Construction method and pile foundation structure suitable for pile foundation with karst cave

Abstract

This invention belongs to the field of pile foundation construction technology and discloses a construction method and pile foundation structure suitable for pile foundations where the pile hole encounters a karst cave. The construction method includes the following steps: S1, detecting the location and height of the karst cave in the pile hole; S2, providing a reinforcing cage and a sleeve, fixing the sleeve around the outside of the reinforcing cage, wherein the length of the sleeve is greater than the height of the karst cave, and the outer diameter of the sleeve is the same as the inner diameter of the pile hole; S3, lowering the reinforcing cage into the pile hole and sealing the karst cave with the sleeve; S4, pouring pile foundation concrete into the pile hole. This invention, by fixing a sleeve with an outer diameter matching the inner diameter of the pile hole and a length greater than the height of the karst cave around the outside of the reinforcing cage, and then sealing the karst cave when lowering the reinforcing cage into the pile hole, can effectively prevent concrete loss during subsequent pile foundation concrete pouring, forming a complete pile body. By constructing the sleeve only for the karst cave section, costs can be significantly reduced.

Description

Technical Field

[0001] This invention belongs to the field of pile foundation construction technology, and specifically relates to a construction method and pile foundation structure suitable for pile foundations where the pile hole encounters a karst cave. Background Technology

[0002] When constructing pile foundations in karst areas, pile holes often encounter karst caves of varying sizes. The presence of these caves can lead to significant concrete loss during pouring, resulting in quality problems such as incomplete pile bodies and insufficient bearing capacity.

[0003] Currently, the traditional approach involves lowering a long steel casing as a whole, but this method is extremely costly and wastes a lot of materials, especially uneconomical for deep and large pile foundations. Another approach is to backfill the karst cave with sand or concrete, but this method is complex, time-consuming, and the quality of the backfill is difficult to control, resulting in poor stability. Therefore, we propose a construction method and pile foundation structure suitable for pile foundations where the pile hole encounters a karst cave to solve the above problems. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a construction method and pile foundation structure suitable for pile foundations where the pile hole encounters karst caves, solving the problems of high cost and difficulty in quality control associated with traditional treatment methods.

[0005] This invention is achieved through the following scheme: a construction method for pile foundations where the pile hole encounters a karst cave, comprising the following steps: S1. Detect the location and height of the karst cave inside the pile hole; S2. Provide a reinforcing cage and a sleeve, and fix the sleeve on the outside of the reinforcing cage. The length of the sleeve is greater than the height of the karst cave, and the outer diameter of the sleeve is the same as the inner diameter of the pile hole. S3. Lower the steel cage into the pile hole and seal the karst cave with the sleeve; S4. Pour the pile foundation concrete into the pile hole.

[0006] A further improvement of the construction method of the present invention for pile foundations where the pile hole encounters a karst cave is that the inner diameter of the sleeve is greater than the outer diameter of the reinforcing cage. When performing step S2, the method further includes the step of providing a connector and fixing the connector together with the reinforcing cage and the sleeve.

[0007] A further improvement of the construction method of the present invention for pile foundations where the pile hole encounters a karst cave is that, when fixing the sleeve and the connector, the sleeve and the reinforcing cage are controlled to be at the same center.

[0008] A further improvement of the construction method for pile foundations where the pile hole encounters a karst cave is that the connector includes a polygonal frame with multiple connecting angles, and the step of fixing the connector together with the reinforcing cage and sleeve includes the following steps: The polygonal frame is fixedly connected to the steel cage, with all connecting corners protruding to the outside of the steel cage. The sleeve is fixed to multiple connecting corners.

[0009] A further improvement of the construction method of the present invention for pile foundations where the pile hole encounters a karst cave is that the sleeve is made of steel, and the wall thickness of the sleeve is calculated using the wall thickness formula when the steel sleeve is prepared. The wall thickness formula is: t=k*P / σ. Where P is the formation pressure, which is calculated using the formula P = (γ×H +γ_w×H_w) / 1000; γ is the weighted average unit weight of the overlying strata; H is the burial depth of the karst cave; γ_w is the unit weight of groundwater; H_w is the groundwater level; σ is the compressive strength of the sleeve material; and k is the safety factor.

