Karst area pile foundation karst slurry leakage treatment method

Abstract

The invention relates to the technical field of building construction, and discloses a karst area pile foundation karst slurry leakage treatment method in order to solve the technical problem of pile foundation slurry leakage caused by pile gene karst and crack development, and the karst area pile foundation karst slurry leakage treatment method comprises the steps that S1, a stratum plugging procedure is implemented through a pre-buried pile casing structure, and the pile casing structure vertically extending downwards along the ground elevation is arranged; the pile is filled with temporary filler with plugging and pressure bearing effects; s2, a pile body interior grouting, plugging and reinforcing system is constructed, pile body grouting holes are formed in a pile body structure, and a slurry material is injected into the pile body grouting holes; s3, the pile periphery circumferential grouting sealing procedure is implemented, pile periphery grouting hole groups which are distributed at intervals in the circumferential direction are arranged in the circumferential area of the pile body structure, and the pile periphery grouting hole groups sequentially penetrate through a ground layer and a rock-soil interface layer; the problems of slurry leakage, hole collapse, insufficient bearing capacity and the like of the pile foundation in the karst area are solved by combining drilling at the periphery of the pile foundation to treat karst fissures, backfilling concrete and grouting on the pile body, and the stability and the bearing capacity of the pile foundation are improved.

Description

Technical Field

[0001] The invention relates to building construction, in particular to a method for treating karst slurry leakage in pile foundations in karst areas. Background Art

[0002] Impact of Karst on Subway Projects

[0003] Karst is widespread in southern my country. When underground projects are located near or through karst caves, they can cause karst collapse, deformation and collapse of support structures, and water and mud inrush from foundation pits. These hazards can impact construction progress and structural safety, while also polluting the ecological environment. Therefore, karst treatment is crucial.

[0004] This is particularly true of the Shidengzi Formation, which is primarily composed of soluble carbonate rocks such as limestone and dolomite. Carbonate rocks are easily dissolved by water, especially water containing carbon dioxide, which can easily form karst landforms such as cavities, underground rivers, and caves. Consequently, the Shidengzi Formation has a strong development of karst caves and fissures, leading to grout leakage during pile foundation construction in this area.

[0005] The complex geological conditions of karst increase construction difficulty and costs, and may also threaten project safety and quality. Therefore, when carrying out construction in karst areas, targeted treatment measures must be taken to reduce the adverse effects of karst and ensure the smooth progress of the project. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for treating karst grout leakage in pile foundations in karst areas, so as to solve the technical problem of pile foundation grout leakage caused by karst and fissure development in the pile foundation.

[0007] To achieve the above object, the present invention provides a method for treating karst grout leakage in pile foundations in karst areas, comprising the following steps:

[0008] Step S1: pre-embed the casing structure in the pile:

[0009] A casing structure is set up that extends vertically downward from the ground level to a predetermined depth. A temporary filling material with a blocking and pressure-bearing effect is filled into the pile through the casing structure to seal potential slurry leakage channels in karst development areas and achieve stratum stabilization.

[0010] Step S2: constructing grouting holes inside the pile body:

[0011] At least one pile grouting hole is arranged in the axial or radial direction in the pile structure, and a pre-proportioned slurry material is injected into the pile grouting hole by a high-pressure grouting device, wherein the slurry material forms a composite stratum reinforcement structure around the pile structure to enhance the mechanical properties of the pile-soil interface;

[0012] Step S3, implementing the pile circumferential grouting sealing process:

[0013] In the circumferential area of ​​the pile body structure, a group of pile-circumferential grouting holes arranged at intervals in the vertical direction are provided, and the pile-circumferential grouting holes sequentially penetrate the ground layer and the rock-soil interface layer; pre-proportioned slurry material is injected into the development area of ​​karst fissures through the grouting hole group to form a blocking layer that closes the slurry loss channel, and the blocking layer fills the karst cave fissure network through the penetration and diffusion of the slurry.

[0014] Furthermore, the lower end of the casing structure is at least 1.5 times the pile diameter away from the top of the karst development area.

