A construction method for artificial ground freezing reinforcement suspended assembly deep well

Abstract

The present invention relates to a construction method for artificial ground freezing reinforcement suspension assembly deep well, comprising: determining the ground reinforcement range and the construction quantity and position of freezing pipes according to the position and load design requirements of the assembly deep well suspension system; installing freezing pipes and horizontal temperature measuring pipes in combination with drilling construction; installing the assembly deep well suspension system after the frozen soil column reaches the freezing curtain thickness requirement, and then excavating the assembly deep well foundation pit and assembling the prefabricated pipe segments; after the construction of the suspended assembly deep well bottom plate is completed and reaches the design strength, the suspension system is removed, the refrigeration circulation pump station is closed, and the freezing pipe system is removed. Compared with the prior art, the present invention organically combines the artificial ground freezing method with the suspension assembly deep well technology, and uses the frozen reinforcement ground as the temporary load-bearing structure of the suspension assembly deep well, which not only protects the stability of the deep well excavation surface in the soft soil area, but also is not limited by the depth, and the construction environment is green and environmentally friendly, with little impact on the surrounding area.

Description

Technical Field

[0001] The invention relates to the field of underground engineering construction, and in particular to a construction method for an artificial ground freezing reinforcement suspended assembly type deep well. Background Art

[0002] As urban underground space becomes increasingly crowded, underground space construction continues to expand to deeper areas, and urban engineering construction has higher and higher requirements for depth and deformation control. The construction of underground structures in soft soil urban areas is slow and easily causes large deformation of the soil, which in turn causes problems for the project and the surrounding environment. Based on this, the suspended assembled deep well technology that can operate underwater came into being. Especially in soft soil areas, the suspension device and ring beam are devices used to bear the weight of the pipe segments and tunneling equipment during the digging and assembly construction process of this deep well technology, thereby protecting the safety and stability of the excavation surface.

[0003] In order to ensure the stability of the soil under the ring beam and prevent groundwater from surging into the shaft, the existing construction method is to cast bored piles under the ring beam in combination with the construction of high-pressure cement soil rotary jet piles. However, there are the following problems: 1) The construction depth of bored piles is currently limited, and its construction technology is difficult to ensure the quality of piles at deeper depths, which also greatly limits the safety of prefabricated deep well technology. 2) This method will greatly slow down the progress of the overall shaft construction, and its quality problems will increase the deformation of the soil during the construction phase, causing certain engineering hazards. At present, in soft soil areas, the reinforcement and bearing treatment of soft soil under the load-conducting system such as the suspension device and the ring beam has become an important factor that seriously restricts the construction quality and engineering progress of the suspended prefabricated deep well technology. Summary of the invention

[0004] The purpose of the present invention is to provide a construction method for artificial ground freezing reinforcement suspension assembly deep well in order to overcome the defects of the above-mentioned prior art. The artificial freezing reinforcement soil is used as the temporary load-bearing structure of the suspension assembly deep well, which not only improves the strength of the surrounding soil under the ring beam, but also meets the anti-seepage requirements. At the same time, the construction is simple and fast, with little impact on the environment, and there is no limit on the construction depth (the maximum vertical depth of the freezing method can reach nearly 2000 meters at present). The application advantages of the assembly deep well technology in soft soil areas can be fully utilized.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A construction method for artificial ground freezing reinforcement suspended assembly deep well, comprising the following steps:

[0007] S1. Determine the scope of ground reinforcement, i.e. the thickness of the freezing curtain, according to the installation location and load design requirements of the assembled deep well suspension system, and then determine the number and location of the freezing pipes;

[0008] S2, drilling a hole at the determined freezing pipe position, installing the freezing pipe in the drilled freezing hole, and connecting the freezing pipe to the refrigeration circulation pump station;

[0009] S3. Arrange temperature measuring tubes in the formation, set up temperature measuring points, and verify the accuracy of temperature monitoring by the temperature measuring tubes;

[0010] S4, the refrigeration circulation pump station is started, and the ground is actively frozen through the freezing pipe. When the frozen ground reaches the bearing condition, the refrigeration circulation pump station is adjusted to the maintenance freezing mode;

[0011] S5. Pour a concrete cushion layer at the installation location of the assembled deep well suspension system and make a reinforced concrete load-bearing ring beam. Install the assembled deep well segment suspension device on the load-bearing ring beam and connect the starting segment.

