Design method and design structure of shear-resistant anchor cable

Abstract

The invention discloses a shear-resistant anchor cable design method and a design structure thereof. The design structure of the shear-resistant anchor cable is composed of an anchoring section, a shear-resistant section, a free section and an anchor head, the diameters of the anchoring section, the shear-resistant section and the free section are the same, the free section is composed of a first free section and a second free section, the anchoring section is formed by bonding an anchor cable placed at the bottom of a hole and cement paste, and the first free section is located between the anchoring section and the shear-resistant section. One end of the second free section is fixedly connected with the shear-resistant section, and the other end of the second free section is fixedly connected with the anchor head. The shear-resistant anchor cable structure can provide high pulling resistance and shear resistance at the same time, and therefore geological disasters can be effectively prevented and controlled.

Description

Technical Field

[0001] The invention relates to a design method and a design structure of a shear-resistant anchor cable, and belongs to the field of landslide, dangerous rock and slope prevention and control projects such as mountain roads, mountain railways, mountain towns, and water conservancy projects. Background Art

[0002] Prestressed anchoring technology is one of the commonly used means to prevent and control landslides, dangerous rocks and slopes in recent years. Due to its large bearing capacity, small construction disturbance and fast construction speed, it has developed rapidly in the fields of geotechnical engineering and geological engineering, and has become an important prevention and control technology for the management of medium and large landslides, dangerous rocks and slopes.

[0003] The main bearing structure of prestressed anchoring technology is the anchor cable, which is a linear structure made of multiple strands of steel wire, so it has a large difference in axial and lateral strength. Usually, the tensile strength of the anchor cable is between 1270MPa and 2360MPa, while the shear strength of the anchor cable is only 128MPa. The former is 10 to 20 times that of the latter. The axial tensile strength of the anchor cable is much greater than the lateral shear strength. Therefore, the shear resistance of the anchor cable is weak. When the prestressed anchoring technology is used to treat landslides, dangerous rocks and slopes, it usually encounters weak sliding surfaces (belts) or sliding surfaces (belts) with large angles. Such geological disasters usually have high shear forces. Under the action of shear forces, the anchor cables used to reinforce geological disasters will produce rotational damage or shear damage, causing the failure of geological disaster prevention and control projects. It can be seen that for landslides, dangerous rocks and slope control projects with high shear forces on sliding surfaces (belts), it is urgent to develop anchor cable structures with high shear bearing capacity and study their design methods. Summary of the invention

[0004] The purpose of the present invention is to overcome the above problems existing in the prior art and provide a shear-resistant anchor cable design method and design structure thereof. The shear-resistant anchor cable structure of the present invention can provide high pull-out resistance and shear resistance at the same time, thereby achieving effective prevention and control of such geological disasters.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for designing a shear-resistant anchor cable, characterized in that it comprises the following steps:

[0007] (1) Obtain the geometric dimensions, strength parameters and design safety factors required for the shear anchor design through landslide, dangerous rock and slope investigation data;

[0008] (2) Based on the calculation results of landslide, dangerous rock and slope stability, the residual sliding force T is obtained, and the pull-out force required by the shear anchor cable is:

[0009]

[0010] The shear resistance is:

[0011]

[0012] Where m is the number of horizontal rows of anchor cables; n is the longitudinal drainage of anchor cables; β i is the angle between the anchor cable and the horizontal plane; θ i is the angle between the sliding surface where the anchor cable is located and the horizontal plane;

[0013] (3) The pull-out resistance should meet the tensile strength requirements of the anchor cable and the tensile strength requirements of the anchor section. The tensile strength of the anchor cable should meet the following verification formula:

[0014]

[0015] The tensile strength of the anchor section should satisfy the following calculation formula:

[0016]

[0017] In the formula, S c is the concrete cross-sectional area of ​​the free section; S p is the cross-sectional area of ​​the anchor cable, S c +S p =πD i 2 / 4; σ t1 and σ t2 are the tensile strength of concrete and anchor cable respectively; L i is the length of the anchoring section; D i is the diameter of the anchoring section; f i is the friction strength between the anchor concrete and the rock mass interface;

