Construction technology of long-distance and large-gradient open pipe jacking encountering groundwater

Abstract

The application discloses a construction process for long-distance and large-gradient open pipe jacking encountering underground water, and the process comprises the following steps: determining the well position of a working well and a receiving well; performing reinforced concrete wall reverse construction on the working well and the receiving well; jacking the pipe of the pipe jacking construction from the working well to the receiving well, stopping jacking before encountering underground water, and grouting and reinforcing; leading and draining the underground water, excavating a pipe supporting pit downward from the pipe bottom of the jacking end of the pipe, drilling a hole in the receiving well along the design axis elevation which is lower than the working well and the receiving well, connecting the receiving well and the pipe supporting pit, and dragging a permeation pipe from the pipe supporting pit to the receiving well; after leading and draining the underground water, backfilling the pipe supporting pit to the design pipe elevation, and continuing jacking the pipe. The application can realize leading and draining the underground water, and solves the problems that the equipment for drilling a dewatering well cannot enter the site and the natural environment of a river is damaged.

Description

Technical Field

[0001] This invention relates to the field of construction technology for diverting and draining groundwater in pipe jacking, and particularly to the construction technology for diverting and draining groundwater in long-distance, steep-slope open pipe jacking. Background Technology

[0002] Open-type pipe jacking is a pipeline construction technique that involves excavating earthwork manually with the aid of auxiliary equipment, and jacking the pipe simultaneously. During the earthwork excavation and pipe jacking process, the groundwater level must be lowered to at least 50cm below the bottom of the working shaft and the bottom of the pipe before normal jacking can proceed. Therefore, ensuring that there is no groundwater within 50cm below the bottom of the pipe and the working shaft is a crucial measure to guarantee the safety and quality of pipeline jacking in open-type pipe jacking.

[0003] The geological conditions of this project section are as follows: groundwater is encountered 1.5m below the ground surface, the permeability coefficient of silty clay is 4-6m / d, and groundwater will be encountered when the pipe jacking reaches 112.5m. Therefore, it is necessary to pump out the groundwater in the pipe jacking.

[0004] If mechanical pipe jacking is used, when pumping groundwater, the elevation of the working well and the receiving well is first adjusted to keep them in the same position before jacking. Then the working well needs to be lowered by 34m to a depth of 50.119m. The foundation pit needs to be constructed with cast-in-place piles and dewatering wells. However, the following problems exist: (1) Cast-in-place piles and dewatering wells are expensive and have a long construction period, which cannot meet the construction period requirements; (2) Cable installation and maintenance are difficult, and it is difficult to go up and down the foundation pit, which cannot meet the relevant power specifications.

[0005] If a steep, open-face pipe jacking system with ground-level dewatering wells is used, the following problems exist: (1) the area from the receiving well to the receiving well plus 60m is on the slope of the plateau, and the dewatering well equipment cannot reach this area; (2) river management requirements do not allow excavation of the plateau slope, which would damage the ecological environment. Therefore, this invention proposes a construction process for long-distance, steep, open-face pipe jacking to divert and drain groundwater. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems existing in the prior art and provide a construction process for diverting and draining groundwater in long-distance, steep-slope open-type pipe jacking. By adopting the groundwater diversion and drainage method of this invention, the problem of not being able to enter the site for dewatering well equipment and the problem of damaging the natural environment of the river channel are solved.

[0007] The technical solution of this invention is: a construction process for diverting and draining groundwater in long-distance, steep-slope open-type pipe jacking, comprising the following steps:

[0008] S1. Determine the locations of the working well and the receiving well;

[0009] S2. Construct the working well and receiving well using the reverse construction method with reinforced concrete retaining wall;

[0010] S3, the pipe of the pipe jacking construction is jacked from the working well to the receiving well, stops jacking before underground water is encountered, and grouting is reinforced;

[0011] S4, underground water is introduced and drained

[0012] At the pipe jacking end, a pipe supporting pit is excavated downwards, and a borehole is drilled in the receiving well along an elevation lower than the design axis elevations of the working well and the receiving well, the receiving well and the pipe supporting pit are connected, and the permeation pipe is pulled into the receiving well from the pipe supporting pit;

[0013] S5, after the underground water is introduced and drained, the pipe supporting pit is backfilled to the design pipe elevation, and the pipe jacking is continued.

[0014] Preferably, in the step S3, small pipe grouting is used for reinforcement within a range of less than 5m in front of the pipe.

[0015] Preferably, in the step S4, the permeation pipe is a PE permeation pipe.

