Supporting method for high slope and foundation pit

Abstract

The invention discloses a method for supporting a high slope and a foundation pit, relates to the field of foundation engineering, and aims to improve the integrity and stability of supporting the high slope by adopting lattice beams and ensure the safety of a supporting structure and construction. According to the technical scheme, the supporting method for the high slope and the foundation pit comprises the steps that an intercepting ditch and a coping beam are constructed on the top of the slope, the slope is excavated in a layered mode from top to bottom according to the designed slope rate, stiffening piles are constructed, the stiffening piles comprise anchoring bodies obtained through high-pressure jet grouting in holes and stress ribs embedded in the anchoring bodies, and lattice beams are constructed; and net hanging and concrete spraying are carried out in the grids of the lattice beams, lattice panels are obtained, the steps are repeated till the slope bottom is constructed, and finally ground beams and drainage ditches are constructed at the slope bottom. The coping beams, the lattice beams, the ground beams and the stiffening piles integrally have a frame hoop effect on the slope body, the soil arching effect of the slope can be effectively dealt with, the integrity and stability of the supporting structure are improved, and the safety of slope supporting is guaranteed. The method is used for supporting design and construction of the high slope and the foundation pit.

Description

Technical Field

[0001] The invention relates to the field of foundation engineering, in particular to a support structure for a high slope and a foundation pit, and a construction method of the support structure. Background Art

[0002] Below the edge of a certain cultivated land is a slope, and the bottom of the slope is construction land. The construction land needs to be excavated with a foundation pit of 12m in depth, that is, it is necessary to excavate a 12-meter-deep foundation pit at the bottom of the slope, and then build a large-volume underground structure project. Due to the red line restrictions of the construction land, cultivated land cannot be occupied, and there is no sufficient slope clearance for the slope. The horizontal distance between the excavation range of the foundation pit and the red line is only 10m, forming a high slope with a height of 26m and close to vertical. The soil layer of the high slope is medium-weathered mudstone and muddy sandstone. Once the high slope becomes unstable and collapses, it will pose a huge threat to the personal and property safety of surrounding residents and construction workers, and even cause serious losses.

[0003] Since the top of the slope is cultivated land, the excavation range cannot be expanded, and the construction plan of graded slope reduction is not feasible. The excavation pit at the bottom of the slope forms an open space without a solid foundation for support, and the high slope gravity retaining wall cannot meet the safety requirements. The high slope is supported by lattice beams, which need to be firmly anchored to the slope. At present, the lattice is generally anchored by anchor rods, but the anchoring effect of the anchor rods on the lattice is not enough, and the integrity of the anchor rods and the lattice is insufficient. The slope support still has a large risk of instability, especially for high slopes. Summary of the invention

[0004] The present invention firstly provides a supporting structure for a high slope and a foundation pit, the purpose of which is to improve the integrity and stability of the high slope supported by lattice beams and ensure the safety of the supporting structure.

[0005] The technical solution adopted by the present invention is: the supporting structure of the high slope and the foundation pit includes a cut-off ditch and a capping beam located at the top of the slope, a lattice beam located on the slope surface, a ground beam located at the bottom of the slope, and a stiffening pile arranged downwardly in the slope body, the stiffening pile includes an anchor body obtained by high-pressure rotary spraying in the hole, and a force-bearing reinforcement embedded in the anchor body;

[0006] The lattice beam includes a horizontally arranged horizontal beam and a vertical beam perpendicular to the horizontal beam. The upper end of each vertical beam is connected to the top beam, and the lower end of each vertical beam is connected to the ground beam. The top beam, lattice beam and ground beam are all reinforced concrete structures. The connection between the horizontal beam and the vertical beam is provided with a fixing hole. The stiffening piles correspond to the fixing holes one by one. The upper end of the force-bearing reinforcement of the stiffening pile passes through the fixing hole and is tensioned and fixed by an anchor.

[0007] Support piles are also arranged at intervals at the bottom of the slope. The center lines of the support piles are vertical and are reinforced concrete structures. The side of the support piles facing away from the slope is the foundation pit excavation area. The lower end of the support pile is lower than the elevation of the bottom of the foundation pit. The upper ends of the support piles are connected by a crown beam. The upper ends of the support piles or the crown beam are anchored to the slope through an anchoring device. There is a drainage ditch between the crown beam and the ground beam.

[0008] In order to prevent the stress reinforcement and anchorage at the upper end of the stiffening pile from rusting, a sealing anchorage body is further provided at the fixing hole of the lattice beam to seal the upper end of the stress reinforcement and the anchorage body. Specifically, the sealing anchorage body is a reinforced concrete structure, and the steel bars of the sealing anchorage body are welded and fixed to the anchorage.

[0009] In order to avoid damage to the structure of the lattice beam, further: the lattice beam is provided with at least one structural seam, the plane corresponding to the structural seam is a vertical plane, and the structural seam is filled with asphalt filler.

[0010] The stiffening piles play the role of reinforcing the slope and tensioning and fixing the lattice beams. Specifically, the stiffening piles are divided into a sediment section and an anchor section from bottom to top. The force-bearing reinforcement of the stiffening piles is a steel strand, which is distributed in the entire anchor section. At least one anchor plate is arranged at intervals along the length of the stiffening piles. The steel strand runs through the anchor plate and is fixedly connected to the anchor plate.

[0011] In order to ensure that the reinforcing piles at different positions can effectively anchor the lattice beam, further: the length directions of the reinforcing piles are parallel to each other, and the length of the reinforcing piles at higher exposed positions is greater than the length of the reinforcing piles at lower exposed positions.

[0012] In order to prevent precipitation from penetrating into the slope through the grid of the lattice beam and promote drainage of the slope, further: the grid of the lattice beam is a lattice panel, the lattice panel includes a steel mesh fixedly connected to the lattice beam, and a concrete slab formed by spraying concrete on the steel mesh, and the lattice panel is also provided with drainage holes.

[0013] The supporting piles are arranged at intervals to ensure the safety of foundation pit excavation. Furthermore, the length of the supporting piles below the elevation of the bottom of the foundation pit is not less than the depth of the foundation pit, and there is a pile retaining wall formed by hanging mesh and spraying concrete between two adjacent supporting piles.

