibility, it can lead to problems such as compression and settlement. Summary of the Invention

[0004] The purpose of this invention is to ensure that when a double-track shield tunnel passes under an existing soft soil railway subgrade, it can effectively control the uneven settlement of the existing structure, reduce the impact on the existing structure, and ensure the safe operation of the existing railway line.

[0005] To achieve the above objectives, a deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade is designed, including the following steps:

[0006] S1. The grouting reinforcement range for the soft soil subgrade beneath the railway in a double-track shield tunnel is determined using surface settlement prediction formulas, including:

[0007] S11. Determine parameters K and VL based on the soft soil strata traversed by the tunnel and the type of tunnel boring machine, where K is the surface settlement trough coefficient and VL is the stratum loss rate.

[0008] S12. Using the Peck settlement prediction model to predict soft soil surface settlement when a single-track shield tunnel passes under it, where:

[0009]

[0010] The This represents the surface subsidence at the distance from the tunnel centerline. Where i is the maximum surface settlement, D is the width of the settlement trough, and Z0 is the diameter of the shield tunnel.

[0011] S13. The width i of the settlement trough in soft soil strata is predicted by the formula i = 0.5h, where h is the burial depth of the shield tunnel;

[0012] S14. Based on the existing prediction of surface settlement caused by single-line shield tunnel crossing and the prediction of surface settlement under double-tunnel excavation, the width of the settlement trough of the surface settlement curve caused by double-line shield tunnel crossing is determined to be α(L+2i), where α is a correction coefficient considering the superposition effect caused by double-line shield tunnel excavation.

[0013] S2. Based on the theory, determine the reinforcement range, mark out the pile positions and grouting hole positions in the reinforcement area, and excavate the trench;

[0014] After the S3.MJS pile main unit is in place, the MJS pile is constructed. Before lowering the drill rod, a test spraying of the drill bit is carried out.

[0015] S4. After the drill rod reaches the specified depth, perform jet grouting until the grout reaches the design elevation, and then move the MJS pile host to the next pile location layout point;

[0016] S5. After the MJS pile reaches the design strength, the drilling rig required for compaction grouting will be positioned, the orientation and inclination will be corrected, and the hole will be drilled to the design depth.

[0017] S6. Use the drill rod of the drilling rig to inject casing material. After the injection is completed, install the sleeve valve pipe to construct the grouting and grout-stopping section.

[0018] Preferably, in step S2, GPS is used to lay out the pile positions in the construction area. Based on the measurement benchmark, a total station is used to measure and lay out the pile positions. Before the measurement and laying out, the measurement benchmark, leveling point and the baseline of the building are checked. The plane error of the pile position measurement and laying out is no more than 5mm.

[0019] Preferably, in step S3, a drilling rig equipped with a guide cutting drill bit is used to perform pre-drilling before the MJS pile is constructed, and the diameter of the pilot hole is determined according to the diameter of the MJS pile; after the pilot hole is completed, a sleeve drill bit is used to sweep the hole, then the hole is cleaned and mud with a specific gravity of not less than 1.1 is poured in to prevent the hole from collapsing.

[0020] Preferably, in step S4, the MJS drill bit and drill rod are lowered using the main power head. After the drill bit reaches the predetermined depth, zeroing begins, and then various process parameters are set, including the swing angle, the extraction speed, and the rotation speed.

[0021] Preferably, in step S4, during the shotcreting process, the ground pressure and mud discharge are closely monitored, and the size of the mud discharge valve is actively controlled to ensure that the ground pressure is within the specified value.

[0022] Preferably, in step S5, after the drilling rig passes the inspection, drilling begins. The drill bit diameter is not less than 110mm, the final hole diameter is not less than 100mm, and mud circulation is used for wall protection after hole formation.

[0023] Preferably, in step S6, after the sleeve valve pipe is installed in place, the grouting and grout-stopping section is constructed; a grouting pipe is inserted into the annular gap between the outer wall of the sleeve valve pipe and the borehole wall in the non-grouting section, and grouting material is pressed into the upper part of the borehole opening until thick grout is returned from the borehole opening. After the grout surface at the borehole opening sinks, grouting should be performed multiple times to ensure the grout-stopping effect.

