Cast-in-place pile capable of penetrating through goaf to reduce negative friction and construction method

Abstract

The invention discloses a cast-in-place pile capable of penetrating through a goaf to reduce negative friction resistance and a construction method.The cast-in-place pile comprises a reinforcement cage, the periphery of the reinforcement cage is sleeved with a plurality of positioning rings at intervals in the axial direction of the reinforcement cage, each positioning ring is provided with a plurality of positioning structures at intervals, and an inner sheath covers the outer circles of the positioning rings; the two ends of the positioning structure are connected with the reinforcement cage and the inner sheath respectively, the movable sheath sleeves the periphery of the inner sheath at intervals, a plurality of sliding structures are distributed between the movable sheath and the inner sheath, the two ends of each sliding structure are connected with the inner sheath and the movable sheath respectively, and the sliding structures are provided with limiting structures. According to the cast-in-place pile construction method, the influence of negative friction resistance of the goaf is remarkably reduced through systematic process design, and the core advantage is that the inner sheath, the reinforcement cage and the cast-in-place pile body can be separated from the surrounding soil body through the movable sheath, so that direct contact between the cast-in-place pile body and the soil body is reduced, and the influence of the negative friction resistance is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of cast-in-place piles, and particularly to a cast-in-place pile for crossing a mined-out area and reducing negative skin friction and a construction method thereof. Background Technique

[0002] When implementing engineering construction in the mined-out area of a mining area, due to the continuous deformation of the underground rock and soil mass affected by mining activities, therefore, when the cast-in-place pile crosses this area, the settlement rate of the soil layer around the pile will be significantly higher than the settlement amount of the pile body itself. At this time, the interaction at the pile-soil interface will trigger a reverse friction effect, that is, the soil applies a downward shear stress (negative skin friction) to the pile body. This reverse acting force will not only increase the additional axial force of the pile body, resulting in the settlement amount of the pile foundation exceeding the design threshold, but may also cause structural damage to the pile body, thus threatening the safety and stability of the upper building. Summary of the Invention

[0003] Object of the Invention: Aiming at the deficiencies in the prior art, the present invention provides a cast-in-place pile for crossing a mined-out area and reducing negative skin friction, which realizes the effective reduction of negative skin friction during the process of crossing the mined-out area. And its construction method is provided.

[0004] Technical Solution: A cast-in-place pile for crossing a mined-out area and reducing negative skin friction includes a steel reinforcement cage. A plurality of positioning rings are sleeved on the outer periphery of the steel reinforcement cage at intervals along its axial direction. A plurality of positioning structures are respectively installed on each positioning ring at intervals. An inner sheath covers the outer ring of the plurality of positioning rings. The two ends of the positioning structure are respectively connected to the steel reinforcement cage and the inner sheath. A movable sheath is sleeved on the outer periphery of the inner sheath at intervals. A plurality of sliding structures are distributed between the two. The two ends of the sliding structure are respectively connected to the inner sheath and the movable sheath. A limiting structure is installed on the sliding structure.

[0005] Further, the plurality of positioning structures are evenly distributed at intervals along the circumferential direction of the positioning ring. The positioning structure includes a positioning sleeve, a connecting rod, and an arc-shaped plate. The positioning sleeve is fixedly installed on the positioning ring. A connecting rod is movably installed inside the positioning sleeve. One end of the connecting rod is fixedly installed with an arc-shaped plate, and the arc-shaped plate is welded to the steel reinforcement cage. The other end of the connecting rod is connected to the inner sheath.

[0006] Preferably, a plurality of positioning slots are spaced apart on the inner peripheral wall of the inner sheath. One end of each connecting rod is fixedly installed in the corresponding positioning slot; a through hole is opened inside the positioning sleeve, and the connecting rod is movably installed inside the through hole.

[0007] Further, the sliding structure comprises a movable sleeve rod and a sliding rod. The movable sleeve rod is provided with a long strip-shaped movable groove with one end open and one end closed. One end of the sliding rod is inserted into the movable groove from the open end, and the other end of the sliding rod is connected to the outer surface of the inner sheath. One end of the movable sleeve rod is rotatably installed on the inner wall of the movable sheath. The movable sleeve rod and the sliding rod are respectively connected to the limiting structure, so that the sliding rod is slidably connected to the movable sleeve rod and limited in the movable groove.