[0014] The anchoring device is used to fix the upper end of the crown beam and the support pile. Furthermore, the anchoring device includes a grouting body poured into the anchor hole, and an anchor cable embedded in the grouting body. The anchor cable is a steel strand and there are at least two of them. The anchoring device is divided into a free section and an anchoring section. The free section is provided with wiring rings at intervals along the length direction, and the anchoring section is provided with wiring rings and tightening rings at intervals. The grouting pipe anchor cable passes through each wiring ring and tightening ring.

[0015] In order to facilitate the arrangement of the anchoring device and ensure that the anchoring device can provide sufficient pull-out resistance, further steps are as follows: the anchoring device is arranged obliquely downward, the crown beam or supporting pile is provided with a reserved hole, the exposed end of the anchor cable passes through the reserved hole, the pad, the diagonal support block, the cover plate and the pressure plate in sequence, and is tensioned and fixed to the supporting pile or the crown beam through the anchor head.

[0016] The present invention also provides a high slope and foundation pit support method, specifically a construction method of the support structure of the high slope and foundation pit, the purpose of which is to improve the integrity and stability of the high slope supported by lattice beams, and ensure the safety of the support structure and the safety of construction. The high slope and foundation pit support method comprises the following steps:

[0017] S1.Construct a drainage ditch on the top of the slope.

[0018] S2. Excavate earth at the top of the slope and construct a top beam, which has dowel bars reserved for connection with the vertical beams of the lattice beam.

[0019] S3. Excavate the slope in layers from top to bottom to the operating platform according to the designed slope, and trim the slope surface.

[0020] S4. To construct reinforcing piles, first determine the hole position of the reinforcing piles on the slope, then drill and clean the holes. The drilling direction is inclined downward, and then a rotary jet drilling rig is used to bring the stress reinforcement into the hole, and high-pressure rotary jet grouting is performed to obtain the anchor body.

[0021] In order to ensure the quality of the hole, further: step S4 uses a down-the-hole drill to drill the hole, and uses casing to follow up the wall drilling.

[0022] The stress reinforcement of a single stiffening pile is often not one. In order to facilitate the simultaneous fixing of each stress reinforcement and to improve the pull-out resistance of the stiffening pile, further: in step S4, the stress reinforcement of the stiffening pile is a steel strand, and the stiffening pile is provided with at least one anchor plate at intervals along its length. The steel strand passes through the anchor plate and is fixedly connected to the anchor plate, and then the stress reinforcement and the anchor plate are brought into the hole by a rotary jet drilling rig. For example, the stress reinforcement of a single stiffening pile is 3 to 4, and the anchor plate is evenly provided with 3 to 4 openings. The stress reinforcement passes through the openings of the anchor plate and is fixed by nuts.

[0023] The pressure of high-pressure rotary jet grouting is determined according to the nature of the stratum. In order to ensure that the stiffening piles can provide a sufficiently large pull-out resistance, further: in step S4, the length directions of the stiffening piles are parallel to each other, the length of the stiffening piles with a high exposed position is greater than the length of the stiffening piles with a low exposed position, and the pressure of the high-pressure rotary jet grouting is not less than 20MPa.

[0024] S5. Construction of lattice beams and installation of steel mesh for lattice panels, including: erecting scaffolding → carving grooves on slopes → making and tying steel bars → installing formwork → pouring concrete and maintaining → removing formwork → tensioning and locking stiffening piles → clearing loose soil and stones on slope surface → hanging steel mesh on slope surface → removing scaffolding; among which, fixing holes are reserved at the connection between the horizontal beam and the vertical beam of the lattice beam, and the stiffening piles correspond to the fixing holes one by one and are tensioned and fixed.

[0025] In order to facilitate the construction of the lattice beam, further: step S4 inserts connecting steel bars into the hole before the slurry solidifies, and the connecting steel bars are partially located in the hole and partially located outside the hole; step S5 connects the connecting steel bars with the steel bars of the lattice beam when making and tying the steel bars.

[0026] In order to avoid corrosion of the stress-bearing bars and anchors at the upper end of the stiffening piles, further steps are as follows: after the stiffening piles are tensioned and locked, a sealing anchor body is constructed in the fixing hole to seal the upper end of the stress-bearing bars and the anchors. The sealing anchor body is a reinforced concrete structure, and the steel bars of the sealing anchor body are welded and fixed to the anchors.

[0027] S6. Spray concrete in the grids of the lattice beam to obtain a lattice panel. In order to ensure the quality of the lattice panel and promote drainage of the slope, further: in step S6, the lattice panel is sprayed at least twice, and the lattice panel is also provided with drainage holes.

[0028] S7. Repeat the above steps S3 to S6 until the construction reaches the bottom of the slope.

[0029] In order to avoid damage to the structure of the lattice beam, further: in steps S3 and S7, the lattice beam is provided with at least one structural seam, the plane corresponding to the structural seam is a vertical plane, and the structural seam is filled with asphalt filler.

[0030] S8. Construct a ground beam at the bottom of the slope, and connect the lower ends of all vertical beams to the ground beam.

[0031] S9.Construct drainage ditches at the bottom of the slope.

[0032] S10. Construct support piles at the bottom of the slope. The center line of the support piles is vertical and they are reinforced concrete structures. The lower end of the support piles is lower than the bottom of the foundation pit.

[0033] S11.Construct the cap beam. The upper ends of the supporting piles are connected through the cap beam.

[0034] S12. Construct anchoring devices, which are tensioned and fixed to the upper ends of the supporting piles or the crown beams.

[0035] The anchoring device is used to fix the upper end of the crown beam and the supporting pile. Furthermore, in step S11, a reserved hole is reserved at the upper end of the supporting pile or the crown beam for construction and fixing the anchoring device; in step S12, drilling is performed through the reserved hole, and the hole is cleaned after the drilling is completed, and then the anchor cable is assembled and inserted into the anchor hole, and then high-pressure grouting is performed into the anchor hole, and finally the anchor cable and the supporting pile or the crown beam are tensioned and fixed.

