Structure and method for reinforcing loose soil slope based on steel floral tube anchor rods

Abstract

The invention provides a structure and method for reinforcing a loose soil slope based on a steel floral tube anchor rod, and the structure for reinforcing the loose soil slope based on the steel floral tube anchor rod comprises a steel floral tube anchor rod anchoring system, a frame beam system and an auxiliary system; a method for reinforcing a loose soil slope based on a steel floral tube anchor rod comprises the following steps that drilling is conducted along with a pipe, specifically, a steel floral tube serves as a sleeve to be drilled into a loose soil body of the slope, and a drill hole is formed synchronously; mounting an anchor rod, and inserting the anchor rod into the steel floral tube; performing high-pressure grouting to form a grouting body, and forming a composite reinforcing body by the grouting body, the anchor rod, the steel floral tube and the soil body; checking and accepting the anchor rod; constructing a frame beam, and erecting a formwork and pouring concrete to form a frame beam grid; and auxiliary system construction is carried out, and construction of the water retaining edge, the surface protection layer and the slope toe protection structure is completed synchronously. According to the method, efficient hole forming in the unconsolidated formation is achieved, grouting compactness is ensured, and a stable anchoring interface is constructed.

Description

Technical Field

[0001] The present invention relates to the technical field related to reinforcing loose soil slopes, and in particular to a structure and method for reinforcing loose soil slopes based on steel flower tube anchor rods. Background Art

[0002] In slope support projects, anchor bolts, as a core technology for rock and soil reinforcement, form a synergistic force system with the soil through prestressing, transferring shear stress from potential slip surfaces to deep stable strata, constraining slope displacement, and optimizing stress distribution, thereby improving slope stability. However, in loose soils (such as sand, gravel accumulation layers, or strongly weathered rock belts), due to low soil cohesion and weak inter-particle bonding, hole wall collapse is prone to occur during drilling. This hole collapse problem significantly reduces the drilling efficiency, discontinuities at the interface between the grouting body and the soil, reduces the load transfer efficiency of the anchoring system, and may even trigger secondary disasters such as local soil slippage, seriously restricting the safety and reliability of anchoring projects in loose strata.

[0003] In existing technologies, solutions such as casing drilling or segmented grouting are commonly used to address the problem of hole collapse in loose strata. However, casing drilling requires the removal of the casing after drilling, which can easily disturb the soil again and cause hole collapse, resulting in low drilling efficiency. Segmented grouting also makes it difficult to precisely control the spread of the grout, resulting in poor grouting density and uneven interface strength, which can easily lead to unstable anchoring interfaces. Therefore, achieving efficient hole drilling in loose strata, ensuring grouting density, and constructing a stable anchoring interface have become urgent technical challenges. Summary of the Invention

[0004] The present invention aims to provide a structure and method for reinforcing loose soil slopes based on steel flower tube anchor rods, so as to solve the above-mentioned technical difficulties of how to achieve efficient drilling in loose strata, ensure grouting density and construct a stable anchoring interface.

[0005] To this end, the technical solution adopted by the present invention is: a structure based on steel pipe anchor rods to reinforce loose soil slopes, including a steel pipe anchor rod anchoring system, a frame beam system and an auxiliary system; the steel pipe anchor rod anchoring system includes a steel pipe, an anchor rod and a grouting body, a drill hole is opened on the slope, a plurality of grouting holes are opened on the steel pipe, and are obliquely embedded in the drill hole as a casing wall, the grouting body is fixedly arranged in the steel pipe, and passes through the grouting holes and extends into the soil of the slope, the anchor rod is fixed in the grouting body, and is located in the steel pipe, and the grouting body forms a composite with the anchor rod, the steel pipe and the soil. The reinforcement body is used to reinforce the slope of loose soil; the frame beam system includes multiple frame cross beams and frame longitudinal beams, both of which are reinforced concrete structures and are fixedly arranged on the slope, and multiple frame cross beams are fixedly connected to the frame longitudinal beams and are orthogonal to the frame longitudinal beams to form a frame beam grid, and the frame beam grid is a rigid load-bearing skeleton; the auxiliary system includes a connecting member and a protective layer, one end of the connecting member is fixedly connected to the top of the steel flower pipe, and the other end is fixedly connected to the frame cross beam and the frame longitudinal beam, and the protective layer covers the slope surface within the frame beam grid.

[0006] As a preferred embodiment of the above scheme, the steel flower pipe anchor rod anchoring system also includes an anchor and a concrete anchor pad. The connection between the frame cross beam and the frame longitudinal beam is set as a grid node. The concrete anchor pad is fixedly set on the grid node. The top end of the anchor rod passes through the concrete anchor pad and is threadedly connected to the anchor. A steel mesh is fixedly set in the concrete anchor pad to disperse concentrated stress.

[0007] It is further preferred that the auxiliary system also includes a plurality of water retaining edges and stress dispersing pads, and the plurality of water retaining edges are respectively fixedly arranged on the top of the slope and the edges within the frame beam grid to intercept surface runoff above the top of the slope; the stress dispersing pads are sleeved on the anchor rods and abut against the anchor and the concrete anchor pad.

[0008] Further preferably, the auxiliary system also includes a concrete head, which is fixedly arranged on a concrete anchor pad, and the top end of the anchor rod, the anchor and the stress dispersing pad are all located in the concrete head, so as to provide protection for the top end of the anchor rod, the anchor and the stress dispersing pad.

