Deformation control method for double-line shield tunnel underneath passing existing railway soft soil roadbed

Abstract

The invention relates to the field of underground engineering and rail traffic engineering, in particular to a deformation control method for a double-line shield tunnel to underpass an existing railway soft soil roadbed, which comprises the following steps: S1, determining a grouting reinforcement range; s2, pile position and grouting hole position lofting is conducted in the reinforcing area, and a groove is excavated; s3, construction is conducted after the MJS pile main machine is in place, and drill bit trial spraying is conducted before a drill rod is placed; s4, after the drill rod reaches the specified depth, jet grouting is conducted till the designed elevation is reached, and the MJS pile main machine is moved to the next pile position sample placing point; s5, after the MJS pile reaches the designed strength, a drilling machine is arranged in place, and a formed hole is drilled to the designed depth; and S6, grouting is conducted, and then grouting and grout stopping section construction is conducted. The method has the advantages that corresponding reinforcement measures are taken in combination with the model, the shear strength of the soft soil is improved, the shear damage risk of the soft soil is reduced, deformation of the soft soil roadbed is controlled in time, and safety and stability in the shield underneath pass construction process are ensured.

Description

Technical Field

[0001] The invention relates to the field of underground engineering and rail transit engineering, and in particular to a deformation control method for a double-line shield tunnel passing under an existing railway soft soil roadbed. Background Art

[0002] Soft soil is a unique soil formed in an underwater sedimentary environment and is widely distributed in my country's coastal areas. Double-line shield tunneling refers to the use of a shield machine to dig two parallel tunnels at the same time. This construction method is particularly common in the construction of urban subways, railways and highway tunnels. With the rapid development of coastal cities, existing urban facilities can no longer meet the growing needs of economic construction. Therefore, many infrastructure projects, such as rail transit, highways, docks and airports, have been included in urban planning. However, the high compressibility, high sensitivity and low strength of soft soil have brought many challenges to engineering construction.

[0003] When shield construction is carried out in soft soil, the physical and mechanical properties of soft soil are crucial to deformation control. Since soft soil usually has low strength and high compressibility, it may cause problems such as squeezing and settlement. Summary of the invention

[0004] The purpose of the present invention is to ensure that when a double-line shield tunnel passes under an existing soft soil railway subgrade, the uneven settlement of the existing structure can be effectively controlled, the impact on the existing structure can be reduced, and the safe operation of the existing railway line can be guaranteed.

[0005] In order to achieve the above purpose, a deformation control method for a double-line shield tunnel passing through an existing railway soft soil embankment is designed, which includes the following steps:

[0006] S1. Determine the scope of grouting reinforcement for the soft soil subgrade of the double-track shield tunnel under the railway by using the surface settlement prediction formula, including:

[0007] S11. Determine the parameters K and VL according to the soft soil layer that the tunnel passes through and the type of shield machine, where K is the surface settlement trough coefficient and VL is the formation loss rate;

[0008] S12. Use the Peck settlement prediction model to predict the settlement of soft soil surface when a single-line shield tunnel passes through, where:

[0009]

[0010] Said is the ground settlement from the center line of the tunnel, is the maximum surface settlement, i is the width of the settlement trough, D is the diameter of the shield tunnel, and Z0 is the tunnel burial depth;

[0011] S13. Predict the width i of the soft soil trough by the formula i=0.5h, where h is the buried depth of the shield tunnel;

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

[0013] S2. Determine the reinforcement scope based on theory, stake out the pile positions and grouting holes in the reinforcement area, and dig trenches;

[0014] S3. After the MJS pile mainframe is in place, the MJS pile is constructed and the drill bit is tested before the drill rod is lowered;

[0015] S4. When the drill pipe reaches the specified depth, grouting is carried out until the grouting reaches the designed elevation, and the MJS pile host is moved to the next pile position setting point;

[0016] S5. After the MJS pile reaches the designed strength, the drilling rig required for compaction grouting is put in place, the azimuth and inclination are corrected, and the hole is drilled to the designed depth;

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

[0018] Preferably, in step S2, GPS is used to carry out stakeout in the construction area, and the stakes are measured and laid out using a total station according to the measurement reference points. Before measurement and laying out, the measurement reference points, leveling points and the baseline of the building are reviewed, and the plane error of the stake measurement and laying out is not greater than 5 mm.

