Foundation pit supporting structure and construction method thereof

Abstract

The invention relates to the field of foundation engineering, and particularly discloses a foundation pit supporting structure and a construction method thereof. The foundation pit supporting structure comprises a surface layer arranged on a slope surface and a soil nail inserted into a soil body, the surface layer is connected with the soil nail, the soil nail comprises a mortar layer and an implant connected with the mortar layer, and the implant comprises a sleeve, a nail head connected to the end of the sleeve and a plurality of anti-pulling mechanisms. The anti-pulling mechanism comprises two symmetrically-arranged anti-pulling plates and a connecting plate connected between the two anti-pulling plates, the anti-pulling plates are connected with a hinge shaft and a connecting shaft, the connecting shaft is located on the side, close to the nail head, of the hinge shaft, the sleeve is provided with through holes allowing the anti-pulling plates to rotate out, and the connecting plate is provided with kidney-shaped holes allowing the connecting shaft to be inserted in. And the plurality of connecting plates are jointly in threaded connection with an anti-pulling screw rod. The implant replaces an original steel bar, so that a plurality of anti-pulling barbs are formed on the outer wall of the soil nail, the connection strength between the soil nail and a soil body is improved, and the soil nail is suitable for being applied to a loose soil layer.

Description

Technical Field

[0001] This invention relates to the field of foundation engineering, and in particular to a foundation pit support structure and its construction method. Background Technology

[0002] Foundation pit support engineering is a crucial part of building construction. Its main purpose is to ensure the stability of the pit walls during excavation, thereby ensuring construction safety and preventing damage to the surrounding environment. Types of foundation pit support include: slope excavation, soil nailing walls, cement-soil gravity retaining walls, steel-cement-soil mixing walls, pile walls, and diaphragm walls. The choice of foundation pit support type typically depends on factors such as the depth of the pit, site conditions, surrounding environment, hydrogeological conditions, and construction schedule requirements.

[0003] Among the above-mentioned types of foundation pit support, soil nailing walls are suitable for soil layers with certain cohesion, such as sandy soil, cohesive soil, and silty soil, and the groundwater level should be lower than the excavated section of the slope. Soil nailing walls consist of a group of soil nails and a concrete surface layer. The construction process is as follows: 1. Drill nail holes according to the soil nail layout diagram; 2. Insert reinforcing bars into the nail holes and grout to form soil nails; 3. Lay a reinforcing mesh on the slope and connect it to the soil nails; 4. Spray concrete onto the slope, forming the surface layer together with the reinforcing mesh.

[0004] Although the above-mentioned foundation pit support structure has advantages such as fast construction speed, simple equipment, and good economy, it still has the following technical defects: for loose soil layers, the connection between the soil nail and the soil is relatively loose, the pull-out resistance of the soil nail is weak, which leads to limited overall bearing capacity and makes it unsuitable for deeper foundation pits, and needs to be improved. Summary of the Invention

[0005] To improve the connection strength between soil nails and soil, this invention provides a foundation pit support structure and its construction method.

[0006] In a first aspect, the foundation pit support structure provided by the present invention adopts the following technical solution:

[0007] A foundation pit support structure includes a surface layer disposed on a slope and soil nails inserted into the soil. The surface layer is connected to the soil nails. The surface layer includes a concrete layer and a steel mesh disposed inside the concrete layer. The soil nails include a mortar layer and an implant connected to the mortar layer. The implant includes a sleeve, a nail head connected to the end of the sleeve, and a plurality of pull-out resistance mechanisms spaced apart along the length of the sleeve. The pull-out resistance mechanism includes two symmetrically arranged pull-out resistance plates and a connecting plate connected between the two pull-out resistance plates. A hinge shaft and a connecting shaft are connected to the end of the pull-out resistance plate near the nail head. The connecting shaft is located on the side of the hinge shaft near the nail head. The sleeve is provided with a through hole for the pull-out resistance plate to rotate out. The inner wall of the through hole is provided with a hinge groove for the hinge shaft to be inserted. The connecting plate is provided with an oblong hole for the connecting shaft to be inserted. A plurality of the connecting plates are threadedly connected to a pull-out resistance screw. One end of the pull-out resistance screw is rotatably connected to the nail head, and the other end is connected to a rotating head.