[0010] A pile foundation structure, formed using a construction method as described above suitable for pile foundations where the pile hole encounters a karst cave, comprising: Reinforcing cage; A sleeve is fixedly fitted onto the outside of the reinforcing cage to seal the karst cave when the reinforcing cage is placed into the pile hole. The length of the sleeve is greater than the height of the karst cave, and the outer diameter of the sleeve is the same as the inner diameter of the pile hole. The concrete body is formed by pouring concrete into the pile hole and allowing it to solidify, and the formed concrete body is anchored together with the reinforcing cage and sleeve as a whole.

[0011] A further improvement of the pile foundation structure of the present invention is that the inner diameter of the sleeve is greater than the outer diameter of the reinforcing cage, and the pile foundation structure also includes a polygonal frame with multiple connecting angles, the polygonal frame being fixedly connected to the reinforcing cage, and the multiple connecting angles protruding to the outside of the reinforcing cage, and the sleeve being fixedly connected to the multiple connecting angles.

[0012] A further improvement of the pile foundation structure of the present invention is that the outer surface of the sleeve is provided with anti-slip texture.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention fixes a sleeve with an outer diameter that matches the inner diameter of the pile hole and a length greater than the height of the karst cave onto the outside of the reinforcing cage. When the reinforcing cage is lowered into the pile hole, the sleeve seals the karst cave, ensuring that concrete loss is effectively prevented during subsequent pile foundation concrete pouring, thus forming a complete pile body. The sleeve is installed only on the karst cave section, which can significantly reduce costs. Attached Figure Description

[0014] Figure 1 A schematic diagram of the sleeve sealing position of the present invention is shown.

[0015] Figure 2A top view schematic diagram of the connection between the sleeve and the reinforcing cage of the present invention is shown.

[0016] In the diagram: 1. Reinforcing cage; 2. Pile hole; 3. Sleeve; 4. Karst cave; 5. Polygonal frame; 6. Stiffening hoop. Detailed Implementation

[0017] To address the problems of high cost and difficulty in quality control associated with traditional methods, this invention provides a construction method and pile foundation structure suitable for pile foundations where the pile hole encounters a karst cave. The following detailed description, in conjunction with accompanying drawings, further illustrates this construction method and pile foundation structure suitable for pile foundations where the pile hole encounters a karst cave.

[0018] See Figures 1-2 As shown, a construction method for pile foundations where the pile hole encounters a karst cave is included, comprising the following steps: S1. Detect (geological drilling or radar detection) the location of the karst cave 4 inside the pile hole 2 and the height of the karst cave 4; S2. Provide a reinforcing cage 1 and a sleeve 3, and fix the sleeve 3 on the outside of the reinforcing cage 1. The length of the sleeve 3 is greater than the height of the karst cave 4, and the outer diameter of the sleeve 3 is the same as the inner diameter of the pile hole 2. S3. Lower the steel cage 1 into the pile hole 2, and make the sleeve 3 seal the karst cave 4; S4. Pour the pile foundation concrete into pile hole 2.

[0019] By fixing a sleeve 3 with an outer diameter that matches the inner diameter of the pile hole 2 and a length greater than the height of the karst cave 4 to the outside of the reinforcing cage 1, and then sealing the karst cave 4 with the sleeve 3 when the reinforcing cage 1 is lowered into the pile hole 2, it is possible to effectively prevent concrete loss during subsequent pile foundation concrete pouring, thus forming a complete pile body. The sleeve 3 is only installed on the karst cave 4 section, which can significantly reduce costs compared to the full-length casing. The sleeve 3 and the reinforcing cage 1 are assembled on the ground, reducing the number of work steps inside the pile hole 2 and improving construction efficiency and safety.

[0020] Wherein, the inner diameter of the sleeve 3 is greater than the outer diameter of the reinforcing cage 1. When performing step S2, the step further includes: providing a connector and fixing the connector together with the reinforcing cage 1 and the sleeve 3.

[0021] By adopting the above design, the steel cage 1 and sleeve 3 are fixedly connected together using connectors, which can improve the connection between sleeve 3 and steel cage 1.