[0016] Preferably, in the step S2, the working well and the receiving well are constructed by the top-down method, each section is not greater than 2m, the construction is carried out in sections to the design well bottom, the guide rail, the back wall and the pipe jacking equipment are installed, the working well and the equipment are accepted, and the top is opened after the working well and the equipment are qualified.

[0017] Preferably, in the step S1, according to the measurement control network, after the well position is laid out, the underground pipeline and the underground structure in the construction range are technically investigated, the underground structure trend and the buried depth are found out, if there are underground pipelines, the underground pipelines are coordinated and relocated, and it is ensured that there are no underground pipelines and structures in the working well and the receiving well.

[0018] Preferably, in the step S5, the pipe jacking is ended, and the permeation pipe is blocked.

[0019] Preferably, in the step S3, the pipe is a D2000mm reinforced concrete pipe.

[0020] Preferably, in the step S4, the borehole position is lower than the design axis elevation by 0.75m, a water collecting pit is excavated in the receiving well, and the water in the water collecting pit is pumped out in time.

[0021] Preferably, in the step S4, the permeation pipe needs to be welded in advance.

[0022] Preferably, in the step S5, the pipe supporting pit is backfilled with concrete.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. The present application solves the problem that the dewatering well equipment cannot enter the site and the construction site must be dewatered, the effect of water introduction and drainage is obvious, the problem of damage to the natural environment of the river is solved, the construction period is ensured, and the engineering cost is reduced.

[0025] 2、The open large slope pipe jacking of the present application ensures that the underground water is 0.5m below the bottom surface of the pipe after jacking into the underground water layer, ensures that there is no water in the pipe during excavation, normal excavation and transportation of earthwork, safety of operating personnel and engineering quality.

[0026] 3、The large slope pipe jacking construction process of the present application solves the problems of large terrain difference and deep working well, is relatively economical and safe, and greatly improves the efficiency of working well construction.

[0027] 4、The process of the present application is simple, environmentally friendly, saves a large amount of labor, materials and economy. BRIEF DESCRIPTION OF DRAWINGS

[0028] Fig. 1 is a schematic diagram of the construction process of pipe jacking of the present application;

[0029] Fig. 2 is a schematic diagram of the completed construction process of pipe jacking of the present application;

[0030] Fig. 3 is an enlarged view of the position of the pipe and the permeation pipe of the present application.

[0031] REFERENCE NUMERALS

[0032] 1. Working well 1, 2. Receiving well 2, 3. Pipe 3, 4. Pipe supporting pit 4, 5. Permeation pipe 5, 6. Water collecting pit 6. DETAILED DESCRIPTION

[0033] One specific embodiment of the present application will be described in detail below with reference to the accompanying drawings, but it should be understood that the scope of protection of the present application is not limited by the specific embodiment.

[0034] EMBODIMENT

[0035] Referring to Figs. 1-3 , the embodiment of the present application provides a long-distance large-slope open pipe jacking construction process for encountering underground water, which comprises the following steps:

[0036] S1, determining the well position of the working well 1 and the receiving well 2;

[0037] S2, constructing the working well 1 and the receiving well 2 by steel reinforced concrete wall reverse construction method;

[0038] S3, the pipe 3 of pipe jacking construction is jacked from the working well 1 to the receiving well 2 by 105m, stops jacking before encountering underground water, and grouting and reinforcing to ensure the stability of the soil;

[0039] S4, after the groundwater is drained, a pipe receiving pit 4 with a length of 2.5 m, a width of 0.5 m and a depth of 1 m is excavated at the bottom of the top end of the pipe 3, a directional drilling machine is installed in the well 2, the drill rod is advanced along the design axis elevation direction of the working well 1 and the receiving well 2 and is lower than the design elevation by 0.75 m, the drill rod enters the pipe receiving pit 4 and a reamer is installed to ream the hole, the infiltration pipe 5 is pulled to the receiving well 2 and a water collecting pit 6 is excavated in the receiving well 2, and a water pump is used to timely pump and drain the water in the water collecting pit 6;

[0040] S5, after the groundwater is drained, the pipe receiving pit 4 is backfilled to the design pipe course elevation, and the pipe 3 is continued to be jacked.

[0041] Further, in the step S3, a small pipe is used for grouting reinforcement within a range of less than 5 m in front of the pipe 3.

[0042] Further, in the step S4, the infiltration pipe 5 is a PE infiltration pipe.

[0043] Further, in the step S2, the working well 1 and the receiving well 2 are constructed by the top-down method, each section is not greater than 2 m, the construction is carried out in sections to the design well bottom, a guide rail, a back wall and pipe jacking equipment are installed, and the working well and the equipment are accepted after being qualified.

