A pile foundation structure for complex strata of soft and hard rock and its construction method

Abstract

This invention discloses a pile foundation structure and its construction method in complex soft and hard rock strata, relating to the field of foundation construction technology. The structure includes a column pile, comprising a cylindrical body with a sliding assembly at the bottom of its chamber. The sliding assembly includes an upper sliding plate and a lower sliding plate. The bottom of the lower sliding plate is connected to the bottom end of the column pile via several first compression springs. A frustum is fixed between the upper and lower sliding plates. From the smaller diameter end to the larger diameter end, the sidewall of the frustum is a concave arc shape with a gradually increasing slope. Several insert rods and several matching through holes are evenly distributed in the circumferential direction of the column pile. One end of each insert rod has a roller, and this roller abuts against the sidewall of the frustum. The other end of each insert rod is inserted into a through hole. This design allows for the fixing of the bottom of the column pile using insert rods, thereby enhancing the pile's stability.

Description

Technical Field

[0001] This invention relates to the field of foundation construction technology, specifically to a pile foundation structure and construction method for complex soft and hard rock strata. Background Technology

[0002] During building construction, in order to improve the stability of the foundation and its seismic performance, a number of concrete piles are usually driven into the foundation, thus setting up a large number of column piles under the building, which can improve the stability of the building to a certain extent.

[0003] With the large-scale construction of buildings, building projects inevitably face high-stress soft rock sections. When column piles penetrate soft rock deformation sections, that is, when there are strongly weathered layers or soft rock layers in the complex strata of soft and hard rock, the overall or local stress on the column pile foundation is too large, which threatens the overall stability of the building project. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a pile foundation structure and its construction method for complex soft and hard rock strata. This solution allows for the fixation of the bottom of the column pile by inserting rods, thereby enhancing the fixation effect of the column pile and improving its stability.

[0005] This invention is achieved through the following technical solution:

[0006] A pile foundation structure for complex strata of soft and hard rock includes:

[0007] A columnar pile, comprising a cylindrical body, wherein the bottom of the cavity of the cylindrical body is provided with a sliding assembly, the sliding assembly comprising an upper sliding plate and a lower sliding plate, the outer diameter of the upper sliding plate and the lower sliding plate being adapted to the inner diameter of the cylindrical body, and both being sealed and slidably connected to the inner side of the cylindrical body, and being able to slide along the axis of the cylindrical body; the bottom of the lower sliding plate is connected to the end of the bottom of the columnar pile through several first compression springs;

[0008] A frustum is fixed between the upper and lower sliding plates. The smaller diameter end of the frustum is located on the lower sliding plate, and the larger diameter end is located on the upper sliding plate. From the smaller diameter end to the larger diameter end, the sidewall of the frustum is a concave arc with a gradually increasing slope.

[0009] The column has several inserted rods and several matching through holes evenly distributed in the circumferential direction. One end of each inserted rod has a roller, and the other end of the inserted rod abuts against the side wall of the frustum through the roller. The other end of the inserted rod is inserted into the through hole.

[0010] Compared to existing technologies, with the large-scale construction of buildings, building projects inevitably face high-stress soft rock sections. When column piles penetrate soft rock deformation sections, i.e., in complex strata of soft and hard rock with interbedded strongly weathered layers or soft rock layers, the overall or local stress on the column pile foundation is too large, thus threatening the overall stability of the building project. This invention provides a pile foundation structure for complex strata of soft and hard rock. Using this solution, the bottom of the column pile can be fixed by inserting rods, thereby strengthening the fixation effect of the column pile and improving stability. In the specific scheme, a cylindrical body is first inserted into the foundation pit. The cylindrical body has an end at the bottom, an internal cavity, and an opening at the top. After the cylindrical body is installed, concrete can be poured into the cylindrical body through the top opening. As gravity increases, it presses down on the upper sliding plate, forcing it to slide downwards, while the lower sliding plate moves accordingly. In this way, as the arc-shaped side of the truncated cone moves downwards, it gradually drives the insert rod to extend outwards from the through hole, thus forcing the insert rod to insert into the external soil layer. Rollers are used to roll on the arc-shaped surface to reduce friction and reduce the magnitude of the force on the insert rod in other directions. This avoids the insert rod from having a tendency to deviate due to excessive force in other directions, which could prevent it from quickly extending out of the through hole or even break. Therefore, this scheme uses the insert rod to fix the bottom of the entire column pile, improving the overall stability of the column pile.

[0011] Because the complex strata of hard and soft rock contain strongly weathered layers or soft rock layers, the overall or local stress on the column pile foundation is too large. Therefore, in order to protect the column pile as a whole and avoid the soft rock area in the middle layer from generating large stress on the column pile, which could lead to instability or even damage to the column pile, a support casing is also included. The outer diameter of the support casing is adapted to the inner diameter of the foundation pit; the column pile is coaxially inserted into the support casing, and the outer diameter of the column pile is adapted to the inner diameter of the support casing; the lower end of the column pile extends beyond the support casing, and the through hole is located outside the support casing.