[0036] In order to improve the pull-out resistance of the anchoring device, further steps are as follows: in step S12, two grouting pipes are used to construct the anchoring device, and high-pressure grouting into the anchor hole is carried out in two times. The anchor cable is a steel strand and there are at least two of them. The anchoring device is divided into a free section and an anchoring section. Wire rings are arranged at intervals in the free section, and wire rings and tightening rings are arranged at intervals in the anchoring section. The anchor cable passes through each wire ring and tightening ring; the anchoring device is arranged obliquely downward, and the exposed end of the anchor cable passes through the reserved hole, the pad, the diagonal support block, the cover plate and the pressure plate from bottom to top, and is tensioned and fixed to the supporting pile or the crown beam through the anchor head.

[0037] S13. Excavate the foundation pit in layers and support the pit wall between the supporting piles.

[0038] The supporting piles are arranged at intervals to ensure the safety of foundation pit excavation. Further, in step S10, the pile holes of the supporting piles are drilled by a rotary drilling rig, and the length of the supporting piles below the elevation of the bottom of the foundation pit is not less than the depth of the foundation pit; in step S13, after the foundation pit is excavated in layers, a mesh is hung between two adjacent supporting piles to spray concrete and form a pile retaining wall.

[0039] The beneficial effects of the present invention are as follows: the capping beam, lattice beam, ground beam and stiffening piles as a whole play a frame hoop effect on the slope, which can effectively deal with the soil arch effect of the slope, improve the integrity and stability of the support structure, and ensure the safety of the slope support. After the stiffening pile is drilled, the force-bearing reinforcement is brought into the hole by a rotary jet drilling rig, and high-pressure rotary jet grouting is performed. The rock and soil around the hole are cut synchronously during the injection process, and the slurry enters the cracks under high pressure to form an anchor body, which reinforces the rock and soil of the slope, connects the unstable rock blocks with the stable rock mass, and also forms an integral structure with the anchor body, the force-bearing reinforcement and the rock and soil at the bottom of the hole and around the hole, so that the stiffening pile is stressed together through the force-bearing reinforcement, the anchor body and the rock and soil around the hole. The anchor body will also form an expanded diameter portion during the high-pressure rotary jet process, that is, the part of the stiffening pile located in the hole has an expanded diameter portion, which increases the pull-out resistance of the stiffening pile. The stiffening piles are tensioned and fixed with the lattice beams. The stiffening piles can effectively control the displacement and internal force of the support structure, effectively restrain the deformation of the slope, and reduce the creep deformation of the slope. The capping beam, lattice beam, ground beam and stiffening piles form the support structure of the high slope, and the supporting piles, crown beam and anchoring device form the support structure of the vertical excavation of the foundation pit. The two support structures together constitute the support structure of the high slope and the foundation pit, reducing the support depth of the supporting piles, reducing the support length and construction difficulty of the stiffening piles, and thus reducing the project cost.

[0040] The present invention is suitable for supporting high slopes with limited land area, high slopes with buildings with high deformation requirements on the top of the slope and limited construction space at the bottom of the slope. It can also be used for the prevention and control of shallow slopes, and slopes with gentle slope changes and small undulations. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic elevation view of an embodiment of a supporting structure for a high slope and a foundation pit of the present invention.

[0042] Figure 2 It is a cross-sectional schematic diagram of an embodiment of the support structure of a high slope and a foundation pit of the present invention.

[0043] Figure 3 It is a schematic diagram of lattice beams and lattice panels in one embodiment of the supporting structure for high slopes and foundation pits of the present invention.

[0044] Figure 4 It is a schematic structural diagram of the tensioning and fixing of stiffening piles and lattice beams in one embodiment of the supporting structure of a high slope and a foundation pit of the present invention.

[0045] Figure 5 It is a schematic elevation view of support piles and inter-pile retaining walls in one embodiment of the support structure for high slopes and foundation pits of the present invention.

[0046] Figure 6 yes Figure 5 A schematic plan view of the supporting piles and the inter-pile retaining wall in the illustrated embodiment.

[0047] Figure 7 yes Figure 2 A schematic diagram of the structure of the anchoring device and the supporting piles being tensioned and fixed in the illustrated embodiment.

[0048] Figure numerals: intercepting ditch 1, top beam 2, lattice beam 3, ground beam 4, reinforcing pile 5, sediment section 5a, anchor section 5b, anchor body 5-1, force-bearing reinforcement 5-2, anchor plate 5-3, supporting pile 6, crown beam 7, anchoring device 8, anchor cable 8-1, wire ring 8-2, tightening ring 8-3, pad 8-4, diagonal support block 8-5, cover plate 8-6, pressure plate 8-7, anchor head 8-8, grouting pipe 8-9, drainage ditch 9, anchor body 10, structural joint 11, lattice panel 12, retaining wall between piles 13, foundation pit bottom elevation h1. DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with the accompanying drawings.

[0050] The first subject of the present invention is a support structure for high slopes and foundation pits. Figure 1 and Figure 2As shown, the support structure of the high slope and foundation pit includes a drainage ditch 1 and a capping beam 2 located at the top of the slope, a lattice beam 3 located on the slope surface, a ground beam 4 located at the bottom of the slope, and a stiffening pile 5 arranged downwardly in the slope body. The drainage ditch 1 is used to prevent surface runoff from entering the slope surface. The side of the drainage ditch 1 facing away from the slope surface is the non-construction area. For example, the side of the drainage ditch 1 facing away from the slope surface is the red line, and the side of the red line facing away from the drainage ditch 1 is the cultivated land. The capping beam 2 is arranged along the top of the slope and connected to the vertical beam of the lattice beam 3 located on the slope surface. The cross-sectional dimensions of the capping beam 2 are determined according to the conditions of the high slope. For example, the cross-sectional dimensions of the capping beam 2 are 0.5m×0.55m. The lattice beam 3 includes a horizontally arranged horizontal beam and a vertical beam perpendicular to the horizontal beam. The horizontal beam and the vertical beam are cast in one piece. The upper ends of the vertical beams are respectively connected to the capping beam 2, and the lower ends of the vertical beams are respectively connected to the ground beam 4. The reinforcing pile 5 includes an anchor body 5-1 obtained by high-pressure rotary spraying in the hole, and a stress-bearing bar 5-2 embedded in the anchor body 5-1. The reinforcing pile 5 plays the role of reinforcing the slope on the one hand, and plays the role of fixing the lattice beam 3 on the other hand. The connection between the horizontal beam and the vertical beam of the lattice beam 3 is provided with a fixing hole, and the reinforcing pile 5 corresponds to the fixing hole one by one. The upper end of the stress-bearing bar 5-2 of the reinforcing pile 5 passes through the fixing hole and is tensioned and fixed by an anchor, that is, the upper end of the stress-bearing bar 5-2 of the reinforcing pile 5 is tensioned and fixed to the lattice beam 3. The top beam 2, the lattice beam 3 and the ground beam 4 are all reinforced concrete structures, and become a whole after pouring. The top beam 2, the lattice beam 3, the ground beam 4 and the reinforcing pile 5 form a support structure for the high slope.

