A method for reinforcing the sleeve valve pipe cofferdam at the end of a subway shield

Abstract

The invention discloses a construction method for reinforcing a cofferdam with sleeve valves at the end of a subway shield. The holes in the outermost row around the end reinforcement area of the shield and the holes in the middle are reinforced to form a "field" - shaped cofferdam. During grouting, the holes in the outermost row around the end reinforcement area of the shield and the holes in the middle are grouted with a double - liquid sleeve valve pipe of cement slurry and water glass, and the sleeve valve pipe of cement slurry is used for grouting in the end reinforcement area of the shield. This construction method for reinforcing a cofferdam with sleeve valves at the end of a subway shield can effectively solve the grouting problems that the cement slurry has a poor coagulation effect and is easily washed away by water in the water - rich pebble stratum, avoid phenomena such as the shield "sinking", "lifting", water gushing and sand gushing during the entry and exit of the tunnel, ensure the safety of the shield during entry and exit, and at the same time enable the unconfined compressive strength of the soil after the end of the shield is reinforced to reach 0.8 - 1 MPa in 28 days, meeting the construction requirements and ensuring the safe and smooth construction of the shield starting or receiving in the subway section.

Description

Technical Field

[0001] The invention relates to the technical field of subway shield end reinforcement, in particular to a subway shield end sleeve valve pipe cofferdam reinforcement construction method. Background Art

[0002] At present, the diameter of the shield end in China is φ800@600 triple-tube jet grouting piles or φ800@600 three-axis mixing piles. The longitudinal reinforcement length is 9m longer than the shield length of the shield machine, the transverse reinforcement width is 3m outside the tunnel outline, and the reinforcement depth is 3m outside the tunnel outline. The reinforced soil should have good uniformity and self-sustaining properties, and its 28d unconfined compressive strength is 0.8~1MPa; at the same time, a dewatering well is arranged at the end of the shield to lower the groundwater level below the bottom of the tunnel when the shield is started or received.

[0003] When reinforcing the shield end of Luoyang Metro, the geology of the shield end is mainly pebbles, with a very high water content and a high water flow rate. The existing triple-tube jet-jet pile or triaxial mixing pile method is used to reinforce the shield end. The reinforced cement slurry is difficult to coagulate and is easily washed away by water, resulting in poor reinforcement effect; it cannot meet the construction requirement that the 28d unconfined compressive strength of the soil after the shield end reinforcement is 0.8~1MPa, which is easy to cause risks such as collapse of the shield starting or receiving end. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned problem and to provide a method for grouting that can effectively solve the problem of poor coagulation effect of cement slurry in water-rich pebble strata and easy to be washed away by water, avoid the phenomena of "sinking", "raising head" and water and sand gushing when entering and exiting the tunnel, ensure the safety of the shield entering and exiting the tunnel, and at the same time make the 28d unconfined compressive strength of the soil after the shield end is reinforced reach 0.8~1MPa, meet the construction requirements, and ensure the safe and smooth construction of the subway section shield starting or receiving.

[0005] To achieve the above object, the technical solution of the present invention is: a subway shield end sleeve valve pipe cofferdam reinforcement construction method, comprising the following steps:

[0006] (1) Measurement and positioning;

[0007] (2) Drilling;

[0008] (3) Lower shell material;

[0009] (4) Install sleeve valve pipe;

[0010] (5) Grouting.

[0011] Preferably, in step (1), total station is used to drill holes at intervals according to the design requirements by using the on-site reference points. The hole drilling positions are below the shield end. After hole drilling, a shield end reinforcement area is formed, and the hole positions are measured and rechecked after hole drilling.

[0012] Preferably, in step (2), for hole formation of sleeve valve pipe grouting, according to the requirements of the design drawings, the grouting hole positions are determined, and an HM90 crawler drill rig is used to drill the grouting holes, with a 90 mm drill bit for drilling.

[0013] Preferably, in step (3), the casing material is a mixture of cement and bentonite slurry. After hole formation, the casing material is used to displace the mud in the hole through the drill pipe. The pipe for circulating the mud is connected to an extrusion grouting machine, and under the action of the grouting pressure, the drill pipe displaces the mud in the hole with the casing material.

