Rock-soil alternating complex foundation pit slope supporting method and structure

Abstract

The invention relates to a rock-soil alternating complex foundation pit slope supporting method and structure, and the supporting method comprises the steps: constructing a reinforced concrete anchoring beam outside a slip crack surface, and pre-burying a tie main reinforcement; after the foundation pit is excavated and the side slope surface is trimmed, joint bars inserted into the rock-soil body are constructed on the side slope surface; paving slope surface main reinforcements connected with the joint bars, and fixedly connecting the slope surface main reinforcements with the tie main reinforcements; and a reinforcing mesh is hung on the side slope surface and concrete is sprayed to form a slope surface concrete layer. According to the supporting structure, a space stress whole is formed by anchoring beams, tie main reinforcements, joint reinforcements, slope surface main reinforcements, a reinforcing mesh and a slope surface concrete layer. Underground anchor rods are replaced by the ground anchoring beams, the problem of drilling and grouting in complex rock stratums is solved, and the method has the advantages of being easy, convenient and rapid to construct, high in adaptability, economical, reliable and easy to popularize, and is particularly suitable for slope supporting of complex geological foundation pits with rock-soil alternation.

Description

Technical Field

[0001] This invention relates to the field of foundation pit slope protection technology, and more specifically, to a method and structure for supporting complex foundation pit slopes with alternating rock and soil. Background Technology

[0002] In urban construction, transportation, and water conservancy projects, situations frequently arise requiring deep foundation pit excavation under complex geological conditions. This is especially true in mountainous, hilly, or old geological areas, where construction sites are often located in areas with complex rock formations and shallow bedrock. These sites exhibit significant variations in bedrock weathering, with strongly and moderately weathered rock layers interspersed, varying in thickness, and exhibiting highly uneven spatial distribution.

[0003] When excavating foundation pits under complex geological conditions involving alternating soil and rock, the slope cross-section often exhibits frequent interfaces between soil and rock. Traditional deep foundation pit slope support methods, such as pile support and diaphragm walls, face significant challenges in pile and trench construction when encountering hard or fractured bedrock, resulting in low efficiency and high costs. While the widely used anchor (cable) support technology is relatively flexible, it faces numerous difficulties when constructing at soil-rock interfaces: First, anchors need to penetrate soil and rock layers of different properties, making drilling difficult, especially on sloping, hard rock surfaces where hole deviation and drill jamming are common; second, the grouting quality of anchors is difficult to guarantee at the soil-rock interface, affecting anchoring force; third, the working surface becomes narrow and uneven due to exposed rock, affecting the positioning of drilling equipment and the efficiency of anchor installation. These problems lead to extended construction periods, increased safety hazards, and difficulty in controlling project costs.

[0004] Therefore, there is an urgent need to develop a new technology for foundation pit slope support that can adapt to complex geological conditions of alternating soil and rock, is easy to construct, fast and efficient, cost-controllable, and safe and reliable, so as to solve the bottleneck problems encountered by traditional support methods under similar working conditions. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method and structure for supporting complex foundation pit slopes with alternating soil and rock, in order to solve the problems existing in the prior art.

[0006] According to a first aspect of the present invention, a method for supporting complex foundation pit slopes with alternating soil and rock is provided, comprising the following steps: S1. Construct anchor beams in stable areas outside the potential slip surface of the foundation pit slope; S2. One end of multiple tie bars is pre-embedded and anchored in the anchoring beam. The tie bars are arranged at intervals along the length of the anchoring beam and extend towards the slope of the foundation pit. S3. Excavate the foundation pit according to the designed slope and trim the slope surface formed by the excavation; S4. On the repaired slope surface, install multiple reinforcing bars inserted into the rock and soil. S5. On the slope surface where the insert is provided, lay multiple slope main bars extending along the slope direction and fix the slope main bars to the exposed ends of the insert. S6. Fix the other end of the tie bar to the corresponding slope bar; S7. Lay a steel mesh on the main reinforcement of the slope and fix the steel mesh to the main reinforcement of the slope and / or the dowel bars. S8. Spray a layer of slope concrete on the slope surface where the steel mesh is fixed to form a complete support surface.

[0007] Preferably, in step S1, the anchoring beam is a cast-in-place reinforced concrete beam, and the cross-sectional dimensions, reinforcement and embedment depth of the anchoring beam are determined according to the stress calculation of the slope support; the anchoring beam can be completely embedded below the ground or partially exposed above the ground.