[0012] S6. Install the deep well drilling host at the deep well location;

[0013] S7, excavating a deep well and injecting bentonite slurry into the gap between the deep well and the surrounding strata;

[0014] S8, assembling the prefabricated segments and then sinking the prefabricated segments in the deep well;

[0015] S9, repeating steps S7 and S8 until the deep well is excavated to the designed depth;

[0016] S10, dismantle the deep well excavation main engine, replace bentonite and seal the bottom of the deep well;

[0017] S11, dismantle the deep well segment suspension device and shut down the refrigeration circulation pump station;

[0018] S12. Remove the frozen pipes to complete the construction of the deep well.

[0019] Furthermore, each freezing pipe is assembled from a top assembled sleeve-type freezing pipe, a bottom sleeve-type freezing pipe and multiple middle sleeve-type freezing pipes; when the freezing pipe is installed in the freezing hole, the bottom sleeve-type freezing pipe is first installed in the freezing hole, and then the middle sleeve-type freezing pipes are continuously assembled, and finally the top sleeve-type freezing pipe is assembled, and the top assembled sleeve-type freezing pipe is connected to the refrigeration circulation pump station.

[0020] Furthermore, the freezing pipe is of a sleeve type, the inner pipe is a freezing liquid inlet channel, and the outer pipe is a liquid return channel.

[0021] Furthermore, the inner tube and the outer tube are connected stably via a cross buckle frame.

[0022] Furthermore, the temperature measuring tube is arranged horizontally, extending horizontally from the position of the frozen soil column to the outer wall of the assembled pipe segment, and multiple temperature measuring points are built in; a temperature measuring tube is arranged vertically at a certain depth in the stratum.

[0023] Furthermore, the distance at each certain depth is 2.5 to 3.5 meters.

[0024] Furthermore, the length of the freezing pipe is greater than the burial depth of the deep well.

[0025] Furthermore, the freezing pipes are arranged in circles with the suspension device as the center, and the distance between adjacent circles is smaller as it is closer to the deep well.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) The present invention organically combines the artificial freezing method with the suspended assembled deep well temporary bearing structure, which can overcome the characteristics of difficult construction and poor engineering quality due to the large foundation treatment depth.

[0028] 2) The present invention can be quickly frozen and constructed, thus reducing the time required for temporary structure foundation treatment.

[0029] 3) The present invention has the effect of quickly isolating and stopping water, thereby reducing the engineering risks in deep well construction.

[0030] 4) Using artificial freezing to treat the foundation of temporary structures can reduce the impact of deep well excavation on the surrounding soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of the present invention.

[0032] Figure 2a It is a bottom sleeve type freezing pipe.

[0033] Figure 2b It is a middle sleeve type freezing pipe.

[0034] Figure 2c It is a top sleeve type freezing pipe.

[0035] Figure numerals: 1. Assembled deep well suspension device, 2. Freezing pipe, 21. Bottom sleeve type freezing pipe, 22. Middle sleeve type freezing pipe, 23. Top cylinder type freezing pipe, 24. Pipe wall, 25. Cross buckle frame, 26. Thread, 27. Liquid outlet, 28. Liquid inlet, 3. Refrigeration circulation pump station, 31. Refrigeration unit, 32. Circulation unit, 4. Frozen soil column, 5. Suspended assembled shaft pipe segment, 6. Freezing system connecting pipe, 7. Temperature measuring tube, 8. Shaft excavation surface. DETAILED DESCRIPTION

[0036] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0037] like Figure 1 As shown, this embodiment provides a construction method for artificial ground freezing reinforcement suspension assembly deep well, comprising the following steps:

