High-water-level soft soil layer shield launching end stratum reinforcement construction method

Abstract

The technical problem to be solved by the invention is to provide the high-water-level soft soil layer shield originating end stratum reinforcement construction method to make up for the defect of a single reinforcement structure of a shield end so as to improve the reinforcement effect of the high-water-level soft soil layer shield originating end stratum. A stratum around the starting well comprises an upper overburden layer above the starting end, a middle soil layer on the side of the starting end and a lower aquifer below the starting end, and the method for reinforcing the stratum around the starting well comprises the following steps that drilling and grouting are conducted on the upper overburden layer; performing high-pressure jet grouting on the middle soil layer; and water pumping and grouting are conducted on the lower aquifer.

Description

Technical Field

[0001] The invention relates to the field of stratum reinforcement construction at the starting end of a shield machine, and in particular to a stratum reinforcement construction method at the starting end of a shield machine in a high-water-level soft soil stratum. Background Art

[0002] In the existing technology, reinforcement measures such as pile foundation support are required for the starting end of the shield machine. If attention is not paid to strengthening the stratum stabilization measures, stratum settlement, rock stratum rupture around the tunnel entrance, and groundwater eruption will occur during the starting process. Therefore, effective measures are taken to reinforce the stratum at the end to ensure the stability of the stratum when the shield machine starts, and to prevent the face and the tunnel entrance from collapsing.

[0003] Traditional technology often does not consider the high-water soft soil layer and the temperature monitoring of the side wall of the starting end. The high-water soft soil layer will cause ground settlement and ground water gushing during the shield starting process. In severe cases, the ground will collapse, causing serious economic losses and threatening the safety of shield construction. The construction project of the soft soil layer requires a lot of support to prevent the soft soil layer from various collapses and settlements due to its own insufficient strength. During the shield starting, the temperature of the side wall of the end rises too quickly, which will damage the rocks on both sides and cause splitting, which will then damage the rock strata and affect the construction progress. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for reinforcing the stratum at the starting end of a shield machine in high water level soft soil strata to make up for the deficiency of a single reinforcement structure at the end of the shield machine so as to improve the stratum reinforcement effect at the starting end of a shield machine in high water level soft soil strata.

[0005] A method for reinforcing the ground at the starting end of a shield tunnel in a high-water-level soft soil layer, wherein the ground around the starting well includes an overlying soil layer above the starting end, an intermediate soil layer on the side of the starting end, and a lower aquifer below the starting end. The ground around the starting well is reinforced, comprising the following steps: S1, drilling and grouting the overlying soil layer; S2, high pressure rotary jet grouting is performed on the middle soil layer; S3. Pump water and inject grout into the lower aquifer.

[0006] Furthermore, in step S1, the slurry for drilling grouting is selected to use 60-80% of local soft soil and the remaining content of cementitious materials, and the water-cement ratio is between 0.25-0.35.

[0007] Furthermore, in step S1, multiple rows of grouting holes are arranged from top to bottom in the overlying soil layer, and the grouting holes in each row are distributed at intervals. The grouting holes in the middle rows are inclined at a slope of 5-6% downwardly, and the grouting holes in the bottom rows are inclined at a slope of 8-9% downwardly.

[0008] Furthermore, in step S3, 40-60% of groundwater is extracted from the lower aquifer by a pump, and 50-80% of local soft soil and gravel and the remaining content of cementitious materials are used to prepare slurry with a water-cement ratio of 0.15-0.25.

[0009] Furthermore, a U-shaped channel is processed on the side wall of the end, and pipes are laid in the channel to form a U-shaped water pipe. A pool is built on the outside of the side wall of the end. The water in the pool is transported to the water inlet of the water pipe by a water pump. The water outlet of the water pipe is connected to the pool. Temperature monitors are installed in the middle and outlet of the water pipe. When the temperature of the side wall of the end rises, water is passed through the water pipe by the water pump to cool it down.

[0010] Further, in step S1, the grouting range of the upper overburden layer is 10-15m outward from the end as the starting point; The lower grouting range of the overlying soil layer is 3-5m outward from the end as the starting point.