[0008] Preferably, in step S2, the main reinforcing bar is a steel bar with a diameter greater than or equal to 18mm, and one end of it is pre-embedded in the anchor beam and connected to the main reinforcing bar in the anchor beam by welding or mechanical connection, and meets the design anchorage length requirements.

[0009] Preferably, in step S4, the reinforcing bars are steel bars or steel rods with a diameter greater than or equal to 14mm, and the reinforcing bars are inserted into the soil and rock of the slope surface at a depth of 1.0m to 2.5m; multiple reinforcing bars are arranged in a quincunx pattern on the slope surface with a spacing of 1.0m to 2.0m.

[0010] Preferably, in step S5, the main reinforcement of the slope is made of threaded steel bar with a diameter greater than or equal to 14mm, and the exposed ends of the main reinforcement of the slope and the dowel bar are fixedly connected by welding.

[0011] Preferably, in step S6, the connection method between the tie bar and the slope bar is selected as either a close connection type or an intermittent connection type, depending on the depth of the foundation pit and the stress condition of the slope; the close connection type means that each slope bar is connected to one tie bar; the intermittent connection type means that one or more slope bars are connected to one tie bar; the tie bar and the slope bar are fixedly connected by welding.

[0012] Preferably, in step S7, the reinforcing mesh is made of steel bars with a diameter of 6mm to 10mm, welded or woven, and the mesh size is 150mm×150mm to 250mm×250mm; the reinforcing mesh is fixedly connected to the main reinforcement of the slope and / or the dowel bars by binding or spot welding.

[0013] Preferably, in step S8, the strength grade of the slope concrete layer is not lower than C20, and the thickness is 80mm~150mm; the spraying operation is carried out in sections and layers to ensure complete coverage of the steel mesh and to achieve the designed thickness.

[0014] According to a second aspect of the present invention, a slope protection structure for complex foundation pits with alternating soil and rock is provided, which is constructed using the slope protection method for complex foundation pits with alternating soil and rock as described above, comprising: Anchor beams are installed in the stable area outside the potential slip surface of the foundation pit slope; Multiple tie bars, one end of which is anchored in the anchoring beam and the other end of which extends toward the slope of the foundation pit; Multiple reinforcing bars inserted into the soil and rock mass of the foundation pit slope; Multiple main slope reinforcement bars are laid on the slope surface and fixedly connected to the reinforcing bars; The other end of the tie bar is fixedly connected to the corresponding slope bar. A steel mesh covering the slope surface and fixedly connected to the main reinforcement bars and / or the dowel bars of the slope surface; And the slope concrete layer covering the steel mesh and the slope surface.

[0015] Preferably, drainage ditches are also provided at the top and / or bottom of the pit.

[0016] The present invention provides a method and structure for supporting complex foundation pit slopes with alternating soil and rock conditions. Anchor beams, main reinforcing bars, dowel bars, slope main reinforcing bars, and steel mesh are integrated into a single unit. The dowel bars are connected to the complex soil mass of the slope through insertion, firmly securing the entire slope. The anchor beams also firmly hold the slope main reinforcing bars, protecting the entire slope surface. Finally, the steel mesh is integrated with the slope main reinforcing bars and / or dowel bars for shotcrete treatment. This method solves the technical challenges of supporting complex soil slopes, simplifies the support scheme, significantly reduces costs, shortens the construction period, and yields substantial benefits. Attached Figure Description

[0017] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0018] Figure 1 A schematic diagram of the plan arrangement of anchor beams and tie bars in a complex foundation pit slope support structure with alternating soil and rock elements according to an embodiment of the present invention is shown.

[0019] Figure 2 A schematic diagram of the connection between the tie main reinforcement and the slope main reinforcement in a complex soil-rock alternating foundation pit slope support structure according to an embodiment of the present invention is shown.

[0020] Figure 3A schematic diagram of the connection between the main reinforcement and the dowel bars on the slope surface in a complex foundation pit slope support structure with alternating soil and rock according to an embodiment of the present invention is shown.

[0021] Figure 4 A schematic diagram of the connection between the steel mesh, the main reinforcement bars on the slope, and the dowel bars in a complex foundation pit slope support structure with alternating soil and rock according to an embodiment of the present invention is shown.