[0008] Preferably, the limiting structure comprises a pressing plate and a spring. The pressing plate is fixed to one end of the sliding rod and close to the closed end of the movable groove. The spring is sleeved on the outer peripheral surface of the sliding rod in the movable groove. One end of the spring is connected to the pressing plate, and the other end is connected to the movable sleeve rod.

[0009] Further, the inner sheath is made of a PVC pipe with a thickness of 5-10 mm, and the movable sheath is made of a PVC pipe with a thickness of 2 mm. The outer diameter of the movable sheath is the same as the pile diameter. The lengths of the inner sheath and the movable sheath are made and assembled in sections according to the construction requirements.

[0010] Further, the sliding structure is arranged in a circle every 4 meters along the axial direction of the steel reinforcement cage, and the number of the sliding structures in each circle is 5.

[0011] A construction method of a cast-in-place pile for crossing a goaf to reduce negative skin friction as described above includes the following steps:

[0012] Step 1: Drilling operation; the hole depth in the drilling should be greater than or equal to the design requirement; the hole diameter of the drilling should be greater than or equal to the distance from the movable sheath to the center of the steel reinforcement cage;

[0013] Step 2: Placing the pile; after the steel reinforcement cage is connected to the inner sheath and the movable sheath, the assembled steel reinforcement cage is hoisted and lowered into the drilling in a natural vertical state. The steel reinforcement cage passes through the overlying rock and soil mass of the goaf from the ground surface and is lowered to the bottom rock stratum below the goaf;

[0014] Step 3: Concrete pouring; the concrete is continuously poured through a cement mixer truck in cooperation with a conduit. The first pouring is carried out by the large hopper isolation ball method. The large hopper is hoisted by a crane and fixed in position with a bracket.

[0015] Preferably, in Step 1, the drilling inclination is greater than or equal to 1%, and the deviation of the cast-in-place pile position is less than or equal to 50 mm.

[0016] Preferably, the movable sheath forms a barrier layer during the concrete pouring process to prevent the poured concrete from penetrating into the goaf.

[0017] Beneficial effects: Compared with the prior art, the advantages of the present invention are:

[0018] (1) The movable sheath can separate the inner sheath, steel reinforcement cage, and cast-in-place pile body from the surrounding soil, and the movable sheath can move relative to the cast-in-place pile body. When the sinking rate of the soil around the cast-in-place pile exceeds that of the cast-in-place pile, a downward negative skin friction will be generated. The movable sheath will follow the soil and sink, while the inner sheath and the cast-in-place pile body can remain relatively stationary, thereby reducing the direct contact between the cast-in-place pile body and the soil and reducing the influence of the negative skin friction.

[0019] (2) When welding the connecting rod to the steel reinforcement cage, the arc-shaped plate can be used to fit the surface of the steel bar to ensure that the connecting rod is perpendicular to the steel bar, avoiding deviation between the connecting rod, the inner sheath, and the steel bar during welding, which may affect the stability. And by passing each connecting rod through the positioning sleeve for welding and fixing, and cooperating with the connection of the positioning rings, the connection stability of the connecting rods can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings. The drawings are schematic and should not be construed as limiting the present invention in any way. In the drawings:

[0021] Figure 1 is a schematic diagram of the opening structure of the present invention;

[0022] Figure 2 is a schematic diagram of the placement of the steel reinforcement cage of the present invention;

[0023] Figure 3 is a schematic diagram of pouring concrete of the present invention;

[0024] Figure 4 is a schematic diagram after the concrete pouring of the present invention is completed;

[0025] Figure 5 is a schematic diagram of the inner sheath structure of the present invention;

[0026] Figure 6 is a schematic diagram of the positioning ring structure of the present invention;

[0027] Figure 7 is a schematic diagram of the positioning sleeve structure of the present invention;

[0028] Figure 8 is a schematic diagram of the cross-sectional structure of the inner sheath of the present invention;

[0029] Figure 9 is a schematic diagram of the cross-sectional structure of the movable sleeve rod of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] The present invention will be further clarified below with reference to specific embodiments. Those skilled in the art should understand that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Modifications of various equivalent forms of the present invention fall within the scope defined by the appended claims of this application.