[0011] Further, in step S2, the grouting range of the upper part of the middle soil layer is 15-20m outward from the end as the starting point; The lower grouting range of the middle soil layer is 3-5m outward from the end as the starting point.

[0012] Furthermore, the spacing between the rows of grouting holes at the upper portion is 900-1100 mm, and the spacing between the rows of grouting holes at the bottom is 1100-1300 mm.

[0013] Furthermore, a bored pile machine, grouting materials, a water tank, a stirrer, a grouting pump, a mixer, an air compressor, a high-pressure pump, a grout stopper, a water pump, a water pipe, and a temperature monitor are prepared at the construction site.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. Drill and grout the overlying soil layer, perform high-pressure rotary jet grouting on the middle soil layer, pump and grout the lower aquifer, and reinforce the strata around the starting well, so as to improve the stratum reinforcement effect of the shield starting end in the high-water-level soft soil stratum, thereby making up for the deficiency of the single reinforcement structure of the shield end in the high-water-level soft soil stratum; 2. The slurry for drilling grouting is selected from 60-80% of local soft soil and the remaining content of cementitious materials. It has strong fluidity and diffusivity. The high water-cement ratio ensures that the slurry can penetrate into the cracks of rocks and strata. The cementitious materials ensure that the slurry is solidified in a short time and reaches a high strength in a short time. It can also fill the internal depressions formed by soft soil at high water content and increase the strength of the overlying soil layer. It uses local materials, saves costs, saves time and effort, has good reinforcement effects, and has guaranteed quality. 3. Use a pump to extract 40-60% of groundwater from the lower aquifer, and use 50-80% of local soft soil and gravel and the remaining cementitious materials to make slurry with a water-cement ratio of 0.15-0.25. The low water-cement ratio ensures that the soft soil can solidify quickly and the gravel improves the strength. Because it needs to be mixed with the remaining groundwater, it does not require too high fluidity; 4. Place temperature monitors in the middle of the water pipe and at the outlet to measure the temperature of the end side wall. When the temperature of the side wall is too high, cold water can be used to automatically cool it down to protect the side wall from internal splitting due to excessive temperature. The circulated water can be recycled after external cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the construction of the stratum reinforcement at the starting end of the shield tunneling in the high water level soft soil stratum according to the present invention; Figure 2 This is a schematic diagram of the internal reaction of grouting in the lower aquifer; Figure 3 This is a schematic diagram of the installation of the temperature monitor of the present invention; In the figure: 1. overlying soil layer, 2. middle soil layer, 3. lower aquifer, 4. water pool, 5. water pump, 6. grouting drilling hole, 7. high-pressure jet jet pile, 8. water pipe, 9. temperature monitor. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0017] In the description of the invention, it should be understood that the terms "front", "rear", "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on directions or positional relationships shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the invention. The invention is further described below in conjunction with the drawings and embodiments.

[0018] like Figure 1As shown, this embodiment discloses a method for reinforcing the ground at the starting end of a shield tunnel in a high-water soft soil layer. The ground around the starting well includes an overburden layer 1 above the starting end, an intermediate soil layer 2 on the side of the starting end, and a lower aquifer 3 below the starting end. Before reinforcing the ground around the starting well, prepare equipment such as a bored pile driver, grouting materials, a water tank 4, a mixer, a grouting pump, a mixer, an air compressor, a high-pressure pump, a grouting plug, a water pump 5, a water pipe 8, and a temperature monitor 9. Then, reinforcing the ground around the starting well includes the following steps: S1, drilling and grouting the overlying soil layer; First, determine the grouting range. The upper grouting range of the overburden layer 1 is 10-15m from the end point, and the lower grouting range of the overburden layer 1 is 3-5m from the end point. This is because the softer the soil is, the more extensive the grouting reinforcement is needed.

[0019] During grouting, it is necessary to drive in grouting boreholes 6. Multiple rows of grouting boreholes 6 are arranged from top to bottom in the overlying soil layer 1. The grouting boreholes 6 in each row are distributed at intervals. The grouting boreholes in the middle rows are inclined at a slope of 5-6% toward the lower end, and the grouting boreholes in the bottom rows are inclined at a slope of 8-9% toward the lower end. This design is because as the soil layer goes down, the harder it is, the harder it is to drive in vertically, and a certain inclination angle is required. The spacing between the rows of grouting boreholes at the top is 900-1100mm, the spacing between the rows of grouting boreholes at the bottom is 1100-1300mm, and the spacing between adjacent rows is 600-900mm, so as to ensure a sufficient grouting effect.