[0012] To enable rapid installation of the column pile, several guide strips are evenly distributed around the circumference of the column pile, and the guide strips are arranged along the axis of the column pile; the through hole is located at the guide strip and extends from the inside of the column pile to the guide strip;

[0013] The inner side of the support casing is evenly distributed with several guide grooves that are adapted to the guide strips. The depth of the guide grooves is less than the width of the guide strips. Insulation material is filled between the support casing and the column pile. In this design, the cooperation of the guide strips and guide grooves enables rapid guidance when inserting the column pile. Furthermore, because the inner wall of the support casing has internal spiral reinforcement, it is impossible to construct deep guide grooves. Therefore, the depth of the guide grooves can be less than the width of the guide strips, thus providing both guidance and radial positioning of the column pile. Insulation material is then filled into the gap between the support casing and the column pile, improving the insulation effect on the column pile.

[0014] To facilitate the detachable connection and replacement of the column pile, a pre-formed concrete column is filled above the upper sliding plate, and a second compression spring is fitted at the insertion rod. In this design, the pre-formed concrete column can be directly inserted into the cavity inside the sleeve. This not only prevents concrete leakage under the upper sliding plate during pouring but also allows for quick removal of the concrete column when replacement is needed. At this time, the upper and lower sliding plates reset, and the insertion rod retracts under the tension of the second compression spring, allowing the sleeve to be removed and the column pile to be replaced.

[0015] In a further embodiment, the support cylinder includes an inner steel cage and an outer steel cage arranged coaxially from the inside to the outside. The inner steel cage and the outer steel cage are connected by straight bars. A gap is left between the outer steel cage and the inner sidewall of the foundation pit, and the lower end of the inner steel cage extends out of the outer steel cage.

[0016] It also includes a first anchor rod, which is used to pass through the side wall of the support cylinder and through the soft rock surface on the local inner side wall of the foundation pit, and extend into the soft rock area. The extension end of the first anchor rod extends from the soft rock area into the hard rock area in sequence and is anchored in the hard rock area.

[0017] The first anchor bolt is set horizontally or inclined upwards. Compared to existing technologies, with the large-scale construction of buildings, building projects inevitably face high-stress soft rock sections. When column piles penetrate soft rock deformation sections, i.e., when there are strongly weathered or soft rock layers interspersed within moderately weathered rock layers, the overall or local stress on the column pile foundation is excessive, thus threatening the overall stability of the building project. This invention provides a foundation pit support structure for complex soft and hard rock strata. Using this solution, not only can the column piles be supported as a whole by sequentially pouring concrete inside and outside the support cylinder, but local support can also be provided for the column piles at the soft rock surface to improve stability. Specifically, the solution includes a support cylinder for supporting the foundation pit and protecting the column piles. This not only protects the column piles and reduces stress damage from external conditions, but also allows for the reuse or rapid replacement of the column piles.

[0018] Furthermore, in existing technologies, support structures or column piles are typically inserted directly into the foundation pit, resulting in an uneven connection between the support structure or column piles and the pit sidewall. Trimming the pit sidewall into a flat surface is time-consuming and labor-intensive. Therefore, in this invention, the support cylinder includes an inner and outer reinforcing cage arranged coaxially from the inside out. The inner and outer reinforcing cages are connected and fixed by several straight bars. After lowering the inner and outer reinforcing cages, steel-reinforced concrete can be sprayed onto the inner reinforcing cage to form an inner formwork. The inner reinforcing cage is constructed from a spiral reinforcing cage, several vertical bars, and a reinforcing mesh. To form a dense steel mesh and reduce the size of the holes, the inner formwork is formed quickly. Since the lower end of the inner steel cage extends beyond the outer steel cage, the inner steel cage can be inserted into the bottom of the foundation pit to form a bottom seal, creating a pouring space between the inner formwork and the inner wall of the foundation pit. At this time, the outer steel cage is located in the pouring space. By pouring concrete in the pouring space, the solidified concrete can be seamlessly connected with the inner wall of the foundation pit, thus forming an integral whole between the support structure and the inner wall of the foundation pit. This strengthens the support of the hard rock and soil layer for the support structure and the column piles, thereby improving the overall support capacity of the support structure for the column piles.

[0019] Secondly, due to the presence of soft rock in certain areas of the inner wall of the foundation pit, when the soft rock is horizontal or slopes upwards away from the pit, the soft rock layer in these areas experiences significant stress and compresses the sidewalls of the retaining casing, generating substantial localized earth pressure. This can lead to localized stress damage to the retaining casing and even reduce its stability. Therefore, anchoring can be achieved by installing a first anchor rod. The first anchor rod passes sequentially through the retaining casing and the soft rock area from the inner wall of the retaining casing and anchors into the hard rock area. This fixation in the hard rock area provides tension anchoring at the stress points of the retaining casing, thereby reducing stress damage at those points. The direction of the first anchor rod must be set along the initial direction of the soft rock area. If this direction cannot anchor it into the hard rock area, the drilling direction can be adjusted circumferentially until it can be anchored into the hard rock area.

[0020] Furthermore, in order to reduce the soil pressure on the support casing in the soft rock area and reduce stress concentration, a force-sharing component is also included. The force-sharing component includes a frame located at the soft rock surface and perpendicular to the principal stress direction of the soft rock surface.

