Method for removing existing open-cut tunnel latticed column pile foundation in soft soil area under operation

Abstract

The application discloses a method for removing existing open-cut tunnel latticed column pile foundation in soft soil area under operation state; a transverse pipe is arranged above the latticed column pile which needs to be removed; an operation platform is arranged at the position of the latticed column pile corresponding to the transverse pipe, and a row frame structure is arranged on the operation platform; then a pipe structure formed by multiple sleeves is arranged outside the latticed column pile through a drilling machine; then the latticed column pile is lifted out through the row frame structure, cut in sections and transported out; finally, the sleeves are recycled section by section, C10 concrete is poured in the hole formed by removing the latticed column pile, and the bottom of the transverse pipe is repaired. The application can remove the pile foundation on demand without affecting the normal operation of the tunnel and without causing great disturbance to the structure.

Description

Technical Field

[0001] This invention relates to the field of column and pile foundation removal technology, and in particular to a method for removing existing open-cut tunnel grid column and pile foundations in soft soil areas under operational conditions. Background Technology

[0002] Currently, with the development of urban underground space, cases of mutual influence between different projects are common, often requiring the removal of existing pile foundations. Literature review reveals numerous cases of pile foundation removal under buildings, bridges, revetments, and other structures. However, cases of removing pile foundations under the foundation slab of underground structures are relatively rare, especially the partial removal of pile foundations in tunnels under operational conditions.

[0003] When lattice piles are not used as engineering piles, they are typically designed as temporary components for foundation pit support. Theoretically, removing lattice piles should not have a long-term impact on the existing tunnel structure should there be any inter-project interference. However, the removal process usually requires breaking up a section of the floor slab, and the vibration of the pile extraction equipment can also affect the tunnel structure, causing uneven settlement and cracks. Furthermore, if there are any issues with the quality of the floor slab repair, it could lead to leakage.

[0004] There are four main methods for removing pile foundations: the first method is to lift the pile directly and cut it in sections; the second method is to use a high-pressure water jet to eliminate the side friction between the pile and the soil and rock, and then pull it out directly; the third method is to use a full-rotation drilling rig to impact the pile with a sleeve until it breaks and then grab the broken pieces; the fourth method is to use a special device to follow up to the bottom of the pile, hold the pile tightly, and then lift and remove it.

[0005] Therefore, the following shortcomings exist in practical applications:

[0006] 1. There are no reported cases of removing pile foundations while the tunnel remains operational, nor is there any such method.

[0007] 2. Direct extraction is typically carried out within the confined space of a tunnel. The high skin friction of the piles makes extraction prone to breakage. This method requires large equipment, impacting normal tunnel operation. Furthermore, it necessitates partial breaching of the tunnel floor, significantly affecting the tunnel structure and waterproofing.

[0008] 3. When removing equipment from the ground, a double-sleeve method is usually used. Although this allows most of the equipment to be placed on the ground, it still inevitably affects the normal operation of the tunnel. This method still requires partial removal of the floor slab, which also has a significant impact on the tunnel structure and waterproofing.

[0009] 4. When using high-pressure water jets for assisted removal, the soil at the bottom of the tunnel will be directly disturbed. In soft soil conditions, the impact will be more extensive and last for a longer period, which can easily cause uneven settlement of the bottom slab.

[0010] 5. Using a full-rotation drilling rig to impact the pile body with a casing until it breaks and removes the debris, the impact drilling operation causes significant disturbance to the tunnel structure and must be carried out under conditions of interruption of tunnel operation. The casing clearing is not a complete removal, and in soft soil conditions, it is easy for the pile foundation to be washed into deeper layers and cannot be completely removed. Moreover, this method is also prone to leaving residual steel bars.

[0011] Therefore, how to remove pile foundations as needed without affecting the normal operation of the tunnel and without causing significant disturbance to the structure has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0012] In view of the above-mentioned deficiencies of the prior art, the present invention provides a method for removing the grid column foundation of existing open-cut tunnels in soft soil areas under operational conditions. The purpose is to remove the pile foundation as needed without affecting the normal operation of the tunnel and without causing significant disturbance to the structure.