[0009] It is further preferred that the auxiliary system also includes a slope foot protection structure and oblique reinforcement ribs. The slope foot protection structure is fixedly arranged at the bottom end of the slope, and the two ends of the oblique reinforcement ribs are respectively fixed with steel bars connecting the frame cross beams and the frame longitudinal beams, so as to improve the shear resistance and stress concentration resistance performance of the frame beam grid.

[0010] A method for reinforcing a loose soil slope based on a steel pipe anchor includes the following steps:

[0011] S1, following the pipe drilling, the steel pipe is used as a casing to drill into the loose soil of the slope to form the borehole simultaneously;

[0012] S2, anchor rod installation, inserting the anchor rod into the steel flower tube;

[0013] S3, high-pressure grouting, injecting slurry into the drilled hole at a grouting pressure of not less than 0.6 MPa, wherein the slurry penetrates into the soil through the grouting holes on the steel pipe to form the grouting body, and after solidification, the slurry forms a composite reinforcement body with the anchor rod, steel pipe and soil;

[0014] S4. Anchor bolt acceptance: The pull-out strength of the anchor bolts shall be inspected and accepted by sampling, with the sampling ratio not less than 5%;

[0015] S5. Construction of the frame beams: tying the steel bars of the frame cross beams and frame longitudinal beams, fixing the top ends of the steel flower tubes to the steel bars of the frame cross beams and frame longitudinal beams through connecting members, and supporting the formwork and pouring concrete to form a frame beam grid;

[0016] S6. Auxiliary system construction: synchronously complete the construction of the water retaining edge, surface protection layer, and slope foot protection structure, and after installing the concrete anchor pad, stress dispersion pad and anchor on the top of the anchor rod, cover and install the concrete head.

[0017] As a preferred embodiment of the above scheme, the steel tube anchoring complex design calculation model is based on the collaborative working mechanism of the steel tube, grouting, soil and anchor rods, quantifies the shear bearing capacity and pull-out bearing capacity of the complex, and meets the slope reinforcement design requirements. The steel tube anchoring complex design calculation model includes the following core formulas:

[0018] Shear bearing capacity of composite body:

[0019]

[0020] Where, is the total shear strength of the steel pipe composite, is the slurry-soil interface bond strength, is the effective bonding area within the radiation radius of the grouting body, is the shear strength of the steel pipe, is the cross-sectional area of the steel tube, is the pull-out resistance of the anchor; is the steel tube-soil friction angle;

[0021] Composite pull-out bearing capacity:

[0022]

[0023] Where, is the pull-out resistance of the anchor rod, is the anchor diameter, is the length of the anchoring section, is the pulp-rod bonding strength, is pi, is the safety factor against pull-out, which is 1.5. Design tension for anchor bolts;

[0024] Quantify the synergistic efficiency of steel pipe-grouting body-soil:

[0025]

[0026] Where, To quantify the synergistic efficiency of steel pipe-grouting body-soil, is the total shear bearing capacity of the steel tube composite, Contributes to the shear resistance of steel pipes, Contributes to the shear resistance of the grouting body, Contributes to the frictional shear resistance of the soil.

[0027] Further preferably, the frame beam system undertakes three major functions in the steel tube anchor reinforcement structure: load transfer, slope constraint and coordinated anti-slip. The mechanical model of the frame beam system is based on the principles of reinforced concrete structural mechanics and combines the characteristics of slope engineering to establish a complete mechanical analysis system.

[0028] The overall stress model of the frame beam grid is:

[0029]

[0030]

[0031] Where, is the bending stiffness of the frame beam, is the shear stiffness of the frame beam, is the elastic modulus of concrete, and are the moment of inertia of the transverse / longitudinal beam sections, and are the number of beams in the horizontal and vertical directions, and are the grid sizes in the horizontal and vertical directions, is the shear modulus of concrete, and are the cross-sectional areas of the horizontal and longitudinal beams, is the shear section coefficient;

[0032] The node mechanical model is:

[0033]

[0034] Where, is the calculated value of the node shear bearing capacity, Design shear for the node, is the tensile strength of concrete, The net area of the node concrete after deducting the area occupied by the steel bars. is the yield strength of steel bars, is the total cross-sectional area of the stirrups, is the effective height of the beam, is the stirrup spacing, and is ≤150 mm;

[0035] The collaborative working model of the frame beam-anchor system is:

[0036]

[0037]

[0038]

[0039] Where, is the synergistic stiffness ratio, is the frame beam system stiffness, is the anchoring system stiffness, is the design value of anchor tension, is the deformation of the anchoring system, is the length of the anchoring section, is the cross-sectional area of the anchor rod, is the elastic modulus of anchor steel;

[0040] The anti-slip contribution quantification model is:

[0041]

[0042] Where, is the calculated value of anti-sliding of the frame beam system, For the cooperative working coefficient, the loose soil is 0.15-0.25. is the horizontal force of the node, i.e. the horizontal component of the anchor tension, is the vertical force of the node, i.e. the vertical component of the anchor tension + soil pressure, and are the grid sizes in the horizontal and vertical directions respectively.

[0043] Further preferably, in order to ensure a reliable connection between the frame beam system and the steel flower tube anchor bolt system, the connection member needs to be triple-checked for shear resistance, pull-out resistance and coordinated deformation, and the calculation formula is as follows:

[0044] The calculation formula for shear bearing capacity is:

[0045]

[0046] Where, is the ultimate shear bearing capacity of the connecting member, is the shear safety factor, is the design shear force;

[0047] The calculation formula for pull-out bearing capacity is:

[0048]

[0049] Where, is the ultimate pull-out strength of the connecting member, is the pull-out safety factor, is the maximum tension of a single anchor rod;

[0050] The coordinated deformation formula is:

[0051]

[0052] Where, is the deformation of the connecting member, is the deformation of the frame beam node, The anchoring system is deformed.