[0051] The reinforcing piles 5 play a dual role in fixing the slope and tensioning and fixing the lattice beams 3. The construction of the reinforcing piles 5 is mainly divided into two steps. The first step is to drill holes, that is, to drill holes in the rock mass at a certain angle by a down-the-hole drill; the second step is for the jet grouting machine to enter the hole with the reinforcement 5-2 and inject grouting at high pressure, that is, the jet grouting machine enters the hole with the reinforcement 5-2 and injects grouting to the bottom of the hole, and then injects high pressure grouting around the hole again while withdrawing the drill bit. From the structural point of view, see Figure 4 The stiffening pile 5 is divided into a sediment section 5a and an anchoring section 5b from bottom to top. The stress reinforcement 5-2 is distributed throughout the anchoring section 5b. The stress reinforcement 5-2 is generally a steel strand. For example, the stress reinforcement 5-2 uses 3φs15.2mm low-relaxation, high-strength, full-length bonded steel strand, and the standard value of the steel strand strength is 1860MPa. In order to make the stress reinforcement 5-2 close to the center line of the hole, the stiffening pile 5 is also spaced along its length. At least one anchor plate 5-3 is provided at intervals. The anchor plate 5-3 is provided with a through hole for the stress reinforcement 5-2 to pass through. The stress reinforcement 5-2 passes through the anchor plate 5-3 and is fixedly connected to the anchor plate 5-3. For example, after the stress reinforcement 5-2 passes through the anchor plate 5-3, the relative fixation of the two is achieved by a nut.

[0052] The reinforcing piles 5 are arranged in a matrix of rows and columns on the entire slope. In order to uniformly reinforce the entire slope, the length directions of the reinforcing piles 5 are parallel to each other, for example, the length directions of the reinforcing piles 5 are parallel to each other, and the acute angle formed with the horizontal line is 15°. In order to ensure that the reinforcing piles 5 of different heights can effectively anchor the lattice beam 3, the length of the reinforcing piles 5 with a high exposed position is greater than the length of the reinforcing piles 5 with a low exposed position, that is, the higher the position of the reinforcing piles 5 on the slope, the longer the length of the reinforcing piles 5. For example, the length of the reinforcing piles 5 is 15.5 to 32.0 m. In order to prevent the stress reinforcement 5-2 and the anchor at the upper end of the reinforcing piles 5 from rusting, a sealing anchor body 10 that seals the upper end of the stress reinforcement 5-2 and the anchor is also provided at the fixing hole of the lattice beam 3. For example, the sealing anchor body 10 is a reinforced concrete structure, and the steel bars of the sealing anchor body 10 are welded and fixed to the anchor. The steel bars of the sealing anchor body 10 are generally threaded steel bars, and the concrete of the sealing anchor body 10 is generally C30 concrete. After the stiffening pile 5 is tensioned and fixed, it is necessary to supplement the grouting from the grouting holes on the steel pad, and then the anchor body 10 is constructed. The net protective layer thickness of the anchor body 10 is not less than 35mm. The exposed part of the force reinforcement 5-2 of the stiffening pile 5 and the steel pad should be rust-free and painted with asphalt ship bottom paint before installation and locking. The exposed part of the force reinforcement 5-2 should be cut with a handheld cutting machine, and its exposed length should be not less than 50mm.

[0053] The lattice beam 3 is arranged on the entire slope surface. In order to avoid damage to the structure of the lattice beam 3, the lattice beam 3 is provided with at least one structural seam 11, the plane corresponding to the structural seam 11 is a vertical plane, and fillers are arranged in the structural seam 11, such as Figure 3 For example, the lattice beam 3 is provided with structural joints 11 at intervals of 20m in the horizontal direction, and the structural joints 11 are filled with asphalt fillers. In order to prevent precipitation from penetrating into the slope from the grid of the lattice beam 3, and also to prevent the slope from falling in the grid of the lattice beam 3, a lattice panel 12 is provided in the grid of the lattice beam 3, and the lattice panel 12 includes a steel mesh fixedly connected to the lattice beam 3, and a concrete slab formed by spraying concrete on the steel mesh, as shown in FIG. Figure 3 For example, the steel mesh of the lattice panel 12 is two layers, the thickness of the concrete slab is 180 mm and C25 concrete is used, and it is sprayed twice. In order to facilitate the discharge of water inside the slope through the slope surface, the lattice panel 12 is also provided with drainage holes, for example, the lattice panel 12 is provided with drainage holes at intervals of 2.0 m.

[0054] Support piles 6 are also arranged at intervals at the bottom of the slope. The center lines of the support piles 6 are vertical and are reinforced concrete structures. The side of the support piles 6 facing away from the slope is the foundation pit excavation area. The support piles 6 are arranged at intervals. In order to ensure the safety of the foundation pit excavation, the lower end of the support piles 6 is lower than the elevation h1 of the bottom of the foundation pit. The elevation h1 of the bottom of the foundation pit is the elevation of the deepest excavation position of the foundation pit. Generally, the length of the support piles 6 below the elevation h1 of the bottom of the foundation pit is not less than the depth of the foundation pit. The upper ends of the support piles 6 are connected by a crown beam 7, so that each support pile 6 forms a whole. Between the crown beam 7 and the ground beam 4 is a drainage ditch 9, and the drainage ditch 9 is used for drainage. For example, the drainage ditch 9 is connected to the drainage system and finally drains to the urban drainage network. After the foundation pit is excavated, in order to ensure the stability of the pit wall, a pile guard wall 13 formed by hanging mesh spraying concrete is provided between two adjacent support piles 6, such as Figure 5 and Figure 6 shown.

