A design method for gravity anchorage suitable for complex mountainous terrain

Abstract

The present invention relates to the field of bridge engineering technology, and provides a design method for gravity anchorages suitable for complex mountainous terrains. By calculating the anti-slip safety factor and anti-overturning safety factor of the current design structure of the anchorage in the area where it is located, when the anti-slip safety factor is less than a first preset threshold value, and the anti-overturning safety factor is less than a second preset threshold value, drainage design is performed on the area where the anchorage is located to lower the groundwater level in the area where the anchorage is located until the anchorage meets the design requirements. The present application innovatively combines drainage and water level reduction design with the anchorage, and by lowering the groundwater level, reduces the buoyancy of the groundwater on the anchorage, and reduces the volume of the anchorage concrete; it can also greatly reduce the later maintenance cost and improve the durability of the anchorage. Its economic effect is significant, making up for the shortcomings of traditional gravity anchorages, and has important guiding significance for guiding the structural design and optimization of gravity anchorages of suspension bridges under complex foundation conditions in mountainous areas.

Description

Technical Field

[0001] The invention relates to the technical field of bridge engineering, in particular to a design method of a gravity anchor suitable for complex mountainous terrain. Background Art

[0002] Suspension bridges have the advantages of large span capacity, beautiful appearance, and clear force, so they are often given priority when selecting large-span bridges. Suspension bridges are usually composed of bridge towers, anchors, main cables, suspenders, and main beams. Among them, the anchor is the anchor body of the main cable. Its main function is to transfer the tension of the main cable to the foundation. Its bearing capacity and reliability are crucial.

[0003] Most suspension bridges use gravity anchors, which are generally composed of an anchor body and a foundation. They rely on their own greater gravity to offset the vertical force of the main cable, while the horizontal force is offset by the friction between the foundation and the anchor foundation. Among them, the key design of the anchor lies in the anti-sliding stability coefficient and anti-overturning stability coefficient of the anchor under the tension of the main cable.

[0004] However, complex mountainous terrains often encountered in actual projects, such as mountainous canyon areas, have the characteristics of steep terrain, large fluctuations in rock formations, developed joints and fissures, and abundant rock fissure water. The traditionally designed gravity anchorage has the following problems:

[0005] 1. The anchor base usually needs to select rock strata with lower weathering degree and better integrity as the bearing layer. However, due to the large vertical and horizontal fluctuations of geological rock strata in mountainous areas, in order for the anchor base to reach the bearing layer, the anchor foundation is buried deep, the mountain excavation is large, and the surrounding environment is severely damaged. At the same time, the high slope formed by the foundation pit excavation also has great safety hazards.

[0006] 2. Due to the abundant water in the mountain fissures, conventional mountain gravity anchorages do not consider drainage design. After the anchorage foundation pit is excavated and the fertilizer trough is backfilled, rainwater infiltration causes groundwater to rise due to poor drainage, forming a water basin effect, which produces upward buoyancy on the anchorage, which will seriously affect the anchorage's force safety. In order to resist the floating groundwater and the huge tension of the main cable, the weight of the anchorage needs to be greatly increased, so the scale of the anchorage foundation is often very large, which does not meet the standards of intensive social development.

[0007] 3. Most of the anchorages of the built suspension bridges have been flooded all year round due to the lack of drainage design, which seriously affects the durability of the anchorages. Water pumping measures have to be taken in the anchor room. Although water pumping is convenient for construction, it is cumbersome to maintain in the later stage, and it is difficult to ensure the timeliness of maintenance, and the cost of the whole life cycle is high.

[0008] In view of this, it is necessary to propose a design method for a gravity anchor suitable for complex mountainous terrain to solve or at least alleviate the above-mentioned defects. Summary of the invention

[0009] The main purpose of the present invention is to provide a design method for gravity anchors suitable for complex mountainous terrain, so as to solve the technical problems in the prior art of anchor design, such as large anchor volume, large foundation pit excavation volume, and failure to consider drainage design, resulting in cumbersome maintenance.

[0010] To achieve the above object, the present invention provides a design method for a gravity anchor suitable for complex mountainous terrain, comprising the following steps:

[0011] S1, determining the basic minimum size of the anchor according to the principle of minimizing the volume of the anchor and minimizing the amount of foundation pit excavation, and obtaining the current design structure of the anchor;

[0012] S2, calculating the anti-slip safety factor and the anti-overturning safety factor of the current design structure of the anchor in the area, and determining whether the anti-slip safety factor is greater than a first preset threshold, and determining whether the anti-overturning safety factor is greater than a second preset threshold. If not, proceed to steps S31 to S34; if yes, proceed to step S35;

[0013] S31, when either the anti-slip safety factor is greater than a first preset threshold value or the anti-overturning safety factor is greater than a second preset threshold value is not established, it is determined that the current design structure of the anchor does not meet the design requirements, and drainage design is performed on the area where the anchor is located to lower the groundwater level in the area where the anchor is located;

[0014] S32, obtaining the design water level of the anchor in the area where it is located, and determining whether the design water level is lower than or equal to the minimum design elevation of the anchor;

[0015] S33, when the design water level is lower than or equal to the minimum design elevation of the anchor, increase the volume of the anchor according to a preset volume increment, and then return to step S2;

[0016] S34, when the designed water level is higher than the minimum elevation of the anchor base, continue to perform drainage design on the area where the anchor is located, so that the groundwater level in the area where the anchor is located continues to drop, and then return to step S2;

[0017] S35, determining whether the current design structure of the anchor meets the design requirements.