[0018] According to equations (3) and (4), the diameter D of the anchoring section can be designed: i , Anchorage length L i , Anchor cable cross-sectional area S p ;

[0019] (4) The shear force should meet the shear force verification requirements of the shear section anchor pipe, as follows:

[0020]

[0021] In the formula, S c1 is the concrete cross-sectional area of ​​the free section; S s is the cross-sectional area of ​​the anchor cable, S c1 +S s =πD i 2 / 4; σ c1 and σ c2 are the shear strengths of concrete and anchor cables, respectively;

[0022] The diameter and wall thickness of the anchor pipe are designed according to formula (5);

[0023] (5) Based on the above anchor cable anchoring section diameter, length, anchor cable diameter, and anchor pipe diameter, the free section length of the shear anchor cable is determined taking into account the landslide, dangerous rock, and slope dimensions.

[0024] A shear-resistant anchor cable design structure, characterized in that it consists of an anchoring section, a shear-resistant section, a free section and an anchor head, the diameters of the anchoring section, the shear-resistant section and the free section are the same, the free section consists of a first free section and a second free section, the anchoring section is formed by bonding an anchor cable placed at the bottom of a hole with cement slurry, the first free section is located between the anchoring section and the shear-resistant section, and both ends are fixedly connected to the anchoring section and the shear-resistant section to form a whole, one end of the second free section is fixedly connected to the shear-resistant section, and the other end is fixedly connected to the anchor head.

[0025] The length of the shear section is not less than 1 m and is 2 to 3 times the width of the shear surface or shear band. When there are multiple shear surfaces or shear bands, multiple shear sections are provided.

[0026] The shear-resistant section is composed of an anchor and an anchor pipe. The anchor is arranged on the ends of the two ends of the anchor pipe. An anchor cable hole and a grouting hole penetrating the anchor are arranged in the anchor.

[0027] The anchor and anchor pipe are welded or integrally cast, the diameter of the grouting hole is greater than 30 mm, the anchor pipe is a steel pipe, the diameter of the steel pipe is the same as the diameter of the shear anchor cable structure, the wall thickness of the steel pipe is not less than 10 mm, and the steel pipe is symmetrically provided with holes for installing anchor cable clips near both ends.

[0028] The anchoring section is located behind the landslide, dangerous rock and slope shear surface or shear zone. When there are multiple shear surfaces or shear zones, the anchoring section is set behind the last shear surface or shear zone and embedded in the rock and soil with bearing capacity.

[0029] The length of the anchoring section is greater than 3m, and the anchor cables of the anchoring section are one bundle or multiple bundles.

[0030] The anchor cable of the anchoring section passes through the first free section and the anchor cable hole on the anchor and is fixedly connected to the clip of the shearing section.

[0031] One end of the anchor cable of the first free section is connected to the anchor at the lower end of the shear resistance section, and the other end is anchored in the anchor section.

[0032] One end of the anchor cable of the second free section is connected to the anchor at the upper end of the shear resistance section, and the other end is fixedly connected to the anchor head.

[0033] The advantages of adopting the present invention are:

[0034] (1) The shear-resistant anchor cable structure can not only bear a high pull-out force, but also a high shear force, which makes up for the deficiency of traditional anchor cables in shear strength.

[0035] (2) The shear-resistant anchor cable structure will not change the construction process and technology of the traditional anchor cable. It only adds shear-resistant anchor pipes through anchor connection, and the construction technology is relatively mature.

[0036] (3) For landslides, dangerous rocks and slope management projects with multiple sliding surfaces (zones), the shear anchor pipes of the shear anchor cable structure can be flexibly set at multiple sliding surface (zone) positions to prevent multiple shear failures in landslides, dangerous rocks and slopes.