[0055] The upper end of the support pile 6 or the crown beam 7 is anchored to the slope through the anchor device 8 to ensure the stability of the support pile 6 and the crown beam 7. The anchor device 8 is used to fix the crown beam 7 and the upper end of the support pile 6. The anchor device 8 includes a grouting body poured into the anchor hole, and an anchor cable 8-1 embedded in the grouting body. For example, the anchor cable 8-1 is a steel strand and there are at least two strands. The anchor device 8 is divided into a free section and an anchor section. The free section is provided with a wire-hanging ring 8-2 at intervals along the length direction. The wire-hanging ring 8-2 is used to ensure that the anchor cable 8-1 is distributed along the center line of the anchor hole. The anchor section is provided with a wire-hanging ring 8-2 and a clamping ring 8-3 at intervals. The grouting pipe 8-9 and the anchor cable 8-1 pass through each wire-hanging ring 8-2 and the clamping ring 8-3. Figure 7 As shown. The wire ring 8-2 is used to ensure that the anchor cable 8-1 is distributed along the center line of the anchor hole. The wire ring 8-2 and the clamp ring 8-3 are arranged at intervals in the anchoring section, which is conducive to improving the integrity of the anchor cable 8-1 and the grouting body, improving the pull-out resistance of the anchoring device 8, and also facilitating the insertion of the anchor cable 8-1 into the anchor hole. For example, in the anchoring section, the wire ring 8-2 and the clamp ring 8-3 are arranged at intervals of 0.70m; in the free section, a wire ring 8-2 is arranged every 2.0m to ensure that the anchor cable 8-1 is straight. The anchoring device 8 is arranged obliquely downward, and the grouting body of the anchoring device 8 and the rock and soil around the anchor hole become a whole. In order to facilitate the arrangement of the anchoring device 8, the crown beam 7 or the supporting pile 6 is provided with a reserved hole, and the reserved hole is used for the construction of the anchoring device 8. Since the anchoring device 8 is arranged obliquely downward, in order to facilitate the tensioning and fixing of the anchor cable 8-1, the exposed end of the anchor cable 8-1 successively passes through the reserved hole, the pad 8-4, the diagonal support block 8-5, the cover plate 8-6 and the pressure plate 8-7, and is tensioned and fixed with the supporting pile 6 or the crown beam 7 through the anchor head 8-8. Figure 7 shown.

[0056] The second subject of the present invention is a method for supporting a high slope and a foundation pit, which is also the construction method of the first subject. The method for supporting a high slope and a foundation pit comprises the following steps.

[0057] S1. Construct an intercepting ditch 1 on the top of the slope. The location and size of the intercepting ditch 1 are determined according to the design and terrain conditions.

[0058] S2. Excavate the earth on the top of the slope and construct the top beam 2, which reserves dowel bars for connecting with the vertical beams of the lattice beam 3. For example, the cross-sectional size of the top beam 2 is 550 mm×400 mm.

[0059] S3. Excavate the slope from top to bottom in layers according to the designed slope rate to the operating platform, and trim the slope surface. The slope excavation is carried out from top to bottom, and loose stones on the slope surface are removed. To ensure safety, the excavation depth of each layer of earth and stone should not exceed 0.8m below the hole position of each row of stiffening piles 5. After excavating the slope from top to bottom according to the designed slope rate to the operating platform, leave an operating platform with a width of 6m for mechanical construction. After the slope surface is repaired and leveled, the construction of stiffening piles 5 is carried out.

[0060] S4. Construction of stiffening piles 5. First, determine the hole positions of the stiffening piles 5 on the slope surface, which correspond to the fixing holes of the lattice beams 3 in step S5, then drill and clean the holes, and arrange the holes obliquely downward. Then, use a jet grouting machine to bring the force-bearing reinforcement 5-2 into the hole, perform high-pressure jet grouting, and obtain the anchor body 5-1.

[0061] The drilling construction of the stiffening pile 5 adopts a mechanical dry hole forming process, such as using a down-the-hole drill, specifically a 90-type down-the-hole drill. In order to ensure the quality of the hole, a casing should be used to follow up the wall protection when the hole wall stability is poor. After the down-the-hole drill is fixed, adjust the azimuth and inclination, check the drilling position, and then tighten all fasteners. Drilling can be started when it is ready. After the drilling is completed, blow the hole with high air pressure; when the dust in the hole is blown away and the hole depth reaches the requirement, pull out the drill rod and drilling tools.

[0062] The stress reinforcement 5-2 of a single stiffening pile 5 is often not one, but multiple. For example, the stress reinforcement 5-2 uses 3φs15.2mm low relaxation, high strength, full-length bonded steel strands, the standard value of the steel strand strength is 1860MPa, the processing length of the steel strand is strictly determined according to the drawings, and the steel strand should be cut with a grinding wheel saw. The stress reinforcement 5-2 includes an anchoring section and an exposed section. To facilitate the tensioning of the jack, the length of the exposed section of the stress reinforcement 5-2 should be greater than 1.5m. In order to ensure that the stiffening piles 5 can provide sufficiently large pull-out resistance, the length directions of the stiffening piles 5 are parallel to each other, the length of the stiffening piles 5 with a higher exposed position is greater than the length of the stiffening piles 5 with a lower exposed position, and the number and length of the steel strands of the stiffening piles 1 in the same row are consistent, that is, the number and length of the steel strands of the stiffening piles 1 at the same height are consistent.

[0063] In order to facilitate simultaneous fixing of each stress-bearing bar 5-2 of a single stiffening pile 5, at least one anchor plate 5-3 is arranged at intervals along the length direction of the stiffening pile 5, and the steel strand passes through the anchor plate 5-3 and is fixedly connected to the anchor plate 5-3, and then the stress-bearing bar 5-2 and the anchor plate 5-3 are brought into the hole by a jet grouting drill. For example, the hole diameter of the stiffening pile 5 is 180 mm, the diameter of the anchor plate 5-3 is 150 mm, and holes are evenly opened on the anchor plate 5-3 according to the number of steel strands, and the diameter of the holes is 20 mm. The steel strands are fixed with nuts after passing through the holes of the anchor plate 5-3.