[0032] The present invention provides a cast-in-place pile for reducing negative skin friction when passing through a gob area and a construction method thereof, as Figures 1 to 9 shown, including the construction process of the cast-in-place pile and the device for reducing negative skin friction on the steel reinforcement cage 100; the construction method mainly includes drilling 601, lowering the steel reinforcement cage 100, and pouring concrete 801.

[0033] The cast-in-place pile includes a steel reinforcement cage 100, and a plurality of positioning rings 200 are movably sleeved on the steel reinforcement cage 100. A positioning structure is connected to the positioning ring 200, an inner sheath 300 is connected to the positioning structure, a sliding structure is connected to the inner sheath 300, a plurality of movable sleeve rods 400 are connected to the sliding structure, a limiting structure is connected to the movable sleeve rod 400, and the limiting structure is connected to the inner sheath 300. During installation, the positioning structure can be used to prevent the installation position of the inner sheath 300 from shifting, and the limiting structure can be used to prevent the sliding structure from sliding with the inner sheath 300 during installation. After installation, the sliding structure contacts the soil around the cast-in-place pile. When the soil around the cast-in-place pile sinks, the sliding structure will move downward with the soil, reducing the influence of negative skin friction on the pile body.

[0034] After the preparatory work for the construction of the cast-in-place pile and the installation of the outer casing are completed, drilling 601 is carried out. After the drilling is completed, the inspection standards are as follows: the hole depth should not be less than the design requirement; the hole diameter should not be less than the position from the movable sheath to the center of the steel reinforcement cage, and the drilling inclination should not be greater than 1%; the deviation of the cast-in-place pile position should not be greater than 50 mm.

[0035] During the production of the inner sheath and the movable sheath, the inner sheath is processed from a PVC pipe with a diameter of 5 - 10 mm, and the movable sheath is processed from a PVC pipe with a diameter of 2 mm. The inner sheath made of a 5 - 10 mm PVC pipe can effectively resist the lateral force exerted by the concrete on the inner sheath during the pouring of concrete. The outer diameter of the movable sheath is the same as the pile diameter, and the lengths of the inner sheath and the movable sheath are fabricated and assembled in segments according to the construction requirements. PVC pipes are corrosion - resistant and not easily eroded by chemical substances such as acids, alkalis, and salts. Compared with metal pipes, no additional anti - corrosion treatment is required, and they have a longer service life. PVC pipes are also lightweight and economical, reducing the construction difficulty and time cost. The smooth inner wall of the PVC pipe can effectively reduce the negative skin friction.

[0036] The positioning structure includes several positioning sleeves 201. The several positioning sleeves 201 are evenly and fixedly installed on the positioning ring 200. A connecting rod 202 is movably installed inside the positioning sleeve 201. One end of the connecting rod 202 is fixedly installed with an arc - shaped plate 203. The arc - shaped plate 203 is welded to the steel reinforcement cage 100. The connecting rod 202 can be attached to the surface of the steel reinforcement by means of the arc - shaped plate 203, ensuring that the connecting rod 202 is perpendicular to the steel reinforcement, preventing the connecting rod 202 from being skewed, and increasing the connection stability of the connecting rod 202 through cooperation with the positioning ring 200.

[0037] A through - hole 204 is formed inside the positioning sleeve 201, and the connecting rod 202 is movably installed inside the through - hole 204. The through - hole 204 can be used to limit the position of the connecting rod 202 and prevent it from shifting.

[0038] Several positioning slots 205 are formed on the inner wall of the inner sheath 300. One end of the connecting rod 202 is fixedly installed in the corresponding positioning slot 205, and the positioning slot 205 can be used to fix the position of the connecting rod 202 inside the inner sheath 300.

[0039] The sliding structure includes a movable sheath 301. The movable sheath 301 is slidably sleeved on the inner sheath 300. A shielding part is provided at the top of the inner sheath 300 to shield the gap between the inner sheath 300 and the movable sheath 301, preventing concrete from entering the area between the inner sheath 300 and the movable sheath 301. The outer side of the movable sheath 301 contacts the soil around the cast - in - place pile. When the soil around the cast - in - place pile subsides, the movable sheath 301 will sink and move with the soil, so that the inner sheath 300 and the pile body can remain relatively stationary, reducing the influence of the negative skin friction on the pile body.