[0024] Preferably, the MJS jet grouting uses ordinary Portland cement with a strength grade of 42.5, a water-cement ratio of 1:1, and a cement content of 700 kg / m3.

[0025] Preferably, the compaction grouting range is from 1D above the top of the tunnel to 0.5D below the tunnel, where D is the tunnel diameter.

[0026] Preferably, the deformation control method further includes the following steps:

[0027] S7. During the construction of MJS piles, monitor the surface settlement in real time;

[0028] S8. Based on monitoring data, dynamically adjust the construction parameters of the MJS piles, including grouting pressure, grouting volume, and grouting time.

[0029] Compared with the prior art, the advantages of this invention are:

[0030] This invention comprehensively considers the geological characteristics and physical properties of soft soil subgrades, as well as the settlement and deformation characteristics caused by shield tunneling, and implements corresponding reinforcement measures based on deformation prediction models. Grouting reinforcement can improve the shear strength of soft soil and reduce the risk of shear failure during shield tunneling. Grouting reinforcement at locations with significant disturbance during shield tunneling enables timely control of soft soil subgrade deformation, ensuring the safety and stability of existing railways during shield tunneling. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the process of controlling the deformation of a double-track shield tunnel passing under an existing railway soft soil subgrade, according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the surface settlement curve of a single-line shield tunnel cross section in an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the surface settlement curve of the cross section of the double-shield tunnel in an embodiment of the present invention;

[0034] Figure 4This is a schematic diagram showing the length of the MJS pile grout-stopping wall curtain in an embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram illustrating the grouting range and its spatial relationship with the shield tunnel in an embodiment of the present invention.

[0036] In the diagram: 1. MJS pile; 2. Grouting reinforcement zone; 3. Shield tunnel. Detailed Implementation

[0037] To make the purpose, principle and structure of the present invention clearer, the following description is provided in conjunction with the accompanying drawings and specific embodiments.

[0038] See Figure 1 This embodiment provides a deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade, including the following steps:

[0039] A. Determine the grouting reinforcement range of the soft soil subgrade under the railway in the double-track shield tunnel 3 by using the surface settlement prediction formula;

[0040] B. Based on the theory, determine the reinforcement range, and then lay out the pile positions and grouting hole positions in the reinforcement area, and excavate the trench;

[0041] C. After the MJS pile main unit is in place, the MJS pile 1 is constructed. Before lowering the drill rod, a test spraying of the drill bit is carried out.

[0042] D. After the drill rod reaches the specified depth, perform jet grouting until the grout reaches the design elevation, and then move the MJS pile host to the next pile location layout point;

[0043] E. After MJS pile 1 reaches the design strength, the drilling rig required for compaction grouting will be positioned, the orientation and inclination will be corrected, and the hole will be drilled to the design depth.

[0044] F. Use the drill rod of the drilling rig to inject casing material. After the injection is completed, install the sleeve valve pipe to construct the grouting and grout-stopping section.

[0045] In step A, parameters K and VL are determined based on the soft soil strata traversed by the tunnel and the type of tunnel boring machine, where K is the surface settlement trough coefficient and VL is the stratum loss rate. After determining parameters K and VL, the Peck settlement prediction model is used to predict the surface settlement of soft soil when a single-line shield tunnel passes under it.

[0046]

[0047] in This represents the surface subsidence at the distance from the tunnel centerline. The maximum surface settlement is given by i, the width of the settlement trough is given by D, the diameter of the shield tunnel is given by D, and the tunnel depth is given by Z0.

[0048] In step A, the width i of the settlement trough in soft soil can also be predicted using an empirical formula, where h is the burial depth of the shield tunnel. According to the Peck formula, the inflection point is a crucial parameter for determining the settlement trough width. Based on the existing surface settlement prediction caused by a single-track shield tunnel underpass, superimposed with the surface settlement prediction under the excavation of a double-track shield tunnel, the settlement trough width of the surface settlement curve caused by the double-track shield tunnel underpass is α(L+2i), where α is a correction coefficient considering the superimposed effect caused by the excavation of the double-track shield tunnel.