[0021] The frame contains several force-sharing regions, and each force-sharing region contains several thin plates. The thin plates are spaced apart, and the orientation of the thin plates is at an angle to the frame.

[0022] Within the same force component region, several thin plates are parallel to each other; between different force component regions, the thin plates are arranged in different directions.

[0023] Several second anchor bolts are sequentially arranged along the circumferential direction of the frame. The extended ends of the second anchor bolts are inserted into the hard rock area and anchored therein, and the second anchor bolts are fixedly connected to the frame. In this scheme, a small amount of excavation can be carried out at the initial end of the soft rock area, i.e., at the soft rock surface, to determine the orientation of the initial end of the soft rock area. This allows for a rough determination of the main stress direction of the soft rock area on the support casing. At this point, a force-sharing component can be installed at the excavation face. The force-sharing component includes a frame, several thin plates, and several second anchor bolts. The several second anchor bolts can be used to firmly anchor the frame at the excavation face, while the several thin plates are inserted into the soft rock area and arranged in different directions. In this way, when the soft rock part loosens and moves and compresses towards the support casing, it can move towards the force-sharing areas in different directions, thereby diverting the main stress and reducing stress concentration.

[0024] To ensure that the thin plate has sufficient length to provide a sufficiently long diversion length, the inner side of the thin plate extends out of the frame and into the soft rock region.

[0025] To achieve overall protection, the dimensions of the frame are adapted to the circumferential dimensions of the soft rock area. The frame shape can be circular, square, or any other shape that fits the circumferential dimensions of the excavation face.

[0026] Since the first anchor bolt needs to be placed at or near the center of the soft rock surface, a sleeve is provided at the center of the frame to facilitate the protrusion position of the first anchor bolt. The sleeve is used for the first anchor bolt to pass through.

[0027] As a fixed connection method, the second anchor rod is welded to the frame.

[0028] To improve the structural strength continuity of the support casing at local locations, several spiral steel bars are installed inside the support casing at the soft rock surface of the inner sidewall of the foundation pit. The two ends of each spiral steel bar are welded to the inner and outer steel reinforcement cages, respectively, and the spiral steel bars are oriented towards the main pressure direction exerted by the soft rock area on the outer wall of the support casing. In this design, the direction of the spiral steel bars is the main pressure direction exerted by the soft rock area on the outer wall of the support casing, meaning that the continuous strength of the spiral steel bars themselves provides resistance to pressure on the local soft rock area.

[0029] Further solutions:

[0030] This invention also provides a construction method for pile foundation structures in complex soft and hard rock strata, comprising the following steps:

[0031] S1: Excavate the foundation pit and form steps at the bottom of the foundation pit;

[0032] S2: Detect soft rock surfaces on the inner wall of the foundation pit and install force-sharing components at the soft rock surfaces;

[0033] S3: Then, the inner and outer steel reinforcement cages are lowered into the foundation pit, so that the lower end of the inner steel reinforcement cage is inserted into the step;

[0034] S4: Then, concrete is sprayed onto the inner steel cage to form the inner formwork;

[0035] S5: Pour concrete into the space between the inner membrane plate and the inner sidewall of the foundation pit to complete the overall casting and shaping of the support cylinder.

[0036] S6: Then drill a hole from the inside of the support casing to the soft rock area at the soft rock surface location and install the first anchor bolt;

[0037] S7: Insert the cylinder into the support casing. After inserting the cylinder, pour concrete inside the cylinder to complete the forming of the column pile.

[0038] S8: Finally, fill the gap between the support casing and the column pile with insulation material to complete the pile foundation construction.

[0039] Furthermore, step S2 also includes the following specific steps:

[0040] S21: After detecting a soft rock surface, excavate along the circumferential direction of the soft rock surface into the soft rock area. When it is sufficient to determine the initial direction of the soft rock area, stop excavating.

[0041] S22: Trim the excavation face to an installation face perpendicular to the initial orientation;

[0042] S23: Install several second anchor rods sequentially along the circumferential direction of the mounting surface, so that the extension end of the second anchor rod penetrates into the hard rock area for anchoring;

[0043] S24: Then, the frame is spliced ​​sequentially along the circumferential direction of the mounting surface, and the frame and the ends of several second anchor rods are welded and fixed.

[0044] S25: Inside the frame, several thin plates are sequentially inserted into the mounting surface, and the thin plates are divided into several force-sharing areas.

[0045] S26: Finally, weld the two ends of several thin plates to the inner wall of the frame to complete the installation of the force-sharing components.

[0046] Furthermore, when inserting several thin plates sequentially into the mounting surface, a cutting device is needed to cut a gap in the mounting surface for the thin plates to be inserted.

[0047] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0048] This invention provides a pile foundation structure and construction method for complex soft and hard rock strata. Using this method, the bottom of the column pile can be fixed by inserting rods, thereby strengthening the fixing effect of the column pile and improving its stability.