[0018] Preferably, the step S1 specifically includes the following steps:

[0019] Establishing an overall bridge model, and calculating the sum of the tensions of the main cables according to the overall bridge model;

[0020] Calculate the required anchor weight based on the sum of the tension of the main cables;

[0021] Obtaining the anchoring mode of the main cable strand, and preliminarily determining the minimum size of the front anchor chamber and the minimum size of the rear anchor chamber according to the anchoring mode of the main cable strand and the weight of the anchor; wherein the anchor comprises an anchor body, a first multi-stage toothed step for preventing the anchor body from sliding in the transverse direction of the bridge, and a second multi-stage toothed step for preventing the anchor body from sliding in the longitudinal direction of the bridge, and a front anchor chamber and a rear anchor chamber are formed inside the anchor body, and the rear anchor chamber and the front anchor chamber are arranged correspondingly;

[0022] Obtaining the rock layer distribution data and the bearing capacity data of the bearing layer in the area where the anchor is located, and determining the minimum burial depth of the anchor body according to the rock layer distribution data, the bearing capacity data of the bearing layer and the weight of the anchor;

[0023] The number of the first multi-level tooth ridges, the number of the second multi-level tooth ridges, the height of each first multi-level tooth ridge and the height of each second multi-level tooth ridge are determined based on the principle of minimum volume and minimum foundation pit excavation.

[0024] Preferably, the anchor body includes an anchor block and a loose-cable saddle pier foundation, the loose-cable saddle pier foundation includes a first part with a flat bottom surface and a second part with the first multi-stage tooth ridges arranged on the bottom surface, the anchor block includes a third part with a flat bottom surface and a fourth part with the second multi-stage tooth ridges arranged on the bottom surface, and the number of the first multi-stage tooth ridges is the same as the number of the second multi-stage tooth ridges.

[0025] Preferably, the step S2 of calculating the anti-slip safety factor of the current design structure of the anchor in the area includes the following steps:

[0026] S21, using the formula

[0027] Obtaining the anti-slip force of the anchor ;in, , G v is the weight of the anchor, G a is the weight of the backfill soil of the anchor pit, N is the sum of the vertical loads of the approach bridge piers set at the top of the anchor, T is the sum of the tension of the main cable, θ is the angle between the main cable and the horizontal plane, S 总 is the anchor base area, The friction angle of the basement rock, c is the cohesion of the basement rock, is the anchor base stress; represents the number of units of the first part divided according to the number of levels of the first multi-level tooth ridge, represents the number of units in the second part divided according to the number of levels of the first multi-level tooth ridge, Indicates the number of units in the third part divided according to the number of levels of the second multi-level tooth ridge, Indicates the number of units in the fourth part divided according to the number of stages of the second multi-stage tooth ridge; F 浮is the buoyancy of the anchor caused by groundwater; is the friction angle of the basement rock layer of the ith unit, is the cohesion of the basement rock layer of the ith unit, is the anchor base area corresponding to the i-th unit;

[0028] S22, using the formula Determine the sliding force on the anchor caused by the sum of the tension of the main cables ;

[0029] S23, using the formula Calculate the anti-slip safety factor of the current design of the anchor in the area where it is located .

[0030] Preferably, the anti-overturning safety factor in step S2 is obtained by the following steps:

[0031] S200, using the formula Calculate the anti-overturning safety factor of the current design configuration of the anchor in the area where it is located ;in, Indicates the number of units divided by the anchorage. Indicates the number of units into which the anchor pit backfill soil is divided. Indicates the number of units divided into the approach bridge piers, G vi is the weight of the anchor unit, G aj is the weight of the anchor pit backfill unit, N k is the vertical load of the approach bridge pier unit, d vi is the distance between the ith anchor unit and the rotation axis, d aj is the distance between the jth anchor pit backfill unit and the rotation axis, d Nk is the distance between the kth approach bridge pier unit and the rotation axis, d 浮 is the distance between the buoyancy of the anchor caused by groundwater and the rotation axis, d T The vertical distance from the rotation axis under the action of the sum of the tension of the main cables; among them, the front toe line of the base of the anchor body is the rotation axis, and the anti-overturning moment The overturning moment is the sum of the weight of the anchor, the weight of the backfill soil of the anchor foundation pit, and the vertical load of the approach bridge set on the top of the anchor on the rotation axis. It is the sum of the tension of the main cable and the sum of the moments generated by the buoyancy generated by the groundwater on the rotating shaft.

[0032] Preferably, the first preset threshold and the second preset threshold are both 2.0.

[0033] Preferably, the step S31 specifically includes the following steps:

[0034] When both of the anti-slip safety factor being less than or equal to the first preset threshold and the anti-overturning safety factor being greater than the second preset threshold are established at the same time, the anti-slip safety factor is calculated by inverse calculation according to the formula in step S21 and the formula in step S23. Buoyancy equal to the first preset threshold ;

[0035] Design drainage holes to drain the area where the anchor is located:

[0036] according to Calculate the target water level to which the groundwater level needs to be lowered, obtain the current groundwater level, and determine the depth of the anchor pit water level drop based on the current groundwater level and the target water level;

[0037] Using formula Obtain the water inflow of the anchor pit ; where k is the permeability coefficient, H is the thickness of the phreatic aquifer, and s is the water level drop of the anchor pit. is the precipitation influence radius, r0 is the equivalent radius of the foundation pit;

[0038] According to the water inflow of the anchor pit Determining drainage hole flow ;

[0039] According to the drainage hole flow Calculate the effective cross-sectional area A of the drainage hole.

[0040] Preferably, the step S31 specifically includes the following steps:

[0041] When both of the anti-slip safety factor being greater than the first preset threshold and the anti-rollover safety factor being less than or equal to the second preset threshold are established at the same time, the anti-rollover safety factor is calculated by inverse calculation according to the formula in step S200. The buoyancy equal to the second preset threshold ;

[0042] Design drainage holes to drain the area where the anchor is located:

[0043] according to Calculate the target water level to which the groundwater level needs to be lowered, obtain the current groundwater level, and determine the depth of the anchor pit water level drop based on the current groundwater level and the target water level;

[0044] Using formula Obtain the water inflow of the anchor pit ;

[0045] According to the water inflow of the anchor pit Determining drainage hole flow ;

[0046] According to the drainage hole flow Calculate the effective cross-sectional area A of the drainage hole.