[0022] In the diagram: 1. Anchor beam; 2. Tie main reinforcement; 3. Slope main reinforcement; 4. Dowel bar; 5. Steel mesh; 6. Slope concrete layer; 7. Drainage pipe; 8. Interception drainage ditch. Detailed Implementation

[0023] Various embodiments of the invention will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements are indicated by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0024] This invention provides a method for supporting complex foundation pit slopes with alternating soil and rock conditions. The method includes the following steps: S1. In the stable area outside the potential slip surface of the foundation pit slope, construct anchor beam 1.

[0025] Specifically, the anchor beam 1 is a cast-in-place reinforced concrete beam, constructed using C25 or higher grade concrete. The anchor beam 1 contains a steel reinforcement cage composed of several main bars and stirrups. The cross-sectional dimensions, reinforcement, and embedment depth of the anchor beam 1 are determined based on slope support stress calculations. During construction, a detailed geological survey is first conducted to determine the distribution, thickness, and physical and mechanical parameters of each soil and rock layer. The location of potential slip surfaces on the foundation pit slope is determined through limit equilibrium methods or numerical simulation analysis. Based on the slope height, gradient, soil and rock mechanical parameters, and safety factor requirements, the support structure design calculations are performed.

[0026] The anchor beam 1 can be completely buried underground, or partially exposed above ground depending on site conditions. When exposed, its top can also serve as the foundation for the edge protection railing of the foundation pit, achieving a multi-functional design. Figure 2 As shown, in this embodiment, the top of the anchor beam 1 is exposed above the ground.

[0027] S2. One end of multiple tie bars 2 is pre-embedded and anchored in the anchoring beam 1. The tie bars 2 are arranged at intervals along the length of the anchoring beam 1 and extend towards the slope of the foundation pit.

[0028] Specifically, the main reinforcing bar 2 is made of steel bar with a diameter of 18mm or greater. One end of the main reinforcing bar is embedded in the anchoring beam 1 and connected to the main reinforcing bar in the anchoring beam 1 by welding or mechanical connection, and meets the design anchorage length requirements.

[0029] Steps S1 and S2 can be performed simultaneously. During construction, the design location is marked out, the foundation trench for anchor beam 1 and the pre-embedded trench for the main reinforcing bars 2 are excavated, the reinforcing bar cage of anchor beam 1 is tied, and the main reinforcing bars 2 are welded firmly to the main reinforcing bars of anchor beam 1 at the design spacing; formwork is erected, C25 or higher grade concrete is poured, vibrated to compact, and cured to the specified strength. The other end of the main reinforcing bars 2 is laid horizontally in the pre-embedded trench facing the foundation pit, without being covered with soil for the time being.

[0030] S3. Excavate the foundation pit according to the designed slope and trim the slope surface formed by the excavation.

[0031] Specifically, the foundation pit is excavated mechanically in layers, with each layer excavated to a depth of about 2m. After excavation, the slope surface is promptly trimmed to make it basically smooth and in line with the design slope, and loose rocks and loose soil blocks are removed.

[0032] S4. On the repaired slope surface, install multiple reinforcing bars 4 inserted into the rock and soil.

[0033] Specifically, the reinforcing bars 4 are steel bars or steel rods with a diameter greater than or equal to 14mm. The reinforcing bars 4 are implanted into the soil and rock of the slope surface at a depth of 1.0m to 2.5m. Multiple reinforcing bars 4 are arranged in a quincunx pattern on the slope surface, with a spacing of 1.0m to 2.0m. In this embodiment, the reinforcing bars 4 are Φ14mm threaded steel bars, implanted to a depth of 1.5m, with 0.05m exposed for welding, arranged in a 1.5m × 1.5m quincunx pattern. During construction, on the prepared slope surface, according to the designed quincunx pattern points, a pneumatic hammer or specialized rebar installation equipment is used to drive the reinforcing bars 4 vertically or slightly downwards into the soil and rock layer, ensuring the implantation depth meets the design requirements and the exposed end height is basically consistent. For locally hard rock layers, small holes can be drilled before implantation.

[0034] S5. On the slope surface where the reinforcing bar 4 is provided, lay multiple main slope reinforcing bars 3 extending along the slope direction, and fix the main slope reinforcing bars 3 to the exposed ends of the reinforcing bars 4.