[0015] Furthermore, the arrangement of the circumferential grouting holes around the pile is as follows:

[0016] The holes are arranged in a plum blossom shape from the center of the pile to the outside, with a hole spacing of 2m, and the vertical hole depth must reach 2m below the pile bottom elevation.

[0017] Furthermore, a method for determining a pile foundation leakage point is also provided, comprising the following steps:

[0018] Step S41, during the pile foundation drilling process, real-time monitoring of the slurry level in the pile hole;

[0019] Step S42: when it is detected that the slurry level drops suddenly within a preset time period, and the drop exceeds a preset threshold, it is determined that there is a slurry leakage point at the current excavation pile bottom elevation;

[0020] Step S43, replenishing slurry into the pile hole through a grouting operation to maintain the slurry liquid level;

[0021] Step S44, calculating the slurry loss rate at the slurry leakage point according to the slurry filling speed of the slurry filling operation;

[0022] Step S44: preliminarily judging the development degree of the rock fissures at the leakage point based on the magnitude of the slurry loss rate. The faster the loss rate, the higher the development degree of the fissures.

[0023] Furthermore, a liquid level sensor and a data acquisition device are provided. The liquid level sensor is electrically connected to the data acquisition device and transmits monitoring data to the control system in real time.

[0024] Furthermore, the preset time period is 1-5 minutes, and the preset threshold is when the mud level drops by more than 1 / 10 of the pile hole diameter.

[0025] Furthermore, the slurry replenishment operation is performed by an automatically controlled mud pump, and the flow rate of the mud pump is adjusted in real time by the control system according to changes in the liquid level.

[0026] Furthermore, the calculation formula of the slurry loss rate is v=tQ;

[0027] Where v is the loss velocity (unit: m 3 / min), Q is the slurry volume per unit time (m 3 ), t is the grouting time (min).

[0028] Furthermore, the criteria for determining the degree of rock fissure development include:

[0029] When the loss velocity v<0.1m 3 / min, it is judged that the degree of fissure development is low;

[0030] When 0.1≤v<0.3m 3 / min, it is judged that the degree of fissure development is moderate;

[0031] When v≥0.3m 3 / min, it is judged that the degree of crack development is high.

[0032] Furthermore, the method also includes suspending the pile foundation drilling operation after determining the leakage point, making geological records of the rock cracks at the leakage point, and adjusting subsequent construction parameters.

[0033] The method for treating karst grout leakage in pile foundations in karst areas provided by the present invention has the following advantages:

[0034] This method is a comprehensive approach for pile foundation construction in karst areas. Through a phased approach, it first uses a pre-buried casing structure to vertically seal the karst development zone from the surface to the shallow layer, forming a concrete pile body structure, sealing potential leakage channels and stabilizing the stratum. Secondly, grouting channels are laid out within the pile body, using high-pressure grouting to enhance the mechanical properties of the pile-soil interface, filling small cracks and blocking leakage paths in the middle layer. Finally, slurry is injected into the deep karst fissures through a group of circumferential grouting holes around the pile, forming a blocking layer that completely seals the karst caves and large crack networks, preventing slurry loss and improving the concrete filling density. This method, through a three-level sealing system of casing sealing, pile body grouting, and circumferential grouting, constructs a three-dimensional protective structure (surface-middle-deep layer). This not only significantly enhances stratum stability and reduces the risk of karst collapse, water and mud inrush, but also improves the bearing capacity of the pile foundation and construction efficiency through the synergistic effect of multi-scale grouting processes. In short, by drilling holes around the pile foundation to treat karst cracks and backfilling with concrete and grouting the pile body, problems such as pile foundation leakage, hole collapse, and insufficient bearing capacity in karst areas can be solved, and the stability and bearing capacity of the pile foundation can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of pile foundation grout leakage provided by the present invention;

[0036] Figure 2 A schematic diagram of a drilling plane provided by the present invention;

[0037] Figure 3 This is a schematic diagram of the construction method provided by the present invention.