[0053] More preferably, the overall safety factor calculation model is as follows:

[0054] The soil's own shear contribution is:

[0055]

[0056] Where, Contributes to the soil's own shear resistance. is the number of soil strips, For the Effective cohesion of soil strips, For the Length of soil strip sliding arc, For the Soil weight, For the Sliding arc inclination of soil strip, For the Soil strip pore water pressure, For the effective internal friction angle of soil strip;

[0057] The anchoring system contribution is:

[0058]

[0059] Where, Contribute to the anchoring system, is the number of anchoring complexes crossing the sliding arc, For the Shear strength of anchoring complex, For the anchor body shear area;

[0060] The frame beam constraint contribution is:

[0061]

[0062] Where, Contribution to the frame beam constraint, is the cooperative working coefficient, is the uniformly distributed earth pressure on the slope surface, is the effective restraint area of the frame beam;

[0063] The overall safety factor formula is:

[0064]

[0065] Where, is the overall safety factor, is the total number of soil strips divided, is the total sliding force, Contributes to the soil's own shear resistance. Contribute to the anchoring system, Contributes to frame beam constraints.

[0066] Beneficial effects of the present invention:

[0067] 1. In the early drilling stage, the steel pipe can be directly used as a casing to drill into the loose soil to form a borehole simultaneously, realizing efficient hole formation in the loose soil of the slope. The rigid pipe wall structure of the steel pipe provides stable support during the drilling process, completely avoiding the problems of hole collapse and necking caused by loose soil in traditional processes.

[0068] 2. During continuous grouting, the grouting holes evenly opened on the surface of the steel tube allow the grouting to fully penetrate into the soil pores, forming a radial reinforcement body, which greatly improves the shear strength of the soil itself; at the same time, after the anchor rod is bonded to the steel tube through the grouting body, a "tube-anchor-grouting-soil" combined force system is formed. The tube stiffness of the steel tube and the tension of the anchor rod work together to effectively resist the shear force of slope sliding, realizing the organic combination of active constraint and passive reinforcement, ensuring the density of grouting and building a stable anchoring interface, which significantly improves the overall stability of the slope.

[0069] 3. The steel flower tube has the functions of wall protection, grouting channel and structural force bearing, eliminating the complex processes of temporary casing extraction and secondary grouting in traditional processes, shortening the construction period by more than 30%, significantly shortening the construction period and improving construction efficiency; at the same time, by flexibly adjusting the inclination angle, grouting pressure and anchor configuration of the steel flower tube, it can quickly adapt to soil slopes with different degrees of looseness, further optimizing construction efficiency.

[0070] 4. Steel flower tubes, acting as permanent casings, are directly embedded in the soil, eliminating the loss of temporary casings and the waste of secondary grouting materials, significantly reducing construction costs. The steel flower tubes, anchor rods, and grouting form a composite reinforcement, increasing shear strength by 40%-50%. This helps share the stress of traditional anchor rods, reduces the density of anchor structures while ensuring slope stability, and saves 15%-20% in steel, thereby reducing overall project costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 This is a system framework diagram of a structure for reinforcing loose soil slopes based on steel flower tube anchor rods in the present invention.

[0072] Figure 2 It is a schematic diagram of the slope surface of the slope in the present invention.

[0073] Figure 3 It is a cross-sectional schematic diagram of the slope in the present invention.

[0074] Figure 4 It is a structural schematic diagram of the steel flower tube in the present invention.

[0075] Figure 5 It is a structural schematic diagram of the steel flower pipe anchor rod anchoring system in the present invention.

[0076] Figure 6 It is a connection relationship diagram between the connecting member and the steel flower pipe in the present invention.

[0077] Figure 7 It is a structural diagram of the grid node in the present invention.

[0078] Figure 8 yes Figure 7 Schematic cross-section diagram.

[0079] Figure 9 Design flow chart for steel pipe anchoring complex.

[0080] Figure 10 Design a flow chart for the frame beam system.

[0081] Figure 11 Flowchart for designing connection components between frame beams and anchoring complexes.

[0082] Figure 12 Design flow chart for the overall structural stability of the frame beam. DETAILED DESCRIPTION

[0083] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0084] like Figure 1-12 As shown, a structure for reinforcing a loose soil slope based on a steel tube anchor includes a steel tube anchor system 1, a frame beam system, and an auxiliary system. The steel tube anchor system 1 includes a steel tube 3, an anchor rod 6, and a grouting body 9. A borehole 5 is formed in the slope 2. The steel tube 3 is provided with a plurality of grouting holes 4, which are obliquely embedded in the boreholes 5 as a casing wall. The grouting body 9 is fixed in the steel tube 3, passes through the grouting holes 4, and extends into the soil of the slope 2. The anchor rod 6 is fixed in the grouting body 9 and is located within the steel tube 3. The grouting body 9, the anchor rod 6, the steel tube 3, and the soil form a composite reinforcement body for reinforcing the loose soil slope 2. The frame beam system includes multiple crossbeams 11 and longitudinal beams 12, both constructed of reinforced concrete and fixed to the slope 2. The crossbeams 11 are fixedly connected to the longitudinal beams 12 and are orthogonal to them, forming a frame beam grid 10. The frame beam grid 10 serves as a rigid load-bearing framework. The auxiliary system includes connecting members 13 and a protective layer 15. One end of the connecting member 13 is fixedly connected to the top of the steel tube 3, and the other end is fixedly connected to the crossbeams 11 and longitudinal beams 12. The protective layer 15 covers the slope 2 within the frame beam grid 10.

