Construction method for underpinning waste pile through shield penetrating pile foundation

Abstract

A construction method for underpinning a waste pile through a shield penetrating pile foundation comprises the steps that firstly, an underpinning pile is driven at an underpinning position, a foundation pit is excavated, and an underpinning bearing platform is constructed below an existing bearing platform; 2, a jack is arranged for jacking, and then the waste pile is cut off within the range of the existing bearing platform and the underpinning bearing platform; 3, after balance is achieved, the jack is finely adjusted and then locked, and a bearing platform is poured after implementation; 4, the foundation pit is backfilled to the ground, a vertical shaft and a transverse channel are constructed, the waste piles are broken downwards from the transverse channel, and a circular pile casing is constructed while the waste piles are broken downwards; 5, backfilling to the transverse channel from bottom to top by adopting a backfilling material; 6, backfilling the transverse channel and the vertical shaft in a layered backfilling mode from bottom to top; 7, shield tunneling construction is conducted; therefore, under the condition that the safety of the existing structure is not affected, the existing waste pile foundation is underpinned, the waste pile is treated, and continuous construction of the shield tunnel is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel and pile foundation underpinning, and particularly to a construction method for a shield tunneling through a pile foundation underpinning of an abandoned pile. Background Art

[0002] With the vigorous development of urban rail transit, utility tunnels and other underground spaces, various tunnels need to be constructed under municipal roads, and underground obstacles are often encountered, especially conflicts with pile foundations of structures when passing through busy traffic sections. In this case, priority is given to avoiding conflicts by adjusting the line. However, due to surrounding conditions, it is often impossible to avoid or the line length increases due to detouring. In this case, some projects choose to adjust the construction method, which brings higher construction costs and engineering risks. Therefore, it is necessary to carry out pile foundation underpinning to handle the abandoned piles without affecting the passage of the shield.

[0003] Patent CN112942147A discloses a method for active underpinning of bridge piles, in which two underpinning operations, namely temporary and permanent underpinning, are required. During the period of jacking up and connecting the first new bearing platform and the second new bearing platform, traffic needs to be restricted or temporarily closed. This method requires a large operating space and is not conducive to implementation. At the same time, the two underpinning operations not only increase the underpinning risk but also increase the underpinning cost.

[0004] Therefore, in view of the above defects, the designers of the present invention, through painstaking research and design, combined with the experience and achievements of being engaged in related industries for many years, have studied and designed a construction method for a shield tunneling through a pile foundation underpinning of an abandoned pile to overcome the above defects. Summary of the Invention

[0005] The purpose of the present invention is to provide a construction method for a shield tunneling through a pile foundation underpinning of an abandoned pile, which can effectively overcome the defects of the prior art, underpin the existing abandoned pile foundations without affecting the safety of the existing structure, and handle the abandoned piles to ensure the continuous construction of the shield tunnel.

[0006] To achieve the above purpose, the present invention discloses a construction method for a shield tunneling through a pile foundation underpinning of an abandoned pile, which is characterized by including the following steps:

[0007] Step 1: At the underpinning position, first drive underpinning piles, then excavate the foundation pit, construct an underpinning bearing platform under the existing bearing platform, anchor the steel bars in the underpinning piles into the underpinning bearing platform before pouring, and at the same time set a plurality of limiting devices inserted into the underpinning bearing platform along the periphery of the existing bearing platform;

[0008] Step 2: Set a jack between the existing bearing platform and the underpinning bearing platform to tighten, and then cut off the abandoned pile within the range of the existing bearing platform and the underpinning bearing platform;

[0009] Step 3: After reaching balance, fine-tune the jack and then lock it, and then construct the post-pouring bearing platform;

[0010] Step 4: Backfill the foundation pit to the ground, then construct the vertical shaft and the horizontal passage, then break the abandoned piles from the horizontal passage downwards, and construct the circular casing while breaking the abandoned piles downwards until 0.5-1.0m below the shield tunnel;

[0011] Step 5: Then use backfill material to backfill the cross channel from bottom to top;

[0012] Step 6: Then backfill the horizontal passage and the vertical shaft in layers from bottom to top;

[0013] Step 7: Shield tunnel construction, cutting the circular casing and backfilling materials before passing through the pile foundation.