[0038] In the figure: 101, casing structure; 102, rock-soil interface; 103, filling material; 104, karst fissure; 105, grouting holes of pile body; 106, grouting hole group around pile. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] See Figures 1 to 3 The present invention provides a method for treating karst grout leakage in pile foundations in karst areas, comprising the following steps:

[0041] Step S1, pre-embed the casing structure 101 in the pile:

[0042] A casing structure 101 is provided, extending vertically downward from the ground level to a predetermined depth. A temporary filling material 103 with a sealing and pressure-bearing effect is poured into the pile through the casing structure 101 to seal potential grout leakage channels in the karst development area and achieve stratum stabilization.

[0043] Step S2: constructing grouting holes inside the pile body:

[0044] At least one pile grouting hole 105 is arranged in the axial or radial direction in the pile structure, and a pre-proportioned slurry material is injected into the pile grouting hole 105 by a high-pressure grouting device. The slurry material forms a composite stratum reinforcement structure around the pile structure to enhance the mechanical properties of the pile-soil interface;

[0045] Step S3, implementing the pile circumferential grouting sealing process:

[0046] In the circumferential area of ​​the pile body structure, a group of pile grouting holes 106 arranged at intervals in the vertical direction are provided, and the group of pile grouting holes 106 sequentially penetrates the ground layer and the rock-soil interface layer; pre-proportioned slurry material is injected into the 104 development zone of the karst fissure through the group of grouting holes to form a blocking layer that closes the slurry loss channel, and the blocking layer fills the karst cave fissure network through the infiltration and diffusion of the slurry.

[0047] The concrete medium is C15 fine stone concrete, and the top surface is at least 2m above the leakage point.

[0048] During the construction process, a multifunctional drilling and grouting machine was used to drill the grouting holes 105 in the pile body. The holes were drilled to 2m below the pile bottom elevation and then grouting was carried out in sections from bottom to top (each section was 0.5m long).

[0049] An XT-1 geological drilling rig is used to drill 106 grouting holes around the piles. The number of holes can be increased or decreased depending on the ground conditions.

[0050] The slump of concrete is controlled within the range of (80±15) mm, and an early strength agent is added to achieve a 28d compressive strength ≥40 MPa.

[0051] The grouting parameters of the internal grouting channel system are as follows:

[0052] The grouting pressure range is (2.5-4.0) MPa, the slurry water-cement ratio is controlled at (0.5-0.8), and the grouting rate does not exceed (40L / min).

[0053] Furthermore, the lower end of the casing structure 101 is at least 1.5 times the pile diameter away from the top of the karst development area.

[0054] Furthermore, the arrangement of the circumferential grouting holes around the pile is as follows:

[0055] The holes are arranged in a plum blossom shape from the center of the pile to the outside, with a hole spacing of 2m, and the vertical hole depth must reach 2m below the pile bottom elevation.

[0056] Furthermore, a method for determining a pile foundation leakage point is also provided, comprising the following steps:

[0057] Step S41, during the pile foundation drilling process, real-time monitoring of the slurry level in the pile hole;

[0058] Step S42: when it is detected that the slurry level drops suddenly within a preset time period, and the drop exceeds a preset threshold, it is determined that there is a slurry leakage point at the current excavation pile bottom elevation;

[0059] Step S43, replenishing slurry into the pile hole through a grouting operation to maintain the slurry liquid level;

[0060] Step S44, calculating the slurry loss rate at the slurry leakage point according to the slurry filling speed of the slurry filling operation;

[0061] Step S44: preliminarily judging the development degree of the rock fissures at the leakage point based on the magnitude of the slurry loss rate. The faster the loss rate, the higher the development degree of the fissures.

[0062] Furthermore, a liquid level sensor and a data acquisition device are provided. The liquid level sensor is electrically connected to the data acquisition device and transmits monitoring data to the control system in real time.

[0063] Furthermore, the preset time period is 1-5 minutes, and the preset threshold is when the mud level drops by more than 1 / 10 of the pile hole diameter.

[0064] Furthermore, the slurry replenishment operation is performed by an automatically controlled mud pump, and the flow rate of the mud pump is adjusted in real time by the control system according to changes in the liquid level.

[0065] Furthermore, the calculation formula of the slurry loss rate is v=tQ;

[0066] Where v is the loss velocity (unit: m 3 / min), Q is the slurry volume per unit time (m 3 ), t is the grouting time (min).