[0014] Preferably, in step (4), after the drill rig forms a hole, a Ф48 mm sleeve valve pipe is lowered and the pipe is fixed. The bottom of the pipe is at least 30 cm higher than the bottom of the hole. When lowering the pipe, the pipes are fixedly connected to each other. A rubber sleeve is tightly fastened outside the pipe at the opening, covering the grouting hole; a conical plug is sleeved at the lower end of the sleeve valve pipe, and a protective cap is sleeved at the upper end.

[0015] Preferably, in step (5), sectional grouting is adopted during grouting. The length of each section of grouting is called the grouting step distance. The length of the perforated pipe is the length of the grouting step distance. The grouting step distance is generally selected as 0.7 - 1 m. After grouting is completed, a blanking cap is covered on the grouting pipe to facilitate re-grouting construction.

[0016] Preferably, the outermost row of holes and the middle holes around the shield end reinforcement area are reinforced to form a "field"-shaped cofferdam; during grouting, the outermost row of holes and the middle holes around the shield end reinforcement area adopt double-fluid sleeve valve pipe grouting with cement slurry and water glass, and cement slurry sleeve valve pipe grouting is adopted within the shield end reinforcement area.

[0017] The beneficial effects of a construction method for reinforcing a shield end of a subway with a sleeve valve pipe cofferdam disclosed by the present invention are as follows: through the "field"-shaped cofferdam, double-fluid sleeve valve pipe grouting and cement slurry sleeve valve pipe grouting, the grouting problems that the cement slurry has poor setting effect and is easily washed away by water in the water-rich pebble stratum are solved, phenomena such as "sinking", "lifting", water inrush and sand inrush of the shield during entering and exiting the tunnel are avoided, the safety of the shield entering and exiting the tunnel is ensured, and at the same time, the unconfined compressive strength of the soil body 28 days after the shield end is reinforced can reach 0.8 - 1 MPa, meeting the construction requirements and ensuring the safe and smooth construction of the shield starting or receiving in the subway section. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the steps of a construction method for reinforcing a shield end of a subway with a sleeve valve pipe cofferdam according to the present invention.

[0019] Figure 2 This is a schematic structural diagram of the shield end reinforcement plane in a construction method for reinforcing a cofferdam with sleeve valves at the shield end of a subway according to the present invention.

[0020] In the figure: 1. Shield end; 2. Shield end reinforcement area; 3. Double-slurry sleeve valve pipe grouting; 4. Cement slurry sleeve valve pipe grouting. Specific implementation manners

[0021] The technical solution of the present invention is as follows: A construction method for reinforcing a cofferdam with sleeve valves at the shield end of a subway. Please refer to Figure 1 , which includes the following steps:

[0022] (1) Measurement and positioning; In step (1), using the on-site reference points, holes are arranged by a total station according to the designed spacing requirements. The hole arrangement positions are below the shield end 1. After the holes are arranged, a shield end reinforcement area 2 is formed. After the holes are arranged, the hole positions are measured and rechecked. Drilling construction can be carried out only after it is confirmed that there is no error.

[0023] Please refer to Figure 2 , the outermost row of holes around the shield end reinforcement area 2 and the middle holes are reinforced to form a "field"-shaped cofferdam. After the "field" frame reinforcement in the shield end reinforcement area is completed, the reinforcement area is divided into 4 small blocks, and the outside water is blocked outside. During grouting, the outermost row of holes around the shield end reinforcement area 2 and the middle holes (the contour of the "field"-shaped cofferdam) adopt double-slurry sleeve valve pipe grouting 3 of cement slurry and water glass. Since water glass combines with cement slurry, the setting time is short, which is convenient for accelerating the formation of the cofferdam; Cement slurry sleeve valve pipe grouting 4 (single slurry) is adopted inside the shield end reinforcement area 2 (inside the "field"-shaped cofferdam). The single liquid slurry of cement slurry has a good diffusion effect, enabling faster soil reinforcement within the shield end range. The unconfined compressive strength of the soil after reinforcement reaches 0.8 - 1 MPa at 28 days; Meeting the requirements for the start or reception of the shield in the subway section; Solving the problems that the cement slurry has a poor coagulation effect and is easily washed away by water in the water-rich pebble stratum.