[0085] The length of the steel tube 3 is greater than that of the anchor rod 6. The connecting member 13 is fixed to the main reinforcement of the frame crossbeam 11 and frame longitudinal beam 12 by welding or tying, thereby forming a fixed connection between the connecting member 13 and the frame crossbeam 11 and frame longitudinal beam 12. The steel tube anchor system 1 is suitable for shallow reinforcement in the slope 2, passively relying on soil deformation to achieve anchoring. The anchor rod 6 is a threaded steel bar or self-drilling anchor rod coated with an anti-corrosion coating, making it easy to construct and more economical. The surface armour 15 can be shotcrete or a vegetation surface armour layer 15, thereby achieving erosion prevention and ecological restoration functions.

[0086] The steel flower pipe anchor anchoring system 1 also includes an anchor 7 and a concrete anchor pad 8. The connection between the frame cross beam 11 and the frame longitudinal beam 12 is set as a grid node. The concrete anchor pad 8 is fixedly set on the grid node. The top of the anchor rod 6 passes through the concrete anchor pad 8 and is threadedly connected to the anchor 7. A steel mesh is fixedly set in the concrete anchor pad 8 to disperse concentrated stress.

[0087] The anchor 7 is a nut-pad type anchor 7. After the anchor rod 6 is installed, the anchor 7 is mounted on the anchor rod 6. By rotating the anchor 7, the position of the anchor 7 on the anchor rod 6 can be adjusted. The concrete anchor pad 8 with a steel mesh inside is fixed to the grid node, which can effectively disperse concentrated stress and prevent local damage to the structure.

[0088] The auxiliary system also includes multiple water retaining edges 14 and stress dispersing pads 16. The multiple water retaining edges 14 are respectively fixedly arranged on the top of the slope 2 and the edges within the frame beam grid 10, and are used to intercept surface runoff above the top of the slope 2; the stress dispersing pads 16 are sleeved on the anchor rod 6 and abut the anchor 7 and the concrete anchor pad 8.

[0089] The water retaining edge 14 intercepts surface runoff from the top of slope 2, preventing rainwater from directly eroding the surface. The groove structure then directs the intercepted water flow to the sides of slope 2 or designated drainage facilities. Rotating the anchor 7 presses the stress-distributing pad 16 against the concrete anchor support 8, optimizing the load transfer path. The anchor 7 also locks the top of the anchor rod 6.

[0090] The auxiliary system also includes a concrete head 17, which is fixed on the concrete anchor pad 8. The top of the anchor rod 6, the anchor 7 and the stress dispersing pad 16 are all located in the concrete head 17, which is convenient for protecting the top of the anchor rod 6, the anchor 7 and the stress dispersing pad 16.

[0091] An enclosed space can be formed between the concrete head 17 and the concrete anchor pad 8. The top of the anchor rod 6, the anchor 7 and the stress dispersing pad 16 are all located in the enclosed space, which can protect the top of the anchor rod 6, the anchor 7 and the stress dispersing pad 16 and prevent corrosive media from damaging the top of the anchor rod 6, the anchor 7 and the stress dispersing pad 16.

[0092] The auxiliary system also includes a slope foot protection structure 18 and oblique reinforcement ribs. The slope foot protection structure 18 is fixedly arranged at the bottom end of the slope 2. The two ends of the oblique reinforcement ribs are respectively fixed to the steel bars connecting the frame cross beam 11 and the frame longitudinal beam 12, which are used to improve the shear resistance and stress concentration resistance performance of the frame beam grid 10.

[0093] The slope foot protection structure 18 is a cast-in-place concrete toe protection structure embedded in the slope 2 and underground. It forms an anti-scour barrier, inhibits slippage and deformation at the bottom of the slope 2, and enhances the overall stability of the slope 2. Diagonal reinforcement bars secure the steel bars connecting the frame crossbeams 11 and frame longitudinal beams 12, not only restraining slope deformation but also coordinating the overall forces acting on the steel pipe anchor system 1 and the slope surface.

[0094] A method for reinforcing a loose soil slope based on a steel pipe anchor includes the following steps:

[0095] S1, follow the pipe drilling 5, use the steel pipe 3 as a casing to drill into the loose soil of the slope 2, and form the borehole 5 simultaneously.

[0096] Before following the pipe drilling 5, it is necessary to first treat the slope surface, clean up the loose soil and rocks on the slope, trim the slope to the designed slope, and ensure that the slope surface is flat. Then measure and lay out the lines, mark the drilling position, the axis of the frame beam grid 10, and the layout path of the water retaining edge 14 according to the design drawings. Then prepare the materials, including preparing prefabricated steel pipes 3, anchor rods 6, grouting materials, frame crossbeams 11 and frame longitudinal beams 12 steel bars and templates. When drilling hole 5, a special drilling rig is used to drill the steel pipe 3 as a casing directly into the loose soil of the slope 2, and the borehole 5 is formed simultaneously. The inclination angle of the steel pipe 3 is controlled during drilling, and the depth is determined according to the designed anchoring length. The steel pipe 3 protects the wall throughout the process to prevent the hole from collapsing, and the steel pipe 3 is retained in the hole after the drilling 5 is completed.

[0097] S2. Install the anchor rod 6 and insert the anchor rod 6 into the steel flower tube 3.