[0049] In step B, GPS is used to lay out the pile positions within the construction area. Based on the survey benchmarks, a total station is used to lay out the pile positions. Before laying out, the survey benchmarks, leveling points, and the baselines of buildings (structures) should be verified; the planar error of the pile position laying out should not exceed 5mm. A trench is excavated along the axis according to the laid-out pile positions. After the trench excavation is completed, the pile positions should be re-measured, and the site should be paved with steel plates, etc., depending on the site conditions to ensure the safety of subsequent operations. The trench bottom width is approximately 1-2m, and the depth is 1-3m.

[0050] In step C, before the MJS pile is constructed, a pre-drilling operation is performed using a drilling rig equipped with a guide cutting drill bit. The diameter of the pilot hole is determined based on the MJS pile diameter. After the pilot hole is completed, a sleeve drill bit is used to clean the hole, followed by filling it with mud with a specific gravity of not less than 1.1 to prevent hole collapse. Before lowering the drill rod, the drill bit is hoisted into the main power head, and a back-suction air adapter and a water tap are installed. Test spraying is then conducted after confirming that all pipelines are unobstructed.

[0051] In step D, the MJS drill bit and drill rod are lowered using the main power head. After the drill bit reaches the predetermined depth, zeroing begins, and then various process parameters are set, including the swing angle, extraction speed, and rotation speed. During the shotcreting process, the ground pressure and mud discharge are closely monitored, and the size of the mud discharge valve is actively controlled to ensure that the ground pressure remains within the specified range.

[0052] In step E, adjust the drilling rig height, align the vertical shaft with the center of the hole, and insert the drill bit into the borehole casing, ensuring that the borehole casing, vertical shaft, and drill rod are on the same vertical line. Simultaneously, check that the drill rod inclination is ≤1%. After the drilling rig passes the positioning inspection, drilling begins. The drill bit diameter should be no less than 110mm, and the final hole diameter should be no less than 100mm. After hole formation, mud circulation is used for wall protection. Once the drilling depth meets the design depth, the drill rod is pulled out, and a grouting pipe is connected and inserted into the hole. A large amount of clean water is pumped into the hole using a grouting pump to flush out the mud and deep cuttings until clean water returns from the borehole opening.

[0053] In step F, after drilling to the designed depth and washing the hole with clean water, casing material is poured into the hole. The casing material is injected using the drill rod of the drilling rig to prevent deformation, displacement, or damage of the sleeve valve grouting pipe during grouting and to ensure the passage of cement grout. After the sleeve valve pipe is installed in place, the grouting and grout-stopping section is constructed. The grouting pipe is lowered into the annular gap between the outer wall of the sleeve valve pipe and the hole wall in the non-grouting section. At the upper part of the hole opening, the grouting and pipe-fixing material is pressed in section by section until thick grout returns from the hole opening. After the grout surface at the hole opening sinks, grouting should be carried out multiple times to ensure the grout-stopping effect. Grouting of the sleeve valve pipe can only be carried out after the grout-stopping material at the hole opening section has solidified. The solidification time should be controlled within 2 to 5 days. The grouting fluid is prepared by mixing 42.5 ordinary cement at a 1:1 (weight ratio). During grouting, a thin grout is first poured into the hole to open it, and then the grout prepared according to the design mix ratio is injected. Grouting can be stopped when the grouting pressure is greater than 1.0 MPa, the grouting rate is less than 2.5 L / min, and the pressure stabilization time reaches more than 10 minutes. If cracks are found on the surface of the soil within the reinforcement area and grout is seen seeping out of the ground, grouting should be stopped immediately. If grout leakage or cross-contamination occurs, grouting should be stopped immediately.

[0054] In this deformation control method, MJS jet grouting uses ordinary Portland cement with a strength grade of 42.5, a water-cement ratio of 1:1, a cement content of 700 kg / m3, and the compaction grouting range is from 1D above the top of the tunnel to 0.5D below the tunnel.

[0055] See Figure 2 , Figure 3 MJS piles serve as a precondition for subsequent grouting reinforcement, acting as a grout-stopping wall. When determining reinforcement measures, the reinforcement range must be defined. According to the Peck formula, the inflection point is a crucial parameter for determining the width of the settlement trough. For a double-shield tunnel, this is equivalent to two settlement troughs superimposed on each other. Based on the existing surface settlement prediction caused by the underpass of single-shield tunnel 3, superimposed with the surface settlement prediction under the excavation of double-shield tunnel 3, the width of the settlement trough caused by the underpass of double-shield tunnel 3 is α = (L + 2i). The length of the grout-stopping wall, determined by the settlement trough width, is α = (L + 2i).