[0008] By adopting the above technical solution, the implant replaces the original steel bar, which makes the outer wall of the soil nail have multiple pull-out barbs, improves the connection strength between the soil nail and the soil, and thus ensures the bearing capacity of the support structure, making it suitable for loose soil layers.

[0009] Optionally, the inner wall of the sleeve is connected to a limiting block for blocking the pull-out plate, and when the pull-out plate abuts against the limiting block, the outer surface of the pull-out plate is flush with the outer surface of the sleeve.

[0010] By adopting the above technical solution, the implant can be easily inserted without disturbing the soil layer.

[0011] Optionally, when the connecting shaft abuts against the inner wall of the end of the waist-shaped hole near the pull-out screw, the included angle between the pull-out plate and the sleeve is 45 degrees.

[0012] By adopting the above technical solution, the pull-out plate can be opened to the most suitable angle after the implant is inserted, resulting in high pull-out resistance of the soil nail.

[0013] Optionally, the inner side of the pull-out plate is connected with multiple reinforcing bars.

[0014] By adopting the above technical solution, the contact area between the pull-out plate and the mortar layer is increased, thereby improving the connection strength between the soil nail and the soil.

[0015] Optionally, the connecting plate is provided with multiple through holes.

[0016] By adopting the above technical solution, the mortar flow into the casing is facilitated.

[0017] Optionally, the nail head includes a tapered portion and a connecting strip fixedly connected to the inner side of the tapered portion, the pull-out screw is rotatably connected to the connecting strip, and a slurry outlet hole is provided at the top of the tapered portion.

[0018] By adopting the above technical solution, mortar can flow out from the mortar outlet and be injected into the front end of the implant, thereby improving the connection strength between the soil nail and the soil.

[0019] Optionally, the connecting strip is slidably connected to a sliding frame, the pull-out screw is fixedly connected to a sealing screw, the sliding frame is threadedly connected to the sealing screw, and the sliding frame is fixedly connected to a plug for sealing the slurry outlet hole.

[0020] By adopting the above technical solution, the plug seals the grout outlet when the implant is inserted, making it difficult for soil clogging to enter through the grout outlet and avoiding the problem of grout outlet blockage. After the implant is inserted, tightening the pull-out screw can drive the plug out of the grout outlet without affecting the mortar injection.

[0021] Optionally, the pitch of the sealing screw is greater than that of the pull-out screw.

[0022] By adopting the above technical solution, the plug can be moved a sufficient distance away from the slurry outlet.

[0023] Optionally, the rotating head is provided with a slot for inserting the reinforcing mesh.

[0024] By adopting the above technical solution, on the one hand, the slot serves as a force-bearing point, facilitating the turning of the head; on the other hand, the slot serves as a connection point between the implant and the steel mesh, thereby improving the tightness of the connection between the surface layer and the soil nail.

[0025] Secondly, the construction method for a foundation pit support structure provided by the present invention adopts the following technical solution:

[0026] A construction method for a foundation pit support structure includes the following steps:

[0027] The first step is to insert the implant directly into the soil according to the soil nail layout diagram, and then rotate the rotating head to make the connecting plate move away from the nail head, and the pull-out plate rotates out of the through hole to squeeze the soil.

[0028] The second step is to inject mortar into the casing. The mortar flows out through the through hole to the pull-out plate and solidifies to form a soil nail with pull-out barbs.

[0029] The third step is to lay a steel mesh on the slope and connect it to the soil nails;

[0030] The fourth step is to spray concrete onto the slope to form a surface layer together with the steel mesh.

[0031] By adopting the above technical solutions, construction is convenient and efficient.