[0013] To achieve the above objectives, this invention discloses a method for removing lattice column foundations of existing open-cut tunnels in soft soil areas under operational conditions; the method for removing lattice column foundations located directly beneath existing tunnels includes the following steps:

[0014] Step 1: Construct two steel caissons on both sides of the existing tunnel, simultaneously located on both sides of the lattice column piles to be removed;

[0015] Step 2: Between the two steel caissons, at the position directly above the lattice column piles, construct a section of jacking tunnel or shield tunnel with an inner diameter of 4 meters ± 10% as a transverse pipeline; during construction, directly cut the lattice column piles to complete the breakthrough.

[0016] Step 3: Inside the transverse pipe, cast-in-place reinforced concrete at the periphery of the upper end of the lattice column pile to form an operating platform with reserved pile extraction holes;

[0017] The soil beneath the operating platform is reinforced by MJS through multiple evenly distributed MJS grouting holes arranged around the pile extraction hole at the bottom of the operating platform.

[0018] Step 4: Inside the operating platform, two longitudinal beams parallel to the transverse pipe are set on both sides of the pile extraction hole through multiple steel columns, and a movable crossbeam that can move back and forth along the length direction of the two longitudinal beams is set between the two longitudinal beams to form a frame structure.

[0019] Step 5: Remove the bottom of the transverse pipe corresponding to the lattice column pile to expose the lattice column pile, and chisel out the main reinforcing steel bars at the top of the lattice column pile;

[0020] Step 6: Using the frame structure for hoisting, multiple sleeves connected end to end are sequentially inserted from the exposed upper end of the lattice column pile, and a drilling rig connected to the sleeves is used to cut downwards along the lattice column pile to form a tube structure formed by multiple sleeves outside the lattice column pile;

[0021] Step 7: After the tube structure formed by the multiple sleeves reaches 500 mm below the bottom of the lattice column pile, stop cutting downwards and rotate the tube structure several times in both the forward and reverse directions to loosen the pressure on the foundation soil.

[0022] Step 8: Using the frame structure for hoisting, the lattice column pile is lifted out from the upper end of the pipe structure. After the lattice column pile is lifted out to a certain height from the upper end of the pipe structure, a pipe clamp is installed at the position of the lattice column pile at the end of the pipe structure to prevent the lattice column pile from falling down along the pipe structure. Then, the part of the lattice column pile above the pipe clamp is cut off with a wire saw, and the cut-off part is transported out.

[0023] Step 9: Repeat step 8 until the lattice column piles are removed;

[0024] Step 10: Retrieve the sleeve section by section, and insert a grouting pipe into the hole formed by clearing the lattice column pile. While removing the sleeve, pour C10 concrete through the grouting pipe.

[0025] Step 11: After all the sleeves have been recycled, lay the steel mesh, seal the water-stop strip, and pour concrete into the reserved hole to repair the bottom of the transverse pipe that was chiseled out at the position of the lattice column pile.

[0026] Preferably, if the existing tunnel has downwardly extending lattice columns at its lower part, the depth of the transverse pipe should satisfy the requirement that the distance between the top of the pipe and the lattice column is not less than 500 mm.

[0027] Preferably, the net distance between each steel caisson and the existing tunnel is not less than one wellhead diameter.

[0028] Preferably, the inner diameter of the pile extraction hole is more than 600 mm larger than the outer diameter of the lattice column pile; the bottom of the operating platform is provided with 8 MJS grouting holes evenly distributed around the pile extraction hole; the diameter of each MJS grouting hole is 50 mm; the grouting diameter of each MJS grouting hole is 1100 mm to 1400 mm; the overlap between any two adjacent MJS grouting holes is not less than 500 mm.

[0029] Preferably, the depth of the MJS reinforcement is determined based on the geological conditions. Specifically, when there is a confined aquifer within the range of the lattice column pile, the confined aquifer is isolated; when there is no confined aquifer within the range of the lattice column pile, the reinforcement depth is selected according to the law of groundwater infiltration, and the reinforcement depth is not less than 5 meters from the bottom of the transverse pipe downward.

[0030] Steel column base embedded parts are reserved on the platform.

[0031] Preferably, the operating platform is provided with a steel column foot pre-embedded part for each of the steel columns, and the corresponding steel column is fixed by each of the steel column foot pre-embedded parts.