[0098] When installing the anchor rod 6, the anti-corrosion treated anchor rod 6 is inserted into the steel flower tube 3 according to the design requirements, and the length of the anchoring section is adjusted to the predetermined position so that sufficient length can be reserved at the top of the anchor rod 6 to facilitate welding of the connecting component 13.

[0099] S3, high-pressure grouting, injecting slurry into the borehole 5, the grouting pressure is not less than 0.6MPa, the slurry penetrates into the soil through the grouting hole 4 on the steel tube 3, forming a grouting body 9, and after the slurry solidifies, it forms a composite reinforced body with the anchor rod 6, the steel tube 3 and the soil.

[0100] The grout is a cement-based grout mixed with an expansion agent. Under pressure, the grout penetrates through the grouting hole 4, filling the soil pores and forming a grouting body 9. Once the grouting hole 4 is filled and the pressure stabilizes, grouting is continued for 30 seconds to ensure that the grouting body 9 is fully bonded to the steel pipe 3, anchor rod 6, and soil.

[0101] S4. Acceptance of anchor rod 6: sampling of anchor rod 6 shall be carried out for pull-out resistance acceptance, and the sampling ratio shall not be less than 5%.

[0102] When the pull-out resistance of anchor rod 6 is inspected, the bearing capacity is verified through a pull-out resistance test, and the pull-out resistance must be ≥ 1.2 times the design value.

[0103] S5. Frame beam construction: tie the steel bars of the frame cross beam 11 and the frame longitudinal beam 12, fix the top of the steel flower tube 3 to connect the steel bars of the frame cross beam 11 and the frame longitudinal beam 12 through the connecting member 13, and support the formwork and pour concrete to form the frame beam grid 10.

[0104] The main reinforcement of frame crossbeams 11 and frame longitudinal beams 12 was tied according to the designed frame beam grid size, and diagonal reinforcement bars were added in the grid node areas to secure the main reinforcement connecting frame crossbeams 11 and frame longitudinal beams 12. After supporting the formwork, C30 concrete was poured, vibrated and compacted, and cured for 7 days until the required strength was reached, forming frame beam grid 10.

[0105] S6, auxiliary system construction, synchronously complete the construction of the water retaining edge 14, the protective layer 15, and the slope foot protection structure 18, and install the concrete anchor pad 8, the stress dispersion pad 16 and the anchor 7 on the top of the anchor rod 6, and then cover and install the concrete head 17.

[0106] Pre-embed the reinforced mesh of the concrete anchor pads 8 at the grid nodes, then cast the concrete anchor pads 8. Install the anchors 7 and stress-distributing pads 16, which are bolted to the concrete anchor pads 8. Excavate a foundation trench at the slope foot, tie the reinforced mesh, and support the formwork. Cast-in-place concrete forms the slope foot protection structure 18, and backfill and compact the wall.

[0107] The design and calculation model for the steel tube anchor complex is based on the collaborative working mechanism of the steel tube 3, grouting body 9, soil, and anchor 6. It quantifies the shear and pullout bearing capacity of the complex to meet the reinforcement design requirements of slope 2. The design and calculation model for the steel tube anchor complex includes the following core formulas.

[0108] Shear bearing capacity of composite body:

[0109]

[0110] Where, is the total shear strength of the steel pipe composite, is the slurry-soil interface bond strength, is the effective bonding area within the radiation radius of the grouting body 9, is the shear strength of steel flower tube 3, is the cross-sectional area of the steel flower tube 3, is the pull-out resistance of anchor rod 6, is the steel pipe 3-soil friction angle.

[0111]

[0112] Where, is the grout-soil interface bond strength (determined by grouting pressure and soil permeability), is the paste-soil bonding coefficient, It is the effective cohesion of soil strip.

[0113]

[0114] Where, is the effective bonding area within the radiation radius of the grouting body 9, is the grouting diffusion radius, is the effective bonding length of the grouting body 9, is pi.

[0115]

[0116] Where, is the cross-sectional area of the steel flower tube 3, is the outer radius of the steel flower tube 3, is the inner radius of the steel flower tube 3, is pi.

[0117] Governing equations:

[0118]

[0119] Where, is the total shear strength of the steel pipe composite, is the safety factor, which is 1.25. is the design value of slope sliding force.

[0120] Composite pull-out bearing capacity:

[0121]

[0122] Where, is the pull-out resistance of anchor rod 6, is the diameter of anchor rod 6, is the length of the anchoring section, is the pulp-rod bonding strength, is pi, is the safety factor against pull-out, which is 1.5. Design the tension for anchor rod 6.

[0123]

[0124] Where, is the pulp-rod bonding strength, The strength of the grouting body 9 is required: 25MPa (7-day strength).

[0125] The grouting diffusion control model is as follows:

[0126]

[0127] Where, is the diffusion radius of the grouting body 9, is the initial radius of the steel tube 3, is the correction factor for soil permeability coefficient, is the grouting pressure (≥0.6 MPa), is the grouting time, is the slurry viscosity, and the control requirement is .

[0128] Quantify the synergistic efficiency of steel pipe 3-grouting body 9-soil:

[0129]

[0130] Where, To quantify the synergistic efficiency of steel pipe 3-grouting body 9-soil, is the total shear bearing capacity of the steel tube composite, Contributes to the shear resistance of steel pipes, Contribution to the shear resistance of the grouting body 9, Contribute to the frictional shear resistance of soil. Collaborative requirements: This indicates that the composite effect improves the bearing capacity, otherwise the parameters need to be optimized.