[0035] Specifically, the main slope reinforcement 3 uses threaded steel bars with a diameter greater than or equal to 14mm, and the exposed ends of the main slope reinforcement 3 and the dowel bars 4 are fixedly connected by welding. In this embodiment, the main slope reinforcement 3 uses Φ14mm threaded steel bars, arranged along the slope direction with a transverse spacing of 1.5m. During construction, the main slope reinforcement 3 is arranged on the slope surface along the slope direction, meeting the exposed ends of the dowel bars 4. Each main slope reinforcement 3 is spot-welded or fully welded to the exposed ends of all intersecting dowel bars 4 to form a stable planar skeleton. In this embodiment, multiple transverse steel bars are also arranged along the slope surface, evenly distributed along the slope direction with a spacing of 1.5m between them. During construction, the transverse steel bars intersect with the exposed ends of the dowel bars 4 and are connected to the dowel bars 4 by welding. In this embodiment, the main slope reinforcement 3 and the transverse steel bars form a 1.5m×1.5m grid-like integral structure.

[0036] S6. Fix the other end of the tie bar 2 to the corresponding slope bar 3.

[0037] Specifically, the connection method between the tie bar 2 and the slope main reinforcement 3 is selected as either a close connection type or an intermittent connection type, depending on the depth of the foundation pit and the stress condition of the slope. The close connection type means that each slope main reinforcement 3 is connected to one tie bar 2; the intermittent connection type means that one or more slope main reinforcements 3 are connected to one tie bar 2. The tie bar 2 and the slope main reinforcement 3 are fixedly connected by welding. During construction, the other end of the pre-embedded tie bar 2 is pulled up and connected to the corresponding slope main reinforcement 3. In this embodiment, the tie bar 2 and the slope main reinforcement 3 are connected in a "skip-one-connect" manner, and the tie bar 2 and the slope main reinforcement 3 are fixedly connected by welding. After welding, the quality of all welding points is checked.

[0038] S7. Lay a steel mesh 5 on the main slope reinforcement 3, and fix the steel mesh 5 to the main slope reinforcement 3 and / or the dowel bars 4. Specifically, the steel mesh 5 is made of steel bars with a diameter of 6mm to 10mm, welded or woven, and the mesh size is 150mm×150mm to 250mm×250mm; the steel mesh 5 is fixedly connected to the main slope reinforcement 3 and / or the dowel bars 4 by binding or spot welding.

[0039] In this embodiment, the reinforcing mesh 5 is a welded steel mesh with a diameter of 8mm and a mesh size of 200mm × 200mm. During construction, the prefabricated 8mm@200mm×200mm reinforcing mesh 5 is laid from top to bottom on the slope surface, closely adhering to the main reinforcing bars 3. Double-stranded iron wire is used to securely tie the reinforcing mesh 5 to all the main reinforcing bars 3 and dowel bars 4 on the slope surface, ensuring that the mesh is flat and without warping.

[0040] S8. Slope concrete layer 6 is sprayed on the slope surface where the steel mesh 5 is fixed to form a complete support surface.

[0041] Specifically, the slope concrete layer 6 has a strength grade of not less than C20 and a thickness of 80mm~150mm; the shotcrete operation is carried out in sections and layers to ensure complete coverage of the reinforcing mesh 5 and achieve the designed thickness. In this embodiment, the slope concrete layer 6 has a strength grade of C25 and a thickness of 100mm. During construction, a wet shotcrete machine is used for shotcrete operation. Before shotcreting, thickness markers are set at the toe of the slope; C25 concrete is shotcreted in sections and layers from bottom to top until the reinforcing mesh 5 is completely covered and the designed thickness of 100mm is achieved. Care should be taken to control the rebound rate during shotcreting. After shotcreting, the surface is smoothed, covered with geotextile, and watered for curing for no less than 7 days.

[0042] In this embodiment, a drainage system is also provided: a water interception ditch is set at the top of the foundation pit 1m from the edge of the foundation pit, and a drainage ditch is set at the bottom of the foundation pit at the toe of the slope. PVC drainage pipes 714 of a certain diameter are pre-embedded at certain intervals within the concrete layer 6 of the slope to draw out any possible groundwater.