[0049] This invention provides a pile foundation structure and its construction method for complex soft and hard rock strata. Using this method, steel-reinforced concrete is sprayed onto the inner reinforcing cage to form an inner formwork. This creates a pouring space between the inner formwork and the inner wall of the foundation pit. The outer reinforcing cage is located within this pouring space. By pouring concrete within this space, the solidified concrete seamlessly connects with the inner wall of the foundation pit, forming a unified structure between the support casing and the inner wall of the foundation pit. This strengthens the support of the hard rock strata for the support structure and the column piles, thereby improving the overall support capacity of the support structure for the column piles.

[0050] This invention provides a pile foundation structure and construction method for complex soft and hard rock strata. In this scheme, the first anchor rod is set for anchoring, thereby reducing the stress damage at the stress location. A force-sharing component is also provided. When the soft rock part loosens and moves and compresses towards the support cylinder, it can move towards the force-sharing area in different directions, thereby diverting the principal stress and reducing stress concentration. Attached Figure Description

[0051] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0052] Figure 1 This is a schematic diagram of the structure of the column pile provided by the present invention;

[0053] Figure 2 A cross-sectional view of the column pile provided by the present invention;

[0054] Figure 3 This is a schematic diagram of the support structure provided by the present invention;

[0055] Figure 4 The isometric distribution diagram of the inner and outer reinforcing cages in the support casing provided by the present invention;

[0056] Figure 5 This is a front view of the inner and outer reinforcing cages in the sheath provided by the present invention.

[0057] Figure 6 Provided by the present invention Figure 3 Enlarged image A in the image;

[0058] Figure 7 This is a schematic diagram of the rear structure of the force-shaping component provided by the present invention.

[0059] The attached diagram shows the markings and corresponding component names:

[0060] 1-Support cylinder, 101-Inner reinforcing cage, 102-Outer reinforcing cage, 103-Helical reinforcing bar, 2-First anchor rod, 3-Force component, 301-Frame, 302-Thin plate, 303-Second anchor rod, 304-Sleeve, 4-Column pile, 401-Cylinder body, 402-Upper sliding plate, 403-Lower sliding plate, 404-Frustum, 405-Insertion rod, 406-First compression spring, 407-End, 408-Guide strip, 409-Concrete column, 410-Second compression spring. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0062] Example 1:

[0063] This embodiment 1 provides a pile foundation structure for complex strata of soft and hard rock, such as Figure 1 and Figure 2 As shown, it includes:

[0064] The column pile 4 includes a cylindrical body 401. The bottom of the chamber of the cylindrical body 401 is equipped with a sliding assembly, which includes an upper sliding plate 402 and a lower sliding plate 403. The outer diameters of the upper sliding plate 402 and the lower sliding plate 403 are adapted to the inner diameter of the cylindrical body 401, and are both sealed and slidably connected to the inner side of the cylindrical body 401, and can slide along the axis of the cylindrical body 401. The bottom of the lower sliding plate 403 is connected to the end 407 at the bottom of the column pile 4 through several first compression springs 406.

[0065] A frustum 404 is fixed between the upper slide plate 402 and the lower slide plate 403. The smaller diameter end of the frustum 404 is located on the lower slide plate 403, and the larger diameter end is located on the upper slide plate 402. From the smaller diameter end to the larger diameter end, the sidewall of the frustum 404 is a concave arc shape with a gradually increasing slope.

[0066] The column pile 4 has several inserted rods 405 and several matching through holes evenly distributed in the circumferential direction. One end of each inserted rod 405 is equipped with a roller, and one end of the inserted rod 405 abuts against the side wall of the frustum 404 through the roller; the other end of the inserted rod 405 is inserted into the through hole.

[0067] Compared to existing technologies, with the large-scale construction of buildings, building projects inevitably face high-stress soft rock sections. When the column pile 4 passes through soft rock deformation sections, that is, in complex strata of soft and hard rock with strong weathered layers or soft rock layers, the overall or local stress on the column pile 4 foundation is too large, thus threatening the overall stability of the building project. This invention provides a pile foundation structure for complex strata of soft and hard rock. Using this solution, the bottom of the column pile 4 can be fixed by the insertion rod 405, thereby strengthening the fixing effect of the column pile 4 and improving stability. In the specific scheme, a cylinder 401 is first inserted into the foundation pit. The bottom of the cylinder 401 has an end 407, and its interior has a cavity with an opening at the top. After the cylinder 401 is installed, concrete can be poured into the cylinder 401 through the top opening. As gravity increases, it presses down on the upper sliding plate 402, forcing it to slide downwards, while the lower sliding plate 403 moves accordingly. In this way, as the arc-shaped side of the truncated cone 404 moves downwards, it gradually drives the insertion rod 405 to extend outwards from the through hole, thereby forcing the insertion rod 405 to be inserted into the external soil layer. Rollers are used to roll on the arc-shaped surface to reduce friction and reduce the magnitude of the force component on the insertion rod 405 in other directions. This avoids the insertion rod 405 from having a tendency to deviate due to excessive force in other directions, which would prevent it from quickly extending out of the through hole or even break. Therefore, this scheme uses the insertion rod 405 to fix the bottom of the entire column pile 4, improving the overall stability of the column pile 4.