[0019] Preferably, in step S3, a drilling rig equipped with a guide cutting drill bit is used to perform pre-drilling construction before the MJS pile is constructed, and the guide hole diameter is determined according to the MJS pile diameter; after the guide hole is completed, a sleeve drill bit is used to sweep the hole, and 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 main engine power head is used to lower the MJS drill bit and the drill rod. After the drill bit reaches a predetermined depth, zero calibration is started, and then various process parameters are set, including the swing angle, the pulling speed, and the number of revolutions.

[0021] Preferably, in step S4, during the grouting process, close attention is paid to the underground pressure and mud discharge, and the size of the mud discharge valve is actively controlled to ensure that the underground pressure is within a specified value.

[0022] Preferably, in step S5, after the drilling rig passes the in-place inspection, drilling begins, the drill bit diameter is not less than 110 mm, the final hole diameter is not less than 100 mm, and mud circulation is used to protect the wall after the hole is formed.

[0023] Preferably, in step S6, after the sleeve valve pipe is installed in place, the grouting and grouting 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, and the grouting pipe-fixing material is pressed into the upper part of the hole mouth until thick slurry returns from the hole mouth. After the slurry surface at the hole mouth sinks, grouting should be performed multiple times to ensure the pipe-fixing and slurry-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 700kg / m3.

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

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

[0027] S7. During the MJS pile construction process, real-time monitoring of ground settlement;

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

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] The present invention comprehensively considers the geological characteristics and physical properties of the soft soil roadbed, as well as the settlement deformation characteristics caused by shield construction, and combines the deformation prediction model to implement corresponding reinforcement measures. Grouting reinforcement can improve the shear strength of soft soil and reduce the risk of shear damage of soft soil during shield construction. Grouting reinforcement is performed on the locations with greater disturbance during shield construction to achieve timely control of soft soil roadbed deformation and ensure the safety and stability of existing railways during shield underpass construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of controlling the deformation of a double-track shield tunnel passing under an existing railway soft soil embankment according to an embodiment of the present invention;

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

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

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

[0035] Figure 5 Schematic diagram of the grouting range and its spatial relationship with the shield tunnel in an embodiment of the present invention.

[0036] In the figure: 1. MJS piles; 2. Grouting reinforcement area; 3. Shield tunnel. DETAILED DESCRIPTION

[0037] In order to make the purpose, principle and structure of the present invention more clear, it is further described below in conjunction with the drawings and specific embodiments.

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

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

[0040] B. Determine the reinforcement scope based on theory, stake out the pile positions and grouting holes in the reinforcement area, and dig trenches;

[0041] C. After the MJS pile mainframe is in place, MJS pile 1 is constructed, and the drill bit is sprayed before the drill rod is lowered;

[0042] D. When the drill rod reaches the specified depth, grouting is carried out until the grouting reaches the designed elevation, and the MJS pile host is moved to the next pile position setting point;

[0043] E. After the MJS pile 1 reaches the designed strength, the drilling rig required for compaction grouting is put in place, the azimuth and inclination are corrected, and the hole is drilled to the designed depth;

[0044] F. Use the drill rig drill rod to pour the casing material. After the pouring is completed, install the sleeve valve pipe to carry out the grouting and stopping section construction.

[0045] In step A, the parameters K and VL are determined according to the soft soil layer that the tunnel passes through and the type of shield machine, where K is the surface settlement trough coefficient and VL is the formation loss rate. After determining the parameters K and VL, the soft soil surface settlement prediction is carried out by using the Peck settlement prediction model when the single-line shield tunnel passes through.

[0046]

[0047] in is the ground settlement from the center line of the tunnel, is the maximum surface settlement, i is the width of the settlement trough, D is the diameter of the shield tunnel, and Z0 is the tunnel depth

[0048] In step A, the width of the settlement trough i in the soft soil layer can also be predicted by using an empirical formula, where h is the buried depth of the shield tunnel. From the Peck formula, it can be seen that the inflection point is an important parameter for determining the width of the settlement trough. According to the surface settlement prediction caused by the existing single-line shield tunnel underpass and the surface settlement prediction under the double-hole shield tunnel excavation, the settlement trough width of the surface settlement curve caused by the double-line shield tunnel underpass is α(L+2i), where α is the correction coefficient considering the superposition effect caused by the double-line shield tunnel excavation.