[0047] Preferably, the step is based on the flow rate of the drainage hole The calculation of the effective cross-sectional area A of the drainage hole specifically includes the following steps: According to the hydraulic calculation formula , calculate the effective cross-sectional area A of the drainage hole; where, is the flow rate, , R is the hydraulic radius, , n is the roughness coefficient of the drainage hole wall, is the wetted perimeter of the drainage hole, and i is the longitudinal slope of the drainage hole.

[0048] Preferably, the drainage hole flow The water inflow of anchor pit 2~3 times of.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention provides a design method for a gravity anchor suitable for complex mountainous terrain. By calculating the anti-slip safety factor and the anti-overturning safety factor of the current design structure of the anchor in the area where it is located, when either the anti-slip safety factor is less than a first preset threshold value or the anti-overturning safety factor is less than a second preset threshold value, a drainage design is performed on the area where the anchor is located to lower the groundwater level in the area where the anchor is located until the anchor meets the design requirements.

[0051] This application innovatively combines drainage and water level reduction design with anchors. By lowering the groundwater level, the buoyancy of groundwater on the anchors is reduced, and the volume of anchor concrete is reduced. It can also greatly reduce the subsequent maintenance costs and improve the durability of the anchors. Its economic effect is significant, which makes up for the shortcomings of traditional gravity anchors. It has important guiding significance for guiding the structural design and optimization of gravity anchors of suspension bridges under complex foundation conditions in mountainous areas.

[0052] Secondly, according to the steep terrain and the large fluctuation of rock formations, the anchor foundation can be set with a three-dimensional tooth sill structure consisting of a first multi-level tooth sill and a second multi-level tooth sill, which can flexibly adapt to terrain changes, reduce mountain excavation, and reduce environmental damage; at the same time, the three-dimensional tooth sill can form a composite bearing with the steep rock mass, which can improve the stress distribution of the anchor base and improve the anti-sliding bearing capacity of the longitudinal and transverse anchors. After considering the anti-sliding effect of the tooth sill, the anchor volume can be further effectively reduced and the engineering cost can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0054] Figure 1 is a schematic flow chart of a design method in one embodiment of the present invention;

[0055] Figure 2 is a three-dimensional schematic diagram of the overall structure in one embodiment of the present invention;

[0056] Figure 3 It is a schematic elevation view of the overall structure in one embodiment of the present invention;

[0057] Figure 4 for Figure 3 Schematic diagram of the cross section along the AA direction;

[0058] Figure 5 for Figure 3 Schematic diagram of the cross section along the BB direction;

[0059] Figure 6 for Figure 3 Schematic diagram of the cross section along CC direction;

[0060] Figure 7 It is a schematic elevation diagram of an application scenario of a drainage system in one embodiment of the present invention;

[0061] Figure 8 It is a schematic plan view of an application scenario of a drainage system in one embodiment of the present invention;

[0062] Fig. 9 It is a schematic elevation view of a combined structure of a seepage ditch, a water collection well and a drainage hole in one embodiment of the present invention;

[0063] Fig.10 It is a side schematic diagram of a water infiltration ditch and a water collection well in one embodiment of the present invention;

[0064] Fig.11 is a schematic cross-sectional view of a water seepage ditch in one embodiment of the present invention;

[0065] Fig.12 is a schematic cross-sectional view of a water collection well in one embodiment of the present invention;

[0066] Fig.13 In one embodiment of the present invention , , Specific division diagram.

[0067] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments.

[0068] Description of Figure Numbers:

[0069] 10. Anchor; 110. Anchor body; 1110. Anchor block; 1111. Second front anchor chamber; 1112. Rear anchor chamber; 1113. Bevel; 1114. First manhole; 1120. Scattered cable saddle pier; 1121. First front anchor chamber; 1122. Second manhole; 1130. Scattered cable saddle pier foundation; 1140. Post-cast strip; 120. First multi-level tooth sill; 130. Second multi-level tooth sill; 20. Seepage ditch; 210. Ditch body; 220. Coarse gravel and crushed stone layer; 230. Permeable pipe; 240. Impermeable geotextile; 30. Collection well; 40. Drainage hole; 410. Overflow hole; 50. Drainage ditch; 60. Intercepting ditch; 70. Drainage ditch. DETAILED DESCRIPTION

[0070] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0071] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0072] In the present invention, the descriptions of "right part", "middle part", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "right part" and "middle part" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0073] Please see attached Figures 1 to 13 In one embodiment of the present invention, a design method for a gravity anchor suitable for complex mountainous terrain includes the following steps:

[0074] S1. Determine the basic minimum size of the anchor 10 according to the principle of minimizing the volume of the anchor 10 and minimizing the amount of foundation pit excavation, and obtain the current design structure of the anchor 10. In order to design an anchor that meets the requirements and minimizes the volume of the anchor 10 and the amount of foundation pit excavation, the present application first determines the basic minimum size of the anchor 10 and obtains the current design structure of the anchor 10.

[0075] As a preferred implementation, step S1 specifically includes the following steps:

[0076] Establishing an overall bridge model, and calculating the sum of the tensions of the main cables according to the overall bridge model;

[0077] The weight of the anchor 10 required is calculated according to the sum of the tension of the main cables. The existing mature technical means can be used to preliminarily calculate the weight of the anchor 10 required according to the sum of the tension of the main cables. For example, if the angle between the line of action of the sum of the tension of the main cables T and the horizontal plane is θ, then the weight of the anchor 10 G=Tsinθ, which will not be elaborated here.