[0056] See Figure 4The grout-stopping wall consists of φ1.8@1.2m MJS jet grouting pile groups. GPS was used to lay out the pile positions within the construction area. Based on the measurement benchmarks, a total station was used to measure and lay out the pile positions. The width of the trench and the positions of the MJS piles were determined to ensure overlap between adjacent pile positions and achieve the grout-stopping effect. Before laying out the piles, the measurement benchmarks, leveling points, and the baselines of the buildings (structures) should be checked. The planar error of the pile position measurement should not exceed 5mm. The trench was excavated along the axis according to the laid-out pile positions. After the trench excavation was completed, the pile positions were re-measured, and the site was paved with steel plates, etc., according to the site conditions to ensure the safety of subsequent operations. The trench bottom width was approximately 1-2m, and the depth was 1-3m. Before the construction of MJS pile 1, a drilling rig equipped with a guide cutting drill bit was used for pre-drilling. The diameter of the pilot hole was determined according to the diameter of MJS pile 1. After the pilot hole was completed, a sleeve drill bit was used to clean the hole, and then mud with a specific gravity of not less than 1.1 was poured in to prevent hole collapse. Before lowering the drill rod, hoist the drill bit into the main power head, install the back-suction air adapter and water tap, and conduct a test spray after confirming that all pipelines are unobstructed. Using the main power head, lower the MJS drill bit and drill rod. After the drill bit reaches the predetermined depth, begin zeroing, and then set various process parameters, including swing angle, extraction speed, and rotation speed. During the grouting process, closely monitor the ground pressure and mud discharge, actively controlling the size of the mud discharge valve to ensure the ground pressure remains within the specified range. Adjust the drilling rig height, align the vertical shaft with the hole center, and insert the drill bit into the borehole pipe, ensuring the borehole pipe, vertical shaft, and drill rod are on the same vertical line. Simultaneously, check that the drill rod inclination is ≤1%. After the drilling rig is in place and passes inspection, begin drilling. The drill bit diameter should be no less than 110mm, and the final hole diameter no less than 100mm. After hole formation, use mud circulation for wall protection. After drilling to the designed depth, the drill rod is pulled out, and the grouting pipe is connected and placed into the hole. A large amount of clean water is pumped into the hole using a grouting pump to flush out the mud and deep slag until clean water returns from the hole opening. After drilling to the designed depth and flushing the hole with clean water, casing material is poured into the hole. The casing material is injected using the drill rod of the drilling rig to prevent deformation, displacement, or damage to the sleeve valve grouting pipe during the grouting process and to ensure the passage of cement grout. After the sleeve valve pipe is installed in place, the grouting and grout-stopping section is constructed. The grouting pipe is inserted into the annular gap between the outer wall of the sleeve valve pipe and the hole wall in the non-grouting section. At the upper part of the hole opening, a section of grouting and pipe-fixing material is pressed in until thick grout returns from the hole opening. After the grout surface at the hole opening sinks, grouting should be carried out multiple times to ensure the grout-stopping effect. Grouting of the sleeve valve pipe should only be carried out after the grout-stopping material at the hole opening has solidified, and the solidification time should be controlled within 2 to 5 days. The grouting fluid is prepared by mixing 42.5 ordinary cement at a 1:1 (by weight) ratio. During grouting, a thin grout is first poured into the opening, and then the grout prepared according to the design mix ratio is injected. Grouting can be stopped when the grouting pressure is greater than 1.0 MPa, the grouting flow rate is less than 2.5 L / min, and the pressure stabilization time reaches more than 10 minutes.

[0057] See Figure 5The grouting reinforcement zone extends from 1D above the top of the tunnel to 0.5D below the tunnel.

[0058] The above description is merely a specific embodiment of the invention, but the scope of protection of the invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the invention, based on the technical solutions and novel concepts of the invention, should be covered within the scope of protection of the invention.