[0040] In order to prevent the sliding of the movable sheath 301 and the inner sheath 300 during the installation process, a limiting structure is provided. The limiting structure includes a pressing plate 401 which is slidably installed inside the movable sleeve rod 400. One end of the movable sleeve rod 400 is rotatably installed on the inner wall of the movable sheath 301. A sliding rod 402 is fixedly installed on one side of the pressing plate 401. One end of the sliding rod 402 penetrates through the movable sleeve rod 400 and is rotatably installed on the outer surface of the inner sheath 300. A spring 403 is slidably sleeved on the sliding rod 402. One end of the spring 403 is fixedly installed on one side of the pressing plate 401, and the other end of the spring 403 is fixedly installed on the inner wall of the movable sleeve rod 400. An activity groove 404 is opened inside the movable sleeve rod 400, and the pressing plate 401 is slidably installed inside the activity groove 404. Under the elastic force of the spring 403, the movable sheath 301 will not displace from the inner sheath 300 without external force, avoiding the sliding of the movable sheath 301 during the installation process. When the soil around the cast-in-place pile subsides, the movable sheath 301 will move down with the soil, causing the corresponding movable sleeve rod 400 driven by the movable sheath 301 to move down. The movable sleeve rod 400 will slide on the pressing plate 401 and the sliding rod 402 through the activity groove 404 and compress the spring 403, so that the inner sheath 300 and the pile body of the cast-in-place pile can remain relatively stationary.

[0041] After the steel reinforcement cage 100 is connected to the inner sheath 300 and the movable sheath 301, the lowering of the steel reinforcement cage begins. The steel reinforcement cage 100 is lifted and lowered in a natural vertical state. The steel reinforcement cage passes through the overlying rock and soil mass 502 of the goaf 503 from the ground surface 501 and is lowered to the floor rock stratum 504 below the goaf 503.

[0042] After the installation of the conduit 701 is completed, the pouring of the concrete 801 begins. The cement mixer truck 704 cooperates with the conduit 701 for continuous pouring, and long-time intervals are strictly prohibited. The first pouring is carried out by the isolation ball method using a large hopper 702. The large hopper 702 is lifted by a crane 705 and fixed in position with a support 704. The movable sheath 301 can form a barrier layer during the concrete pouring process, effectively preventing the concrete from penetrating into the goaf 503, thus ensuring the continuity and density of the concrete filling.

[0043] To ensure the quality of the pile head concrete, within 1 hour after the concrete pouring is completed, the casing must be pulled out. First, the soil outside the casing is cleaned to reduce the soil pressure, and the crane slowly and evenly lifts the casing. Subsequently, the pile head is broken and the pile foundation is tested.

Claims

1. A cast-in-place pile for crossing a goaf to reduce negative skin friction, characterized in that: It includes a steel reinforcement cage (100). A plurality of positioning rings (200) are sleeved on the outer periphery of the steel reinforcement cage (100) at intervals along its axial direction. A plurality of positioning structures are respectively and spacedly installed on each positioning ring (200). An inner sheath (300) covers the outer circle of the plurality of positioning rings (200). The two ends of the positioning structure are respectively connected to the steel reinforcement cage (100) and the inner sheath (300). A movable sheath (301) is spacedly sleeved on the outer periphery of the inner sheath (300). A plurality of sliding structures are distributed between the two. The two ends of the sliding structure are respectively connected to the inner sheath (300) and the movable sheath (301). A limiting structure is installed on the sliding structure.

2. The cast-in-place pile for reducing negative skin friction when passing through a goaf according to claim 1, wherein: The plurality of positioning structures are evenly distributed at intervals along the circumferential direction of the positioning ring (200). The positioning structure includes a positioning sleeve (201), a connecting rod (202), and an arc-shaped plate (203). The positioning sleeve (201) is fixedly installed on the positioning ring (200). A connecting rod (202) is movably installed inside the positioning sleeve (201). One end of the connecting rod (202) is fixedly installed with an arc-shaped plate (203). The arc-shaped plate (203) is welded to the steel reinforcement cage (100). The other end of the connecting rod (202) is connected to the inner sheath (300).