[0038] Step S1, determine the scope of stratum reinforcement, i.e., the thickness of the freezing curtain, according to the installation position of the assembled deep well suspension system 1 and the load design requirements, and then determine the number and position of the freezing pipes to be constructed. The outer circle of the freezing pipes at the deep well position is arranged in layers, and the number of freezing holes arranged in the inner circle should be more than the number of freezing holes arranged in the outer circle. The freezing pipes are arranged in layers with the suspension device as the center, and the closer to the deep well, the smaller the spacing between adjacent circles. Step S2, drill holes at the determined freezing pipe positions, install freezing pipes 2 at the drilled holes, and connect the freezing pipes 2 to the refrigeration circulation pump station 33. The specific process is: use a drilling rig to drill holes, and assemble the sinking sleeve-type freezing pipe 2 in the drilled freezing holes. As Figure 2a to Figure 2c As shown, the freezing pipe 2 is assembled by a top sleeve type freezing pipe 23, a bottom sleeve type freezing pipe 21 and a plurality of middle sleeve type freezing pipes 22. When the freezing pipe 2 is installed in the freezing hole, the bottom sleeve type freezing pipe 21 is first installed in the freezing hole, and then the middle sleeve type freezing pipe 22 is continuously assembled, and finally the top sleeve type freezing pipe 23 is assembled, and the top sleeve type freezing pipe 23 is connected to the refrigeration circulation pump station 33 through the freezing system connecting pipe 6. The pipelines of the top sleeve type freezing pipe 23, the bottom sleeve type freezing pipe 21 and the plurality of middle sleeve type freezing pipes 22 are all 5m long and 89mm in diameter. The top sleeve type freezing pipe 23, the plurality of middle sleeve type freezing pipes 22 and the bottom sleeve type freezing pipe 21 are connected to each other by threads 26. The freezing pipe 2 is a sleeve type, the inner pipe is a freezing liquid inlet channel, and has a liquid inlet 28; the outer pipe is a liquid return channel, and has a liquid outlet 27, to ensure that the temperature of the freezing pipe 2 is uniform; the inner pipe and the outer pipe are connected and stabilized by a cross buckle frame 25. The refrigeration circulation pump station 33 includes a refrigeration unit 31 and a circulation unit 32.

[0039] Step S3, laying out the temperature measuring tube 7 in the stratum, with built-in temperature measuring points, and verifying the accuracy of temperature monitoring at the temperature measuring points. The temperature measuring tube 7 is arranged horizontally, and a temperature measuring tube 7 is set at a certain depth in the stratum vertically; the temperature measuring tube 7 extends horizontally from the position of the frozen soil column 4 to the outer wall of the assembled pipe segment, and at least a plurality of measuring points such as the inner circle of the frozen pipe, the outer circle of the frozen pipe, the edge of the frozen curtain and the outer wall of the pipe segment are set. The distance at each certain depth is generally 2.5 to 3.5 meters, preferably 3 meters.

[0040] Step S4, the refrigeration circulation pump station 33 is started, and the ground is actively frozen through the freezing pipe 2. When the frozen ground reaches the bearing condition, the refrigeration circulation pump station 33 is adjusted to the maintenance freezing mode. Specifically, the freezing pipe 2 is cooled by cold salt water or liquid nitrogen to actively freeze the soil, and the freezing state of the soil is monitored by the temperature measuring tube 7, especially the temperature change of the edge of the freezing curtain and the outer wall of the pipe segment.

[0041] Step S5, deep well structure construction. Observe the temperature of the temperature monitoring point in real time. When the soil temperature at the outer edge of the designed frozen soil column 4 drops below -10°C, the frozen soil column 4 is completely frozen to form a frozen curtain wall. The freezing station is adjusted to the maintenance freezing mode. Pour a concrete cushion layer at the installation position of the assembled deep well suspension system 1 and make a reinforced concrete load-bearing ring beam. Install the assembled deep well segment suspension device 1 on the load-bearing ring beam and connect the starting segment. Through this structure, the load of the segment structure can be transferred from the suspension device 1 and the ring beam to the frozen curtain wall.

[0042] Step S6: installing the deep well drilling host at the deep well location.

[0043] Step S7: excavate a deep well and inject bentonite slurry into the gap between the deep well and the surrounding strata.

[0044] Step S8: Continuously assemble the prefabricated segments while sinking the deep well segments, and inject water into the deep well to keep the water level in the well flush with the groundwater level or slightly higher than the groundwater level. At the same time, the effect of excavation on the stability of the frozen soil column 4 is monitored by the temperature of the outer wall of the segments.

[0045] Step S9, repeat step S7 and step S8 until the deep well is excavated to the designed depth.

[0046] Step S10: Use a suspension device to dismantle the deep well excavation main machine, replace the bentonite and seal the bottom of the deep well.

[0047] Step S11, after the bottom plate construction is completed, the water in the deep well is pumped out, the assembled deep well suspension device 1 is removed, and the refrigeration unit 31 is removed and put into storage. Then the refrigeration station is closed and the freezing pipe 2 is slowly pulled out while disassembling and recycled for next recycling.