[0049] In step B, GPS is used to stake out the pile positions in the construction area. The total station is used to measure and lay out the pile positions according to the measurement benchmark points. Before measurement and laying out, the measurement benchmark points, leveling points and the baseline of the building (structure) should be verified, and the plane error of the pile position measurement and laying out shall not exceed 5mm. According to the measured pile positions, trenches are excavated along the axis. After the trench excavation is completed, the pile positions should be re-measured, and according to the site conditions, the site should be paved with steel plates to ensure the safety of subsequent operations. The width of the trench bottom is about 1 to 2m and the depth is 1 to 3m.

[0050] In step C, a drilling rig equipped with a guide cutting drill bit is used for pre-drilling before the MJS pile is constructed. The lead hole diameter is determined according to the MJS pile diameter. After the lead hole is completed, a sleeve drill bit is used to sweep the hole, then the hole is cleaned and filled with mud with a specific gravity of not less than 1.1 to prevent the hole from collapsing. Before lowering the drill rod, the drill bit is hoisted into the main engine power head, and the reverse air adapter and faucet are installed. After confirming that all pipelines are unobstructed, test spraying is performed.

[0051] In step D, the MJS drill bit and drill rod are lowered by the main engine power head. After the drill bit reaches the predetermined depth, zero calibration is started, and then various process parameters are set, including swing angle, extraction speed, number of revolutions, etc. During the grouting 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.

[0052] In step E, adjust the height of the drill rig, align the vertical pole with the center of the hole, put the drill bit into the orifice pipe, and make the orifice pipe, vertical shaft and drill pipe on the same vertical line. At the same time, check that the inclination of the drill pipe is ≤1%. After the drilling rig is in place and the inspection is qualified, start drilling. The diameter of the drill bit is not less than 110mm, and the diameter of the final hole is not less than 100mm. After the hole is formed, the mud circulation wall protection is used. After the drilling depth meets the designed hole depth, pull out the drill pipe, connect the grouting pipe and put it into the hole, and use a grouting pump to pump a large amount of clean water into the hole to flush the mud and deep slag in the hole out of the hole until clean water returns from the hole mouth.

[0053] In step F, after drilling to the designed depth and washing the hole with clean water, pour the casing material into the hole. The casing material is poured using the drill rod of the drilling rig to prevent the sleeve valve grouting pipe from deformation, displacement or damage during the grouting process, and to ensure the passage of cement slurry. After the sleeve valve pipe is installed in place, the grouting and grouting stop section is constructed. The grouting pipe is lowered into the annular gap between the outer wall of the sleeve valve pipe in the non-grouting section and the hole wall. At the upper part of the orifice, the grouting solid pipe material is pressed into the section until the orifice returns the thick slurry. After the orifice slurry surface sinks, grouting should be done multiple times to ensure the effect of solid pipe grouting. The sleeve valve pipe grouting can only be carried out after the orifice section grouting material solidifies. The setting time is controlled within 2 to 5 days. The grouting liquid is mixed with 42.5 ordinary cement at a ratio of 1:1 (weight ratio). When grouting, the thin slurry is first poured into the hole, and then the slurry mixed according to the design mix ratio is injected. When the grouting pressure is greater than 1.0Mp, the grouting volume is less than 2.5L / min, and the stable pressure time reaches more than 10min, the grouting can be stopped. If cracks are found on the surface of the soil in the reinforcement range and slurry emerges from the ground, the grouting should be stopped immediately. If slurry channeling or slurry leakage occurs seriously, the 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 700kg / m3, and a compaction grouting range of 1D above the tunnel top to 0.5D below the tunnel.

[0055] See also Figure 2 , Figure 3 , MJS piles are used as stop walls to provide preconditions for subsequent grouting reinforcement. When determining reinforcement measures, the reinforcement range must be determined. From the Peck formula, it can be seen that the inflection point is an important parameter for determining the width of the settlement trough. For double-track shield tunnels, it is equivalent to two settlement troughs superimposed on each other. According to the surface settlement prediction caused by the underpass of the existing single-track shield tunnel 3 and the surface settlement prediction under the excavation of the double-hole shield tunnel 3, the width of the settlement trough of the surface settlement curve caused by the underpass of the double-track shield tunnel 3 is α=(L+2i). The length of the stop wall determined by the width of the settlement trough is α=(L+2i).