[0078] Obtain the anchoring method of the main cable strand, and preliminarily determine the minimum size of the front anchor chamber and the minimum size of the rear anchor chamber 1112 according to the anchoring method of the main cable strand and the weight of the anchor 10; wherein the anchor 10 comprises an anchor body 110, a first multi-stage tooth sill 120 for preventing the anchor body 110 from sliding in the transverse direction of the bridge, and a second multi-stage tooth sill 130 for preventing the anchor body 110 from sliding in the longitudinal direction of the bridge, and a front anchor chamber and a rear anchor chamber 1112 are formed inside the anchor body 110, and the rear anchor chamber 1112 and the front anchor chamber are arranged correspondingly;

[0079] Specifically, the anchoring methods are mainly divided into steel anchoring system and prestressed anchoring system. The present application preferably adopts the prestressed anchoring system. According to the sum of the tension of the main cable and the design strength of each prestressed strand, the total number of prestressed strands required can be calculated, and the size of the prestressed strand can be obtained, and then the minimum size of the front anchor chamber and the rear anchor chamber 1112 can be obtained. This part is an existing mature technical means and will not be elaborated here.

[0080] The rock layer distribution data and the bearing capacity data of the bearing layer in the area where the anchor 10 is located are obtained, and the minimum burial depth of the anchor body 110 is determined according to the rock layer distribution data, the bearing capacity data of the bearing layer and the weight of the anchor 10; specifically, the hydrogeological conditions can be ascertained by geological surveys, drilling, in-situ tests, hydrological tests and other survey methods, so as to obtain the rock layer distribution data and the bearing capacity data of the bearing layer; the base of the anchor body 110 generally needs to enter moderately weathered rock, and the rock layer strength needs to be greater than the base stress, and the anchor base stress = anchor weight / base area.

[0081] The number of the first multi-level tooth ridges 120, the number of the second multi-level tooth ridges 130, the height of each first multi-level tooth ridge 120, and the height of each second multi-level tooth ridge 130 are determined according to the principle of minimum volume and minimum foundation pit excavation. Preferably, the height of each tooth ridge should not be too high, usually about 5 meters, and the number of levels can be roughly determined according to the height difference of the rock layer.

[0082] In this embodiment, according to the situation of steep terrain and large fluctuations in rock formations, toothed ridge structures in the transverse and longitudinal directions are set at the bottom of the anchor body 110, which can flexibly adapt to terrain changes, reduce mountain excavation, and reduce environmental damage; at the same time, the toothed ridge structures in the transverse and longitudinal directions can form a composite bearing with the steep rock mass, which can improve the stress distribution at the base of the anchor 10 and enhance the anti-slip bearing capacity of the longitudinal and transverse anchors 10. After considering the anti-slip effect of the toothed ridges, the volume of the anchor 10 can be further effectively reduced, thereby reducing the project cost.

[0083] S2, calculating the anti-slip safety factor and the anti-overturning safety factor of the current design structure of the anchor 10 in the area, and determining whether the anti-slip safety factor is greater than a first preset threshold, and determining whether the anti-overturning safety factor is greater than a second preset threshold. If not, proceed to steps S31 to S34; if yes, proceed to step S35;

[0084] It can be understood by those skilled in the art that the anti-slip safety factor is a measure of the ability of the anchor 10 structure to resist sliding damage when subjected to horizontal forces (such as main cable tension). When the anti-slip safety factor is large enough, the anchor 10 structure can remain stably in place and will not slip due to horizontal forces; the anti-overturning safety factor is a measure of the ability of the anchor 10 structure to resist overturning damage when subjected to overturning moments. When the anti-overturning safety factor is large enough, the anchor 10 structure can resist the overturning moment generated by the main cable tension and maintain the stability of the structure. This helps prevent the anchor 10 structure from overturning damage under extreme weather or load conditions. If both the anti-slip safety factor is greater than the first preset threshold value and the anti-overturning safety factor is greater than the second preset threshold value, it can be determined that the anchor 10 meets the design requirements of these two key indicators. If any one of them is not met, it means that the anchor 10 does not meet the design requirements.

[0085] S31, when either the anti-slip safety factor is greater than a first preset threshold value or the anti-overturning safety factor is greater than a second preset threshold value is not established, it is determined that the current design structure of the anchor 10 does not meet the design requirements, and drainage design is performed on the area where the anchor 10 is located to lower the groundwater level in the area where the anchor 10 is located;

[0086] It is worth noting that when any one of the anti-slip safety factor being greater than the first preset threshold value and the anti-overturning safety factor being greater than the second preset threshold value is not established, either the anti-slip safety factor does not meet the design requirements, or the anti-overturning safety factor does not meet the design requirements, or both the anti-slip safety factor and the anti-overturning safety factor do not meet the design requirements; it should be noted that in the prior art, after the excavation of the foundation pit of the anchor 10 and the backfilling of the fertilizer trough, the infiltration of rainwater causes the groundwater to rise due to poor drainage, forming a water basin effect, which generates an upward buoyancy on the anchor 10, which will seriously affect the force safety of the anchor 10. Due to the influence of the groundwater buoyancy, the anchor 10 is displaced too much, and even slips or overturns, resulting in a reduction in the anti-slip safety factor and / or the anti-overturning safety factor or the anti-overturning safety factor, thereby seriously affecting the structural safety.

[0087] S32, obtaining the design water level of the anchor 10 in the area where it is located, and determining whether the design water level is lower than or equal to the minimum design elevation of the anchor 10; wherein the design water level can be adaptively adjusted, for example, the current design structure corresponds to a current design water level, and the design water level rises after the anchor volume is increased. The minimum design elevation is usually a fixed value after the design, and the buoyancy of the anchor 10 can be determined according to the difference between the design water level of the area where the anchor 10 is located and the minimum design elevation of the anchor 10, using the Archimedean buoyancy calculation formula , ρ is the density of water, g is a constant, is the volume of the anchor 10 below the groundwater level, which can be calculated based on the groundwater level elevation and the minimum design elevation of the anchor 10 (eg, base elevation).

[0088] S33, when the design water level is lower than or equal to the minimum design elevation of the anchor 10, increase the volume of the anchor 10 according to the preset volume increment, and then return to step S2; when the design water level is lower than or equal to the minimum design elevation of the anchor 10, that is, the buoyancy of the water is 0, when either the anti-slip safety factor is greater than the first preset threshold value, and the anti-overturning safety factor is greater than the second preset threshold value, it is necessary to adjust the structure of the anchor 10 and increase the volume of the anchor 10. The preset volume increment can be a volume increment of 5% each time, and then return to step S2 until the anti-slip safety factor and the anti-overturning safety factor meet the design requirements.