[0014] Wherein: the underpinning pile in step 1 is ensured to be no less than 0.5 to 1 m away from the shield tunnel in the long side direction of the underpinning foundation, and the underpinning pile diameter is selected to be a large diameter pile of 1.0 m to 1.5 m to facilitate flexible construction on site.

[0015] Among them: the horizontal setting interval of the limit device in step 1 is 1.0~2.0m, the depth of the limit device inserted into the replacement base is not less than half of the thickness of the replacement base, and at the same time, the upper part of the limit device is closely attached to the side of the existing base and flush with the top of the existing base. The plane displacement of the existing base can be effectively limited by multiple limit devices.

[0016] Among them: During the pile cutting process in step 2, the deformation of the existing cap should be monitored more strictly. The deformation monitoring is to monitor the horizontal and vertical deformation of the existing cap through the limit device and the deformation monitoring points arranged on the top surface of the existing cap. When the deformation of the monitoring point is too large, the servo system is used to adjust the jack to lift the existing cap upward by the same displacement to ensure that the vertical displacement of the existing cap is within a safe range.

[0017] Wherein: the post-cast cap described in step 3 is connected to the existing cap by casting through the steel bar embedding technology, and the casting surface should be roughened, the plane position of the post-cast cap is aligned with the center of the existing cap, the plane size is larger than the existing cap, each side exceeds the existing cap by no less than 0.8 to 1.5m, and the height size is flush with the top of the existing cap.

[0018] Among them: the outer wall of the circular casing in step 4 is circular, the inner wall is a wedge-shaped narrow at the top and wide at the bottom, each section of the circular casing is 0.5 to 1.0 m long, and multiple lifting ears are pre-buried at the upper and lower ends of the circular casing for easy lifting.

[0019] Among them: in step 5, the backfill material is foam concrete, fluidized solidified soil or liquid fly ash, and the strength of the backfill material should be controlled at 0.5-1.0MPa to facilitate the subsequent shield machine cutting; the fluidity is controlled at 200mm-250mm to achieve a self-leveling effect, which is convenient for backfilling in a small space.

[0020] Among them: the fluidized solidified soil is mixed by a curing agent, soil and water, wherein the amount of the curing agent is controlled at 3% to 10%; the foamed concrete is prepared by adding a cement foaming agent to concrete, wherein the amount of the cement foaming agent is 20% to 30%; the liquid fly ash is mixed by cement, fly ash and water, wherein the cement is 5% to 12% and the fly ash is 95% to 88%.

[0021] Among them: the lower part of the horizontal channel is backfilled in layers with plain soil + compaction, and the thickness of each layer is controlled to be 10cm~15cm. It is backfilled to 1.0~1.5m away from the arch. Liquid fly ash is used for backfilling, and grouting pipes are pre-buried at the arch position to facilitate filling and compaction. The vertical shaft 7 is backfilled in layers with plain soil + compaction. The thickness of each layer should be controlled to be 10cm~15cm until the ground. The compaction degree of each layer of soil is 93%~95%.

[0022] From the above content, it can be known that the construction method of the present invention for replacing abandoned piles with a shield tunnel through a pile foundation has the following effects:

[0023] 1. The underpinning piles are removed by circular casing and then backfilled with materials that are easy for shield cutting and dense, thus reducing the risk of shield cutting pile foundations.

[0024] 2. The one-time underpinning method can be implemented in a smaller space, and the vertical shaft and horizontal passage scheme is used to remove the underpinning piles. The construction is flexible and is less affected by on-site traffic. At the same time, the present invention does not require traffic control and has little impact on traffic.

[0025] The details of the present invention can be obtained from the following description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The cross-sectional position relationship diagram of the existing pile foundation and the shield tunnel in the present invention is shown.

[0027] Figure 2 The cross-sectional schematic diagram shows the pile foundation underpinning and the removal of abandoned piles in the vertical shaft cross passage in the present invention.

[0028] Figure 3 A cross-sectional schematic diagram of a circular casing in the present invention is shown.