[0022] When fixing the sleeve 3 to the connector, the sleeve 3 and the steel cage 1 are controlled to be at the same center.

[0023] By adopting the above design, the pile body can be formed with better quality during subsequent concrete pouring.

[0024] The connector includes a polygonal frame 5 with multiple connecting angles, and the step of fixing the connector together with the reinforcing cage 1 and the sleeve 3 includes the following steps: The polygonal frame 5 is fixedly connected to the steel cage 1, and the multiple connecting corners protrude to the outside of the steel cage 1. Connect and fix the sleeve 3 to multiple connecting corners.

[0025] Further, see Figure 2 The polygonal frame 5 includes two triangular hoops connected to each other. The multiple connecting angles are the corner positions of the two triangular hoops. The multiple connecting angles are arranged at intervals along the outer periphery of the steel cage 1. The steel cage 1 is fixedly connected to stiffening hoops 6 on both the inner and outer sides of the sleeve 3 connection area. The two triangular hoops are fixedly connected to the stiffening hoops 6. By adopting the above design, a high-rigidity modular connection node is formed, which can more effectively transfer the lateral pressure borne by the sleeve 3 to the entire steel cage 1, and significantly improve the shear and torsional resistance of the connection.

[0026] The sleeve 3 is made of steel, and the wall thickness of the sleeve 3 is calculated using the wall thickness formula when the steel sleeve 3 is prepared. The wall thickness formula is: t=k*P / σ. Wherein, P is the comprehensive formation pressure (unit: MPa), which is calculated by the formula P = (γ×H +γ_w×H_w) / 1000 (dividing by 1000 is to convert kPa to MPa); γ is the weighted average unit weight of the overlying strata based on the geological survey report (kN / m³); H is the burial depth of the karst cave 4 (m); γ_w is the unit weight of groundwater (10kN / m³); H_w is the groundwater level (m); σ is the compressive strength of the sleeve 3 material (MPa); k is the safety factor, ranging from 1.5 to 2.0, used to cover dynamic loads and uncertainties such as concrete flow impact and geological variations.

[0027] This calculation model combines dynamic geological parameters with material mechanical properties and engineering safety reserves, realizing the scientific quantitative design of the sleeve thickness 3, which is different from the traditional empirical values ​​or conventional formula applications that only consider hydrostatic pressure.

[0028] Calculation example (for reference): A certain karst cave has a burial depth of H=25m. The geological survey report shows that its overlying strata are 10m thick clay (unit weight γ1=20kN / m³) and 15m thick sandstone (unit weight γ2=24kN / m³). The groundwater level is located 5m below the ground surface (i.e. H_w=20m).

[0029] Calculate the weighted average bulk density: γ = (20×10 + 24×15) / (10+15) = 22.4 kN / m³.

[0030] Calculate the overall formation pressure: P = (22.4 × 25 + 10 × 20) = 760 kPa = 0.76 MPa.

[0031] Q345 steel (σ=345 MPa) is selected, and the safety factor k=1.8 is taken.

[0032] The theoretical thickness of sleeve 3 is calculated as follows: t = 1.8 × 0.76 / 345 ≈ 0.00396 m = 3.96 mm.

[0033] Taking into account machining and corrosion allowances, the final thickness of sleeve 3 was determined to be 25 mm.

[0034] By adopting the above design, not only is the material usage of the steel sleeve 3 saved, but the wall thickness of the steel sleeve 3 calculated by the above formula also fully meets the usage requirements, ensuring the overall rigidity of the steel sleeve 3. The length of the sleeve 3 can be 1.5 to 2.0 times the height of the karst cave 4 to ensure that both ends are anchored into stable strata. The preferred material for the sleeve 3 is Q345 low-alloy high-strength steel.