[0032] In summary, the present invention has the following beneficial effects:

[0033] The implant of this invention replaces the original steel bar, resulting in multiple pull-out barbs on the outer wall of the soil nail, which improves the connection strength between the soil nail and the soil, thereby ensuring the bearing capacity of the support structure and making it suitable for use in loose soil layers. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the foundation pit support structure according to an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the implant in the deployed state according to an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the implant in the closed state according to an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of the anti-pull-out mechanism according to an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of the sleeve structure according to an embodiment of the present invention;

[0039] Figure 6 This is a cross-sectional schematic diagram of the nail head according to an embodiment of the present invention;

[0040] Figure 7 This is a schematic diagram of the sliding frame and the plug according to an embodiment of the present invention.

[0041] Explanation of reference numerals in the attached drawings: 1. Surface layer; 2. Soil nail; 3. Concrete layer; 4. Reinforcing mesh; 5. Mortar layer; 6. Implant; 61. Sleeve; 611. Hinge groove; 612. Through hole; 613. Limiting block; 62. Nail head; 621. Conical part; 6211. Grout outlet hole; 622. Connecting strip; 63. Pull-out mechanism; 631. Pull-out plate; 6311. Reinforcing bar; 632. Connecting plate; 6321. Waist-shaped hole; 6322. Perforation; 633. Hinge shaft; 634. Connecting shaft; 64. Pull-out screw; 65. Rotating head; 651. Slot; 66. Sliding frame; 67. Plug; 68. Sealing screw. Detailed Implementation

[0042] The following is in conjunction with the appendix Figures 1-7 The present invention will be described in further detail below.

[0043] This invention discloses a foundation pit support structure and its construction method, which is suitable for loose soil layers and has a good support effect.

[0044] Reference Figure 1The foundation pit support structure includes a surface layer 1 covering the slope and soil nails 2 inserted into the soil, with the surface layer 1 connected to the soil nails 2. The surface layer 1 includes a steel mesh 4 laid on the slope and a shotcrete layer 3 covering the slope, with the steel mesh 4 located within the concrete layer 3. Multiple soil nails 2 are spaced apart and perpendicular to the slope. Each soil nail 2 includes an implant 6 inserted into the soil and a mortar layer 5 injected into the soil along the implant 6, with the implant 6 connected to the steel mesh 4.

[0045] Reference Figure 2 , Figure 3 The implant 6 includes a sleeve 61, a nail head 62 fixedly connected to the end of the sleeve 61, multiple pull-out resistance mechanisms 63 spaced apart along the length of the sleeve 61, and pull-out resistance screws 64 connected to the multiple pull-out resistance mechanisms 63. The implant 6 has an unfolded state and a closed state, and the pull-out resistance mechanism 63 is activated by turning the pull-out resistance screws 64. When inserted, the implant 6 is in the closed state, which facilitates insertion into the soil; when in use, the implant 6 is unfolded, which facilitates the flow of mortar to the outside of the implant 6 to form pull-out resistance barbs.

[0046] Reference Figure 4 , Figure 5 The pull-out mechanism 63 includes two symmetrically arranged pull-out plates 631. The sleeve 61 has a through hole 612 on its side wall for the pull-out plates 631 to rotate out. The inner wall of the through hole 612 near the nail head 62 has a hinge groove 611. The end of the pull-out plate 631 near the nail head 62 is fixedly connected to a hinge shaft 633. The hinge shaft 633 is inserted into the hinge groove 611, so the pull-out plate 631 can rotate around the hinge shaft 633, so that the two pull-out plates 631 rotate towards or away from each other.

[0047] Reference Figure 4 , Figure 5 A connecting shaft 634 is fixedly connected to one end of the pull-out plate 631 near the nail head 62. The connecting shaft 634 is located on the side of the hinge shaft 633 near the nail head 62. A connecting plate 632 is connected between the two pull-out plates 631. The connecting plate 632 is I-shaped, and both ends of the connecting plate 632 have oblong holes 6321 for the connecting shaft 634 to be inserted. The middle of the connecting plate 632 is threadedly connected to the pull-out screw 64. Tightening the pull-out screw 64 can drive the connecting plate 632 to move axially along the pull-out screw 64, thereby pulling the connecting shaft 634 to move closer to or away from the nail head 62, so that the two pull-out plates 631 rotate towards or away from each other.