[0089] S34, when the designed water level is higher than the minimum elevation of the base of the anchor 10, continue to perform drainage design on the area where the anchor 10 is located, so that the groundwater level in the area where the anchor 10 is located continues to drop, and then return to step S2;

[0090] When the design water level is higher than the minimum elevation of the base of the anchor 10, the anchor 10 is affected by the buoyancy of the groundwater. When any one of the anti-slip safety factor being greater than the first preset threshold and the anti-overturning safety factor being greater than the second preset threshold is not true, it indicates that the current water buoyancy has a large influence, and therefore the water level needs to be lowered. This step continues to perform drainage design on the area where the anchor 10 is located, so that the groundwater level in the area where the anchor 10 is located continues to drop. After the water level drops, the anchor 10 will be affected by the buoyancy of the groundwater and will also drop accordingly. Then, the process returns to step S2 until the anti-slip safety factor and the anti-overturning safety factor meet the design requirements.

[0091] S35, determining whether the current design structure of the anchor 10 meets the design requirements.

[0092] The present application innovatively combines the drainage and water level reduction design with the anchor 10, reduces the buoyancy of the groundwater on the anchor 10 by lowering the groundwater level, and reduces the concrete volume of the anchor 10; it can also greatly reduce the subsequent maintenance costs and improve the durability of the anchor 10. Its economic effect is significant, making up for the shortcomings of the traditional gravity anchor 10, and has important guiding significance for guiding the structural design and optimization of the gravity anchor 10 of the suspension bridge under complex foundation conditions in mountainous areas.

[0093] As a preferred embodiment, the anchor body 110 includes an anchor block 1110 and a loose cable saddle buttress foundation 1130. The loose cable saddle buttress foundation 1130 includes a first portion with a flat bottom surface and a second portion with the first multi-stage tooth ridge 120 arranged on the bottom surface. The anchor block 1110 includes a third portion with a flat bottom surface and a fourth portion with the second multi-stage tooth ridge 130 arranged on the bottom surface. The first multi-stage tooth ridge 120 has the same number of stages as the second multi-stage tooth ridge 130. That is, the loose cable saddle buttress foundation 1130 is divided into a first portion and a second portion, and the anchor block 1110 is divided into a third portion and a fourth portion. The first portion, the second portion, the third portion, and the fourth portion are all three-dimensional structures.

[0094] Furthermore, the calculation of the anti-slip safety factor of the current design structure of the anchor 10 in the area in step S2 specifically includes the following steps:

[0095] S21, using the formula

[0096] Get the anti-slip force of anchor 10 ;in, , G v is the weight of anchor 10, unit: kN, G ais the weight of the backfill soil of the foundation pit of anchor 10, unit: kN, N is the sum of the vertical loads of the approach bridge piers set on the top of anchor 10, unit: kN, T is the sum of the tension of the main cable, unit: kN, θ is the angle between the main cable and the horizontal plane, S 总 is the base area of ​​anchor 10, unit: m 2 , The friction angle of the basement rock, c is the cohesion of the basement rock, unit: kpa, is the anchor 10 base stress, unit: kPa, which can be obtained from the geological survey report; represents the number of units of the first part divided according to the number of stages of the first multi-stage tooth ridge, represents the number of units in the second part divided according to the number of levels of the first multi-level tooth ridge, Indicates the number of units in the third part divided according to the number of levels of the second multi-level tooth ridge, Indicates the number of units in the fourth part divided according to the number of stages of the second multi-stage tooth ridge; F 浮 is the buoyancy of the groundwater on the anchor 10; unit: kN, is the friction angle of the basement rock layer of the ith unit, is the cohesion of the basement rock layer of the ith unit, is the anchor base area corresponding to the i-th unit;

[0097] S22, using the formula Determine the sliding force generated by the sum of the tension of the main cables on the anchor 10 ;

[0098] S23, using the formula Calculate the anti-slip safety factor of the current design structure of the anchor 10 in the area where it is located .

[0099] Furthermore, the anti-overturning safety factor in step S2 is obtained by the following steps:

[0100] S200, using the formula Calculate the anti-overturning safety factor of the current design structure of the anchor 10 in the area where it is located ;in, Indicates the number of units divided by the anchorage. Indicates the number of units into which the anchor pit backfill soil is divided. Indicates the number of units divided into the approach bridge piers, G vi The weight of the anchor 10 unit, unit: kN, G aj The weight of the anchor pit backfill unit, unit: kN, N k is the vertical load of the approach bridge pier unit, unit: kN, d viis the distance between the ith anchor 10 unit and the rotation axis, unit: m, d aj is the distance between the jth anchor pit backfill unit and the rotation axis, unit: m, d Nk is the distance between the kth approach bridge pier unit and the rotation axis, unit: m, d 浮 is the distance between the buoyancy generated by groundwater on the anchor 10 and the rotation axis, that is, the distance from the vertical center of the anchor base plane to the rotation axis along the longitudinal bridge direction, unit: m;

[0101] dT is the vertical distance from the rotation axis under the action of the sum of the tension of the main cable, unit: m; where the front toe line of the base of the anchor body 110 is the rotation axis, and the anti-overturning moment It is the sum of the weight of the anchor 10, the weight of the backfill soil of the foundation pit of the anchor 10, and the moment generated by the vertical load of the approach bridge set on the top of the anchor 10 on the rotation axis, unit: , overturning moment It is the sum of the tension of the main cable and the sum of the moments generated by the buoyancy of the groundwater on the rotating axis, unit: .

[0102] like Figure 4 As shown, the base front toe line is Figure 4 The bottom horizontal line.

[0103] As a specific example, is 7, that is, the number of units divided into anchor 10 is 7, is 2, indicating that the number of units divided into the anchor pit backfill soil is 2. is 2, indicating that the number of units divided into the approach bridge pier is 2. Fig.13 As shown, through reasonable division, the irregular shape can be divided into regular units as much as possible, which facilitates calculation and improves the final calculation accuracy.