[0035] A pile foundation structure, formed using a construction method as described in claim 1 applicable to pile foundations where the pile hole 2 encounters a karst cave 4, comprising: Reinforcing cage 1; Sleeve 3 is fixedly sleeved on the outside of the reinforcing cage 1 and is used to seal the karst cave 4 when the reinforcing cage 1 is placed into the pile hole 2. The length of sleeve 3 is greater than the height of karst cave 4, and the outer diameter of sleeve 3 is the same as the inner diameter of pile hole 2. The concrete body is formed by pouring concrete into the pile hole 2 and allowing it to solidify. The concrete body formed is anchored together with the reinforcing cage 1 and the sleeve 3 to form a whole.

[0036] The pile foundation structure also includes a polygonal frame 5 with multiple connecting angles. The polygonal frame 5 is fixedly connected to the reinforcing cage 1, and the multiple connecting angles protrude to the outside of the reinforcing cage 1. The sleeve 3 is connected and fixed to the multiple connecting angles.

[0037] The outer surface of the sleeve 3 is provided with anti-slip texture to enhance mechanical engagement with the hole wall and anti-slip capability.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0039] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. Those skilled in the art can make various modifications to the present invention based on the above description. Therefore, certain details in the embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention shall be defined by the appended claims.

Claims

1. A construction method for pile foundations where the pile hole encounters a karst cave, characterized in that, Includes the following steps: S1. Detect the location and height of the karst cave inside the pile hole; S2. Provide a reinforcing cage and a sleeve, and fix the sleeve on the outside of the reinforcing cage. The length of the sleeve is greater than the height of the karst cave, and the outer diameter of the sleeve is the same as the inner diameter of the pile hole. S3. Lower the steel cage into the pile hole and seal the karst cave with the sleeve; S4. Pour the pile foundation concrete into the pile hole.

2. The construction method for pile foundations where the pile hole encounters a karst cave, as described in claim 1, is characterized in that... The inner diameter of the sleeve is greater than the outer diameter of the reinforcing cage. When performing step S2, the step further includes: providing a connector and fixing the connector to the reinforcing cage and the sleeve together.

3. The construction method for pile foundations where the pile hole encounters a karst cave, as described in claim 2, is characterized in that... When fixing the sleeve to the connector, ensure that the sleeve and the reinforcing cage are at the same center.

4. The construction method for pile foundations where the pile hole encounters a karst cave, as described in claim 3, is characterized in that... The connector includes a polygonal frame with multiple connecting angles, and the step of fixing the connector together with the reinforcing cage and the sleeve includes the following steps: The polygonal frame is fixedly connected to the steel cage, with all connecting corners protruding to the outside of the steel cage. The sleeve is fixed to multiple connecting corners.

5. The construction method for pile foundations where the pile hole encounters a karst cave, as described in claim 2, is characterized in that... The sleeve is made of steel, and the wall thickness of the sleeve is calculated using the wall thickness formula when the steel sleeve is prepared. The wall thickness formula is: t=k*P / σ; Where P is the formation pressure, which is calculated using the formula P = (γ×H +γ_w×H_w) / 1000; γ is the weighted average unit weight of the overlying strata; H is the burial depth of the karst cave; γ_w is the unit weight of groundwater; H_w is the groundwater level; σ is the compressive strength of the sleeve material; and k is the safety factor.

6. A pile foundation structure, formed using the construction method described in claim 1 for pile foundations where the pile hole encounters a karst cave, characterized in that, include: Reinforcing cage; A sleeve is fixedly fitted onto the outside of the reinforcing cage to seal the karst cave when the reinforcing cage is placed into the pile hole. The length of the sleeve is greater than the height of the karst cave, and the outer diameter of the sleeve is the same as the inner diameter of the pile hole. The concrete body is formed by pouring concrete into the pile hole and allowing it to solidify, and the formed concrete body is anchored together with the reinforcing cage and sleeve as a whole.

7. The pile foundation structure as described in claim 6, characterized in that, The inner diameter of the sleeve is greater than the outer diameter of the reinforcing cage. The pile foundation structure also includes a polygonal frame with multiple connecting angles. The polygonal frame is fixedly connected to the reinforcing cage, and the multiple connecting angles protrude to the outside of the reinforcing cage. The sleeve is fixedly connected to the multiple connecting angles.

8. The pile foundation structure as described in claim 6, characterized in that, The outer surface of the sleeve is provided with anti-slip texture.

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