[0044] Further, in the step S1, after the well site is located according to the measurement control network, technical investigation is carried out on underground pipelines and structures in the construction range, the trend and buried depth of underground structures are found out, if there are underground pipelines, coordination and improvement are carried out, and it is ensured that there are no underground pipelines and structures in the working well 1 and the receiving well 2.

[0045] Further, in the step S5, after the pipe 3 is jacked, the infiltration pipe 5 is blocked.

[0046] Further, in the step S3, the pipe is a D2000 mm reinforced concrete pipe.

[0047] Further, in the step S4, the infiltration pipe 5 needs to be welded in advance.

[0048] Further, in the step S5, the pipe receiving pit 4 is backfilled with concrete.

[0049] Embodiment

[0050] A 330KV power pipeline project passes through a river and then goes up a hill along Chang'an Avenue, with a total length of 3380 m, a pipe diameter of D2000 mm, and an up-hill pipeline length of 170 m. The ground elevation of the working well 1 on the hill is 481.116, the pipeline buried depth is 16.119 m, the ground elevation of the receiving well 2 below the hill is 443.920, the pipeline buried depth is 12.904 m, and the pipeline slope is 20%. The geological conditions of this section of the project are that underground water is found 1.5 m below the ground of the working well 1, the permeability coefficient of silty clay is 4-6 m / d, and the working well is jacked by 112.5 m to the receiving well 2 and encounters underground water.

[0051] Selection of pipe jacking process is needed when pipe jacking

[0052] (1) The following difficulties exist in the pipe jacking process from top to bottom: large slope, 5m long machine head, 32 tons of pipe jacking machine, 1m higher tail than head of pipe jacking machine, risk of head deviation during jacking, possibility of machine head getting lower and lower, and unguaranteed pipe jacking quality.

[0053] (2) The following difficulties exist in the pipe jacking process from bottom to top: ① large slope, 5m long machine head, 32 tons of pipe jacking machine, 1m lower tail than head of pipe jacking machine, increasing resistance with the increase of jacking length, huge pressure on pipe, and risk of deformation of back wall and working well. ② If grouting is used to reduce resistance, the cylinder of the pipe jacking jack is retracted, and the jacked pipe has the hidden danger of sliding down, which cannot guarantee safety.

[0054] (3) The following difficulties exist in the pipe jacking process of reducing the pipe elevation of working well 1 to the pipe elevation of receiving well 2: receiving well 2 needs to be lowered by 34m, the depth reaches 50.119m, the foundation pit needs to be constructed by cast-in-place pile and dewatering well, the cast-in-place pile and dewatering well have high cost and long construction period, cannot meet the construction period requirement, the discharge cable and cable operation and maintenance are difficult, and the up and down of the foundation pit is difficult, which cannot meet the specification requirement.

[0055] (4) The following difficulties exist in the open pipe jacking with large slope and the ground with dewatering well: the dewatering well equipment cannot enter the range from receiving well 2 to receiving well 2 plus 60m on the slope of the terrace, and the river management department does not allow excavation and damage to the slope of the terrace.

[0056] The construction process of open pipe jacking with large slope and drainage pumping after jacking the pipe into the groundwater layer solves the problems of the dewatering well equipment cannot enter the site and damage to the natural environment of the river, guarantees the construction period, and reduces the engineering cost. The drainage pumping after jacking the pipe into the groundwater layer ensures that the groundwater is 0.5m below the bottom of the pipe 3, guarantees that there is no water in the pipe 3 during excavation, and the soil is normally excavated and transported, the safety of the operating personnel and the engineering quality.

[0057] Before construction, according to the measurement control network, the well position is put out, the underground pipeline and structure in the construction range are technically briefed, the trend and buried depth of underground structures are found out. If there are underground pipelines, special personnel are arranged to move and improve the pipelines with the pipeline property unit to ensure that there are no underground pipelines and structures in working well 1 and receiving well 2, and then the working well 1 and receiving well 2 are constructed by the reinforced concrete reverse construction method. The reverse construction method is constructed in sections not more than 2m per section, and the construction is divided into sections to the designed well bottom, the guide rail, back wall and pipe jacking equipment are installed. After the working well and equipment are accepted and qualified, the pipe jacking is started.

[0058] The vertical height of the bottom wall of the working well 1 from the top of the terrace is 16.1 m, the vertical height of the bottom wall of the receiving well 2 from the top of the terrace is 48.9 m, and the bottom wall of the receiving well 2 is located at the underground level of 12.9 m.