[0067] Furthermore, the criteria for determining the degree of rock fissure development include:

[0068] When the loss velocity v<0.1m 3 / min, it is judged that the degree of fissure development is low;

[0069] When 0.1≤v<0.3m 3 / min, it is judged that the degree of fissure development is moderate;

[0070] When v≥0.3m 3 / min, it is judged that the degree of crack development is high.

[0071] Furthermore, the method also includes suspending the pile foundation drilling operation after determining the leakage point, making geological records of the rock cracks at the leakage point, and adjusting subsequent construction parameters.

[0072] Description of the overall construction process:

[0073] 1. Construction Preparation

[0074] Complete site surveys, equipment inspections, material preparations, and safety measures arrangements to ensure construction conditions meet requirements.

[0075] 2. Concrete backfill

[0076] Carry out preliminary backfill or foundation reinforcement in the construction area to provide a stable foundation for subsequent drilling (the location may be adjusted according to project requirements).

[0077] 3. Drilling and injection molding machine in place

[0078] Move the drilling and injection machine to the designed location of the pile foundation, adjust the equipment to a horizontal state, and ensure that the drill bit is aligned with the target area.

[0079] 4. Drilling

[0080] Start the drilling and injection molding machine to drill holes, drill to the predetermined position according to the designed depth and diameter, and remove debris from the hole.

[0081] 5. Pile foundation grouting reinforcement

[0082] Cement slurry or other reinforcement materials are injected into the main pile hole through a drilling and injection machine to improve the bearing capacity of the foundation.

[0083] 6. Move the drilling and injection machine to the surrounding area of ​​the pile foundation

[0084] Move the equipment to the predetermined location around the pile foundation and prepare to reinforce the surrounding area.

[0085] 7. Drilling around the pile foundation

[0086] Drill multiple holes around the pile foundation at designed intervals to form a reinforced mesh structure.

[0087] 8. Feeding / grouting

[0088] Inject slurry into the surrounding boreholes to enhance the density and stability of the soil around the pile foundation.

[0089] 9. End processing

[0090] Check the grouting effect of all grouting holes to ensure that the design strength is reached and clean up the construction site.

[0091] 10. Sealing

[0092] Seal the grouting holes with concrete or special materials to prevent slurry from leaking out or being contaminated by the outside world.

[0093] 11. Carry out subsequent construction

[0094] After completing the pile foundation reinforcement, carry out superstructure construction or other related projects.

[0095] The method for treating karst grout leakage in pile foundations in karst areas provided by the present invention has the following advantages:

[0096] The pre-buried casing structure seals potential grout leakage channels in the shallow strata. Combined with the three-level sealing system of the grouting channel inside the pile body and the circumferential grouting hole group around the pile, a three-dimensional protective structure of "surface-middle-deep layer" is formed, which effectively blocks the slurry loss path of the cave and crack network, significantly improving the impermeability and stratum stability of the pile foundation construction; C15 fine stone concrete is used in combination with an early strength agent to achieve rapid curing and high strength, and by precisely controlling the concrete slump, grouting pressure, water-cement ratio and other parameters, it is ensured that the slurry evenly fills the cracks and forms a dense reinforcement layer. ; Equipped with real-time liquid level monitoring and automatic grouting system, the leakage point is determined by the sudden drop of mud liquid level, and the degree of crack development is evaluated in combination with the loss rate classification, so as to realize dynamic adjustment of construction parameters and rapid response to leakage risk, which not only reduces slurry waste but also avoids hole collapse accidents; at the same time, a multi-functional drilling and grouting machine is used to work in coordination with a geological drilling rig. Through segmented grouting, circumferential and angular hole arrangement, and vertical drilling design that penetrates the rock-soil interface layer, the construction efficiency and comprehensive grouting coverage are ensured, effectively solving the problem of pile foundation leakage in karst areas and ensuring the long-term stability of the project.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for treating karst grout leakage in pile foundations in karst areas, characterized in that: The steps include: Step S1, pre-embedding a casing structure (101) in the pile: A casing structure (101) is provided that extends vertically downward from the ground elevation to a predetermined depth, and a temporary filling material (103) having a blocking and pressure-bearing effect is filled into the pile through the casing structure (101) to seal potential slurry leakage channels in the karst development area and achieve stratum stabilization treatment; Step S2: constructing grouting holes inside the pile body: At least one pile body grouting hole (105) is arranged in the pile body structure along the axial direction or the radial direction, and a pre-proportioned slurry material is injected into the pile body grouting hole (105) by a high-pressure grouting device, wherein the slurry material forms a composite stratum reinforcement structure around the pile body structure to enhance the mechanical properties of the pile-soil interface; Step S3, implementing the pile circumferential grouting sealing process: In the circumferential area of ​​the pile body structure, a group of pile circumferential grouting holes (106) arranged at intervals in the vertical direction is provided, and the group of pile circumferential grouting holes (106) sequentially penetrates the ground layer and the rock-soil interface layer; pre-proportioned slurry material is injected into the (104) development area of ​​the karst fissure through the group of grouting holes to form a blocking layer that closes the slurry loss channel, and the blocking layer fills the karst cave fissure network through the infiltration and diffusion of the slurry.

