Soil nailing wall supporting structure and foundation pit reinforcing method

Abstract

The invention provides a soil nailing wall supporting structure and a foundation pit reinforcing method. The soil nailing wall supporting structure comprises a center rod, a centering support and a reinforcing mesh. The plurality of centering brackets are mounted on the center rod to form a soil nail rod; the centering supports are evenly arranged on the center rod and are symmetrically arranged in the axial direction of the center rod, so that the centering supports are in a shuttle shape. A plurality of anchor holes are formed in the soil nailing wall, and the diameter of the anchor holes is matched with the diameter of the centering support; a reinforcing mesh is arranged on the wall surface of the soil nailing wall; the reinforcing mesh and the center rod are fixedly connected through an L-shaped hook. Through the anchoring effect of the soil nails, the shear strength of the soil body is enhanced, and therefore the stability of the whole slope surface is improved.

Description

Technical Field

[0001] The invention belongs to the field of foundation pit construction, and in particular relates to a soil nail wall supporting structure and a foundation pit reinforcement method. Background Art

[0002] There are many construction problems in urban foundation pit excavation. When the excavation depth is large, the complexity and risk of the construction will increase, especially when it is close to existing buildings. Because there are residential areas and roads around the construction area in the city, special attention should be paid to the impact of the construction on the surrounding environment to avoid interference with residents' lives. The amount of earth excavation is huge. In addition, during the excavation process, it may be affected by groundwater, and effective measures should be taken to prevent the collapse of the foundation pit. Summary of the invention

[0003] In view of this, the present invention aims to propose a soil nail wall support structure and a foundation pit reinforcement method, which can enhance the shear strength of the soil through the anchoring effect of the soil nails, thereby improving the stability of the entire slope.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows: The soil nail wall support structure comprises a center rod, a centering bracket and a steel mesh; a plurality of centering brackets are installed on the center rod to form a soil nail rod; The centering brackets are evenly arranged on the center rod, and the centering brackets are symmetrically arranged along the axis of the center rod, so that the centering brackets form a shuttle shape; A plurality of anchor holes are arranged on the soil nail wall, and the diameter of the anchor holes matches the diameter of the centering bracket; A steel mesh is arranged on the wall surface of the soil nail wall; the steel mesh and the center rod are fixedly connected by an L-shaped hook.

[0005] Furthermore, the interval between each two centering brackets is 2-3m.

[0006] Furthermore, each center rod is fixed to the steel mesh through two symmetrically arranged L-shaped hooks.

[0007] Furthermore, on the soil nail wall, the spacing between the anchor holes is 1500 mm.

[0008] The foundation pit reinforcement method comprises the following steps: S1. Measurement and laying out; S2, excavation of earth and stone and slope finishing; S3, positioning, laying out and drilling; S4, soil nail rod installation; S5, grouting; S6. Laying steel mesh and welding reinforcement bars; S7, shotcrete surface layer; S8. Maintenance.

[0009] Furthermore, in step S1, the measurement is verified, and the closing error of the leveling points is ±12√L (mm), where L is the distance between the leveling points, in kilometers; the closing error of the coordinate wire of the control pile is verified to be ≤±16√N, where N is the number of measuring stations; and temporary leveling points are set at a stable and collision-resistant location, with a spacing of no more than 200mm, and calibrated before each use.

[0010] Furthermore, in step S2, excavation is carried out from top to bottom, in sections and layers, and the layered excavation depth is 0.5m below the elevation of each soil nail mouth; after the grouting strength of the soil nails and the sprayed concrete surface layer on the upper working surface reaches 70% of the design strength, the next layer of earth and stone is excavated; During the excavation process, according to the different soil types of the slope, about 300mm thick soil is reserved. The excavator cooperates with the slope repair personnel to use a shovel to repair the slope. The deviation of the slope flatness is 20mm. Before the slope surface is sprayed with concrete support, the loose soil is removed to ensure the flatness of the sprayed concrete surface layer; the slope slope is measured by hanging lines.

[0011] Furthermore, in step S3, the diameter of the hole is 100 mm, the inclination angle is 10°, and the hole depth is greater than the designed length of 100 mm.