[0068] Because the complex strata of soft and hard rock contain strongly weathered layers or soft rock layers, the overall or local stress on the column pile 4 foundation is too large. Therefore, in order to protect the column pile 4 as a whole and avoid the soft rock area in the middle layer from generating large stress on the column pile 4, which could lead to instability or even damage to the column pile 4, a support cylinder 1 is also included. The outer diameter of the support cylinder 1 is adapted to the inner diameter of the foundation pit. The column pile 4 is coaxially inserted into the support cylinder 1, and the outer diameter of the column pile 4 is adapted to the inner diameter of the support cylinder 1. The lower end of the column pile 4 extends beyond the support cylinder 1, and the through hole is located outside the support cylinder 1.

[0069] To enable rapid installation of the column pile 4, a plurality of guide strips 408 are evenly distributed around the circumferential side of the column pile 4, and the guide strips 408 are arranged along the axis of the column pile 4; the through hole is located at the guide strip 408 and extends from the inside of the column pile 4 to the guide strip 408.

[0070] The inner side of the support cylinder 1 is evenly distributed with several guide grooves that are adapted to the guide strips 408. The depth of the guide grooves is less than the width of the guide strips 408. Furthermore, insulation material is filled between the support cylinder 1 and the column pile 4. In this design, the cooperation of the guide strips 408 and the guide grooves enables rapid guidance when inserting the column pile 4. Additionally, because the inner wall of the support cylinder 1 has internal spiral ribs, it is impossible to construct deep guide grooves. Therefore, the depth of the guide grooves can be less than the width of the guide strips 408. This provides guidance while also radially positioning the column pile 4. Subsequently, insulation material is filled into the gap between the support cylinder 1 and the column pile 4, improving the insulation effect on the column pile 4.

[0071] To facilitate the detachable connection of the column pile 4 for replacement, a pre-formed concrete column 409 is filled above the upper sliding plate 402, and a second compression spring 410 is sleeved at the insertion rod 405. In this design, the pre-formed concrete column 409 can be directly inserted into the cavity inside the sleeve 304. This not only prevents concrete leakage below the upper sliding plate 402 during pouring, but also allows for quick removal of the concrete column 409 when the column pile 4 needs to be replaced. At this time, the upper sliding plate 402 and lower sliding plate 403 reset, and under the tension of the second compression spring 410, the insertion rod 405 retracts to remove the sleeve 304, thus realizing the replacement of the column pile 4.

[0072] Example 2:

[0073] This embodiment 2 further defines the limitations based on embodiment 1, such as... Figures 3-7 As shown, a specific implementation method of a foundation pit support structure is provided.

[0074] In this embodiment, the support cylinder 1 includes an inner steel cage 101 and an outer steel cage 102 arranged coaxially from the inside to the outside. The inner steel cage 101 and the outer steel cage 102 are connected by straight bars. A gap is left between the outer steel cage 102 and the inner sidewall of the foundation pit, and the lower end of the inner steel cage 101 extends out of the outer steel cage 102.

[0075] It also includes a first anchor bolt 2, which is used to pass through the side wall of the support cylinder 1 and through the soft rock surface on the local inner side wall of the foundation pit, and extend into the soft rock area. The extension end of the first anchor bolt 2 extends from the soft rock area into the hard rock area in sequence and is anchored in the hard rock area.

[0076] The first anchor bolt 2 is set horizontally or inclined upwards. Compared to existing technologies, with the large-scale construction of buildings, building projects inevitably face high-stress soft rock sections. When the column pile 4 penetrates a soft rock deformation section, i.e., when there are strongly weathered or soft rock layers interspersed within moderately weathered rock layers, the overall or local stress on the column pile 4 foundation is excessive, thus threatening the overall stability of the building project. This invention provides a foundation pit support structure for complex soft and hard rock strata. Using this solution, not only can the column pile 4 be supported as a whole by sequentially pouring concrete inside and outside the support cylinder 1, but it can also provide local support for the column pile 4 at the soft rock surface to improve stability. Specifically, the solution includes a support cylinder 1 used to support the foundation pit and protect the column pile 4. This not only protects the column pile 4 and reduces stress damage from external conditions, but also allows the column pile 4 to be reused or quickly replaced.

[0077] Furthermore, in existing technologies, support structures or column piles 4 are typically inserted directly into the foundation pit, resulting in an uneven connection between the support structure or column piles 4 and the foundation pit sidewall. Trimming the foundation pit sidewall into a flat surface is time-consuming and labor-intensive. Therefore, in this invention, the support cylinder 1 includes an inner reinforcing cage 101 and an outer reinforcing cage 102 arranged coaxially from the inside out. The inner and outer reinforcing cages 101 and 102 are connected and fixed by several straight reinforcing bars. After lowering the inner and outer reinforcing cages 102, steel-reinforced concrete can be sprayed onto the inner reinforcing cage 101 to form an inner formwork. The inner reinforcing cage 101 is constructed using spiral reinforcing bars 103, several vertical reinforcing bars, and steel... The inner formwork is made of a mesh to form a dense steel mesh, reducing the size of the holes and quickly forming the inner formwork. Since the lower end of the inner steel cage 101 extends out of the outer steel cage 102, the inner steel cage 101 can be inserted into the bottom of the foundation pit to form a bottom seal, creating a pouring space between the inner formwork and the inner wall of the foundation pit. At this time, the outer steel cage 102 is located in the pouring space. By pouring concrete in the pouring space, the solidified concrete can be seamlessly connected with the inner wall of the foundation pit, thus forming an integral whole between the support structure and the inner wall of the foundation pit. This strengthens the support of the hard rock and soil layer for the support structure and the column piles 4, thereby improving the overall support capacity of the support structure for the column piles 4.