[0104] As a specific example, the first preset threshold and the second preset threshold are both 2.0.

[0105] As a preferred implementation, step S31 specifically includes the following steps:

[0106] When both of the anti-slip safety factor being greater than the first preset threshold and the anti-overturning safety factor being less than or equal to the second preset threshold are established at the same time, the anti-slip safety factor is calculated by back-calculating the anti-slip safety factor according to the formula in step S21 and the formula in step S23. Buoyancy equal to the first preset threshold ;

[0107] Design the drainage hole 40 to drain the area where the anchor 10 is located:

[0108] according to Calculate the target water level to which the groundwater level needs to be lowered, obtain the current groundwater level, and determine the water level drop depth of the anchor 10 foundation pit according to the current groundwater level and the target water level;

[0109] Using formula Get the water inflow of anchor 10 foundation pit ; Unit: m 3 / s, where k is the permeability coefficient, unit: m / d, H is the thickness of the phreatic aquifer, unit: m, which can be obtained from geological exploration drilling, and s is the water level drop of the anchor 10 foundation pit, unit: m, is the precipitation impact radius, unit: m, preferably, ; r0 is the equivalent radius of the foundation pit, unit: m; when the foundation pit is irregular in shape, ;

[0110] According to the water inflow of the anchor 10 foundation pit Determine the flow rate of drainage hole 40 , unit: m 3 / s;

[0111] According to the drainage hole 40 flow Calculate the effective cross-sectional area A of drainage hole 40, unit: m 2 .

[0112] Preferably, the steps are performed according to the flow rate of the drainage hole 40. The calculation of the effective cross-sectional area A of the drainage hole 40 specifically includes the following steps: according to the hydraulic calculation formula , calculate the effective cross-sectional area A of drainage hole 40, unit: m 2 ;in, is the flow rate, unit: m / s, , R is the hydraulic radius, unit: m, , n is the roughness coefficient of the drainage hole 40 wall, unit: , is the 40° wet perimeter of the drainage hole, unit: m, and i is the 40° longitudinal slope of the drainage hole.

[0113] Therefore, by designing the effective cross-sectional area A of the water flow, the corresponding buoyancy can be Meet the requirements, so that the anti-slip safety factor The design requirements are met. For drainage holes 40 with different cross-sectional shapes, it is sufficient to control the cross-sectional area to the effective cross-sectional area A of the water flow.

[0114] As another preferred implementation, the step S31 specifically includes the following steps:

[0115] When both of the anti-slip safety factor being greater than the first preset threshold and the anti-rollover safety factor being less than or equal to the second preset threshold are established at the same time, the anti-rollover safety factor is calculated by inverse calculation according to the formula in step S200. The buoyancy equal to the second preset threshold ;

[0116] Design the drainage hole 40 to drain the area where the anchor 10 is located:

[0117] according to Calculate the target water level to which the groundwater level needs to be lowered, obtain the current groundwater level, and determine the water level drop depth of the anchor 10 foundation pit according to the current groundwater level and the target water level;

[0118] Using formula Get the water inflow of anchor 10 foundation pit ;

[0119] According to the water inflow of the anchor 10 foundation pit Determine the flow rate of drainage hole 40 ;

[0120] According to the drainage hole 40 flow Calculate the effective cross-sectional area A of the water flow in drainage hole 40.

[0121] Therefore, by designing the effective cross-sectional area A of the water flow, the corresponding buoyancy can be Meet the requirements, so that the anti-overturning safety factor The design requirements are met. For drainage holes 40 with different cross-sectional shapes, it is sufficient to control the cross-sectional area to the effective cross-sectional area A of the water flow.

[0122] Preferably, the drainage hole 40 has a flow rate of The water inflow of anchor 10 foundation pit 2~3 times of.

[0123] Preferably, the roughness coefficient n of the wall of the drainage hole 40 is 0.013-0.014. For example, the drainage hole 40 is a reinforced concrete structure.

[0124] Please see attached Figures 2 to 6 As a preferred embodiment, the anchor 10 includes an anchor body 110, a first multi-stage tooth ridge 120 and a second multi-stage tooth ridge 130, wherein the first multi-stage tooth ridge 120 and the second multi-stage tooth ridge 130 are both arranged at the bottom of the anchor body 110, the first multi-stage tooth ridge 120 is used to prevent the anchor body 110 from sliding in the transverse direction, and the second multi-stage tooth ridge 130 is used to prevent the anchor body 110 from sliding in the longitudinal direction.

[0125] Specifically, the anchor body 110 is the main part that bears and transmits the tension. The first multi-stage tooth ridge 120 is used to prevent the anchor body 110 from sliding in the transverse direction of the bridge. The second multi-stage tooth ridge 130 is used to prevent the anchor body 110 from sliding in the longitudinal direction of the bridge, and can also prevent overturning in the longitudinal direction of the bridge. Through the multi-stage design, the tooth ridge can be more effectively embedded in the foundation rock layer, increasing the contact area and friction with the rock layer, thereby improving the anti-slip and anti-overturning effects. Through the multi-stage tooth ridge design in two directions, the contact area and friction between the anchor 10 and the foundation soil can be significantly increased, thereby improving the stability of the anchor 10 in complex terrain.

[0126] According to the present application, the anchor 10 foundation can be provided with a first multi-stage tooth ridge 120 and a second multi-stage tooth ridge 130 structure according to the situation of steep terrain and large fluctuations of rock formations, which can flexibly adapt to terrain changes, reduce mountain excavation, and reduce environmental damage; at the same time, the three-dimensional tooth ridge formed by the first multi-stage tooth ridge 120 and the second multi-stage tooth ridge 130 can form a composite bearing with the steep rock mass, which can improve the stress distribution of the anchor 10 base and improve the anti-sliding bearing capacity of the longitudinal and transverse anchor 10. After considering the anti-sliding effect of the tooth ridge, the volume of the anchor 10 can be further effectively reduced, and the engineering cost can be reduced.