[0012] Furthermore, in step S5, pure cement slurry is used for grouting, PO42.5 composite silicate cement is used for cement, the water-cement ratio of the grouting body is 0.5-0.6, and the strength grade of the grouting body is not less than 20MPa; Before the cement slurry begins to set, it is necessary to make up the grout 1 to 2 times to ensure that the total grouting volume of the soil nail slurry meets the requirements and is tightly combined with the soil; the slurry length is not less than the soil nail hole length minus 50cm; Before grouting, clean up the residual or loose soil in the hole. When grouting starts or stops for more than 30 minutes, lubricate the grouting pump and its pipeline with water or dilute cement slurry. When grouting, insert the grouting pipe to 250-550mm from the bottom of the hole, and a grouting plug and exhaust pipe should be installed at the hole mouth.

[0013] Further, in step S6, the steel mesh uses dΦ10 straightened steel bars with a spacing of 150 mm×150 mm and a lap length of 300 mm; During the laying process, the mesh is laid in layers and sections according to the working surface, tied with wires, and laid along the slope. Pads are used between the mesh and the slope to ensure that the distance between the steel mesh and the slope is greater than 30mm.

[0014] Compared with the prior art, the soil nail wall support structure of the present invention has the following advantages: (1) The soil nail wall support structure and foundation pit reinforcement method of the present invention can enhance the shear strength of the soil through the anchoring effect of the soil nails, thereby improving the stability of the entire slope; the soil nail wall can effectively control the settlement of the building or foundation and prevent structural damage caused by soil deformation; the construction process is relatively simple, the construction speed is fast, and the impact on the environment is small, and the noise and vibration are low.

[0015] (2) The soil nail wall support structure and foundation pit reinforcement method of the present invention can effectively prevent slope landslides and collapses, and are suitable for areas prone to landslides such as mountains and slopes. They can solve the settlement problem of buildings on uneven soil layers and protect the safety of structures. By reinforcing the soil, the erosion of water on the slope surface can be reduced, thereby extending the service life of the soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of the soil nail rod structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the soil nail wall structure according to an embodiment of the present invention; Figure 3 It is a schematic diagram of the cooperation between the steel mesh and the soil nail rod in the anchor hole according to an embodiment of the present invention.

[0017] Description of reference numerals: 1. Center rod; 2. Centering bracket; 3. Steel mesh; 4. L-shaped hook; 5. Anchor hole. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0019] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0020] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0021] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0022] The soil nail wall support structure comprises a central rod 1, a centering bracket 2 and a steel mesh 3; a plurality of centering brackets 2 are installed on the central rod 1 to form a soil nail rod; The centering bracket 2 is evenly arranged on the center rod 1, and the centering bracket 2 is symmetrically arranged along the axis of the center rod 1, so that the centering bracket 2 forms a shuttle shape; A plurality of anchor holes 5 are provided on the soil nail wall, and the diameter of the anchor holes 5 matches the diameter of the centering bracket 2; A steel mesh 3 is provided on the wall surface of the soil nail wall; the steel mesh 3 and the central rod 1 are fixedly connected via an L-shaped hook 4.

[0023] Preferably, the interval between every two centering brackets 2 is 2-3 m.

[0024] Preferably, each center rod 1 is fixed to the steel mesh 3 via two symmetrically arranged L-shaped hooks 4 .

[0025] Preferably, on the soil nail wall, the spacing between the anchor holes 5 is 1500 mm.

[0026] The foundation pit reinforcement method comprises the following steps: S1. Measurement and laying out; Surveyors shall carefully review the drawings, master the relevant data, and carry out the survey work timely and accurately according to the progress of the project; timely calibrate and repair the measuring instruments; and carry out the following survey work before the project starts: During the survey verification, the leveling point closure error is ±12√L (mm), where L is the distance between leveling points, in km; the closure error of the coordinate traverse of the control pile should be ≤ ±16√N, where N is the number of measuring stations. Temporary leveling points should be set up at stable and non-collision-prone locations, with a spacing of no more than 200 mm, and should be calibrated before each use; based on the survey control points handed over by the construction unit, the survey control points should be encrypted according to the on-site construction conditions. The site selection should meet the requirements of front and back visibility, no interference during construction, and the control point foundation should be firm and not sink. After the encrypted points are laid out, joint measurement should be carried out in a timely manner, and the joint measurement results should be reported to the supervision unit for review.