Claims

1. A deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade, characterized in that... The method includes the following steps S1. The grouting reinforcement range for the soft soil subgrade under the railway of the double-track shield tunnel is determined using the surface settlement prediction formula, including: S11. Determine parameters K and V based on the soft soil strata traversed by the tunnel and the type of tunnel boring machine. L Where K is the surface settlement trough coefficient, and V L Formation loss rate; S12. Using the Peck settlement prediction model to predict soft soil surface settlement when a single-track shield tunnel passes under it, where: ； ； ； The The lateral distance from the centerline of the tunnel is Surface subsidence at the location This represents the maximum surface subsidence. D is the width of the settlement trough, and D is the diameter of the shield tunnel. For tunnel burial depth; S13. Through formula =0.5h Predicted width of settlement trough in soft soil layer In the formula, h is the burial depth of the shield tunnel; S14. Based on the existing surface settlement prediction caused by a single-track shield tunnel underpass, and superimposed with the surface settlement prediction under the excavation of a double-tunnel shield tunnel, the width of the settlement trough in the surface settlement curve caused by the double-track shield tunnel underpass is determined to be... In the formula, α is a correction coefficient considering the superposition effect caused by the excavation of the double-shield tunnel, and L is the horizontal distance between the axes of the two tunnels. S2. Determine the reinforcement range based on theory, and lay out the pile positions and grouting hole positions in the reinforcement area, and excavate the trench; After the S3.MJS pile main unit is in place, the MJS pile is constructed. Before lowering the drill rod, a test spraying of the drill bit is carried out. S4. After the drill rod reaches the specified depth, perform jet grouting until the grout reaches the design elevation, and then move the MJS pile host to the next pile location layout point; S5. After the MJS pile reaches the design strength, the drilling rig required for compaction grouting will be positioned, the orientation and inclination will be corrected, and the hole will be drilled to the design depth. S6. Use the drill rod of the drilling rig to inject casing material. After the injection is completed, install the sleeve valve pipe to construct the grouting and grout-stopping section.

2. The deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade as described in claim 1, characterized in that... In step S2, GPS is used to lay out the pile positions in the construction area. Based on the measurement benchmark, a total station is used to measure and lay out the pile positions. Before the measurement and laying out, the measurement benchmark, leveling point and the baseline of the building are checked. The plane error of the pile position measurement and laying out is no more than 5mm.

3. The deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade as described in claim 1, characterized in that... In step S3, before the MJS pile is constructed, a drilling rig equipped with a guide cutting drill bit is used to perform pre-drilling. The diameter of the pilot hole is determined according to the diameter of the MJS pile. After the pilot hole is completed, a sleeve drill bit is used to sweep the hole, then the hole is cleaned and mud with a specific gravity of not less than 1.1 is poured in to prevent the hole from collapsing.

4. The deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade as described in claim 1, characterized in that... In step S4, the MJS drill bit and drill rod are lowered using the main power head. After the drill bit reaches the predetermined depth, zeroing begins, and then various process parameters are set, including swing angle, extraction speed, and rotation speed.

5. The deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade as described in claim 1, characterized in that... In step S4, during the shotcreting process, close attention is paid to the ground pressure and mud discharge, and the size of the mud discharge valve is actively controlled to ensure that the ground pressure is within the specified value.

6. The deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade as described in claim 1, characterized in that... In step S5, after the drilling rig passes the inspection, drilling begins. The drill bit diameter is not less than 110mm, and the final hole diameter is not less than 100mm. After the hole is formed, mud circulation is used to protect the hole wall.

7. The deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade as described in claim 1, characterized in that... MJS jet grouting uses ordinary Portland cement with a strength grade of 42.5, a water-cement ratio of 1:1, and a cement content of 700 kg / m³. 3 .

8. A deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade as described in claim 1, characterized in that... The compaction grouting range is from 1D above the top of the tunnel to 0.5D below the tunnel, where D is the tunnel diameter.

9. A deformation control method for a double-track shield tunnel passing under an existing railway soft soil subgrade as described in claim 1, characterized in that... It also includes the following steps: S7. During the construction of MJS piles, monitor the surface settlement in real time; S8. Based on monitoring data, dynamically adjust the construction parameters of the MJS piles, including grouting pressure, grouting volume, and grouting time.

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