[0048] Reference Figure 3To facilitate the rotation of the pull-out screw 64, one end of the pull-out screw 64 is rotatably connected to the nail head 62, and the other end is fixedly connected to a rotating head 65. The rotating head 65 is provided with a slot 651 for the steel mesh 4 to be inserted. On the one hand, the slot 651 serves as a force-bearing point, facilitating the tightening of the rotating head 65; on the other hand, the slot 651 serves as a connection point between the implant 6 and the steel mesh 4, thereby improving the tightness of the connection between the surface layer 1 and the soil nail 2.

[0049] Reference Figure 3 , Figure 5 To restrict the rotational position of the pull-out plate 631, a limiting block 613 is fixedly connected to the inner wall of the sleeve 61 to block the pull-out plate 631. When the pull-out plate 631 abuts against the limiting block 613, the outer surface of the pull-out plate 631 is flush with the outer surface of the sleeve 61, facilitating easy insertion of the implant 6 without disturbing the soil layer. When the pull-out screw 64 rotates to move the connecting plate 632, the connecting shaft 634 moves along the oblong hole 6321. When the connecting shaft 634 abuts against the inner wall of the oblong hole 6321 near the end of the pull-out screw 64, the two pull-out plates 631 rotate in opposite directions to the unfolded state, and the included angle between the pull-out plate 631 and the sleeve 61 is 45 degrees. After unfolding, mortar is injected into the casing 61. The mortar flows out from the through hole 612 and solidifies, forming multiple pull-out barbs on the outer wall of the soil nail 2, which improves the connection strength between the soil nail 2 and the soil, thereby ensuring the bearing capacity of the support structure. It is suitable for use in loose soil layers.

[0050] Reference Figure 4 Multiple reinforcing bars 6311 are fixedly connected to the inner side of the tensile plate 631, which increases the contact area between the tensile plate 631 and the mortar layer 5, thereby improving the connection strength between the soil nail 2 and the soil. The connecting plate 632 is provided with two square perforations 6322 to facilitate the flow of mortar into the sleeve 61.

[0051] Reference Figure 6 , Figure 7The nail head 62 includes a tapered portion 621, a connecting strip 622 fixedly connected to the inner side of the tapered portion 621, and an anti-pull-out screw 64 rotatably connected to the connecting strip 622. A grout outlet hole 6211 is provided at the top of the tapered portion 621. A sliding frame 66 is slidably connected to the connecting strip 622. A sealing screw 68 is fixedly connected to one end of the anti-pull-out screw 64 near the grout outlet hole 6211, and the pitch of the sealing screw 68 is greater than that of the anti-pull-out screw 64. The sliding frame 66 is threadedly connected to the sealing screw 68, and a plug 67 for sealing the grout outlet hole 6211 is fixedly connected to one end of the sliding frame 66 near the grout outlet hole 6211. When the implant 6 is inserted, the plug 67 seals the grout outlet hole 6211, making it difficult for soil clods to enter through the grout outlet hole 6211, thus avoiding the problem of clogging the grout outlet hole 6211. After the implant 6 is inserted, the anti-pull-out screw 64 is turned, which can drive the plug 67 to disengage from the grout outlet 6211. The mortar can flow out from the grout outlet 6211 and be injected into the front end of the implant 6, thereby improving the connection strength between the soil nail 2 and the soil.

[0052] A construction method for a foundation pit support structure includes the following steps:

[0053] First, according to the soil nail 2 layout diagram, directly insert the implant 6 into the soil, then turn the rotating head 65 so that the connecting plate 632 moves away from the nail head 62, the pull-out plate 631 rotates to 45 degrees to the unfolded state, the soil is squeezed to form a cavity for mortar injection, and at this time the plug 67 moves away from the mortar outlet 6211, and the mortar outlet 6211 opens.

[0054] The second step is to inject mortar into the casing 61. The mortar flows out through the through hole 612 into the cavity, and some of the mortar flows out from the mortar outlet hole 6211. After solidification, a mortar layer 5 is formed, which makes the soil nail 2 have pull-out barbs.

[0055] The third step is to lay steel mesh 4 on the slope and make the nodes of steel mesh 4 fit into the slots 651.

[0056] The fourth step is to spray concrete onto the slope to form the surface layer 1 together with the steel mesh 4.