[0020] If the strength of the overburden soil layer 1 is very poor or the thickness is very large, grouting can be carried out on the stratum according to the situation of the overburden soil layer 1. The grouting material is selected to use 60-80% of the local soft soil and the remaining content of cementitious materials, and the water-cement ratio is between 0.25-0.35. It has strong fluidity and diffusivity. The higher water-cement ratio ensures that the grouting can penetrate into the cracks of the rock and stratum. The cementitious material ensures that the solidification is completed in a short time and reaches a high strength in a short time. It can also fill the internal depression formed by the soft soil at a high water content, thereby increasing the strength of the overburden soil layer 1. S2, high pressure rotary jet grouting is performed on the middle soil layer; First, determine the grouting range. The grouting range for the upper part of the middle soil layer 2 is 15-20m outward from the end head as the starting point; the grouting range for the lower part of the middle soil layer 2 is 3-5m outward from the end head as the starting point.

[0021] Before drilling, the air compressor and grouting pump should be debugged to ensure that the equipment operates normally; the length of the drill rod should be checked, and the depth line should be marked with red paint next to the drilling tower to ensure that the bottom elevation of the hole meets the designed depth; the drilling rig construction should first be tested on the ground, and after the drilling machine operates normally, the hole should be started. During the drilling process, the number of drill rod sections should be recorded in detail to ensure the accuracy of the drilling depth; First, construct two rows of closed area edge walls consisting of high-pressure rotary jet piles 7. The closed area edge wall reinforcement depth reaches the bottom of the middle soil layer 2. The closed area edge wall will form a closed space in the vertical reinforcement area. After each high-pressure rotary jet pile of the closed area edge wall reaches a certain strength, the construction of each high-pressure rotary jet pile in the closed area edge wall will be carried out. The rotation and lifting of the drill rod should be carried out continuously without interruption. If a drilling rig fails, the drilling rod lifting and rotation should be stopped to prevent pile breakage, and the fault should be repaired and eliminated immediately. To improve the quality of the bottom end of the pile, the drill rod grouting rotary jetting time within the range of 1.0 at the bottom of the pile is 30-60 seconds. During the rotary jet lifting process, the rotary jetting parameters can be adjusted according to different soil layers to complete the construction of each high-pressure rotary jet pile in the vertical reinforcement area of ​​the high-pressure rotary jet pile; S3, pumping and grouting the lower aquifer; According to the geophysical prospecting report, the location and volume of the underlying aquifer are detected, and 40-60% of the groundwater is extracted by a pump 5 to ensure that there will be no ground subsidence due to the extraction of excessive groundwater, and to ensure that the extraction of too little groundwater will affect the grouting effect. 50-80% of the local soft soil and gravel and the remaining content of cementitious materials are used, and the water-cement ratio is between 0.15-0.25. The low water-cement ratio ensures that the soft soil can be quickly solidified, and the gravel improves the strength. It does not require too high fluidity because it needs to be mixed with the remaining groundwater.

[0022] like Figure 2 As shown, when grouting is performed in the underground aquifer 3, because the density of the mixed slurry is greater than that of water, the groundwater will escape upward, and the high-density stones will move downward, making the lower part of the aquifer more solid. The slurry of soft soil and cementitious materials will solidify in the middle. Because the aquifer loses too much water, water will flow into the aquifer from both sides. A part of the slurry will absorb too much water, and its fluidity and diffusivity will become stronger, so it will move to the cracks on both sides. The water squeezed in the upper part of the aquifer will also be slowly absorbed and solidified by the slurry in the middle, which plays a role in strengthening the stratum.