[0064] Before the reinforcement 5-2 is placed in the hole, first check whether the number of the reinforcing pile 5 is consistent with the hole number. After confirming that the hole depth and the length of the reinforcement 5-2 are correct, use the guide probe to explore the hole. If there is no obstruction, use the jet drilling rig to bring the reinforcement 5-2 into the hole and perform high-pressure jet grouting. The pressure of high-pressure jet grouting depends on the nature of the stratum. The pressure of high-pressure jet grouting is generally not less than 20MPa, and the water-cement ratio of the slurry is generally 0.8:1.

[0065] After the down-the-hole drill drills and loosens the soil layer, the jet drilling machine advances and brings in the stress reinforcement 5-2 to the designed depth. After high-pressure jet grouting, the slurry directly impacts and cuts the soil and breaks the rock. The slurry is mixed with soil particles and debris and solidified to form an anchor body 5-1, which plays the role of replacement, compaction, anchoring, etc., to achieve the reinforcement of the rock and soil. The anchor body 5-1 is generally M30. The shape of the anchor body 5-1 of the stiffening pile 5 is different in different strata. Through repeated stirring, increasing the slurry injection pressure and other measures, an expanded diameter portion will be formed, that is, the part of the anchor body 5-1 of the stiffening pile 5 located in the hole has an expanded diameter portion, which can increase the pull-out resistance of the stiffening pile 5. When constructing the stiffening pile 5, the diameter of the drilled hole is 180mm, and the diameter of the anchor body 5-1 is generally 300-500mm, which can effectively reduce the stress level of the soil around the stiffening pile and reduce the plastic deformation of the stress reinforcement 5-2. Pre-tensioning the force-bearing reinforcement 5-2 can effectively control the displacement and internal force of the support structure, effectively restrain deformation, and reduce creep deformation. For rock slopes, the force-bearing reinforcement 5-2 of the stiffening pile 5 can penetrate into the stable rock mass and connect the unstable rock blocks with the stable rock mass. In particular, for some rock slopes with joints and cracks, the force-bearing reinforcement 5-2 can pass through the cracks to tighten the broken rock blocks and prevent them from falling.

[0066] In order to facilitate the subsequent construction of the lattice beam 3, after the high-pressure jet grouting pile is completed and before the slurry solidifies, a connecting steel bar is inserted into the hole, and the connecting steel bar is partially located inside the hole and partially located outside the hole. When tying the steel bars of the lattice beam 3, the connecting steel bar plays a role in preliminarily fixing the steel bars of the lattice beam 3, and the connecting steel bar can also improve the connection strength between the lattice beams 3 and the lattice beams 3. For example, the total length of the connecting steel bar is 1.50m, 0.60m is exposed, and the diameter is φ12mm.

[0067] S5. Construction of lattice beams 3 and installation of steel mesh for lattice panels 12, including: erecting scaffolding → carving grooves on slopes → making and tying steel bars → installing formwork → pouring concrete and curing → removing formwork → tensioning and locking stiffening piles 5 → clearing loose soil and stones on the slope → hanging steel mesh on the slope → removing scaffolding; wherein, fixing holes are reserved at the connection between the horizontal beams and vertical beams of the lattice beams 3, and the stiffening piles 5 correspond to the fixing holes one by one and are tensioned and fixed.

[0068] The lattice beam 3 includes a horizontally arranged horizontal beam and a vertical beam perpendicular to the horizontal beam. The horizontal beam and the vertical beam are cast in one piece, and the upper ends of the vertical beams are connected to the top beam 2 respectively. The size and spacing of the lattice beam 3 are determined according to the slope conditions. For example, the cross-sectional size of the lattice beam 3 is 0.40m×0.55m, and the spacing is 2.50m×2.50m. The connection between the horizontal beam and the vertical beam of the lattice beam 3 is provided with a fixing hole, and the stiffening piles 5 correspond to the fixing holes one by one. The upper end of the stress reinforcement 5-2 of the stiffening pile 5 passes through the fixing hole and is tensioned and fixed by an anchor. The stress reinforcement 5-2 is tensioned and fixed to the lattice beam 3 to form a comprehensive support system to improve the overall stability of the slope.

[0069] In order to prevent the stress reinforcement 5-2 and the anchor from being corroded at the upper end of the stiffening pile 5, after the construction of one layer of lattice beam 2 is completed, after the stiffening pile 5 is tensioned and fixed by the anchor, it is necessary to supplement the grouting from the grouting hole on the steel pad of the anchor, and then construct the anchor body 10 that seals the upper end of the stress reinforcement 5-2 and the anchor in the fixing hole. For example, the anchor body 10 is a reinforced concrete structure, and the steel bars of the anchor body 10 are welded and fixed to the anchor.

[0070] S6. Hang a mesh in the grid of the lattice beam 3 and spray concrete to obtain a lattice panel 12. The lattice panel 12 includes a steel mesh fixedly connected to the lattice beam 3, and a concrete slab formed by spraying concrete onto the steel mesh, such as Figure 3 For example, the steel mesh of the lattice panel 12 is two layers, the thickness of the concrete slab is 150 mm and C25 concrete is used, and the spraying is carried out twice, and a 25-ton crane is used to assist the spraying. In order to facilitate the discharge of water inside the slope through the slope surface, the lattice panel 12 is also provided with drainage holes, for example, the lattice panel 12 is provided with drainage holes at intervals of 2.0 m.

[0071] S7. Repeat the above steps S3 to S6 until the construction reaches the bottom of the slope.

[0072] The area of ​​the slope is large, and the lattice beam 3 is arranged on the entire slope. In order to avoid damage to the structure of the lattice beam 3, in steps S3 and S7, the lattice beam 3 is provided with at least one structural seam 11, and the plane corresponding to the structural seam 11 is a vertical plane. Fillers are arranged in the structural seam 11, such as Figure 3 For example, the lattice beam 3 is provided with structural joints 11 at intervals of 20 m in the horizontal direction, and the structural joints 11 are filled with asphalt fillers.

[0073] S8. construct the ground beam 4 at the bottom of the slope, and the lower ends of the vertical beams are connected to the ground beam 4. After the construction of the ground beam 4 is completed, the support of the entire high slope is completed.

[0074] S9. Construct drainage ditch 9 at the bottom of the slope. The slope earthwork is excavated to the bottom of the slope, and drainage ditch 9 is constructed at the foot of the slope. The drainage ditch 9 is connected to the drainage system and finally drained to the urban drainage network.