[0027] S2, excavation of earth and stone and slope finishing; According to the design requirements, the excavation should be carried out from top to bottom, in sections and layers. The layered excavation depth should be 0.5m below the elevation of each soil nail mouth, and over-excavation is not allowed. During the excavation process, the excavator shall not collide with the soil nail wall panel. After the grouting strength of the soil nails on the upper working surface and the sprayed concrete surface layer reach 70% of the design strength, the next layer of earth and stone excavation shall be carried out.

[0028] During the excavation process, according to the different soil types of the slope, about 300mm thick soil is reserved. The excavator cooperates with the slope repair personnel to use a shovel to repair the slope surface. The allowable deviation of the slope flatness is 20mm. Before the slope surface is sprayed with concrete support, the loose soil should be removed to ensure the flatness of the sprayed concrete surface layer. At the same time, the slope slope is measured by hanging a line to ensure that the slope foot does not invade the structure.

[0029] S3, positioning, laying out and drilling; The surveying technicians will place and mark the position of each soil nail hole according to the design drawings. The holes are drilled mechanically with a diameter of 100mm, an inclination of 10°, and a hole depth greater than the designed length of 100mm.

[0030] After drilling, the hole should be cleaned immediately with an air compressor to blow out the rock debris. Local water seepage, hole collapse or loose soil in the hole should be dealt with immediately. After the hole is formed, soil nails, steel bars and grouting should be installed in time. During the hole forming process, hole forming records should be kept, and the characteristics of the soil removed, the quality of the hole, and the accident handling should be recorded one by one according to the soil nail number. The soil removed should be compared with the soil identified in the preliminary design, and the design parameters of the soil nails should be modified in time if there is a deviation.

[0031] S4, soil nail rod installation; The soil nail reinforcement is made of 1E18 steel bars. A centering bracket 2 is set every 2.0m along the axis of the soil nail. The centering bracket 2 is made of dΦ6 steel bars and welded to the rod body after processing. The joints of the soil nail reinforcement are lap welded. The quality of the soil nail should be carefully checked before it is placed in the anchor hole 5. The soil nail should be placed as soon as possible after the hole is made.

[0032] S5, grouting; Pure cement slurry is used for grouting, and PO42.5 composite silicate cement is used as cement. The water-cement ratio of the grouting body is 0.5-0.6, and the strength grade of the grouting body is not less than 20MPa.

[0033] Grouting is done by jet grouting, and grouting can be stopped only when slurry flows out of the hole. Grouting needs to be supplemented 1 to 2 times before the initial setting of cement slurry to ensure that the total grouting volume of the soil nail slurry meets the requirements and is tightly combined with the soil. The length of the grouting body should not be less than the length of the soil nail hole minus 50cm.

[0034] Each time grouting is done into the hole, the required slurry volume is calculated in advance and the actual slurry volume injected into the hole is calculated based on the number of strokes of the grouting pump to confirm that the actual grouting volume exceeds the volume of the hole.

[0035] When the working degree of the slurry cannot meet the requirements during construction, add high-efficiency water reducing agent, and do not increase the amount of water arbitrarily. The slurry should be stirred evenly and used immediately. The pipeline should be flushed with water before starting grouting, pausing in the middle or after the operation.

[0036] Before grouting, the residual or loose soil in the hole should be cleaned up. When the grouting starts or stops for more than 30 minutes, the grouting pump and its pipeline should be lubricated with water or thin cement slurry. During grouting, the grouting pipe should be inserted to 250-550mm from the bottom of the hole, and a grout stopper and exhaust pipe should be installed at the hole mouth.

[0037] S6, laying steel mesh 3 and welding reinforcing bars; The steel mesh 3 of this project uses dΦ10 straightened steel bars with a spacing of 150mm×150mm and an overlap length of 300mm.