[0024] (2) Drilling; In step (2), for the hole formation of sleeve valve pipe grouting, according to the requirements of the design drawing, the grouting hole positions are determined, and an HM90 crawler drill rig is used to drill the grouting holes, with a 90 mm drill bit for drilling; Before starting drilling, the angle of the drill rig should be adjusted to ensure the drilling angle. During the drilling process, record the drilling speed and seriously analyze the geological conditions as the basis for pressure adjustment during grouting.

[0025] (3) Putting casing material; In step (3), the casing material is a mixture of cement and bentonite slurry. After the hole is formed, the casing material replaces the mud in the hole through the drill pipe, and is connected to the extrusion grouting machine through the circulating mud pipe. Under the action of grouting pressure, the drill pipe replaces the mud in the hole with casing material. Under the action of pressure, the casing material enters the bottom of the borehole through the drill pipe. As the casing material enters, the mud is replaced from the ground hole. The replaced mud is discharged into the mud circulation pool through the mud groove at the borehole. When it is found that the discharged mud contains casing material, the replacement is stopped. The casing material ratio is cement: bentonite: water = 1: (2.5-4): 1.

[0026] (4) Installing sleeve valve pipes; in step (4), after the drilling rig forms a hole, a Ø48 mm sleeve valve pipe is lowered and fixed, with the bottom of the pipe at least 30 cm above the bottom of the hole. When lowering the pipe, the pipes are fixedly connected, and a rubber sleeve is tightly clamped outside the pipe at the opening to cover the grouting hole; a conical plug is sleeved at the bottom end of the sleeve valve pipe, and a protective cap is sleeved at the top end to prevent mud or casing material in the hole from entering the sleeve valve pipe. When lowering the pipe, fill it with clean water to reduce the influence of buoyancy, so that the pipe sinks smoothly and the curvature of the pipe is reduced. The sleeve valve pipe is fixed by configuring the casing material according to the required mix ratio. The sleeve valve pipe should be located in the middle of the borehole as much as possible and kept vertical. Water glass mixed with cement and sand is used to fill and seal at a distance of more than 0.5 m from the hole mouth. Grouting can only be started after the strength of the casing material reaches a certain level. In order to save time, an early strength agent can be added to the casing material.

[0027] (5) Grouting: In step (5), segmented grouting is adopted during grouting. The length of each grouting section is called the grouting step length. The length of the flower tube is the grouting step length. The grouting step length is generally selected to be 0.7 to 1 m, which can effectively reduce the influence of stratum heterogeneity on the grouting effect. For sand layers, the grouting step length should be low; for sand and gravel or broken rock layers, the grouting step length should be high. During the grouting process, after each section of grouting is completed, the core tube length of one step is moved up or down. It is advisable to use lifting equipment to move it, or to manually use two pipe clamps to symmetrically clamp the core tube, and apply force evenly on both sides at the same time to move the core tube. After completing the grouting length of 3 to 4 m, a section of the grouting core tube should be removed. After the grouting is completed, a cover is placed on the grouting tube to facilitate the re-injection construction.

[0028] The double-track starting and ending mileages of the Shijiawan Station to Tawan Station section are both CK21+401.806~CK22+569.679, with a total length of 1167.873m, a centerline distance of 15m between the left and right lines, a tunnel bottom slab burial depth of 16.32~24.19m, a tunnel top slab burial depth of 10.0~17.9m, and a shield tunnel diameter of about 6.2m. It is planned to use the shield method for construction; a connecting channel is set up at mileage CK21+970.000 and mileage CK22+330.000 respectively.