[0057] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A foundation pit support structure comprising a facing layer (1) arranged on a slope surface and a soil nail (2) inserted into a soil body, the facing layer (1) being connected with the soil nail (2), the facing layer (1) comprising a concrete layer (3) and a steel bar mesh (4) arranged inside the concrete layer (3), the soil nail (2) comprising a mortar layer (5) and an implant (6) connected with the mortar layer (5), characterized in that: The implant (6) comprises a sleeve (61), a nail head (62) connected to the end of the sleeve (61), and a plurality of anti-pulling mechanisms (63) arranged along the length direction of the sleeve (61), the anti-pulling mechanism (63) comprises two symmetrically arranged anti-pulling plates (631), a connecting plate (632) connected between the two anti-pulling plates (631), the end of the anti-pulling plate (631) close to the nail head (62) is connected with a hinged shaft (633) and a connecting shaft (634), the connecting shaft (634) is located on the side of the hinged shaft (633) close to the nail head (62), the sleeve (61) is provided with a through hole (612) for the anti-pulling plate (631) to turn out, the inner wall of the through hole (612) is provided with a hinged groove (611) for the hinged shaft (633) to insert, the connecting plate (632) is provided with a waist-shaped hole (6321) for the connecting shaft (634) to insert, a plurality of the connecting plates (632) are threadedly connected with an anti-pulling screw (64) together, one end of the anti-pulling screw (64) is rotatably connected with the nail head (62), and the other end is connected with a rotating head (65).

2. The excavation support structure of claim 1, wherein: The inner wall of the sleeve (61) is connected with a limiting block (613) for blocking the anti-pulling plate (631), when the anti-pulling plate (631) abuts against the limiting block (613), the outer surface of the anti-pulling plate (631) is flush with the outer surface of the sleeve (61).

3. The excavation support structure of claim 1, wherein: When the connecting shaft (634) abuts against the inner wall of the waist-shaped hole (6321) close to the anti-pulling screw (64), the included angle between the anti-pulling plate (631) and the sleeve (61) is 45 degrees.

4. A foundation pit retaining structure according to claim 3, wherein: The inner side of the anti-pulling plate (631) is connected with a plurality of ribs (6311).

5. The excavation support structure of claim 1, wherein: The connecting plate (632) is provided with a plurality of perforations (6322).

6. The excavation support structure of claim 1, wherein: The nail head (62) comprises a tapered portion (621) and a connecting strip (622) fixedly connected to the inner side of the tapered portion (621), the anti-pulling screw (64) is rotatably connected with the connecting strip (622), and the top end of the tapered portion (621) is provided with a grout outlet hole (6211).

7. A foundation pit retaining structure according to claim 6, wherein: The connecting strip (622) is slidably connected with a sliding frame (66), the anti-pulling screw (64) is fixedly connected with a plugging screw (68), the sliding frame (66) is threadedly connected with the plugging screw (68), and the sliding frame (66) is fixedly connected with a plug (67) for plugging the grout outlet hole (6211).

8. A foundation pit retaining structure according to claim 7, wherein: The pitch of the plugging screw (68) is greater than that of the anti-pulling screw (64).

9. The excavation support structure of claim 1, wherein: The rotating head (65) is provided with a clamping groove (651) for clamping the steel mesh (4).

10. A method of constructing a foundation pit support structure according to any one of claims 1 to 9, characterized by, The method comprises the following steps: In the first step, according to the soil nail (2) arrangement diagram, the implant (6) is directly inserted into the soil body, and then the rotating head (65) is screwed and rotated, so that the connecting plate (632) moves away from the nail head (62), and the anti-pulling plate (631) turns out of the through hole (612) and extrudes the soil body; In the second step, the sleeve (61) is filled with mortar, the mortar flows out to the anti-pulling plate (631) through the through hole (612), and after solidification, the soil nail (2) with anti-pulling barbs is formed; In the third step, the steel mesh (4) is laid on the slope surface and connected with the soil nail (2). In the fourth step, the concrete is sprayed on the slope to form the surface layer (1) together with the reinforcement mesh (4).

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