[0029] Reference numerals:

[0030] 1. Ground, 2. Existing cap, 3. Abandoned piles, 4. Underpinning cap, 5. Underpinning piles, 6. Shield tunnel, 7. Vertical shaft, 8. Cross passage, 9. Circular casing, 10. Backfill material, 11. Jack, 12. Post-cast cap, 13. Limiting device, 14. Embedded lifting lugs. DETAILED DESCRIPTION

[0031] As shown Figure 1 in the figure, the sectional position relationship between the existing pile foundation and the shield tunnel of the present invention is shown. The existing pile foundation structure includes an existing bearing platform 2 under the ground 1, and a discarded pile (piled to be replaced) 3 is arranged under the existing bearing platform 2. There is a spatial conflict between the shield tunnel 6 and the discarded pile (piled to be replaced) 3. Before the construction of the shield tunnel 6, the discarded pile (piled to be replaced) 3 should be piled to be replaced, and the discarded pile (piled to be replaced) 3 should be treated before passing through.

[0032] Among them, as Figures 1 to 2 shown in the figure, a construction method for a shield tunneling through a pile foundation to replace a discarded pile of the present invention is shown. The construction method includes the following steps:

[0033] Step 1: At the piling to be replaced position, first drive the piling to be replaced 5, then excavate the foundation pit, construct the piling to be replaced bearing platform 4 under the existing bearing platform 2. Before pouring, anchor the steel bars in the piling to be replaced 5 into the piling to be replaced bearing platform 4, and at the same time, arrange a plurality of limiting devices 13 inserted into the piling to be replaced bearing platform 4 along the periphery of the existing bearing platform 2.

[0034] The piling to be replaced bearing platform 4 and the piling to be replaced 5 need to meet the following requirements: First, the long side direction of the piling to be replaced bearing platform 4 should be long enough to ensure that the distance between the piling to be replaced 5 and the shield tunnel 6 is not less than 0.5 - 1 m; Second, the diameter of the piling to be replaced 5 is preferably a large diameter pile of 1.0 m - 1.5 m, so as to facilitate on-site flexible construction. Under the condition of meeting the net distance condition with the shield tunnel 6, the number of the piling to be replaced 5 is preferably increased to reduce the thickness of the piling to be replaced bearing platform 4.

[0035] The horizontal setting spacing of the limiting device 13 is preferably 1.0 - 2.0 m, the depth of the limiting device inserted into the piling to be replaced bearing platform 4 is not less than half of the thickness of the piling to be replaced bearing platform, and at the same time, the upper part of the limiting device is closely attached to the side of the existing bearing platform 2 and flush with the top of the existing bearing platform 2. Through a plurality of limiting devices, the plane displacement of the existing bearing platform 2 can be effectively restricted. Preferably, the limiting device 13 can adopt an I-beam with strong stiffness, and at the same time, a displacement monitoring device is arranged on the upper half of the I-beam, and the horizontal displacement of the existing bearing platform 2 can be effectively monitored.

[0036] Step 2: Set a jack 11 between the existing bearing platform 2 and the piling to be replaced bearing platform 4 to tighten, and then cut off the discarded pile (piled to be replaced) 3 within the range of the existing bearing platform 2 and the piling to be replaced bearing platform 4. During the pile cutting process, the deformation of the existing bearing platform 2 should be strengthened for monitoring, and the deformation of the existing bearing platform 2 is compensated by fine-tuning the jack 11 to ensure the safety of the upper structure.

[0037] Deformation monitoring is to monitor the horizontal and vertical deformation of the existing cap 2 through the limit device 13 and the deformation monitoring points arranged on the top surface of the existing cap 2. When the deformation of the monitoring point is too large, the jack 11 is adjusted by the servo system to lift the existing cap 2 upward by the same displacement to ensure that the vertical displacement of the existing cap 2 is within a safe range.

[0038] Step 3: After reaching balance, fine-tune the jack 11 and lock it, and then cast the cap 12.

[0039] The post-cast foundation 12 is connected to the existing foundation 2 by casting through the steel bar embedding technology, and the casting surface should be roughened.

[0040] The post-casting cap 12 is not limited to Figure 2 As shown, its plane position should be aligned with the center of the existing base 2, the plane size can be larger than the existing base 2, each side exceeds the existing base 2 by no less than 0.8 to 1.5 m, and the height dimension can be flush with the top of the existing base 2.

[0041] Step 4: Backfill the foundation pit to the ground 1, then construct the vertical shaft 7 and the horizontal passage 8, then break down the abandoned piles (underpinning piles) 3 from the horizontal passage 8, and construct the circular casing 9 while breaking down the abandoned piles (underpinning piles) 3, until 0.5 to 1.0 m below the shield tunnel 6.