[0056] See also Figure 4The grout-stopping wall is composed of φ1.8@1.2mMJS jet-jet pile group, and GPS is used to stake out the pile position in the construction area. According to the measurement benchmark, the total station is used to measure and lay out the pile position. The width of the trench is determined, and the pile position of the MJS pile is also determined to ensure that adjacent pile positions overlap and achieve the grout-stopping effect. Before measurement and placement, the measurement benchmark, leveling point and the baseline of the building (structure) should be reviewed, and the plane error of the pile position measurement and placement shall not exceed 5mm. According to the measured pile position, the trench is excavated along the axis. After the trench excavation is completed, the pile position should be re-measured, and according to the site conditions, the site should be paved with steel plates to ensure the safety of subsequent operations. The width of the trench bottom is about 1 to 2m and the depth is 1 to 3m. Before the construction of MJS pile 1, a drilling rig equipped with a guide cutting drill bit is used for pre-drilling construction, and the diameter of the lead hole is determined according to the diameter of MJS pile 1. After the lead 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 to prevent the hole from collapsing. Before lowering the drill pipe, the drill bit is hoisted into the main engine power head, and the reverse air adapter and faucet are installed. Confirm that all pipelines are unobstructed before test spraying. Use the main engine power head to lower the MJS drill bit and drill pipe. After the drill bit reaches the predetermined depth, start zeroing, and then set various process parameters, including swing angle, extraction speed, number of revolutions, etc. During the grouting process, pay close attention to the underground pressure and mud discharge, actively control the size of the mud discharge valve, and ensure that the underground pressure is within the specified value. Adjust the height of the drilling rig, align the vertical pole with the center of the hole, and put the drill bit into the orifice pipe so that the orifice pipe, vertical axis and drill pipe are on the same vertical line. At the same time, it is required to check that the inclination of the drill pipe is ≤1%. After the drilling rig is in place and the inspection is qualified, start drilling. The diameter of the drill bit is not less than 110mm, and the diameter of the final hole is not less than 100mm. After the hole is formed, mud circulation is used to protect the wall. After the drilling depth meets the designed hole depth, pull out the drill rod, connect the grouting pipe and put it into the hole, and use the grouting pump to pump a large amount of clean water into the hole to flush the mud and deep residue in the hole out of the hole until clean water returns from the hole mouth. After drilling to the designed depth and washing the hole with clean water, pour the shell material into the hole. The shell material is poured using the drill rod of the drilling rig to prevent the sleeve valve grouting pipe from deforming, displacing or being damaged during the grouting process, and to ensure the passage of cement slurry. After the sleeve valve pipe is installed in place, the grouting and grouting stop 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 mouth, the grouting solid pipe material is pressed into the meter section until the thick slurry returns from the hole mouth. After the slurry surface of the hole mouth sinks, grouting should be done multiple times to ensure the effect of solid pipe grouting. Grouting of the sleeve valve pipe can only be carried out after the grouting material of the hole mouth section solidifies, and the setting time is controlled within 2 to 5 days. The grouting liquid is made of 42.5 ordinary cement at a ratio of 1:1 (weight ratio). When grouting, first pour the slurry into the hole, and then inject the slurry mixed according to the designed mix ratio. When the grouting pressure is greater than 1.0Mp, the grouting volume is less than 2.5L / min, and the stable pressure time reaches more than 10min, the grouting can be stopped.

[0057] See also Figure 5, grouting reinforcement zone 2 ranges from 1D above the tunnel top to 0.5D below the tunnel.