[0037] In summary, the present invention proposes a shear anchor design method and structure for landslides, dangerous rocks and slope management projects with high shear forces on the sliding surface (belt). The shear anchor structure can provide high pull-out resistance and shear resistance at the same time, thereby achieving effective prevention and control of such geological disasters. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the slope reinforcement by the shear anchor cable structure in the present invention;

[0039] Figure 2 This is a schematic diagram of the shear anchor structure;

[0040] Figure 3 It is the schematic diagram of the shear section structure;

[0041] Figure 4 for Figure 3 A-A' cross-sectional structural diagram;

[0042] Figure 5 for Figure 3 Schematic diagram of the B-B' cross-section structure;

[0043] The markings in the figure are: 1. anchoring section; 2. shear section; 3. first free section; 4. anchor head; 5. shear surface or shear band; 6. anchor; 7. anchor pipe; 8. anchor hole; 9. grouting hole; 10. second free section. DETAILED DESCRIPTION

[0044] The invention is suitable for landslides, dangerous rocks and slope management projects with high shear force on the sliding surface (belt). Figure 1 ) provides pull-out resistance and shear resistance to achieve engineering reinforcement of landslides, dangerous rocks and slopes.

[0045] The shear anchor cable structure should be set in the middle and upper part of the landslide, dangerous rock and slope, and the angle with the horizontal plane should be 10-15°. The length, diameter and other parameters of the shear anchor cable structure should be designed based on pull-out and shear calculations.

[0046] The shear anchor cable structure can be arranged in multiple rows, with longitudinal and transverse spacing of 3 to 6 meters, and arranged in a plum blossom shape. The specific spacing should be designed based on pull-out and shear calculations.

[0047] The shear anchor cable structure is composed of an anchoring section 1, a shear section 2, a first free section 3, a second free section 10 and an anchor head 4. Figure 2 ), the diameter D of each section is the same, and the total length of the shear anchor cable structure is the sum of the lengths of the anchoring section 1, the shear section 2, the first free section 3 and the second free section 10.

[0048] The anchoring section 1 should be located behind the landslide, dangerous rock and slope shear surface or shear zone 5. If there are multiple shear surfaces or shear zones 5, it should be set behind the last shear surface or shear zone 5, and should be embedded in the rock and soil with a certain bearing capacity; the length of the anchoring section 1 should be designed based on the pull-out force verification of the anchor cable, and the length should be greater than 3m.

[0049] The anchor cables of the anchoring section 1 can be multiple bundles. After the anchor cables are placed at the bottom of the hole, cement slurry should be injected to bond the anchor cables and cement slurry to form an anchor body. The anchor cables of the anchoring section 1 and the anchor 6 of the shear section 2 are connected by clips.

[0050] The shear section 2 is composed of two anchors 6 and an anchor pipe 7 at the end. The anchor 6 and the anchor pipe 7 can be welded or cast as one piece. The material is 40Cr steel. The anchor 6 contains an anchor hole 8 and a grouting hole 9 ( Figure 4 ), the diameter of the grouting hole should be greater than 30mm; the anchor pipe 7 is a 40Cr steel thick-walled steel pipe, and the diameter of the steel pipe should be the same as the diameter of the shear anchor cable structure ( Figure 5 ), the wall thickness of the steel pipe shall not be less than 10mm, and the specific wall thickness shall be designed according to the shear and pull-out calculations; the steel pipe shall have symmetrical openings near both ends ( Figure 3 ) to facilitate the installation of anchor clips.

[0051] The length of the shear section 2 should be no less than 1 m and should be 2 to 3 times the width of the shear surface or shear band 5. If there are multiple shear surfaces or shear bands 5, multiple shear sections 2 should be set.

[0052] After cement slurry is injected into the steel pipe of the shear section 2, the steel pipe and cement jointly provide resistance to resist landslides, dangerous rocks and slope shear forces, thereby achieving the purpose of shear resistance of the anchor cable structure.

[0053] One end of the anchor cable of the first free section 3 is connected to the anchor at the lower end of the shear section, and the other end is anchored in the anchor section. The anchor cable of the second free section 10 is connected to the anchor 6 at the upper end of the shear section 2, and the outer end of the second free section 3 is connected to the anchor head 4; the length of the free section should be determined comprehensively based on the geometric dimensions of the landslide, dangerous rock and slope.