[0043] This invention also provides a slope protection structure for complex foundation pits with alternating soil and rock conditions, which is constructed using the slope protection method for complex foundation pits with alternating soil and rock conditions described above. See [link to relevant documentation]. Figures 1 to 4 The complex soil-rock alternating slope support structure for the foundation pit includes: anchor beams 1 set in the stable area outside the potential slip surface of the foundation pit slope; multiple tie bars 2 with one end anchored in the anchor beams 1 and the other end extending towards the foundation pit slope; multiple insert bars 4 inserted into the soil and rock mass of the foundation pit slope surface; multiple slope main bars 3 laid on the slope surface and fixedly connected to the insert bars 4; wherein the other end of each tie bar 2 is fixedly connected to the corresponding slope main bar 3; a steel mesh 5 covering the slope surface and fixedly connected to the slope main bars 3 and / or the insert bars 4; and a slope concrete layer 6 covering the steel mesh 5 and the slope surface. The anchor beams 1, tie bars 2, insert bars 4, slope main bars 3, steel mesh 5, and slope concrete layer 6 together constitute a spatially load-bearing whole.

[0044] Furthermore, the slope protection structure for the complex alternating soil and rock foundation pit is also equipped with intercepting drainage ditches 8 at the top and / or bottom of the foundation pit.

[0045] The working principle of the complex soil-rock alternating foundation pit slope support structure provided by this invention lies in the transmission and balance of forces. After the foundation pit is excavated, the slope soil and rock mass tends to slide into the pit. The soil pressure generated by this sliding tendency first acts on the solid slope concrete layer 6 and the tightly bonded steel mesh 5 and slope main reinforcement 3 system. The slope main reinforcement 3 transfers part of the load directly to the deeper and more stable soil and rock mass through the dowel bars 4, achieving shallow anchorage. At the same time, the slope main reinforcement 3 transfers most of the horizontal tension backward to the reinforced concrete anchor beam 1 set in the stable area through the tie bars 2. The anchor beam 1 relies on its own weight, friction with the foundation, and its underlying weight (if buried underground) to balance this tension, thus forming a stable force balance system. The entire system transforms the traditional deep anchorage into a combination mode of "shallow dowel bar anchorage + far-end ground beam anchorage", cleverly avoiding the construction difficulties of deep anchorage in complex rock strata.

[0046] Compared with the prior art, the present invention has the following significant advantages and positive effects: This invention completely replaces underground anchors that require drilling in complex soil and rock layers with anchor beams that can be easily constructed on the ground. Anchor beam construction is carried out on the surface, unaffected by irregular bedrock underneath, making construction quality easy to control and highly efficient. Slope reinforcement installation is simple and quick, requiring no complex machinery or grouting processes, making it particularly suitable for slopes with alternating soil and rock conditions and limited working space.

[0047] This invention constructs a three-in-one spatial stress system consisting of "ground anchorage (anchor beam and tie bar) - slope anchorage (inserted bars) - surface reinforcement (steel mesh and slope concrete layer)". The tie bar transfers the earth pressure on the slope system to the anchor beam behind it; the insert bars anchor the unstable surface soil and rock mass into the deeper stable body, and form a grid framework with the slope main bars and steel mesh; the slope concrete layer provides sealing and erosion protection. The three work together to effectively constrain slope deformation.

[0048] This invention is uniquely adaptable to complex geological conditions involving alternating soil and rock layers, thin upper soil layers, and undulating lower bedrock. Support parameters (such as anchor beam dimensions, reinforcement depth and spacing, and reinforcement specifications) can be flexibly adjusted based on specific geological survey results and design calculations. It is applicable not only to mixed soil and rock slopes but also to soil slopes or fractured rock slopes, making it highly versatile.

[0049] This invention eliminates the need for expensive anchor drilling, grouting equipment, and materials. The main materials are conventional steel bars and concrete, which can be sourced locally or easily procured. Construction is fast, significantly shortening the construction period and thus reducing overall costs. It also reduces environmental problems such as construction noise and mud pollution.

[0050] All key processes in this invention (reinforcement welding, concrete pouring and spraying) are carried out on the ground or in exposed conditions, facilitating quality supervision and inspection throughout the process. The resulting support structure has strong integrity and a high safety margin.

[0051] In summary, this invention provides an innovative slope protection solution for foundation pits under complex geological conditions involving alternating soil and rock. It has outstanding advantages such as convenient construction, strong adaptability, economic efficiency, and safety and reliability, and has good application prospects and promotion value.