[0042] like Figure 3 As shown, the circular casing 9 provides side wall safety support for the abandoned pile (underpinning pile) 3 that breaks the conflict range with the shield tunnel 6. In order to improve the safety performance and protection function, the outer wall of the circular casing 9 is circular, and the inner wall is a wedge-shaped narrow at the top and wide at the bottom. The length of each section of the circular casing 9 is 0.5 to 1.0 m, and the entire protective wall can be formed by superimposing multiple circular casings 9. Preferably, the outer wall diameter of the circular casing 9 is consistent with the diameter of the abandoned pile (underpinning pile) 3, so as to facilitate on-site construction. The upper and lower ends of the circular casing 9 are pre-buried with multiple lifting ears 14 for easy lifting.

[0043] Step 5: Then backfill the horizontal channel 8 from bottom to top with backfill material 10. The backfill material 10 is required to be a material that is easy to compact, does not require rolling, has low strength and is easy to implement, such as foam concrete, fluidized solidified soil, liquid fly ash, etc.

[0044] Among them, the strength of the backfill material 10 should be controlled at 0.5-1.0 MPa to facilitate the subsequent shield machine cutting; the fluidity should be controlled at 200mm-250mm to achieve a self-leveling effect, which is convenient for backfilling in a small space.

[0045] In one of the embodiments, the fluidized solidified soil is mixed with a curing agent, soil and water, wherein the amount of the curing agent is controlled at 3% to 10%; the foamed concrete is prepared by adding a cement foaming agent to concrete, wherein the amount of the cement foaming agent is 20% to 30%; the liquid fly ash is mixed with cement, fly ash and water, wherein the cement is 5% to 12% and the fly ash is 95% to 88%.

[0046] Step 6: Then, the horizontal passage 8 and the vertical shaft 7 are backfilled in layers from bottom to top. The backfill material is mainly plain soil + liquid fly ash.

[0047] The lower part of the transverse passage 8 is backfilled in layers with plain soil + compaction, and the thickness of each layer is controlled to be 10cm-15cm. It is backfilled to 1.0-1.5m from the arch. Liquid fly ash can be used for backfilling, and grouting pipes are pre-buried at the arch position to facilitate filling and compaction. The vertical shaft 7 is backfilled in layers with plain soil + compaction, and the thickness of each layer should be controlled to be 10cm-15cm until the ground. The compaction degree of each layer of soil is 93%-95%.

[0048] Step 7: The shield tunnel excavation construction successfully passes through the pile foundation range after cutting the circular casing 9 and backfilling material 10.

[0049] It can be seen that the present invention has the following advantages:

[0050] 1. The present invention can ensure the continuous excavation of the shield tunnel, avoid the risks of dark excavation pile cutting and replacement, shield pile grinding, etc., greatly reduce the risk of project implementation, and effectively control the investment cost.

[0051] 2. The abandoned piles 3 are processed by means of vertical shaft and horizontal passage, which is flexible in construction and less affected by ground traffic. At the same time, glass fiber reinforcement is built into the circular casing 9, and the backfill material 10 is made of a material that is easy to compact, does not require rolling, has low strength and is easy to implement, so that the shield machine can directly cut through.

[0052] 3. By means of the jack 11 arranged between the existing cap 2 and the underpinning cap 4, the deformation of the existing cap 2 can be effectively controlled.

[0053] It is obvious that the above description and record are only examples and are not intended to limit the disclosure, application or use of the present invention. Although the embodiments have been described in the embodiments and described in the drawings, the present invention is not limited to the specific examples of the teachings of the present invention as the best mode currently considered by the drawings and described in the embodiments, and the scope of the present invention will include any embodiment falling within the previous description and the attached claims.

Claims

1. A construction method for replacing abandoned piles by a shield tunneling through a pile foundation, characterized in that The steps include: Step 1: At the underpinning position, first drive the underpinning piles, then excavate the foundation pit, construct the underpinning cap under the existing cap, anchor the steel bars in the underpinning piles into the underpinning cap before pouring, and at the same time set multiple limit devices inserted into the underpinning cap along the periphery of the existing cap; Step 2: Set a jack between the existing cap and the underpinning cap to tighten it, and then cut off the abandoned piles within the range of the existing cap and the underpinning cap; Step 3: After reaching balance, fine-tune the jack and lock it, and then cast the cap; Step 4: Backfill the foundation pit to the ground, then construct the vertical shaft and the horizontal passage, then break the abandoned piles from the horizontal passage downwards, and construct the circular casing while breaking the abandoned piles downwards until 0.5-1.0m below the shield tunnel; Step 5: Then use backfill material to backfill the cross channel from bottom to top; Step 6: Then backfill the horizontal passage and the vertical shaft in layers from bottom to top; Step 7: Shield tunnel construction, cutting the circular casing and backfilling materials before passing through the pile foundation.