[0032] Preferably, in step 6, when the drilling rig connected to the sleeve is cutting downwards along the lattice column pile, mud is injected while cutting and drilling through the grouting holes provided in each sleeve, and the mud level is always maintained at a position 500 mm below the operating platform; the specific gravity of the mud is controlled between 1.1 and 1.4.

[0033] In step 10, C10 concrete is poured through the grouting pipe while the mud is extracted to maintain the mud level.

[0034] Preferably, in step 6, when the drill connected to the sleeve is cutting downward along the lattice column pile, multiple guide frames are arranged around the outside of the pipe structure formed by the multiple sleeves on the operating platform; each guide frame is padded with sponge between itself and the pipe structure.

[0035] The beneficial effects of this invention are:

[0036] This invention enables the removal of pile foundations as needed without affecting the normal operation of the tunnel or causing significant disturbance to the structure.

[0037] The cleaning operation of this invention does not occupy tunnel space and does not affect the operation of existing tunnels.

[0038] The application of this invention will not damage the existing tunnel structure floor, thus avoiding potential hazards to tunnel use.

[0039] The jacking or shield tunneling sections formed in this invention can be used for rainwater, electricity, or pedestrian crossings, and are not discarded.

[0040] This invention employs a casing and mud wall protection method for pile extraction, along with a closed-loop water-proofing measure, making it safer and more reliable.

[0041] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0042] Figure 1 This diagram illustrates the state of MJS reinforcement completed in one embodiment of the present invention.

[0043] Figure 2 This diagram illustrates the cross-sectional state of the transverse pipe located directly above the lattice column pile after MJS reinforcement is completed in one embodiment of the present invention.

[0044] Figure 3 This diagram shows a schematic plan view of the operating platform inside the transverse pipe after MJS reinforcement is completed in one embodiment of the present invention.

[0045] Figure 4 This diagram shows a cross-sectional view of the first sleeve section being hoisted into a transverse pipe after the frame structure is installed in one embodiment of the present invention.

[0046] Figure 5 This is a plan view showing the completion of the frame structure setup and hoisting of the first sleeve within a transverse pipe according to an embodiment of the present invention.

[0047] Figure 6 This diagram illustrates the state of the first sleeve being in place according to an embodiment of the present invention.

[0048] Figure 7 This diagram illustrates the state of the second sleeve being in place according to an embodiment of the present invention.

[0049] Figure 8 This diagram shows a cross-sectional view of a transverse pipe in one embodiment of the present invention, with all sleeves in place.

[0050] Figure 9 This diagram illustrates the overall state along the longitudinal direction of the pipe after all sleeves have been installed in one embodiment of the present invention.

[0051] Figure 10 This diagram illustrates the hoisting process of a lattice column pile in one embodiment of the present invention.

[0052] Figure 11 This diagram illustrates the state of a lattice column pile being suspended by a pipe clamp in one embodiment of the present invention.

[0053] Figure 12 This diagram shows a cross-sectional view of a lattice column pile when the pipe clamp is used to hold the lattice column pile in one embodiment of the present invention.

[0054] Figure 13 This diagram illustrates the state of each sleeve being recycled according to an embodiment of the present invention.

[0055] Figure 14 This diagram illustrates the state of the transverse pipe after C10 concrete pouring and bottom repair in one embodiment of the present invention.

[0056] Figure 15 This diagram illustrates the overall state of the pipeline along its longitudinal direction after pouring C10 concrete and repairing the bottom of the transverse pipeline, according to an embodiment of the present invention. Detailed Implementation

[0057] Example

[0058] like Figures 1 to 15 As shown, a method for removing the lattice column foundation of an existing open-cut tunnel in soft soil area under operational conditions; used to remove the lattice column 2 located directly below the existing tunnel 1, including the following steps:

[0059] Step 1: Construct two steel caissons 3 on both sides of the existing tunnel 1, and simultaneously on both sides of the lattice column piles 2 to be removed;

[0060] Step 2: Between the two steel caissons 3, at the position directly above the lattice column pile 2, construct a section of jacking tunnel or shield tunnel with an inner diameter of 4 meters ± 10% as a transverse pipe 4; during construction, directly cut the lattice column pile 2 to complete the breakthrough.