[0048] Step S12: Make a connection structure between the deep well and the load-bearing ring beam to complete the construction of the deep well.

[0049] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

[0050] In summary, this embodiment uses artificially frozen reinforced soil as a temporary load-bearing structure for the suspended assembled deep well, which not only improves the strength of the surrounding soil under the ring beam, but also meets the anti-seepage requirements. At the same time, the construction is simple and fast, with little impact on the environment, and there is no limit on the construction depth (the maximum vertical depth of the freezing method can reach nearly 2,000 meters at present). The application advantages of assembled deep well technology in soft soil areas can be fully utilized.

Claims

1. A construction method for artificial ground freezing reinforcement suspension assembly deep well, characterized in that: The steps include: S1. Determine the scope of stratum reinforcement, i.e. the thickness of the freezing curtain, according to the installation position and load design requirements of the assembled deep well suspension system, and then determine the number and location of the freezing pipes; S2, drilling a hole at the determined freezing pipe position, installing the freezing pipe in the drilled freezing hole, and connecting the freezing pipe to the refrigeration circulation pump station; S3. Arrange temperature measuring tubes in the formation, set up temperature measuring points, and verify the accuracy of temperature monitoring by the temperature measuring tubes; S4, the refrigeration circulation pump station is started, and the ground is actively frozen through the freezing pipe. When the frozen ground reaches the bearing condition, the refrigeration circulation pump station is adjusted to the maintenance freezing mode; S5. Pour a concrete cushion layer at the installation location of the assembled deep well suspension system and make a reinforced concrete load-bearing ring beam. Install the assembled deep well segment suspension device on the load-bearing ring beam and connect the starting segment. S6. Install the deep well drilling host at the deep well location; S7, excavating a deep well and injecting bentonite slurry into the gap between the deep well and the surrounding strata; S8, assembling the prefabricated segments and then sinking the prefabricated segments in the deep well; S9, repeating steps S7 and S8 until the deep well is excavated to the designed depth; S10, dismantle the deep well excavation main engine, replace bentonite and seal the bottom of the deep well; S11. Dismantle the assembled deep well segment suspension device and shut down the refrigeration circulation pump station; S12. Remove the frozen pipes to complete the construction of the deep well.

2. The construction method of an artificial ground freezing reinforcement suspension assembly deep well according to claim 1 is characterized in that: Each freezing pipe is assembled from a top sleeve type freezing pipe, a bottom sleeve type freezing pipe and multiple middle sleeve type freezing pipes; when the freezing pipe is installed in the freezing hole, the bottom sleeve type freezing pipe is first installed in the freezing hole, and then the middle sleeve type freezing pipes are continuously assembled, and finally the top sleeve type freezing pipe is assembled, and the top sleeve type freezing pipe is connected to the refrigeration circulation pump station.

3. The construction method of an artificial ground freezing reinforcement suspended assembly deep well according to claim 1 is characterized in that: The freezing pipe is of sleeve type, the inner pipe is a freezing liquid inlet channel, and the outer pipe is a liquid return channel.

4. The construction method of an artificial ground freezing reinforcement suspended assembly deep well according to claim 3 is characterized in that: The inner tube and the outer tube are connected by a cross buckle frame to maintain stability.

5. The construction method of an artificial ground freezing reinforcement suspension assembly deep well according to claim 1 is characterized in that: The temperature measuring tube is arranged horizontally, extending horizontally from the position of the frozen soil column to the outer wall of the assembled pipe segment, and multiple temperature measuring points are built in; a temperature measuring tube is arranged vertically at a certain depth in the stratum.

6. The construction method of an artificial ground freezing reinforcement suspended assembly deep well according to claim 5 is characterized in that: The distance at each certain depth is 2.5 to 3.5 meters.

7. The construction method of an artificial ground freezing reinforcement suspended assembly deep well according to claim 1 is characterized in that: The length of the freezing pipe is greater than the burial depth of the deep well.

8. The construction method of an artificial ground freezing reinforcement suspended assembly deep well according to claim 1, characterized in that: The freezing pipes are arranged in circles with the assembled deep well pipe segment suspension device as the center, and the distance between adjacent circles is smaller as it is closer to the deep well.

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