2. The construction method of shield tunneling through pile foundation to replace abandoned piles as claimed in claim 1, characterized in that: In step 1, the underpinning piles should be at least 0.5 to 1 m away from the shield tunnel in the long side direction of the underpinning cap, and large diameter piles of 1.0 to 1.5 m should be used for the underpinning piles to facilitate flexible construction on site.

3. The construction method of shield tunneling through pile foundation to replace abandoned piles as claimed in claim 1, characterized in that: The horizontal spacing of the limit devices in step 1 is 1.0 to 2.0 m, the depth of the limit devices inserted into the replacement platform is not less than half the thickness of the replacement platform, and at the same time, the upper part of the limit devices is tightly attached to the side of the existing platform and flush with the top of the existing platform. The planar displacement of the existing platform can be effectively limited by multiple limit devices.

4. The construction method of shield tunneling through pile foundation to replace abandoned piles as claimed in claim 1, characterized in that: During the pile cutting process in step 2, the deformation of the existing cap should be monitored more strictly. The deformation monitoring is to monitor the horizontal and vertical deformation of the existing cap through the limit device and the deformation monitoring points arranged on the top surface of the existing cap. When the deformation of the monitoring point is too large, the servo system is used to adjust the jack to lift the existing cap upward by the same displacement to ensure that the vertical displacement of the existing cap is within a safe range.

5. The construction method of shield tunneling through pile foundation to replace abandoned piles as claimed in claim 1, characterized in that: The post-cast cap described in step 3 is connected to the existing cap by casting through the steel bar embedding technology, and the casting surface should be roughened. The plane position of the post-cast cap is aligned with the center of the existing cap, the plane size is larger than the existing cap, each side exceeds the existing cap by no less than 0.8 to 1.5m, and the height dimension is flush with the top of the existing cap.

6. The construction method of shield tunneling through pile foundation to replace abandoned piles as claimed in claim 1, characterized in that: The outer wall of the circular casing in step 4 is circular, and the inner wall is a wedge-shaped narrow at the top and wide at the bottom. The length of each section of the circular casing is 0.5 to 1.0 m. The upper and lower ends of the circular casing are pre-buried with multiple lifting ears for easy lifting.

7. The construction method of replacing abandoned piles with a shield tunneling through a pile foundation as claimed in claim 1, characterized in that: In step 5, the backfill material is foam concrete, fluidized solidified soil or liquid fly ash. The strength of the backfill material should be controlled at 0.5-1.0 MPa to facilitate the subsequent shield machine cutting; the fluidity is controlled at 200mm-250mm to achieve a self-leveling effect, which is convenient for backfilling in a small space.

8. The construction method of shield tunneling through pile foundation to replace abandoned piles as claimed in claim 7, characterized in that: The fluidized solidified soil is mixed with a curing agent, soil and water, wherein the amount of the curing agent is controlled at 3% to 10%; the foamed concrete is prepared by adding a cement foaming agent to concrete, wherein the amount of the cement foaming agent is 20% to 30%; the liquid fly ash is mixed with cement, fly ash and water, wherein the cement is 5% to 12% and the fly ash is 95% to 88%.

9. The construction method of shield tunneling through pile foundation to replace abandoned piles as claimed in claim 1, characterized in that: The lower part of the horizontal channel is backfilled in layers with plain soil + compaction. The thickness of each layer is controlled to be 10cm~15cm. It is backfilled to 1.0~1.5m away from the arch. Liquid fly ash is used for backfilling, and grouting pipes are pre-buried at the arch position to facilitate dense filling. The vertical shaft is backfilled in layers with plain soil + compaction. The thickness of each layer should be controlled to be 10cm~15cm until the ground. The compaction degree of each layer of soil is 93%~95%.

Images