[0061] Step 3: Inside the transverse pipe 4, cast-in-place reinforced concrete at the periphery of the upper end of the lattice column pile 2 to form an operating platform 7 with a reserved pile extraction hole 6;

[0062] The soil below the operating platform 7 is reinforced by MJS through multiple evenly distributed MJS grouting holes 15 arranged around the pile extraction hole 6 at the bottom of the operating platform 7.

[0063] Step 4: Inside the operating platform 7, two longitudinal beams 9 parallel to the transverse pipe 4 are set on both sides of the pile extraction hole 6 through multiple steel columns 8, and a movable crossbeam 10 that can move back and forth along the length direction of the two longitudinal beams 9 is set between the two longitudinal beams 9 to form a frame structure.

[0064] Step 5: Remove the bottom of the transverse pipe 4 corresponding to the lattice column pile 2 to expose the lattice column pile 2, and chisel out the main load-bearing steel bars at the top of the lattice column pile 2.

[0065] Step 6: Using a frame structure for hoisting, multiple sleeves 13 connected end to end are sequentially inserted from the exposed upper end of the lattice column pile 2, and a drilling rig connected to the sleeves 13 is used to cut downward along the lattice column pile 2 to form a pipe structure formed by multiple sleeves 13 outside the lattice column pile 2.

[0066] Step 7: After the tube structure formed by multiple sleeves 13 reaches 500 mm below the bottom of the lattice column pile 2, stop cutting downwards and rotate the tube structure several times in both the forward and reverse directions to loosen the pressure on the foundation soil.

[0067] Step 8: Using a frame structure for hoisting, the lattice column pile 2 is lifted out from the upper end of the pipe structure. After the lattice column pile 2 is lifted out to a certain height from the upper end of the pipe structure, a pipe clamp 14 is installed at the position of the lattice column pile 2 at the end of the pipe structure to prevent the lattice column pile 2 from falling down along the pipe structure. Then, the part of the lattice column pile 2 above the pipe clamp 14 is cut off with a wire saw, and the cut-off part is transported out.

[0068] Step 9: Repeat step 8 until the lattice column pile 2 is removed;

[0069] Step 10: Recover the sleeve 13 section by section, and insert the grouting pipe into the hole formed by clearing the lattice column pile 2. While removing the sleeve 13, pour C10 concrete through the grouting pipe.

[0070] Step 11: After all sleeves 13 have been recovered, lay steel mesh, seal with water-stop strips, and pour concrete into the reserved hole to repair the bottom of the lattice column pile 2 at the position of the transverse pipe 4 that has been chiseled away.

[0071] The present invention constructs two steel caissons 3 on both sides of the existing tunnel 1 as working shafts, and uses pipe jacking or shield tunneling to construct a section of pipeline to form a transverse pipeline 4.

[0072] The design of the cutting tools and cutterhead for jacking or shield tunneling equipment takes into account the cutting of pile foundations, and the diameter of the transverse pipe 4 can meet the space requirements for clearing the lattice column piles 2 and auxiliary measures.

[0073] Then, auxiliary measures such as water-stopping and operating platform are constructed in the horizontal pipe 4. Steel sleeves 13 are inserted into the remaining piles of the lattice column pile 2 section by section. The lattice column pile 2 is lifted and cut out section by section.

[0074] Finally, sleeve 13 was lifted out and low-grade concrete was poured simultaneously to seal the bottom of the transverse pipe 4.

[0075] In practical applications, the design and construction of the steel caisson 3 is an existing technology and will not be elaborated here. Its size is determined according to the diameter of the pipe and the construction operation space. The inner diameter can be selected from 5 to 6 meters. The depth is determined according to the depth of the transverse pipe 4 and the construction space, that is, the height of the bottom of the transverse pipe 4 from the top of the bottom sealing concrete, the bottom sealing thickness of the steel caisson 3, and the thickness of the soil plug. Usually, the soil plug thickness in soft soil can be controlled at about 3m, the bottom sealing concrete thickness is about 2m, and the construction space should not be less than 1m.

[0076] A pipe jacking tunnel or shield tunnel with an inner diameter of 4 meters ± 10% can provide sufficient space for internal pile extraction and the implementation of auxiliary measures in the transverse pipe 4.

[0077] After the construction is completed, the repaired horizontal pipe 4 and steel caisson 3 can be used as rainwater pipes, power passageways, or converted into main pedestrian crossings.