3. The cast-in-place pile for reducing negative skin friction when passing through a goaf according to claim 2, wherein: A plurality of positioning slots (205) are spacedly opened on the inner peripheral wall of the inner sheath (300). One end of each connecting rod (202) is fixedly installed in the corresponding positioning slot (205); a through hole (204) is opened inside the positioning sleeve (201), and the connecting rod (202) is movably installed inside the through hole (204).

4. The cast-in-place pile for reducing negative skin friction when passing through a goaf according to claim 1, characterized in that: The sliding structure includes a movable sleeve rod (400) and a sliding rod (402). A long strip-shaped movable slot (404) with one end open and one end closed is opened on the movable sleeve rod (400). One end of the sliding rod (402) passes through the movable slot (404) from the open end. The other end of the sliding rod (402) is connected to the outer surface of the inner sheath (300). One end of the movable sleeve rod (400) is rotatably installed on the inner wall of the movable sheath (301). The movable sleeve rod (400) and the sliding rod (402) are respectively connected to the limiting structure, so that the sliding rod (402) is slidably connected to the movable sleeve rod (400) and is limited in the movable slot (404).

5. The cast-in-place pile for reducing negative skin friction when passing through a goaf according to claim 4, wherein: The limiting structure includes a pressing plate (401) and a spring (403). The pressing plate (401) is fixed to one end of the sliding rod (402) and is close to the closed end of the movable slot (404). The spring (403) is sleeved on the outer peripheral surface of the sliding rod (402) inside the movable slot (404). One end of the spring (403) is connected to the pressing plate (401), and the other end is connected to the movable sleeve rod (400).

6. The cast-in-place pile for reducing negative skin friction when passing through a goaf according to claim 1, wherein: The inner sheath (300) is processed from a PVC pipe with a thickness of 5 - 10 mm. The movable sheath (301) is processed from a PVC pipe with a thickness of 2 mm. The outer diameter of the movable sheath (301) is the same as the pile diameter. The lengths of the inner sheath (300) and the movable sheath (301) are made and assembled in sections according to construction requirements.

7. The cast-in-place pile for reducing negative skin friction when passing through a goaf according to claim 1, wherein: The sliding structure is arranged in a circle every 4 meters along the axial direction of the steel reinforcement cage (100), and the number of sliding structures in each circle is 5.

8. A construction method for a cast-in-place pile that reduces negative skin friction when passing through a gob area as described in any one of claims 1 to 7, characterized in that It includes the following steps: Step 1: Drilling operation; The hole depth in the drill hole (601) shall be greater than or equal to the design specified requirements; the hole diameter of the drill hole (601) shall be greater than or equal to the distance from the movable sheath (301) to the center of the steel reinforcement cage (100); Step 2: Lower the pile; after the steel reinforcement cage (100) is connected to the inner sheath (300) and the movable sheath (301), the assembled steel reinforcement cage (100) is lifted and lowered into the drill hole (601) in a natural vertical state. The steel reinforcement cage (100) passes through the overlying rock and soil mass (502) of the goaf from the ground surface (501) and is lowered to the floor rock stratum (504) below the goaf (503); Step 3: Concrete pouring; the pouring of concrete (801) is continuously carried out through a cement mixer truck (704) in cooperation with a conduit (701). The first pouring is carried out by the isolation ball method using a large hopper (702). The large hopper (702) is lifted by a crane (705) and fixed in position with a support (704).

9. The construction method of a cast-in-place pile for reducing negative skin friction when passing through a gob area as described in claim 8, characterized in that: In Step 1, the inclination of the drill hole (601) is greater than or equal to 1%, and the deviation of the cast-in-place pile position is less than or equal to 50 mm.

10. The construction method of a cast-in-place pile for reducing negative skin friction when passing through a goaf as claimed in claim 8, wherein: The movable sheath (301) forms a barrier layer during the concrete pouring process to prevent the poured concrete (801) from penetrating into the goaf.

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