[0023] S4, monitoring the cooling of the end side wall; like Figure 3As shown, a plurality of U-shaped channels are processed on the side wall of the end, and a plastic pipe is arranged in each channel to form a U-shaped water pipe 8. A pool 4 is built on the outside of the side wall of the end. The water in the pool 4 is transported to the water inlet of the water pipe 8 by a pump 5. The water outlet of the water pipe 8 is connected to the pool 4. A temperature monitor 9 is installed in the middle and outlet of the water pipe 8. When the temperature of the side wall of the end rises, the water is cooled by water in the water pipe 8 through the pump 5. When the temperature of the side wall is too high, cold water can be used to cool it down to protect the side wall from internal splitting due to excessive temperature. The circulated water can be recycled after external cooling. Fast water flow can take away more temperature. The water circulation can be stopped only after the temperature reaches the specified temperature, and the inlet and outlet are blocked with a wooden plug to prevent blockage. The temperature monitor 9 is connected to the external pump 5. When the temperature inside the wall reaches a certain value, the pump 5 will be automatically turned on to cool it down. After the temperature drops to a certain temperature, the pump 5 will be automatically stopped.

Claims

1. A method for reinforcing the ground at the starting end of a shield tunnel in a high-water soft soil layer, characterized in that: The strata around the starting well include the overlying soil layer above the starting end, the middle soil layer on the side of the starting end, and the lower aquifer below the starting end. The strata around the starting well are reinforced, including the following steps: S1, drilling and grouting the overlying soil layer; S2, high pressure rotary jet grouting is performed on the middle soil layer; S3. Pump water and inject grout into the lower aquifer.

2. The method for reinforcing the ground at the starting end of a shield tunnel at a high water level soft soil layer according to claim 1 is characterized in that: In step S1, the slurry for drilling grouting is selected to use 60-80% of local soft soil and the remaining content of cementitious materials, and the water-cement ratio is between 0.25-0.

35.

3. The method for reinforcing the ground at the starting end of a shield tunnel at a high water level soft soil layer according to claim 2 is characterized in that: In step S1, multiple rows of grouting holes are arranged from top to bottom in the overlying soil layer, and the grouting holes in each row are distributed at intervals. The grouting holes in the middle rows are inclined at a slope of 5-6% downward, and the grouting holes in the bottom rows are inclined at a slope of 8-9% downward.

4. The method for reinforcing the ground at the starting end of a shield tunnel at a high water level soft soil layer according to claim 1, characterized in that: In step S3, 40-60% of groundwater is extracted from the lower aquifer by a pump, and 50-80% of local soft soil and gravel and the remaining cementitious material are used to prepare slurry with a water-cement ratio of 0.15-0.

25.

5. The method for reinforcing the ground at the starting end of a shield tunnel at a high water level soft soil layer according to claim 1, characterized in that: A U-shaped channel is processed on the side wall of the end, and pipes are laid in the channel to form a U-shaped water pipe. A pool is built on the outside of the side wall of the end. The water in the pool is transported to the water inlet of the water pipe by a water pump. The water outlet of the water pipe is connected to the pool. Temperature monitors are installed in the middle and outlet of the water pipe. When the temperature of the side wall of the end rises, water is passed through the water pipe through the water pump to cool it down.

6. The method for reinforcing the ground at the starting end of a shield tunnel at a high water level soft soil layer according to claim 1, characterized in that: In step S1, the grouting range of the upper overburden layer is 10-15m outward from the end as the starting point; The lower grouting range of the overlying soil layer is 3-5m outward from the end as the starting point.

7. The method for reinforcing the ground at the starting end of a shield tunnel at a high water level soft soil layer according to claim 1, characterized in that: In step S2, the grouting range of the upper part of the middle soil layer is 15-20m outward from the end as the starting point; The lower grouting range of the middle soil layer is 3-5m outward from the end as the starting point.

8. The method for reinforcing the ground at the starting end of a shield tunnel at a high water level soft soil layer according to claim 3, characterized in that: The spacing between the rows of grouting holes at the top is 900-1100mm, and the spacing between the rows of grouting holes at the bottom is 1100-1300mm.

9. The method for reinforcing the ground at the starting end of a shield tunnel at a high water level soft soil layer according to any one of claims 1 to 8, characterized in that: Prepare the pile boring machine, grouting materials, water tank, agitator, grouting pump, mixer, air compressor, high-pressure pump, grouting plug, water pump, water pipe and temperature monitor at the construction site.

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