[0058] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent substitutions or changes according to the technical solutions and novel concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A deformation control method for a double-line shield tunnel passing through an existing railway soft soil embankment, characterized in that The method comprises the following steps S1. Determine the scope of grouting reinforcement for the soft soil subgrade of the double-track shield tunnel under the railway by using the surface settlement prediction formula, including: S11. Determine the parameters K and VL according to the soft soil layer that the tunnel passes through and the type of shield machine, where K is the surface settlement trough coefficient and VL is the formation loss rate; S12. Use the Peck settlement prediction model to predict the settlement of soft soil surface when a single-line shield tunnel passes through, where: i=K·Z0 The S ν (χ) is the ground settlement from the center line of the tunnel, S ν,max is the maximum surface settlement, i is the width of the settlement trough, D is the diameter of the shield tunnel, and Z0 is the tunnel burial depth; S13. Predict the width i of the soft soil trough by the formula i=0.5h, where h is the buried depth of the shield tunnel; S14. Based on the prediction of surface settlement caused by the existing single-line shield tunnel underpass and the prediction of surface settlement caused by the double-hole shield tunnel excavation, the width of the settlement trough of the surface settlement curve caused by the double-line shield tunnel underpass is determined to be α(L+2i), where α is the correction coefficient considering the superposition effect caused by the double-line shield tunnel excavation; S2. Determine the reinforcement scope based on theory, stake out the pile positions and grouting holes in the reinforcement area, and dig trenches; S3. After the MJS pile mainframe is in place, the MJS pile is constructed and the drill bit is tested before the drill rod is lowered; S4. When the drill pipe reaches the specified depth, grouting is carried out until the grouting reaches the designed elevation, and the MJS pile host is moved to the next pile position setting point; S5. After the MJS pile reaches the designed strength, the drilling rig required for compaction grouting is put in place, the azimuth and inclination are corrected, and the hole is drilled to the designed depth; S6. Use the drill rod of the drilling rig to inject the casing material. After the injection is completed, install the sleeve valve pipe to carry out the grouting and stopping section construction.

2. A deformation control method for a double-track shield tunnel passing under an existing railway soft soil embankment as claimed in claim 1, characterized in that In step S2, GPS is used to carry out stakeout in the construction area. The stakes are measured and laid out using a total station according to the measurement reference points. Before the measurement and laying out, the measurement reference points, leveling points and the baseline of the building are checked. The plane error of the stake measurement and laying out is not greater than 5 mm.

3. A deformation control method for a double-track shield tunnel under an existing railway soft soil embankment as claimed in claim 1, characterized in that In step S3, a pre-drilling construction is performed using a drilling rig equipped with a guide cutting drill bit before the MJS pile is constructed, and the lead hole diameter is determined according to the MJS pile diameter; after the lead hole is completed, a sleeve drill bit is used to sweep the hole, and 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. A deformation control method for a double-track shield tunnel passing under an existing railway soft soil embankment as claimed in claim 1, characterized in that In step S4, the main engine power head is used to lower the MJS drill bit and the drill rod. After the drill bit reaches the predetermined depth, zero calibration is started, and then various process parameters are set, including the swing angle, the pulling speed, and the number of revolutions.

5. The deformation control method for a double-track shield tunnel passing through an existing railway soft soil embankment as claimed in claim 1, characterized in that In step S4, during the grouting 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. A deformation control method for a double-track shield tunnel passing under an existing railway soft soil embankment as claimed in claim 1, characterized in that In step S5, after the drilling rig passes the in-place inspection, drilling begins, the drill bit diameter is not less than 110 mm, the final hole diameter is not less than 100 mm, and mud circulation is used to protect the wall after the hole is formed.

7. A deformation control method for a double-track shield tunnel passing under an existing railway soft soil embankment as claimed in claim 1, characterized in that In step S6, after the sleeve valve pipe is installed in place, the grouting and grouting 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, and the grouting pipe-fixing material is pressed into the upper part of the hole mouth until thick slurry returns from the hole mouth. After the slurry surface at the hole mouth sinks, grouting should be performed multiple times to ensure the pipe-fixing and slurry-stopping effect.

8. The deformation control method for a double-line shield tunnel passing through an existing railway soft soil embankment as claimed 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 700kg / m3.

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

10. A deformation control method for a double-track shield tunnel passing through an existing railway soft soil embankment as claimed in claim 1, characterized in that The following steps are also included: S7. During the MJS pile construction process, real-time monitoring of ground settlement; S8. According to the monitoring data, dynamically adjust the construction parameters of MJS piles, including grouting pressure, grouting volume and grouting time.

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