[0052] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0053] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for supporting complex foundation pit slopes with alternating soil and rock conditions, characterized in that, Includes the following steps: S1. Construct anchor beams in stable areas outside the potential slip surface of the foundation pit slope; S2. One end of multiple tie bars is pre-embedded and anchored in the anchoring beam. The tie bars are arranged at intervals along the length of the anchoring beam and extend towards the slope of the foundation pit. S3. Excavate the foundation pit according to the designed slope and trim the slope surface formed by the excavation; S4. On the repaired slope surface, install multiple reinforcing bars inserted into the rock and soil. S5. On the slope surface where the insert is provided, lay multiple slope main bars extending along the slope direction and fix the slope main bars to the exposed ends of the insert. S6. Fix the other end of the tie bar to the corresponding slope bar; S7. Lay a steel mesh on the main reinforcement of the slope and fix the steel mesh to the main reinforcement of the slope and / or the dowel bars. S8. Spray a layer of slope concrete on the slope surface where the steel mesh is fixed to form a complete support surface.

2. The method for supporting complex foundation pit slopes with alternating soil and rock conditions according to claim 1, characterized in that, In step S1, the anchoring beam is a cast-in-place reinforced concrete beam. The cross-sectional dimensions, reinforcement, and embedment depth of the anchoring beam are determined based on the stress calculation of the slope support. The anchoring beam can be completely embedded below the ground or partially exposed above the ground.

3. The method for supporting complex foundation pit slopes with alternating soil and rock conditions according to claim 2, characterized in that, In step S2, the main reinforcing bar is made of steel bar with a diameter of 18mm or greater. One end of the main reinforcing bar is embedded in the anchoring beam and connected to the main reinforcing bar in the anchoring beam by welding or mechanical connection, and meets the design anchorage length requirements.

4. The method for supporting complex foundation pit slopes with alternating soil and rock conditions according to claim 1, characterized in that, In step S4, the reinforcing bars are steel bars or steel rods with a diameter of 14 mm or greater. The reinforcing bars are inserted into the soil and rock of the slope surface at a depth of 1.0 m to 2.5 m. Multiple reinforcing bars are arranged in a quincunx pattern on the slope surface with a spacing of 1.0 m to 2.0 m.

5. The method for supporting complex foundation pit slopes with alternating soil and rock conditions according to claim 1, characterized in that, In step S5, the main reinforcement of the slope is made of threaded steel bar with a diameter of 14mm or greater, and the exposed ends of the main reinforcement of the slope and the dowel bar are fixedly connected by welding.

6. The method for supporting complex foundation pit slopes with alternating soil and rock conditions according to claim 1, characterized in that, In step S6, the connection method between the tie bar and the slope bar is selected as either a close connection or an intermittent connection, depending on the depth of the foundation pit and the stress condition of the slope. The close connection means that each slope bar is connected to one tie bar. The intermittent connection means that one or more slope bars are connected to one tie bar. The tie bar and the slope bar are fixedly connected by welding.

7. The method for supporting complex foundation pit slopes with alternating soil and rock conditions according to claim 1, characterized in that, In step S7, the steel mesh is made of steel bars with a diameter of 6mm to 10mm, welded or woven, and the mesh size is 150mm×150mm to 250mm×250mm; the steel mesh is fixedly connected to the main reinforcement of the slope and / or the dowel bars by binding or spot welding.

8. The method for supporting complex foundation pit slopes with alternating soil and rock conditions according to claim 1, characterized in that, In step S8, the strength grade of the slope concrete layer is not lower than C20, and the thickness is 80mm~150mm; the spraying operation is carried out in sections and layers to ensure complete coverage of the steel mesh and to achieve the designed thickness.

9. A slope protection structure for complex foundation pits with alternating soil and rock conditions, characterized in that, The method for supporting complex foundation pit slopes with alternating soil and rock as described in any one of claims 1-8 is constructed, comprising: Anchor beams are installed in the stable area outside the potential slip surface of the foundation pit slope; Multiple tie bars, one end of which is anchored in the anchoring beam and the other end of which extends toward the slope of the foundation pit; Multiple reinforcing bars inserted into the soil and rock mass of the foundation pit slope; Multiple main slope reinforcement bars are laid on the slope surface and fixedly connected to the reinforcing bars; wherein, the other end of the tie bar is fixedly connected to the corresponding main slope reinforcement bar; A steel mesh covering the slope surface and fixedly connected to the main reinforcement bars and / or the dowel bars of the slope surface; And the slope concrete layer covering the steel mesh and the slope surface.

10. The slope protection structure for complex foundation pits with alternating soil and rock conditions according to claim 9, characterized in that, Drainage ditches are also provided at the top and / or bottom of the foundation pit.

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