[0054] A design method for shear anchor cables is as follows:

[0055] (1) Obtain the geometric dimensions, strength parameters, design safety factors and other parameters required for the design of shear anchor cables through landslide, dangerous rock and slope investigation data.

[0056] (2) Based on the calculation results of landslide, dangerous rock and slope stability, the residual sliding force T is obtained. The pull-out force required by the shear anchor cable is:

[0057]

[0058] The shear resistance is,

[0059]

[0060] Where m is the number of horizontal rows of anchor cables; n is the longitudinal drainage of anchor cables; β i is the angle between the anchor cable and the horizontal plane; θ i It is the angle between the sliding surface where the anchor cable is located and the horizontal plane.

[0061] (3) The pull-out resistance should meet both the tensile strength requirements of the anchor cable and the tensile strength requirements of the anchor body. The tensile strength of the anchor cable should meet the following verification formula:

[0062]

[0063] The tensile strength of the anchor body should satisfy the following calculation formula:

[0064]

[0065] In the formula, S c is the concrete cross-sectional area of ​​the free section; S p is the cross-sectional area of ​​the anchor cable, S c +S p =πD i 2 / 4; σ t1 and σ t2 are the tensile strength of concrete and anchor cable respectively; L i is the length of the anchoring section; D i is the anchor body diameter; f i It is the friction strength between the anchor concrete and rock interface.

[0066] According to equations (3) and (4), the diameter D of the anchor body can be designed as i , Anchorage length L i , Anchor cable cross-sectional area S p And other parameters.

[0067] (4) The shear force should meet the shear force verification requirements of the shear section anchor pipe, as follows:

[0068]

[0069] In the formula, S c1 is the concrete cross-sectional area of ​​the free section; S s is the cross-sectional area of ​​the anchor cable, S c1 +S s =πD i 2 / 4; σ c1 and σ c2 are the shear strengths of concrete and anchor cables, respectively.

[0070] According to formula (5), the diameter and wall thickness of the anchor pipe can be designed. The length of the anchor pipe should be no less than 1 m and 2 to 3 times the width of the shear surface or shear band 5. If there are multiple shear surfaces or shear bands 5, multiple shear sections 2 should be set.

[0071] (5) Based on the above anchor cable anchoring section diameter, length, anchor cable diameter, and anchor pipe diameter, the free section length of the shear anchor cable is determined taking into account the landslide, dangerous rock, and slope dimensions.

[0072] The present invention proposes a shear-resistant anchor cable structure and design method for landslide, dangerous rock and slope prevention and control projects with high shear force on the sliding surface (belt). Due to the difference in axial and lateral strength of traditional anchor cables, the axial tensile strength of the anchor cables is much greater than the lateral shear strength. Therefore, traditional anchor cables cannot bear high shear forces. During the landslide, dangerous rock and slope prevention and control reinforcement process, the anchor cables often suffer from rotational damage or shear damage, causing the prevention and control project to fail.

[0073] Aiming at the characteristic of high shear force at the sliding surface (belt), the present invention adopts anchor pipes with high tensile and shear strengths to replace anchor cables, so as to increase the shear strength of the anchor cables at the sliding surface (belt), thereby achieving the purpose of the anchor cables bearing large shear force.