[0075] S10. Construct support piles 6 at the bottom of the slope. The center line of the support piles 6 is vertical and is a reinforced concrete structure. The lower end of the support piles 6 is lower than the elevation h1 of the bottom of the foundation pit.

[0076] The support piles 6 are arranged at intervals along the bottom of the slope, and the side of the support piles 6 facing away from the slope is the foundation pit excavation area. For example, the pile diameter of the support piles 6 is 1.0m, and the pile spacing is 3.0m. For another example, the support piles 6 are bored cast-in-place piles, and the hole-forming process adopts mechanical rotary drilling, and the pile body concrete strength grade is C30. In order to ensure the safety of foundation pit excavation, the lower end of the support pile 6 is lower than the elevation h1 of the bottom of the foundation pit, and the elevation h1 of the bottom of the foundation pit is the elevation of the deepest excavation position of the foundation pit. Generally, the pile hole of the support pile 6 is dug by a rotary drilling rig, and the length of the support pile 6 below the elevation h1 of the bottom of the foundation pit is not less than the depth of the foundation pit. When constructing the support piles 6, first locate and lay out the lines to determine the pile positions. The support piles 6 are arranged in a row along the longitudinal direction, and the rotary drilling rig jumps to dig holes. The drilling operation should be carried out continuously. After the holes are formed, the steel cage is hoisted and then concrete is poured. The conduit method is used for pouring. The pile body concrete should be poured continuously at one time, and finally the integrity of the pile body is tested.

[0077] S11. Construct the crown beam 7 , and connect the upper ends of the supporting piles 6 via the crown beam 7 .

[0078] The upper ends of the supporting piles 6 are connected by the cap beam 7, so that the supporting piles 6 form a whole. For example, the cross-sectional size of the cap beam 7 is 1.20m×0.8m, and it is C30 reinforced concrete. There is a drainage ditch 9 between the cap beam 7 and the ground beam 4, and the drainage ditch 9 is used for drainage. For example, the drainage ditch 9 is connected to the drainage system and finally drains to the urban drainage network. The construction of the cap beam 7 includes excavating the earthwork of the cap beam 7 → breaking the floating slurry at the head of the supporting pile 6 → tying the steel bars of the cap beam 7 → installing and reinforcing the formwork → casting the cap beam 7 → curing and removing the formwork.

[0079] The support piles 6 and the crown beams 7 are constructed. To facilitate the construction of the anchoring device 8, the upper end of the support piles 6 or the crown beams 7 are reserved with reserved holes for constructing and fixing the anchoring device 8. For example, the reserved holes are set when tying the steel bars of the crown beams 7.

[0080] S12. Construct the anchoring device 8, which is tensioned and fixed to the upper end of the supporting pile 6 or the crown beam 7.

[0081] The anchor device 8 is mainly used to fix the crown beam 7 and the upper end of the support pile 6. The anchor device 8 includes a grouting body poured into the anchor hole, and an anchor cable 8-1 embedded in the grouting body. For example, the anchor cable 8-1 is a steel strand and there are at least two of them, and the anchor device 8 is divided into a free section and an anchor section. The structure of the anchor device 8 is the same as the relevant description of the first topic, and will not be repeated here. When the anchor cable 8-1 is a steel strand, it is necessary to degrease and rust the steel strand in advance, apply butter to the free section, cover the anti-skid tube, and reserve enough tensioning sections outside the anchor hole. After the foundation pit is stable, the excess part can be cut off. In order to improve the pull-out resistance of the anchor device 8, two grouting pipes 8-9 are used to construct the anchor device 8, and high-pressure grouting into the anchor hole is carried out twice, that is, secondary grouting is used. For example, the grouting pressure is 0.20~0.50MPa, and the slurry uses M30 cement slurry with a water-cement ratio of 0.50~0.55. After placing the device including the anchor cable 8-1, the wire ring 8-2, the tightening ring 8-3, the wall protection tube, the guide cap and the grouting pipe 8-9 into the anchor hole, set a grouting stop ring at the junction of the free section and the anchor section, start the first grouting, pull out the wall protection tube while grouting, and stop grouting after the cement slurry overflows from the hole mouth; after grouting, when the slurry level drops, the hole mouth should be grouted; after the consolidation strength of the slurry reaches 5MPa, carry out secondary grouting, the grouting pipe 8-9 used for the secondary grouting should be firmly tied to the device, and the pressure to terminate the grouting should not be less than 1.5MPa.

[0082] The anchor device 8 is arranged obliquely downward, and the grouting body of the anchor device 8 and the rock and soil body around the anchor hole become a whole. For example, the direction of the anchor device 8 is consistent with the direction of the stiffening pile 5, and the anchor device 8 is anchored into the original soil body around the foundation pit at an inclination of 15°. In order to facilitate the arrangement of the anchor device 8, the crown beam 7 or the support pile 6 is provided with a reserved hole, and the reserved hole is used for the construction of the anchor device 8. For example, the crown beam 7 is provided with a reserved hole, and the drill rod is inserted into the reserved hole of the crown beam 7. The drill rod is fixed to the drilling rig, the azimuth and inclination are adjusted, and then all fasteners are tightened. After the drilling is completed, the hole is blown with high wind pressure. When the dust in the hole is blown away and the hole depth reaches the requirement, the drill rod and the drill tool are pulled out, and the above device is inserted into the anchor hole, and then high-pressure grouting is performed. After the slurry reaches 75% strength, the anchor cable 8-1 is tensioned and fixed. Since the anchor device 8 is arranged obliquely downward, in order to facilitate the tensioning and fixing of the anchor cable 8-1, the exposed end of the anchor cable 8-1 passes through the reserved hole, the pad 8-4, the diagonal support block 8-5, the cover plate 8-6 and the pressure plate 8-7 in sequence, and is tensioned and fixed to the support pile 6 or the crown beam 7 through the anchor head 8-8. Figure 7 shown.

[0083] S13. Excavate the foundation pit in layers and support the pit wall between the support piles 6.

[0084] After the anchoring device 8 is tensioned and fixed with the supporting pile 6 or the crown beam 7, the foundation pit is excavated, and the foundation pit is excavated vertically downward in layers. The foundation pit wall is repaired simultaneously, and a mesh is hung between two adjacent supporting piles 6 to spray concrete and form an inter-pile protective wall 13, such as Figure 5 and Figure 6 In order to ensure the stability of the steel mesh of the pile protection wall 13, connecting steel bars are implanted in the support piles 6, and the steel mesh of the pile protection wall 13 is connected to the connecting steel bars.