[0078] Secondly, due to the presence of soft rock in certain areas of the inner wall of the foundation pit, when the soft rock is horizontal or slopes upwards away from the pit, the soft rock layer in these areas experiences significant stress and compresses the sidewall of the retaining cylinder 1, generating substantial local soil pressure on the retaining cylinder 1. This can lead to localized stress damage and even reduce the stability of the retaining cylinder 1. Therefore, anchoring can be achieved by installing a first anchor rod 2. The first anchor rod 2 passes sequentially from the inner wall of the retaining cylinder 1 through the retaining cylinder 1 and the soft rock area, and anchors into the hard rock area. In this way, by fixing the hard rock area, the first anchor rod 2 is tension-anchored at the stress point of the retaining cylinder 1, thereby reducing the stress damage at the stress point. The direction of the first anchor rod 2 should be set along the initial direction of the soft rock area. If this direction cannot anchor it into the hard rock area, the drilling direction can be adjusted circumferentially until it can be anchored into the hard rock area.

[0079] Furthermore, in order to reduce the soil pressure on the support cylinder 1 in the soft rock area and reduce stress concentration, a force-shaping component 3 is also included. The force-shaping component 3 includes a frame 301, which is located at the soft rock surface and perpendicular to the principal stress direction of the soft rock surface.

[0080] The frame 301 has several force-sharing regions, and each force-sharing region has several thin plates 302. The thin plates 302 are spaced apart, and the orientation of the thin plates 302 and the frame 301 are at an angle to each other.

[0081] Within the same force component region, several thin plates 302 are parallel to each other; between different force component regions, the thin plates 302 are arranged in different directions.

[0082] A plurality of second anchor rods 303 are sequentially arranged along the circumferential direction of the frame 301. The protruding ends of the second anchor rods 303 are inserted into the hard rock area and anchored therein, and the second anchor rods 303 are fixedly connected to the frame 301. In this scheme, a small amount of excavation can be carried out at the initial end of the soft rock area, i.e., at the soft rock surface, to determine the orientation of the initial end of the soft rock area. This allows for a rough determination of the main stress direction of the soft rock area on the support cylinder 1. At this time, a force-sharing component 3 can be set at the excavation face. The force-sharing component 3 includes the frame 301, a plurality of thin plates 302, and a plurality of second anchor rods 303. The plurality of second anchor rods 303 can be used to anchor the frame 301 at the excavation face, while the plurality of thin plates 302 are inserted into the soft rock area and arranged in different directions. In this way, when the soft rock part loosens and moves and compresses towards the support cylinder 1, it can move towards the force-sharing areas in different directions, thereby diverting the main stress and reducing stress concentration.

[0083] To ensure that the thin plate 302 has sufficient length to provide a sufficiently long diversion length, the inner side of the thin plate 302 extends out of the frame 301 and into the soft rock region.

[0084] To achieve overall protection, the dimensions of the frame 301 are adapted to the circumferential dimensions of the soft rock area. The shape of the frame 301 can be circular, square, etc., as long as it can adapt to the circumferential dimensions of the excavation face.

[0085] Since the first anchor rod 2 needs to be placed at or near the center of the soft rock surface, a sleeve 304 is provided at the center of the frame 301 to facilitate the protrusion position of the first anchor rod 2. The sleeve 304 is used for the first anchor rod 2 to pass through.

[0086] As a fixed connection method, the second anchor rod 303 and the frame 301 are welded together.

[0087] To improve the structural strength continuity of the support casing 1 at local locations, several spiral steel bars 103 are installed inside the support casing 1 at the soft rock surface of the local inner wall of the foundation pit. The two ends of each spiral steel bar 103 are welded to the inner steel cage 101 and the outer steel cage 102, respectively, and the spiral steel bars 103 are oriented towards the main pressure direction exerted by the soft rock area on the outer wall of the support casing 1. In this design, the direction of the spiral bars is the main pressure direction exerted by the soft rock area on the outer wall of the support casing 1, meaning that the continuous strength of the spiral bars themselves provides resistance to pressure on the local soft rock area.

[0088] Example 3:

[0089] This embodiment 3 further expands upon embodiment 2 and provides a construction method for pile foundation structures in complex soft and hard rock strata, including the following specific steps:

[0090] Excavate a foundation pit at the selected location to form a columnar foundation pit, and form a step at the bottom of the foundation pit so that the bottom diameter is smaller than the top diameter.