[0078] In some embodiments, if the lower part of the existing tunnel 1 is provided with a downwardly extending lattice column 5, the depth of the transverse pipe 4 should meet the requirement that the distance between the top and the lattice column 5 is not less than 500 mm.

[0079] In practical applications, the depth of the transverse pipe 4 should ensure that the distance between the top and the lattice column 5 is not less than 500 mm to avoid the need to cut the lattice column during construction.

[0080] In some embodiments, the net distance between each steel caisson 3 and the existing tunnel 1 is not less than one wellhead diameter.

[0081] In practical applications, the diameter of the wellhead of the steel caisson is usually 5 to 6 meters.

[0082] By rationally selecting the depth of the transverse pipe 4 and the net distance between each steel caisson 3 and the existing tunnel 1, the impact on the existing tunnel 1 can be reduced, and the investment in the transverse pipe 4 can be saved.

[0083] In some embodiments, the inner diameter of the pile extraction hole 6 is more than 600 mm larger than the outer diameter of the lattice column pile 2; the bottom of the operating platform 7 is provided with 8 MJS grouting holes 15 evenly distributed around the pile extraction hole 6; the diameter of each MJS grouting hole 15 is 50 mm; the grouting diameter of each MJS grouting hole 15 is 1100 mm to 1400 mm; the overlap between any two adjacent MJS grouting holes 15 is not less than 500 mm.

[0084] In some embodiments, the depth of MJS reinforcement is determined based on geological conditions. Specifically, when there is a confined aquifer within the range of the lattice column pile 2, the confined water is isolated; when there is no confined water within the range of the lattice column pile 2, the reinforcement depth is selected according to the law of groundwater seepage, and the reinforcement depth is not less than 5 meters from the bottom of the transverse pipe 4 downwards. Steel column footings are pre-embedded on the platform.

[0085] In some embodiments, the operating platform 7 is provided with a steel column foot embedded part 71 for each steel column, and the corresponding steel column 8 is fixed by each steel column foot embedded part 71.

[0086] In some embodiments, in step 6, when the drilling rig connected to the sleeve 13 cuts downward along the lattice column pile 2, mud is injected while cutting and drilling through the grouting holes set in each sleeve 13, and the mud level is always maintained at a position 500 mm below the operating platform 7; the specific gravity of the mud is controlled between 1.1 and 1.4.

[0087] In step 10, C10 concrete is poured through the grouting pipe while mud is extracted to maintain a constant mud level.

[0088] During the removal of the grid column pile 2, by maintaining the mud at a certain safe level, the mud can play a protective role on the wall.

[0089] In some embodiments, in step 6, when the drill connected to the sleeve 13 is cutting downward along the lattice column pile 2, multiple guide frames 11 are arranged around the outside of the pipe structure formed by multiple sleeves 13 on the operating platform 7; each guide frame 11 is padded with a sponge 12 between itself and the pipe structure.