[0127] As a preferred embodiment, the anchor body 110 includes an anchor block 1110, a loose cable saddle buttress 1120, and a loose cable saddle buttress foundation 1130, wherein the loose cable saddle buttress 1120 is cast on the top of the anchor block 1110 and the loose cable saddle buttress foundation 1130, and the loose cable saddle buttress 1120 is provided with a first front anchor chamber 1121;

[0128] A second front anchor chamber 1111 corresponding to the first front anchor chamber 1121 is formed in the anchor block 1110, and the first front anchor chamber 1121 and the second front anchor chamber 1111 together form a front anchor chamber (not shown) for placing the main cable saddle. A rear anchor chamber 1112 is also formed in the anchor block 1110 at the end away from the saddle buttress 1120. The first front anchor chamber 1121, the second front anchor chamber 1111 and the rear anchor chamber 1112 are sequentially arranged along the extension direction of the main cable, and the anchor block 1110 and the saddle buttress foundation 1130 are connected by a post-cast strip 1140.

[0129] The first multi-stage toothed step 120 is disposed at the bottom of the loose cable saddle buttress foundation 1130 , and the second multi-stage toothed step 130 is disposed at the bottom of the anchor block 1110 .

[0130] Specifically, the anchor block 1110 is the core load-bearing component of the anchor 10, preferably a huge concrete structure, which uses its own weight to anchor the main cable of the suspension bridge with strong tension. The anchoring of the main cable is as follows: first, a steel tie rod or prestressed pipe is pre-buried in the anchor body at the position corresponding to the main cable strand, and then the cable strand tension is transmitted to the anchor tie rod or prestressed steel strand through the main cable strand anchor head, and finally dispersed to the rear anchor surface of the anchor body.

[0131] As a closed space, the front anchor room protects the main cable strands and is composed of a top plate, a front wall, and side walls. The top plate preferably adopts a prefabricated hollow plate structure, which avoids the construction of cast-in-place brackets, saves the volume of concrete, and makes prefabricated hoisting construction simpler and saves construction time.

[0132] The rear anchor chamber 1112 is disposed in the anchor block 1110 and is a prestressing tensioning space in the anchor block 1110. The size of the rear anchor chamber 1112 is determined according to the space for the tensioning operation of the prestressed steel strand model in the anchor body.

[0133] The loose cable saddle buttress 1120 mainly bears the radial pressure of the main cable transmitted by the loose cable saddle, and preferably adopts a solid structure with better overall force-bearing performance.

[0134] The supporting reaction force of the main cable at the saddle of the anchor 10 is transmitted to the loose cable saddle pier foundation 1130 through the loose cable saddle pier 1120, and the loose cable saddle pier foundation 1130 evenly spreads the reaction force to the foundation. The loose cable saddle pier foundation 1130 is designed to use the medium weathered rock as the bearing layer. According to the boundary of the rock layer and the strength of the rock foundation itself, multiple tooth sills are set in the transverse direction of the bridge, and each tooth sill is 1 meter high. It can not only reduce the excavation of the mountain, but also improve the lateral stability of the anchor 10 under the unbalanced action of the main cable.

[0135] As the anchor 10 is subjected to the tension of the main cable, it has a tendency to overturn around the front edge of the loose cable saddle pier foundation 1130. A multi-stage toothed sill is set in the longitudinal direction of the front end of the anchor block 1110, and a large chamfer (beveled surface 1113) is set at the back to adapt to the change of the stratum, which can not only reduce excavation and improve the anti-sliding bearing capacity of the anchor 10, but also move the center of gravity of the anchor block 1110 backward, increase the distance between the front edge of the loose cable saddle pier foundation 1130 and the center of gravity of the anchor block 1110, and improve the overall anti-overturning property of the anchor 10.

[0136] In order to reduce the construction difficulty and avoid hydration thermal cracking of the large volume concrete of the anchor 10, a post-casting strip 1140 is provided, and the post-casting strip 1140 preferably uses 2m thick micro-expansion concrete.

[0137] Furthermore, the top surface of the anchor block 1110 and the top surface of the loose cable saddle pier foundation 1130 are both flat surfaces, and the top surface of the anchor block 1110 is flush with the top surface of the loose cable saddle pier foundation 1130. The flat top surface makes the measurement, positioning and installation work during the construction process easier. Workers can more easily ensure the alignment of the anchor block 1110 and the loose cable saddle pier foundation 1130 in the vertical direction, reducing construction errors and complexity.

[0138] As a preferred example, there are two loose cable saddle buttresses 1120, and the two loose cable saddle buttresses 1120 are arranged at intervals along the transverse direction of the bridge. The two loose cable saddle buttresses 1120 are arranged at intervals along the transverse direction of the bridge to form a more stable support structure. This layout helps to disperse and balance the load from the main cable and reduce the risk of structural damage caused by excessive force on a single buttress.

[0139] As a preferred embodiment, it also includes a bridge approach pier (not shown) cast on the top of the anchor block 1110. In order to improve the force efficiency of the anchor 10, the anchor 10 is usually arranged on both sides of the bridge axis, and there is often a conflict between the anchor 10 structure and the bridge approach pier and foundation. In a preferred embodiment, the bridge approach pier is set on the top of the loose cable saddle pier foundation 1130 and the top of the anchor block 1110 to realize that the anchor 10 body also serves as the pier, which can avoid the construction of the bridge approach pier foundation and improve the utilization efficiency of the anchor 10 structure.

[0140] Preferably, the top surface of the anchor block 1110 is downwardly provided with a first manhole 1114 connected to the rear anchor chamber 1112. The rear anchor chamber 1112 is an important part of the structure of the anchor 10, and its internal equipment and structure need to be regularly maintained and repaired. Through the first manhole 1114, the staff can easily enter the rear anchor chamber 1112 to perform necessary inspections and repairs to ensure the normal operation and safety of the anchor 10 structure.