Claims

1. The support method for high slopes and foundation pits is characterized by: The steps include: S1. Construction of intercepting ditch on the top of the slope (1); S2 excavation at the top of the slope, and the construction of the top beam (2), the top beam (2) is reserved for the vertical beam connection with the lattice beam (3) dowel; S3. Excavate the slope layer by layer from top to bottom to the operating platform according to the designed slope rate, and trim the slope surface; S4. Construction of stiffening piles (5), first determine the position of the stiffening piles (5) on the slope, then drill and clean the holes, the drilling direction is tilted downward, and then the jet grouting rig is used to bring the force bar (5-2) into the hole, and high-pressure jet grouting is performed to obtain the anchor body (5-1); S5. Construction of lattice beams (3) and installation of steel mesh for lattice panels (12), including: erecting scaffolding → notching the slope → making and tying steel bars → installing formwork → pouring concrete and curing → removing formwork → tensioning and locking of stiffening piles (5) → cleaning loose soil and stones on the slope → hanging steel mesh on the slope → removing scaffolding; wherein, fixing holes are reserved at the connection between the horizontal beam and the vertical beam of the lattice beam (3), and the stiffening piles (5) correspond to the fixing holes one by one and are tensioned and fixed; S6. Spray concrete in the grid of the lattice beam (3) to obtain a lattice panel (12); S7. Repeat the above steps S3 to S6 until the construction reaches the bottom of the slope; S8. Construction of the ground beam (4) at the bottom of the slope, the lower ends of the vertical beams are connected to the ground beam (4); S9. Construct drainage ditches at the bottom of the slope (9); S10. Construction of support piles (6) at the bottom of the slope, the center line of the support piles (6) is vertical and is a reinforced concrete structure, the lower end of the support piles (6) is lower than the bottom elevation of the foundation pit (h1); S11. Construction of the crown beam (7), the upper ends of the support piles (6) are connected by the crown beam (7); S12. Construction anchoring device (8), anchoring device (8) and the upper end of the support pile (6) or the crown beam (7) are tensioned and fixed; S13. Excavate the foundation pit in layers and support the pit wall between the support piles (6).

2. The method for supporting high slopes and foundation pits according to claim 1, characterized in that: In step S4, a down-the-hole drill is used to drill a hole, and casing is used to follow up the wall drilling.

3. The method for supporting high slopes and foundation pits according to claim 1, characterized in that: In step S4, the stress-bearing reinforcement (5-2) of the stiffening pile (5) is a steel strand, and at least one anchor plate (5-3) is arranged at intervals along the length direction of the stiffening pile (5). The steel strand passes through the anchor plate (5-3) and is fixedly connected to the anchor plate (5-3). Then, a jet-jet drilling rig is used to bring the stress-bearing reinforcement (5-2) and the anchor plate (5-3) into the hole.

4. The method for supporting high slopes and foundation pits according to claim 1, characterized in that: In step S4, the length directions of the reinforcing piles (5) are parallel to each other, the length of the reinforcing piles (5) with a higher exposed position is greater than the length of the reinforcing piles (5) with a lower exposed position, and the pressure of the high-pressure rotary jet grouting is not less than 20 MPa.

5. The method for supporting high slopes and foundation pits according to claim 1, characterized in that: Step S4: before the slurry solidifies, a connecting steel bar is inserted into the hole, wherein the connecting steel bar is partially located inside the hole and partially located outside the hole; Step S5: when manufacturing and tying the steel bars, the connecting steel bar is connected to the steel bars of the lattice beam (3).

6. The method for supporting high slopes and foundation pits according to claim 1, characterized in that: After the reinforcing pile (5) is tensioned and locked, a sealing anchor body (10) is constructed in the fixing hole to seal the upper end of the stress reinforcement (5-2) and the anchor. The sealing anchor body (10) is a reinforced concrete structure, and the steel bars of the sealing anchor body (10) are welded and fixed to the anchor.

7. The method for supporting high slopes and foundation pits according to claim 1, characterized in that: In step S6, the lattice panel (12) is sprayed at least twice, and the lattice panel (12) is also provided with a drainage hole.

8. The method for supporting a high slope and a foundation pit according to any one of claims 1 to 7, characterized in that: In step S11, a reserved hole for constructing and fixing the anchor device (8) is reserved at the upper end of the support pile (6) or the crown beam (7); in step S12, drilling is performed through the reserved hole, the hole is cleaned after the drilling is completed, and then the anchor cable (8-1) is assembled and inserted into the anchor hole, and then high-pressure grouting is performed into the anchor hole, and finally the anchor cable (8-1) and the support pile (6) or the crown beam (7) are tensioned and fixed.

9. The method for supporting high slopes and foundation pits as claimed in claim 8, characterized in that: In step S12, two grouting pipes (8-9) are used to construct the anchoring device (8), and high-pressure grouting is performed in two times in the anchor hole. The anchor cables (8-1) are at least two steel strands. The anchoring device (8) is divided into a free section and an anchoring section. The free section is provided with wire-tie rings (8-2) at intervals, and the anchoring section is provided with wire-tie rings (8-2) and tightening rings (8-3) at intervals. The anchor cables (8-1) pass through each wire-tie ring (8-2) and tightening ring (8-3). The anchoring device (8) is arranged downwardly at an angle, and the exposed end of the anchor cable (8-1) passes through the reserved hole, the pad (8-4), the diagonal support block (8-5), the cover plate (8-6) and the pressure plate (8-7) in sequence from bottom to top, and is tensioned and fixed to the support pile (6) or the crown beam (7) through the anchor head (8-8).

10. The method for supporting a high slope and a foundation pit according to any one of claims 1 to 7, characterized in that: In step S10, the pile hole of the supporting pile (6) is drilled by a rotary drilling rig, and the length of the supporting pile (6) below the elevation (h1) of the bottom of the foundation pit is not less than the depth of the foundation pit; in step S13, after the foundation pit is excavated in layers, a mesh is hung between two adjacent supporting piles (6) to spray concrete and form a lattice panel (13).

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