[0091] During excavation, soft rock surfaces are simultaneously detected on the inner wall of the foundation pit. When a soft rock surface is detected, a small amount of excavation is carried out along the circumferential direction of the soft rock surface into the soft rock area. Excavation is stopped when enough is available to determine the orientation of the initial end position of the soft rock area. At this point, the principal stress direction of the soft rock area on the support cylinder 1 can be determined, i.e., the principal stress direction of the initial end position of the soft rock area on the support cylinder 1. The excavation surface is then adjusted to be perpendicular to the principal stress direction. Then, holes are drilled sequentially along the circumferential direction of the installation surface. Through direction adjustment or scanning detection, the holes are made to extend into the hard rock layer. Subsequently, several second anchor rods 303 are installed at the drilled holes, and the extension ends of the second anchor rods 303 are inserted into the hard rock area for anchoring. Then, along the circumferential direction of the installation surface... The frame 301 is assembled sequentially, and the ends of the frame 301 and several second anchor rods 303 are welded and fixed. Then, inside the frame 301, a slot for inserting the thin plate 302 is cut on the mounting surface using a cutting device. Subsequently, several thin plates 302 are inserted sequentially on the mounting surface, and the thin plates 302 are divided into several force-shaping areas, each with a different orientation. Finally, the two ends of the thin plates 302 are welded to the inner wall of the frame 301 to complete the installation of the force-shaping component 3. Under the action of the force-shaping component 3, when the soft rock part loosens and moves and is squeezed towards the support cylinder 1, it can move towards the force-shaping areas in different directions, thereby diverting the main stress and reducing stress concentration.

[0092] After the several component components 3 are set up, the inner steel cage 101 and the outer steel cage 102 are then assembled and welded. A circumferential groove is excavated at the step, and then the inner steel cage 101 and the outer steel cage 102 are lowered into the foundation pit so that the lower end of the inner steel cage 101 is inserted into the circumferential groove. In this way, when the shotcrete forms the inner formwork, the concrete flows downward into the circumferential groove to form an overall closed structure.

[0093] Subsequently, steel-reinforced concrete is sprayed onto the inner reinforcing cage 101 to form an inner formwork inside the support cylinder 1. This creates a pouring space between the inner formwork and the inner wall of the pit. At this time, the outer reinforcing cage 102 is located within the pouring space. Then, concrete is poured in the space between the inner formwork and the inner wall of the pit to complete the overall pouring and forming of the support cylinder 1. The solidified concrete can then be seamlessly connected to the inner wall of the pit, thus forming an integral whole between the support cylinder 1 and the inner wall of the pit. This strengthens the support of the hard rock and soil layer for the support structure and the column piles 4, thereby improving the overall support capacity of the support structure for the column piles 4.

[0094] After the support casing 1 solidifies, a hole is drilled from the inside of the support casing 1 to the soft rock area at the soft rock surface location, and the first anchor rod 2 is installed. A groove can be set on the inside of the support casing 1 so that the end of the first anchor rod 2 is located in the groove, so that the anchor rod does not affect the insertion of the column pile 4 inside the support casing 1.

[0095] Subsequently, the cylinder 401 of the column pile 4 is inserted into the support cylinder 1. Guided by the guide strip 408 and the guide groove, the cylinder 401 is lowered into place. Then, concrete is poured into the cylinder 401. At this time, as gravity increases, the lower part of the cylinder 401 is squeezed downwards, causing the upper sliding plate 402 to slide downwards, while the lower sliding plate 403 moves accordingly. In this way, as the arc-shaped side of the truncated cone 404 moves downwards, it will gradually drive the insertion rod 405 to extend outwards through the through hole, thereby forcing the insertion rod 405 to be inserted into the external soil layer. The insertion rod 405 is used to fix the bottom of the entire column pile 4, improving the overall stability of the column pile 4.

[0096] After the column pile 4 is formed, the gap between the support casing 1 and the column pile 4 is filled with insulation material to complete the pile foundation construction.