Claims

1. A shear anchor cable design method, characterized in that: The steps include: (1) Obtain the geometric dimensions, strength parameters and design safety factors required for the design of shear anchor cables through landslide, dangerous rock and slope survey data; (2) Based on the calculation results of landslide, dangerous rock and slope stability, the residual sliding force T is obtained, and the pull-out force required by the shear anchor cable is: The shear resistance is: Where m is the number of horizontal rows of anchor cables; n is the longitudinal drainage of anchor cables; β i is the angle between the anchor cable and the horizontal plane; θ i is the angle between the sliding surface where the anchor cable is located and the horizontal plane; (3) The pull-out resistance should meet the tensile strength requirements of the anchor cable and the tensile strength requirements of the anchor section. The tensile strength of the anchor cable should meet the following verification formula: The tensile strength of the anchor section should satisfy the following calculation formula: In the formula, S c is the concrete cross-sectional area of ​​the free section; S p is the cross-sectional area of ​​the anchor cable, S c +S p =πD i 2 / 4; σ t1 and σ t2 are the tensile strength of concrete and anchor cable respectively; L i is the length of the anchoring section; D i is the diameter of the anchoring section; f i is the friction strength between the anchor concrete and the rock mass interface; According to equations (3) and (4), the diameter D of the anchoring section can be designed: i , Anchorage length L i , Anchor cable cross-sectional area S p ; (4) The shear force should meet the shear force verification requirements of the shear section anchor pipe, as follows: In the formula, S c1 is the concrete cross-sectional area of ​​the free section; S s is the cross-sectional area of ​​the anchor cable, S c1 +S s =πD i 2 / 4; σ c1 and σ c2 are the shear strengths of concrete and anchor cables, respectively; The diameter and wall thickness of the anchor pipe are designed according to formula (5); (5) Based on the above anchor cable anchoring section diameter, length, anchor cable diameter, and anchor pipe diameter, the free section length of the shear anchor cable is determined taking into account the landslide, dangerous rock, and slope dimensions.

2. The design structure of a shear anchor cable design method according to claim 1, characterized in that: The invention comprises an anchoring section (1), a shear section (2), a free section (3) and an anchor head (4); the anchoring section (1), the shear section (2) and the free section have the same diameter; the free section comprises a first free section (3) and a second free section (10); the anchoring section (1) is formed by bonding an anchor cable placed at the bottom of a hole with cement slurry; the first free section (3) is located between the anchoring section (1) and the shear section (2); the two ends of the first free section (3) are respectively fixedly connected to the anchoring section (1) and the shear section (2) to form a whole; one end of the second free section (10) is fixedly connected to the shear section (2) and the other end is fixedly connected to the anchor head (4).

3. The design structure of a shear anchor cable design method according to claim 2, characterized in that: The length of the shear section (2) is not less than 1 m and is 2 to 3 times the width of the shear surface or shear band (5). When there are multiple shear surfaces or shear bands (5), the shear section (2) is provided in multiples.

4. The design structure of a shear anchor cable design method according to claim 3, characterized in that: The shear-resistant section (2) is composed of an anchor (6) and an anchor pipe (7). The anchor (6) is arranged on the ends of both ends of the anchor pipe (7). An anchor cable hole (8) and a grouting hole (9) penetrating the anchor (6) are arranged in the anchor (6).

5. The design structure of a shear anchor cable design method according to claim 4, characterized in that: The anchor (6) and the anchor pipe (7) are welded or integrally cast, the diameter of the grouting hole (9) is greater than 30 mm, the anchor pipe (7) is a steel pipe, the diameter of the steel pipe is the same as the diameter of the shear anchor cable structure, the wall thickness of the steel pipe is not less than 10 mm, and the steel pipe is symmetrically provided with holes for installing anchor cable clips near both ends.

6. The design structure of a shear anchor cable design method according to claim 5, characterized in that: The anchoring section (1) is located behind the landslide, dangerous rock and slope shear surface or shear zone (5). When there are multiple shear surfaces or shear zones (5), the anchoring section (1) is arranged behind the last shear surface or shear zone (5) and is embedded in the rock and soil body with bearing capacity.

7. The design structure of a shear anchor cable design method according to claim 6, characterized in that: The length of the anchoring section (1) is greater than 3 m, and the anchor cables of the anchoring section (1) are one bundle or multiple bundles.

8. The design structure of a shear anchor cable design method according to claim 7, characterized in that: The anchor cable of the anchoring section (1) passes through the first free section (3) and the anchor cable hole (8) on the anchor (6) and is fixedly connected to the clip of the shear-resistant section (2).

9. The design structure of a shear anchor cable design method according to claim 8, characterized in that: One end of the anchor cable of the first free section (3) is connected to the anchor (6) at the lower end of the shear resistance section (2), and the other end is anchored in the anchor section (1).

10. The design structure of a shear anchor cable design method according to claim 9, characterized in that: One end of the anchor cable of the second free section (10) is connected to the anchor (6) at the upper end of the shear resistance section (2), and the other end is fixedly connected to the anchor head (4).

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