[0038] During the laying process, the mesh is laid in layers and sections according to the working surface, tied with wires, and laid along the slope. Pads are used between the mesh and the slope to ensure that the distance between the steel mesh 3 and the slope is greater than 30mm.

[0039] After the steel mesh 3 is laid, the reinforcement is welded on the surface of the steel mesh 3. The transverse and longitudinal reinforcements are made of 1E14 steel bars, and are welded to the soil nail steel bars with double "L" hooks. The length of the "L" hook is 20cm, and the material used is the same as the soil nail body steel bar. After the steel mesh 3 is installed, the hidden acceptance is carried out in time after the self-inspection is qualified.

[0040] S7, shotcrete surface layer; The thickness of the shotcrete surface layer is 80mm, the cement is PO42.5 grade cement, the concrete surface strength grade is C20, and the dry method is used for construction. The raw materials of the shotcrete anchor are all purchased from outside. The actual material amount is converted by manual on-site according to the mix ratio. After mixing evenly, it can be added to the sprayer. The water-cement ratio is 0.5. The shotcrete is turned upside down at 80cm on the top of the slope. When spraying concrete, the nozzle should be kept vertical to the sprayed surface, and the distance should be kept at 0.6m~1.0m. The spraying sequence of the working surface is from bottom to top, spraying from the bottom of the excavation layer upward. The water consumption should be controlled during spraying to prevent the spraying surface layer from having dry spots or overflowing. Before spraying the surface layer concrete of the slope, drainage holes should be properly set according to the seepage situation of the pit wall.

[0041] The upper and lower layers of shotcrete are left with oblique stubble, and the overlap length is more than twice the shotcrete thickness. For larger local over-excavation and small landslides, they are filled with shotcrete plus short friction anchors and 3 steel meshes, and smoothly connected with other parts.

[0042] S8. Maintenance.

[0043] After 2 hours of final setting, shotcrete should be sprayed with water for curing to keep the concrete surface moist. The curing time is determined according to the temperature and should be 3-7 hours.

[0044] Hanging mesh spraying concrete: 1. Shotcrete is sprayed by a sprayer, and the fineness modulus of the fine aggregate used should be greater than 2.5. The coarse aggregate used in shotcrete should be pebbles or crushed stones, and the particle size should not be greater than 10mm. The initial setting time of cement slurry should not exceed 5 minutes, and the final setting time should not exceed 10 minutes. When using alkaline accelerators, active silica stone should not be used.

[0045] 2. The deviation of the weight of each plate of shotcrete raw materials should meet the following conditions: cement: soil 2%; coarse and fine aggregate: soil 3%; water and admixtures: ±2%.

[0046] 3. The strength of shotcrete is C20, the chloride ion content in the concrete should not be greater than 0.06%, and the alkali content should not be greater than 3.0 kg / m³. Shotcrete should be cured after 2 hours, and the curing time should not be less than 14 days.

[0047] 4. The surface of shotcrete should be flat (the allowable deviation is 30mm, and the arrow-chord ratio is not greater than 1 / 6), without cracks and slag, and no exposed steel bars.

[0048] 5. The mesh spacing of steel mesh 3 is 250×250mm, and the allowable deviation of the mesh size is ±30mm. The overlap length of steel mesh 3 should be 1-2 meshes, and the allowable deviation is ±50mm. The steel bars should be used after cold drawing, and there should be no cracks, oil stains, granular or flaky rust on the surface of the steel bars.

[0049] 6. The slope of the foundation pit is protected by hanging mesh and spraying. A6 steel mesh 3 is laid on the slope with a spacing of 25cm×25cm. 50mm thick C20 concrete is sprayed, and the sprayed concrete is turned up 80cm at the top of the slope.

[0050] 7. A50PVC drainage holes are set on the inner wall of the foundation pit, with a spacing of 3m×3m along the inner wall of the foundation pit and a depth of 1.0~1.5m. The drainage holes should be accurately pre-buried. After the excavation is completed, the drainage holes should be pre-buried and temporarily blocked to prevent blockage during concrete spraying.