[0090] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for removing a lattice column pile (2) located directly below an existing tunnel (1) in a soft soil area under operation; for removing a lattice column pile (2) located directly below an existing tunnel (1); characterized in that, Includes the following steps: Step 1: Construct two steel caissons (3) on both sides of the existing tunnel (1) and on both sides of the grid column piles (2) to be removed. Step 2: Between the two steel caissons (3), a section of jacking tunnel or shield tunnel with an inner diameter of 4 meters ± 10% is constructed as a transverse pipeline (4) at the position directly above the lattice column pile (2); during the construction process, the lattice column pile (2) is directly cut to complete the connection. Step 3: Inside the transverse pipe (4), cast-in-place reinforced concrete at the periphery of the upper end of the lattice column pile (2) to form an operating platform (7) with a reserved pile extraction hole (6). The soil below the operating platform (7) is reinforced by MJS by providing multiple evenly distributed MJS grouting holes (15) around the pile extraction hole (6) at the bottom of the operating platform (7). Step 4: Inside the operating platform (7), two longitudinal beams (9) parallel to the transverse pipe (4) are set on both sides of the pile extraction hole (6) by multiple steel columns (8), and a movable crossbeam (10) that can move back and forth along the length direction of the two longitudinal beams (9) is set between the two longitudinal beams (9) to form a frame structure. Step 5: Remove the bottom of the transverse pipe (4) corresponding to the lattice column (2) to expose the lattice column (2), and remove the main reinforcing steel bars at the top of the lattice column (2); Step 6: The frame structure is hoisted and multiple sleeves (13) connected end to end are sequentially inserted from the exposed upper end of the lattice column (2). The drilling machine connected to the sleeves (13) cuts downward along the lattice column (2) and forms a tube structure formed by multiple sleeves (13) outside the lattice column (2). Step 7: After the tube structure formed by the multiple sleeves (13) reaches 500 mm below the bottom of the lattice column pile (2), stop cutting downwards and rotate the tube structure several times in both the forward and reverse directions to loosen the pressure on the foundation soil; Step 8: The lattice column (2) is hoisted from the upper end of the pipe structure using the frame structure. After the lattice column (2) is hoisted out of the upper part of the pipe structure, a pipe clamp (14) is installed at the end of the pipe structure to prevent the lattice column (2) from falling down along the pipe structure. Then, the part of the lattice column (2) above the pipe clamp (14) is cut off with a wire saw and the cut part is transported out. Step 9: Repeat step 8 until the lattice column piles (2) are removed. Step 10: Retrieve the sleeve (13) section by section, and insert a grouting pipe into the hole formed by clearing the lattice column pile (2). While removing the sleeve (13), pour C10 concrete through the grouting pipe. Step 11: After all the sleeves (13) have been recycled, lay the steel mesh, seal the water-stop strip, and pour concrete into the reserved hole to repair the bottom of the transverse pipe (4) that was chiseled out at the position of the lattice column pile (2).

2. The method according to claim 1, wherein, If the existing tunnel (1) has a downwardly extending lattice column (5) at its lower part, the depth of the transverse pipe (4) should satisfy that the distance between the top and the lattice column (5) is not less than 500 mm.

3. The method according to claim 1, wherein, The net distance between each of the steel caissons (3) and the existing tunnel (1) is not less than 1 times the diameter of the caisson opening.

4. The method for removing the lattice column pile foundation of the existing open-cut tunnel in the soft soil area in operation according to claim 1, characterized in that, The inner diameter of the pile extraction hole (6) is more than 600 mm larger than the outer diameter of the lattice column pile (2); the bottom of the operating platform (7) is provided with 8 MJS grouting holes (15) evenly distributed around the pile extraction hole (6); the diameter of each MJS grouting hole (15) is 50 mm; the grouting diameter of each MJS grouting hole (15) is 1100 mm to 1400 mm; the overlap between any two adjacent MJS grouting holes (15) is not less than 500 mm.

5. The method for removing existing open-cut tunnel grid column foundations in soft soil areas under operational conditions, as described in claim 1, is characterized in that... The depth of the MJS reinforcement is determined based on the geological conditions. Specifically, when there is a confined water layer within the range of the lattice column (2), the confined water is isolated; when there is no confined water within the range of the lattice column (2), the reinforcement depth is selected according to the law of groundwater infiltration. The reinforcement depth is not less than 5 meters from the bottom of the transverse pipe (4), and steel column foot embedded parts are reserved on the platform.

6. The method for removing existing open-cut tunnel grid column foundations in soft soil areas under operational conditions, as described in claim 1, is characterized in that... The operating platform (7) is equipped with a steel column foot pre-embedded part (71) for each steel column, and the corresponding steel column (8) is fixed by each steel column foot pre-embedded part (71).

7. The method for removing existing open-cut tunnel grid column foundations in soft soil areas under operational conditions, as described in claim 1, is characterized in that... In step 6, when the drilling rig connected to the sleeve (13) cuts downward along the lattice column pile (2), mud is injected while cutting and drilling through the grouting holes set in each sleeve (13), and the mud level is always maintained at a height of 500 mm below the operating platform (7); the specific gravity of the mud is controlled between 1.1 and 1.

4. In step 10, C10 concrete is poured through the grouting pipe while the mud is extracted to maintain the mud level.

8. The method for removing existing open-cut tunnel grid column foundations in soft soil areas under operational conditions, as described in claim 1, is characterized in that... In step 6, when the drill connected to the sleeve (13) cuts downward along the lattice column pile (2), on the operating platform (7), a plurality of guide frames (11) are arranged around the outside of the tube structure formed by the plurality of sleeves (13); each guide frame (11) is padded with a sponge (12) between itself and the tube structure.

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