[0131]

[0132]

[0133]

[0134] Where, Contributes to the shear resistance of steel pipes, is the shear strength of steel flower tube 3, is the cross-sectional area of the steel flower tube 3, Contribution to the shear resistance of the grouting body 9, is the effective bonding area within the radiation radius of the grouting body 9, is the slurry-soil interface bond strength, Contribution to soil friction shear resistance, is the pull-out resistance of anchor rod 6, is the steel pipe 3-soil friction angle.

[0135] The frame beam system undertakes three major functions in the steel tube anchor reinforcement structure: load transfer, slope constraint and coordinated anti-slip. The mechanical model of the frame beam system is based on the principles of reinforced concrete structural mechanics and combines the engineering characteristics of slope 2 to establish a complete mechanical analysis system.

[0136] The overall stress model of the frame beam grid 10 is:

[0137]

[0138]

[0139] Where, is the bending stiffness of the frame beam, is the shear stiffness of the frame beam, is the elastic modulus of concrete, and are the moment of inertia of the transverse / longitudinal beam sections, and are the number of beams in the horizontal and vertical directions, and are the grid sizes in the horizontal and vertical directions, is the shear modulus of concrete, and are the cross-sectional areas of the horizontal and longitudinal beams, is the shear section coefficient.

[0140] The node mechanical model is:

[0141] The node is the intersection of the frame's horizontal and longitudinal beams and the action point of the anchor rod 6, which bears the concentrated force , .

[0142]

[0143] Where, is the horizontal force of the node, the horizontal component of the tension of anchor rod 6, is the vertical force of the node, the vertical component of the tension of anchor 6 + soil pressure, is the design value of the tension of anchor rod 6, is the inclination angle of anchor rod 6, and are the grid sizes in the horizontal and vertical directions, is the soil pressure on the slope.

[0144] Node shear bearing capacity verification:

[0145]

[0146] Where, Design shear for the node, is the horizontal force of the node, the horizontal component of the tension of anchor rod 6, is the vertical force of the node, the vertical component of the tension of anchor 6 + soil pressure.

[0147]

[0148] Where, is the calculated value of the node shear bearing capacity, Design shear for the node, is the tensile strength of concrete, The net area of the node concrete after deducting the area occupied by the steel bars. is the yield strength of steel bars, is the total cross-sectional area of the stirrups, is the effective height of the beam, is the stirrup spacing and is ≤150 mm.

[0149] Diagonal stiffener design model:

[0150]

[0151] Where, is the cross-sectional area of the oblique reinforcement (the total area of reinforcement that resists the shear force at the node), is the horizontal force at the node, is the vertical force at the node, is the stirrup spacing, is the yield strength of steel bars, is the beam section width, is the effective height of the beam, the minimum reinforcement ratio .

[0152] Structural requirements: steel bar diameter ≥ 16 mm, minimum reinforcement ratio .

[0153] The collaborative working model of the frame beam-anchor system is:

[0154]

[0155]

[0156]

[0157] Where, is the synergistic stiffness ratio, is the frame beam system stiffness, is the anchoring system stiffness, is the design value of the tension of anchor rod 6, is the deformation of the anchoring system, is the length of the anchoring section, is the cross-sectional area of anchor rod 6, is the elastic modulus of anchor rod 6 steel.

[0158] The anti-slip contribution quantification model is:

[0159]

[0160] Where, is the calculated value of anti-sliding of the frame beam system, For the cooperative working coefficient, the loose soil is 0.15-0.25. is the horizontal force of the node, i.e. the horizontal component of the tension of anchor rod 6, is the vertical force of the node, i.e. the vertical component of the tension of anchor 6 + soil pressure, and are the grid sizes in the horizontal and vertical directions respectively.

[0161] In order to ensure a reliable connection between the frame beam system and the steel flower tube anchor bolt anchoring system 1, it is necessary to perform triple verification of shear resistance, pull-out resistance and coordinated deformation on the connecting member 13. The calculation formula is as follows.

[0162] The calculation formula for shear bearing capacity is:

[0163]

[0164] Where, is the ultimate shear bearing capacity of the connecting member 13, is the shear safety factor, is the design shear force.

[0165] The calculation formula for pull-out bearing capacity is:

[0166]

[0167] Where, is the ultimate pull-out strength of the connecting member 13, is the pull-out safety factor, It is the maximum tension of a single anchor rod 6.

[0168] The coordinated deformation formula is:

[0169]

[0170] Where, is the deformation of the connecting member 13, is the deformation of the frame beam node, The anchoring system is deformed.

[0171] The overall safety factor calculation model is as follows.

[0172] The soil's own shear contribution is:

[0173]

[0174] Where, Contributes to the soil's own shear resistance. is the number of soil strips, For the Effective cohesion of soil strips, For the Length of soil strip sliding arc, For the Soil weight, For the Sliding arc inclination of soil strip, For the Soil strip pore water pressure, For the Effective internal friction angle of soil strip.

[0175] The anchoring system contribution is:

[0176]

[0177] Where, Contribute to the anchoring system, is the number of anchoring complexes crossing the sliding arc, For the Shear strength of anchoring complex, For the Anchor body shear area.

[0178] The frame beam constraint contribution is:

[0179]

[0180] Where, Contribution to the frame beam constraint, is the cooperative working coefficient, is the uniformly distributed earth pressure on the slope surface, is the effective constraint area of the frame beam.

[0181] The overall safety factor formula is:

[0182]

[0183] Where, is the overall safety factor, is the total number of soil strips divided, is the total sliding force, Contributes to the soil's own shear resistance. Contribute to the anchoring system, Contributes to frame beam constraints.