[0029] The tunnel at the starting and receiving shaft of the shield machine between Tawan Station and Shijiawan Station is mainly located in the pebble soil layer. The main strata above the tunnel top plate at the starting or receiving shaft end position are soft strata such as fill layer, loess-like silt, and pebble soil from top to bottom. This stratum is not conducive to the starting of the shield machine, and the starting end of the shield machine needs to be reinforced.

[0030] For the reinforcement of the starting receiving end of the shield tunnel between Tawan Station and Shijiawan Station, our project department adopted the sleeve valve pipe cofferdam reinforcement construction method for the starting end of the subway shield tunnel. The reinforcement range of the stratum at the end of the shield tunnel in this section is as follows: the longitudinal reinforcement length is 10m, the transverse reinforcement width is 3m outside the tunnel outline, and the reinforcement depth is 3m outside the tunnel outline; the HM90 crawler drilling vehicle is used to drill the grouting holes, and the 90mm drill bit is used to guide the holes. The grouting conduit adopts a plastic sleeve valve pipe arranged in a plum blossom shape with a spacing of 1mx1m and Ф48×4mm. The outermost row of holes in the reinforcement range and the holes in the middle are reinforced to form a "field"-shaped cofferdam structure, and cement slurry and cement water glass slurry are used for double slurry grouting, and the rest are grouting with cement slurry single slurry, and the grouting pressure is 0.4~0.8MPa; the soil after reinforcement should have good uniformity and self-sustaining properties, and its 28d unconfined compressive strength reaches 0.8~1.0MPa.

[0031] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A subway shield end sleeve valve pipe cofferdam reinforcement construction method, characterized in that: The steps include the following: (1) Measurement and positioning: Using the on-site reference points, holes are arranged by a total station according to the designed spacing requirements. The hole arrangement positions are below the shield end. After the holes are arranged, a shield end reinforcement area is formed. After the holes are arranged, the hole positions are measured and rechecked; the outermost row of holes around the shield end reinforcement area and the holes in the middle are reinforced to form a "field"-shaped cofferdam; during grouting, the outermost row of holes around the shield end reinforcement area and the holes in the middle are grouted with a double slurry of cement slurry and water glass through a sleeve valve pipe, and the shield end reinforcement area is grouted with a cement slurry sleeve valve pipe. (2) Drilling holes; (3) Lowering the casing material; (4) Installing the sleeve valve pipe; (5) Grouting.

2. The subway shield end sleeve valve pipe cofferdam reinforcement construction method according to claim 1 is characterized in that: In step (2), for the hole formation of sleeve valve pipe grouting, according to the requirements of the design drawing, the positions of the grouting holes are determined, and a HM90 crawler drill rig is used to drill the grouting holes, and a 90 mm drill bit is used for drilling.

3. The subway shield end sleeve valve pipe cofferdam reinforcement construction method according to claim 1 is characterized in that: In step (3), the casing material is a mixture of cement and bentonite slurry. After the hole is formed, the casing material is used to displace the mud in the hole through the drill pipe. The pipe for circulating the mud is connected to an extrusion grouting machine. Under the action of the grouting pressure, the drill pipe displaces the mud in the hole with the casing material.

4. The subway shield end sleeve valve pipe cofferdam reinforcement construction method according to claim 1 is characterized in that: In step (4), after the drill rig forms a hole, a Ф48 mm sleeve valve pipe is lowered and the pipe is fixed. The bottom of the pipe is at least 30 cm higher than the bottom of the hole. When the pipes are lowered, they are fixedly connected to each other. A rubber sleeve is tightly fitted outside the pipe at the opening to cover the grouting hole; a conical plug is sleeved at the lower end of the sleeve valve pipe, and a protective cap is sleeved at the upper end.

5. The subway shield end sleeve valve pipe cofferdam reinforcement construction method according to claim 2 is characterized in that: In step (5), during grouting, sectional grouting is adopted. The length of each grouting section is called the grouting step distance. The length of the perforated pipe is the length of the grouting step distance. The grouting step distance is selected to be 0.7 - 1 m. After the grouting is completed, a blank cap is covered on the grouting pipe to facilitate re-grouting construction.

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