[0097] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pile foundation structure for complex strata of soft and hard rock, characterized in that, include: A columnar pile (4) includes a cylindrical body (401). The bottom of the chamber of the cylindrical body (401) is equipped with a sliding assembly. The sliding assembly includes an upper sliding plate (402) and a lower sliding plate (403). The outer diameters of the upper sliding plate (402) and the lower sliding plate (403) are adapted to the inner diameter of the cylindrical body (401) and are sealed and slidably connected to the inner side of the cylindrical body (401). They can slide along the axis of the cylindrical body (401). The bottom of the lower sliding plate (403) is connected to the end (407) at the bottom of the columnar pile (4) through several first compression springs (406). A frustum (404) is fixed between the upper sliding plate (402) and the lower sliding plate (403). The smaller diameter end of the frustum (404) is located on the lower sliding plate (403), and the larger diameter end is located on the upper sliding plate (402). From the smaller diameter end to the larger diameter end, the sidewall of the frustum (404) is a concave arc with a gradually increasing slope. The column pile (4) has several inserted rods (405) and several matching through holes evenly distributed in the circumferential direction. One end of the inserted rod (405) is equipped with a roller, and one end of the inserted rod (405) abuts against the side wall of the truncated cone (404) through the roller; the other end of the inserted rod (405) is inserted into the through hole. It also includes a support cylinder (1), the outer diameter of which is adapted to the inner diameter of the foundation pit; the column pile (4) is coaxially inserted into the support cylinder (1), and the outer diameter of the column pile (4) is adapted to the inner diameter of the support cylinder (1); the lower end of the column pile (4) extends beyond the support cylinder (1), and the through hole is located outside the support cylinder (1); The support cylinder (1) includes an inner steel cage (101) and an outer steel cage (102) arranged coaxially from the inside to the outside. The inner steel cage (101) and the outer steel cage (102) are connected by straight bars. There is a gap between the outer steel cage (102) and the inner sidewall of the foundation pit, and the lower end of the inner steel cage (101) extends out of the outer steel cage (102). It also includes a first anchor rod (2), which is used to pass through the side wall of the support cylinder (1) and through the soft rock surface on the local inner side wall of the foundation pit, and extend into the soft rock area. The extension end of the first anchor rod (2) extends from the soft rock area into the hard rock area in sequence and is anchored in the hard rock area. The first anchor bolt (2) is set horizontally or inclined upwards; It also includes a force-shaping component (3), which includes a frame (301) located at the soft rock surface and perpendicular to the principal stress direction of the soft rock surface; The frame (301) has several force-sharing regions, and each force-sharing region has several thin plates (302). The thin plates (302) are spaced apart, and the orientation of the thin plates (302) and the frame (301) are at an angle to each other. Within the same force component region, several thin plates (302) are parallel to each other; between different force component regions, the thin plates (302) are arranged in different directions; A plurality of second anchor rods (303) are sequentially arranged along the circumferential direction of the frame (301). The protruding end of the second anchor rod (303) is inserted into the hard rock area and anchored, and the second anchor rod (303) and the frame (301) are fixedly connected.

2. The pile foundation structure for complex soft and hard rock strata according to claim 1, characterized in that, The column pile (4) has a plurality of guide strips (408) evenly distributed around its circumference, and the guide strips (408) are arranged along the axis of the column pile (4); the through hole is located at the guide strip (408) and extends from the inside of the column pile (4) to the guide strip (408). The inner side of the support cylinder (1) is evenly distributed with a number of guide grooves that are adapted to the guide strip (408), the depth of the guide groove is less than the width of the guide strip (408); and the support cylinder (1) and the column pile (4) are filled with thermal insulation material.

3. The pile foundation structure for complex soft and hard rock strata according to claim 1, characterized in that, The upper slide plate (402) is filled with a pre-formed concrete column (409), and a second compression spring (410) is sleeved on the insert rod (405).

4. A pile foundation structure for complex strata of soft and hard rock as described in claim 1, characterized in that, The inner side of the thin plate (302) extends out of the frame (301) and into the soft rock region.

5. A pile foundation structure for complex strata of soft and hard rock according to claim 1, characterized in that, At the soft rock surface of the inner sidewall of the foundation pit, a number of spiral steel bars (103) are also provided inside the support cylinder (1). The two ends of the spiral steel bars (103) are welded to the inner steel cage (101) and the outer steel cage (102) respectively, and the spiral steel bars (103) are set towards the main pressure direction of the soft rock area on the outer sidewall of the support cylinder (1).

6. A construction method for pile foundation structures in complex soft and hard rock strata according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Excavate the foundation pit and form steps at the bottom of the foundation pit; S2: Detect soft rock surfaces on the inner wall of the foundation pit and install force-sharing components (3) at the soft rock surfaces. S3: Then, the inner steel cage (101) and the outer steel cage (102) are lowered into the foundation pit, so that the lower end of the inner steel cage (101) is inserted into the step; S4: Then, spray concrete onto the inner steel cage (101) to form the inner formwork; S5: Pour concrete in the space between the inner template and the inner sidewall of the foundation pit to complete the overall casting and forming of the support cylinder (1); S6: Then drill a hole from the inside of the support cylinder (1) to the soft rock area at the soft rock surface location and install the first anchor rod (2). S7: Insert the cylinder (401) into the support cylinder (1). After inserting the cylinder (401), pour concrete inside the cylinder (401) to complete the forming of the column pile (4). S8: Finally, fill the gap between the support casing (1) and the column pile (4) with thermal insulation material to complete the pile foundation construction.

7. The construction method for a pile foundation structure in complex soft and hard rock strata according to claim 6, characterized in that, Step S2 further includes the following specific steps: S21: After detecting a soft rock surface, excavate along the circumferential direction of the soft rock surface into the soft rock area. When it is sufficient to determine the initial direction of the soft rock area, stop excavating. S22: Trim the excavation face to an installation face perpendicular to the initial orientation; S23: Install a plurality of second anchor rods (303) in sequence along the circumferential direction of the mounting surface, so that the protruding end of the second anchor rod (303) is inserted into the hard rock area for anchoring; S24: Then, the frame (301) is spliced ​​sequentially along the circumferential direction of the mounting surface, and the ends of the frame (301) and several second anchor rods (303) are welded and fixed. S25: Inside the frame (301), a number of thin plates (302) are sequentially inserted into the mounting surface, and the number of thin plates (302) are divided into a number of force-sharing areas; S26: Finally, weld the two ends of several thin plates (302) to the inner wall of the frame (301) to complete the installation of the force component (3).

Images