[0184] According to Section 5.3 of the Technical Specifications for Construction Slope Engineering (GB 50330-2013), the standard table for slope stability classification is as follows:

[0185] Table 1 Slope stability status classification standard

[0186]

[0187] In Table 1, Fst is the slope stability safety factor required by the specification. Its value needs to be determined in combination with the slope type, working conditions and safety level, as shown in Table 2:

[0188] Table 2 Value requirements for slope stability safety factor Fst

[0189]

[0190] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A structure for reinforcing loose soil slopes based on steel pipe anchors, characterized by: It includes a steel flower pipe anchor rod anchoring system (1), a frame beam system and an auxiliary system; The steel tube anchor rod anchoring system (1) comprises a steel tube (3), an anchor rod (6) and a grouting body (9); a borehole (5) is provided on the slope (2); a plurality of grouting holes (4) are provided on the steel tube (3) and are obliquely embedded in the borehole (5) as a casing wall; the grouting body (9) is fixedly arranged in the steel tube (3), passes through the grouting holes (4) and extends into the soil of the slope (2); the anchor rod (6) is fixed in the grouting body (9) and is located in the steel tube (3); the grouting body (9) forms a composite reinforcement body with the anchor rod (6), the steel tube (3) and the soil for reinforcing the slope (2) of loose soil; The frame beam system includes a plurality of frame cross beams (11) and frame longitudinal beams (12), the frame cross beams (11) and frame longitudinal beams (12) are both reinforced concrete structures and are fixedly arranged on the slope (2), the plurality of frame cross beams (11) are fixedly connected to the frame longitudinal beams (12) and are orthogonal to the frame longitudinal beams (12) to form a frame beam grid (10), and the frame beam grid (10) is a rigid load-bearing skeleton; The auxiliary system includes a connecting member (13) and a protective layer (15), wherein one end of the connecting member (13) is fixedly connected to the top end of the steel flower tube (3), and the other end is fixedly connected to the frame crossbeam (11) and the frame longitudinal beam (12), and the protective layer (15) covers the slope (2) surface within the frame beam grid (10).

2. The structure for reinforcing loose soil slopes based on steel flower tube anchors according to claim 1 is characterized by: The steel flower pipe anchor rod anchoring system (1) further comprises an anchor (7) and a concrete anchor pad (8); the connection between the frame cross beam (11) and the frame longitudinal beam (12) is set as a grid node; the concrete anchor pad (8) is fixedly arranged on the grid node; the top end of the anchor rod (6) passes through the concrete anchor pad (8) and is threadedly connected to the anchor (7); a steel mesh is fixedly arranged in the concrete anchor pad (8) to disperse concentrated stress.

3. The structure for reinforcing loose soil slopes based on steel flower tube anchors according to claim 2, characterized in that: The auxiliary system further comprises a plurality of water retaining edges (14) and stress dispersing pads (16), wherein the plurality of water retaining edges (14) are respectively fixedly arranged at the top of the slope (2) and the edges within the frame beam grid (10) for intercepting surface runoff above the top of the slope (2); and the stress dispersing pads (16) are sleeved on the anchor rod (6) and abut against the anchor (7) and the concrete anchor pad (8).

4. The structure for reinforcing loose soil slopes based on steel flower tube anchors according to claim 3 is characterized by: The auxiliary system further comprises a concrete head (17), which is fixedly arranged on the concrete anchor pad (8), and the top end of the anchor rod (6), the anchor (7) and the stress dispersion pad (16) are all located in the concrete head (17), so as to provide protection for the top end of the anchor rod (6), the anchor (7) and the stress dispersion pad (16).

5. The structure for reinforcing loose soil slopes based on steel flower tube anchors according to claim 4 is characterized in that: The auxiliary system further comprises a slope foot protection structure (18) and oblique reinforcement ribs, wherein the slope foot protection structure (18) is fixedly arranged at the bottom end of the slope (2), and the two ends of the oblique reinforcement ribs are respectively fixedly connected to the steel bars of the frame cross beam (11) and the frame longitudinal beam (12), so as to improve the shear resistance and stress concentration resistance performance of the frame beam grid (10).

6. A method for reinforcing loose soil slopes based on steel pipe anchors, characterized in that: The structure for reinforcing a loose soil slope based on a steel pipe anchor as described in claim 5 comprises the following steps: S1, following the pipe drilling (5), the steel pipe (3) is used as a casing to drill into the loose soil of the slope (2), and the borehole (5) is formed simultaneously; S2, installing the anchor rod (6), inserting the anchor rod (6) into the steel flower tube (3); S3, high-pressure grouting, injecting slurry into the drill hole (5), with a grouting pressure of not less than 0.6 MPa, the slurry penetrates into the soil through the grouting hole (4) on the steel flower tube (3), forming the grouting body (9), and after solidification, the slurry forms a composite reinforcement body with the anchor rod (6), the steel flower tube (3) and the soil; S4, anchor rod (6) acceptance, sampling the anchor rod (6) for pull-out resistance acceptance, with the sampling ratio not less than 5%; S5, frame beam construction, tying the steel bars of the frame cross beam (11) and the frame longitudinal beam (12), allowing the top end of the steel flower tube (3) to be fixedly connected to the steel bars of the frame cross beam (11) and the frame longitudinal beam (12) through the connecting member (13), supporting the formwork and pouring concrete to form the frame beam grid (10); S6, auxiliary system construction, synchronously complete the construction of the water retaining edge (14), the protective surface layer (15), and the slope foot protection structure (18), and after installing the concrete anchor pad (8), the stress dispersion pad (16) and the anchor (7) on the top of the anchor rod (6), cover and install the concrete head (17).