[0059] The pipeline is jacked and the groundwater is drained, the pipeline is jacked 105 m from the working well 1 to the receiving well 2, the jacking is stopped before the groundwater is encountered, the soil is stabilized by grouting through a small pipe within a range of 5 m in front of the pipeline 3, then a pipe supporting pit 4 with a length of 2.5 m, a width of 0.5 m and a depth of 1 m is artificially excavated below the bottom of the pipeline 3 at the jacking end of the pipeline 3, a directional drilling machine is installed on the south side of the receiving well 2, the drill rod of the directional drilling machine enters from the hole on the south side of the receiving well 2, the drill rod is guided to advance along the design axis elevation direction of the receiving well 2 and the working well 1 and below the design elevation by 0.75 m, after the drill rod enters the pipe supporting pit 4 with a length of 2.5 m, a width of 0.5 m and a depth of 1 m which is excavated, a reamer is installed on the drill rod to ream, then a PE permeation pipe 5 is pulled to the receiving well 2, a water pump is installed in the water collecting pit excavated in the receiving well 2 to drain, which ensures that the groundwater is below the bottom surface of the pipeline 3 by 0.5 m, ensures that there is no water in the pipeline 3 during excavation, the soil is normally excavated and transported, the safety of the operating personnel and the engineering quality, when the pipe jacking continues, the pipe supporting pit with a length of 2.5 m, a width of 0.5 m and a depth of 1 m is artificially backfilled with concrete to the design pipe bottom elevation, then the small pipe grouting reinforcement is damaged, the pipe jacking continues, and the permeation pipe 5 is blocked when the pipeline 3 jacking is completed.

[0060] The above only discloses several specific embodiments of the present application, but the embodiments of the present application are not limited to this, any changes that can be thought of by those skilled in the art should fall within the protection scope of the present application.

Claims

1. A construction process for long-distance and large-gradient open pipe jacking encountering groundwater, characterized in that, The method comprises the following steps: S1, determining the well positions of the working well (1) and the receiving well (2); S2, constructing the working well (1) and the receiving well (2) by the reinforced concrete wall reverse construction method; S3, the pipe (3) of the pipe jacking construction is jacked from the working well (1) to the receiving well (2), and the jacking is stopped before underground water is encountered, and grouting reinforcement is performed, and small guide pipe grouting reinforcement is adopted within a range of less than 5 m in front of the pipe (3); S4, guiding and draining underground water A pipe supporting pit (4) is excavated downward at the pipe jacking end of the pipe (3), and a borehole is drilled in the receiving well (2) along an elevation lower than the design axis of the working well (1) and the receiving well (2), the receiving well (2) and the pipe supporting pit (4) are connected, the permeation pipe (5) is pulled into the receiving well (2) from the pipe supporting pit (4), the borehole position is 0.75 m lower than the design axis elevation, and a water collecting pit (6) is excavated in the receiving well (2), and water in the water collecting pit (6) is pumped out in time; S5, after the underground water is guided and drained, the pipe supporting pit (4) is backfilled to the design pipe elevation, and the pipe (3) jacking is continued.

2. The long-distance and large-gradient open pipe jacking construction process in the presence of groundwater according to claim 1, characterized in that, In the step S4, the permeation pipe (5) is a PE permeation pipe.

3. The long-distance and large-gradient open pipe jacking construction process in the presence of groundwater according to claim 1, characterized in that, In the step S2, the working well (1) and the receiving well (2) are constructed by the reverse construction method, each section is not greater than 2 m, the construction is performed in sections to the design well bottom, guide rails, back walls and pipe jacking equipment are installed, the working well is accepted, and the equipment is qualified, and then the pipe jacking is started.

4. The long-distance and large-gradient open pipe jacking construction process in the presence of groundwater according to claim 1, characterized in that, In the step S1, after the well positions are laid out according to the measurement control network, technical investigation is performed on underground pipelines and structures in the construction range, the trends and depths of underground structures are found out, if there are underground pipelines, the pipelines are coordinated and relocated, and it is ensured that there are no underground pipelines and structures in the working well (1) and the receiving well (2).

5. The long-distance and large-gradient open pipe jacking construction process in the presence of groundwater according to claim 1, characterized in that, In the step S5, the pipe (3) jacking is ended, and the permeation pipe (5) is blocked.

6. The long-distance and large-gradient open pipe jacking construction process in the presence of groundwater according to claim 1, characterized in that, The pipe in the step S3 is a D2000 mm reinforced concrete pipe.

7. The long-distance and large-gradient open pipe jacking construction process in the presence of groundwater according to claim 1, characterized in that, In the step S4, the permeation pipe (5) needs to be welded in advance.

8. The long-distance and large-gradient open pipe jacking construction process in the presence of groundwater according to claim 1, characterized in that, In the step S5, the pipe supporting pit (4) is backfilled with concrete.

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