[0051] Through the anchoring effect of soil nails, the shear strength of the soil is enhanced, thereby improving the stability of the entire slope; the soil nail wall can effectively control the settlement of buildings or foundations and prevent structural damage caused by soil deformation; the construction process is relatively simple, the construction speed is fast, and the impact on the environment is small, with low noise and vibration.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Soil nail wall support structure, characterized by: It includes a center rod, a centering bracket and a steel mesh; a plurality of centering brackets are installed on the center rod to form a soil nail rod; The centering brackets are evenly arranged on the center rod, and the centering brackets are symmetrically arranged along the axis of the center rod, so that the centering brackets form a shuttle shape; A plurality of anchor holes are arranged on the soil nail wall, and the diameter of the anchor holes matches the diameter of the centering bracket; A steel mesh is arranged on the wall surface of the soil nail wall; the steel mesh and the center rod are fixedly connected by an L-shaped hook.

2. The soil nail wall support structure according to claim 1 is characterized in that: The interval between each two centering brackets is 2-3m.

3. The soil nail wall support structure according to claim 1, characterized in that: Each center rod is fixed to the steel mesh through two symmetrically arranged L-shaped hooks.

4. The soil nail wall support structure according to claim 1, characterized in that: On the soil nail wall, the spacing between the anchor holes is 1500mm.

5. A foundation pit reinforcement method, using the soil nail wall support structure according to any one of claims 1 to 4, characterized in that: The steps include: S1. Measurement and laying out; S2, excavation of earth and stone and slope finishing; S3, positioning, laying out and drilling; S4, soil nail rod installation; S5, grouting; S6. Laying steel mesh and welding reinforcement bars; S7, shotcrete surface layer; S8. Maintenance.

6. The foundation pit reinforcement method according to claim 5, characterized in that: In step S1, the measurement is verified, and the closure error of the leveling points is ±12√L (mm), where L is the distance between the leveling points, in kilometers; the closure error of the coordinate wire of the control pile is verified to be ≤±16√N, where N is the number of measuring stations; and temporary leveling points are set at a stable and collision-resistant location, with a spacing of no more than 200mm, and calibrated before each use.

7. The foundation pit reinforcement method according to claim 5, characterized in that: In step S2, excavation is carried out from top to bottom, in sections and layers, and the layered excavation depth is 0.5m below the elevation of each soil nail mouth; after the grouting strength of the soil nails on the upper working surface and the sprayed concrete surface layer reach 70% of the design strength, the next layer of earth and stone is excavated; During the excavation process, according to the different soil types of the slope, about 300mm thick soil is reserved. The excavator cooperates with the slope repair personnel to use a shovel to repair the slope. The deviation of the slope flatness is 20mm. Before the slope surface is sprayed with concrete support, the loose soil is removed to ensure the flatness of the sprayed concrete surface layer; the slope slope is measured by hanging lines.

8. The foundation pit reinforcement method according to claim 5, characterized in that: In step S3, the diameter of the hole is 100 mm, the inclination angle is 10°, and the hole depth is greater than the designed length of 100 mm.

9. The foundation pit reinforcement method according to claim 5, characterized in that: In step S5, pure cement slurry is used for grouting, PO42.5 composite silicate cement is used for cement, the water-cement ratio of the grouting body is 0.5-0.6, and the strength grade of the grouting body is not less than 20MPa; Before the cement slurry begins to set, it is necessary to make up the grout 1 to 2 times to ensure that the total grouting volume of the soil nail slurry meets the requirements and is tightly combined with the soil; the slurry length should not be less than the soil nail hole length minus 50cm; Before grouting, clean up the residual or loose soil in the hole. When grouting starts or stops for more than 30 minutes, lubricate the grouting pump and its pipeline with water or dilute cement slurry. When grouting, insert the grouting pipe to 250-550mm from the bottom of the hole, and a grouting plug and exhaust pipe should be installed at the hole mouth.

10. The foundation pit reinforcement method according to claim 5, characterized in that: In step S6, the steel mesh uses dΦ10 straightened steel bars with a spacing of 150mm×150mm and a lap length of 300mm; During the laying process, the mesh is laid in layers and sections according to the working surface, tied with wires, and laid along the slope. Pads are used between the mesh and the slope to ensure that the distance between the steel mesh and the slope is greater than 30mm.

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