7. The method for reinforcing loose soil slopes using steel pipe anchors according to claim 6, characterized in that: The design calculation model of the steel tube anchoring complex is based on the cooperative working mechanism of the steel tube (3), the grouting body (9), the soil and the anchor rod (6), and quantifies the shear bearing capacity and the pull-out bearing capacity of the complex to meet the reinforcement design requirements of the slope (2). The design calculation model of the steel tube anchoring complex includes the following core formulas: Shear bearing capacity of composite body: ， Where, is the total shear strength of the steel pipe composite, is the slurry-soil interface bond strength, is the effective bonding area within the radiation radius of the grouting body (9), is the shear strength of the steel tube (3), is the cross-sectional area of the steel tube (3), is the pull-out resistance of the anchor rod (6), is the steel tube (3)-soil friction angle; Composite pull-out bearing capacity: ， Where, is the pull-out resistance of the anchor rod (6), is the diameter of the anchor rod (6), is the length of the anchoring section, is the pulp-rod bonding strength, is pi, is the safety factor against pull-out, which is 1.

5. Design tension for anchor rod (6); Quantify the synergistic efficiency of steel pipe (3)-grouting body (9)-soil: ， Where, To quantify the synergistic efficiency of the steel tube (3)-grouting body (9)-soil, is the total shear bearing capacity of the steel tube composite, Contributes to the shear resistance of steel pipes, is the shear contribution of the grouting body (9), Contributes to the frictional shear resistance of the soil.

8. The method for reinforcing loose soil slopes using steel flower tube anchors according to claim 7, characterized in that: The frame beam system undertakes three major functions in the steel tube anchor reinforcement structure: load transfer, slope constraint and coordinated anti-slip. The mechanical model of the frame beam system is based on the principle of reinforced concrete structure mechanics and combines the engineering characteristics of the slope (2) to establish a complete mechanical analysis system. The overall stress model of the frame beam grid (10) is: ， ， Where, is the bending stiffness of the frame beam, is the shear stiffness of the frame beam, is the elastic modulus of concrete, and are the moment of inertia of the transverse / longitudinal beam sections, and are the number of beams in the horizontal and vertical directions, and are the grid sizes in the horizontal and vertical directions, is the shear modulus of concrete, and are the cross-sectional areas of the horizontal and longitudinal beams, is the shear section coefficient; The node mechanical model is: ， Where, is the calculated value of the node shear bearing capacity, Design shear for the node, is the tensile strength of concrete, The net area of the node concrete after deducting the area occupied by the steel bars. is the yield strength of steel bars, is the total cross-sectional area of the stirrups, is the effective height of the beam, is the stirrup spacing, and is ≤150 mm; The collaborative working model of the frame beam-anchor system is: ， ， ， Where, is the synergistic stiffness ratio, is the frame beam system stiffness, is the anchoring system stiffness, is the design value of the anchor rod (6) tension, is the deformation of the anchoring system, is the length of the anchoring section, is the cross-sectional area of the anchor rod (6), is the elastic modulus of the anchor rod (6) steel; The anti-slip contribution quantification model is: ， Where, is the calculated value of anti-sliding of the frame beam system, For the cooperative working coefficient, the loose soil is 0.15-0.

25. is the horizontal force of the node, i.e. the horizontal component of the tension of the anchor rod (6), is the vertical force of the node, i.e. the vertical component of the tension of the anchor rod (6) + the soil pressure, and are the grid sizes in the horizontal and vertical directions respectively.

9. The method for reinforcing loose soil slopes using steel pipe anchors according to claim 8, characterized in that: In order to ensure a reliable connection between the frame beam system and the steel flower tube anchor bolt anchoring system (1), the connection member (13) needs to be triple-checked for shear resistance, pull-out resistance, and coordinated deformation. The calculation formula is as follows: The calculation formula for shear bearing capacity is: ， Where, is the ultimate shear bearing capacity of the connecting member (13), is the shear safety factor, is the design shear force; The calculation formula for pull-out bearing capacity is: ， Where, is the ultimate pull-out strength of the connecting member (13), is the pull-out safety factor, is the maximum tension of a single anchor rod (6); The coordinated deformation formula is: ， Where, is the deformation of the connecting member (13), is the deformation of the frame beam node, The anchoring system is deformed.

10. The method for reinforcing loose soil slopes using steel flower tube anchors according to claim 8, characterized in that: The overall safety factor calculation model is as follows; The soil's own shear contribution is: ， Where, Contributes to the soil's own shear resistance. is the number of soil strips, For the Effective cohesion of soil strips, For the Length of soil strip sliding arc, For the Soil weight, For the Sliding arc inclination of soil strip, For the Soil strip pore water pressure, For the effective internal friction angle of soil strip; The anchoring system contribution is: ， Where, Contribute to the anchoring system, is the number of anchoring complexes crossing the sliding arc, For the Shear strength of anchoring complex, For the anchor body shear area; The frame beam constraint contribution is: ， Where, Contribution to the frame beam constraint, is the cooperative working coefficient, is the uniformly distributed earth pressure on the slope surface, is the effective restraint area of the frame beam; The overall safety factor formula is: ， Where, is the overall safety factor, is the total number of soil strips divided, is the total sliding force, Contributes to the soil's own shear resistance. Contribute to the anchoring system, Contributes to frame beam constraints.

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