2. The method for treating karst grout leakage in pile foundations in karst areas according to claim 1, characterized in that: The lower end of the casing structure (101) is at least 1.5 times the pile diameter away from the top of the karst development zone.

3. The method for treating karst grout leakage in pile foundations in karst areas according to claim 1, characterized in that: The arrangement of the pile circumferential grouting hole group is as follows: The holes are arranged in a plum blossom shape from the center of the pile to the outside, with a hole spacing of 2m, and the vertical hole depth must reach 2m below the pile bottom elevation.

4. The method for treating karst grout leakage in pile foundations in karst areas according to claim 1, characterized in that: Also included is a method for determining a pile foundation leakage point, comprising the following steps: Step S41, during the pile foundation drilling process, real-time monitoring of the slurry level in the pile hole; Step S42: when it is detected that the slurry level drops suddenly within a preset time period, and the drop exceeds a preset threshold, it is determined that there is a slurry leakage point at the current excavation pile bottom elevation; Step S43, replenishing slurry into the pile hole through a grouting operation to maintain the slurry liquid level; Step S44, calculating the slurry loss rate at the slurry leakage point according to the slurry filling speed of the slurry filling operation; Step S44: preliminarily judging the development degree of the rock fissures at the leakage point based on the magnitude of the slurry loss rate. The faster the loss rate, the higher the development degree of the fissures.

5. The method for treating karst grout leakage in pile foundations in karst areas according to claim 4, characterized in that: A liquid level sensor and a data acquisition device are provided. The liquid level sensor is electrically connected to the data acquisition device and transmits monitoring data to the control system in real time.

6. The method for treating karst grout leakage in pile foundations in karst areas according to claim 5, characterized in that: The preset time period is 1-5 minutes, and the preset threshold is when the mud level drops by more than 1 / 10 of the pile hole diameter.

7. The method for treating karst grout leakage in pile foundations in karst areas according to claim 6, characterized in that: The slurry replenishment operation is performed by an automatically controlled mud pump, and the flow rate of the mud pump is adjusted in real time by the control system according to changes in the liquid level.

8. The method for treating karst grout leakage in pile foundations in karst areas according to claim 7, characterized in that: The calculation formula of the slurry loss rate is v=tQ; Among them, v is the loss velocity, Q is the volume of slurry replenished per unit time, and t is the slurry replenishment time.

9. The method for treating karst grout leakage in pile foundations in karst areas according to claim 8, characterized in that: The criteria for determining the degree of rock fissure development include: When the loss velocity v<0.1m 3 / min, it is judged that the degree of fissure development is low; When 0.1≤v<0.3m 3 / min, it is judged that the degree of fissure development is moderate; When v≥0.3m 3 / min, it is judged that the degree of crack development is high.

10. The method for treating karst grout leakage in pile foundations in karst areas according to claim 9, characterized in that: It also includes suspending the pile foundation drilling operation after determining the leakage point, making geological records of the rock cracks at the leakage point, and adjusting subsequent construction parameters.

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