[0141] Preferably, the loose cable saddle buttress 1120 is provided with a second manhole 1122 connected to the front anchor chamber. The front anchor chamber is an important structure formed by the loose cable saddle buttress 1120 and the anchor block 1110, and its internal equipment and structure need to be regularly maintained and inspected. Through the second manhole 1122, the staff can easily enter the front anchor chamber to inspect, repair or replace the internal equipment to ensure the normal operation and safety of the front anchor chamber.

[0142] Preferably, the post-cast strip 1140 is a post-cast strip 1140 formed by post-casting micro-expansion concrete. Micro-expansion concrete not only has the effect of reducing shrinkage cracks, but also can significantly improve the anti-permeability performance of concrete.

[0143] Preferably, a chamfered surface 1113 is provided at the tail end of the anchor block 1110 near the bottom surface.

[0144] Preferably, the first multi-stage tooth ridge 120 and the second multi-stage tooth ridge 130 both have two stages.

[0145] Please see attached Figures 7 to 12 In a preferred embodiment, an active drainage system for an anchor is provided, comprising a seepage ditch 20, a sump 30 and a drainage hole 40 arranged below the anchor 10; wherein the seepage ditch 20 is arranged below the anchor 10, and is used to collect bottom seepage water of the anchor 10; the sump 30 is connected to the seepage ditch 20, and the sump 30 is used to drain water from the seepage ditch 20 to the drainage hole 40; the drainage hole 40 is arranged below the sump 30 and is connected to the sump 30, and the drainage hole 40 is used to drain water from the sump 30.

[0146] Specifically, the complex mountainous terrain encountered in actual engineering projects, such as mountainous canyon areas, has the characteristics of steep terrain, large fluctuations in rock formations, developed joints and fissures, and abundant rock fissure water. Due to the abundant mountain fissure water, the present application sets the infiltration ditch 20 below the anchor 10 to collect the seepage water in the bottom area of ​​the anchor 10. The seepage water collected by the infiltration ditch 20 flows into the collection well 30 along the extension direction of the infiltration ditch 20. The water in the collection well 30 is discharged through the drainage hole 40. The coordinated work of the infiltration ditch 20, the collection well 30 and the drainage hole 40 constitutes an effective infiltration and drainage path.

[0147] The present application innovatively combines the drainage system with the anchor 10. The permanent drainage system adopted in the present application can not only effectively lower the groundwater level and reduce the buoyancy of the groundwater on the anchor 10, thereby reducing the concrete design volume of the anchor 10; it can also greatly reduce the subsequent maintenance costs and improve the durability of the anchor 10, and its economic effect is significant.

[0148] As a preferred embodiment, the infiltration ditch 20 includes a ditch body 210 extending in a transverse direction, a coarse gravel layer 220 arranged in the ditch body 210, and a permeable pipe 230 extending along the extension direction of the ditch body 210, the permeable pipe 230 is pre-buried in the coarse gravel layer 220, the ditch body 210 has two water outlets (not shown in the figure) arranged opposite to each other along its own extension direction, the water outlets are connected to the corresponding water collection wells 30, and the ditch body 210 has a drainage slope from the middle of the ditch body 210 toward the water outlet.

[0149] Specifically, the seepage ditch 20 can effectively collect the seepage water along the direction of the bottom of the anchor 10 through the design of the ditch body 210 extending in the transverse direction. The coarse gravel layer 220 provides good filtering and permeability, so that water can pass smoothly and flow to the permeable pipe 230. The permeable pipe 230 is pre-buried in the coarse gravel layer 220, further enhancing the drainage efficiency. The ditch body 210 has a drainage slope from the middle toward the water outlet, so that the water in the ditch body 210 can flow to the water outlet and be discharged faster.

[0150] As a preferred embodiment, it also includes a drainage ditch 50 arranged at the periphery of the anchor 10, the drainage ditch 50 is connected to the infiltration ditch 20, the drainage ditch 50 has a drainage slope toward the infiltration ditch 20, and the drainage ditch 50 is used to collect surface water on the slope.

[0151] Specifically, Figures 7 and 8 As shown, the arrow represents the direction of water flow. The drainage ditch 50 is set at the periphery of the anchor 10 to collect surface water from the slope, such as rainwater, snowmelt water and other surface runoff that may flow to the anchor 10 area. The drainage ditch 50 helps to reduce the scouring and erosion of the anchor 10 and the surrounding soil by water, thereby protecting the stability of the foundation of the anchor 10. The drainage ditch 50 is connected to the infiltration ditch 20, and the water collected in the drainage ditch 50 is finally discharged through the drainage hole 40.

[0152] As another preferred embodiment, it also includes a cut-off ditch 60 and a drainage ditch 70 located at the top of the slope, wherein the cut-off ditch 60 is used to intercept surface water from the top of the slope, and the drainage ditch 70 is connected to the cut-off ditch 60, and the drainage ditch 70 is used to drain the water from the cut-off ditch 60.

[0153] Specifically, the intercepting ditch 60 is set at the top of the slope, and its main function is to intercept the surface water from the top of the slope. By effectively intercepting the surface water, the scouring and erosion of the slope by the water flow is reduced, thereby protecting the stability of the slope. The drainage ditch 70 is connected to the intercepting ditch 60, and the surface water intercepted by the intercepting ditch 60 will be guided into the drainage ditch 70 and flow along the drainage ditch 70 to the designated discharge area.

[0154] Furthermore, a flow hole 410 communicating with the water collecting well 30 is opened at the top of the drainage hole 40 , and water from the water collecting well 30 enters the drainage hole 40 through the flow hole 410 .

[0155] Specifically, the setting of the flow hole 410 of this embodiment allows the water in the water collection well 30 to be discharged directly through the drainage hole 40 without passing through other complicated drainage paths, thereby reducing the risk of poor drainage or blockage caused by complicated paths.

[0156] Furthermore, an impermeable geotextile 240 is laid on the inner bottom surface of the ditch body 210. The impermeable geotextile 240 has excellent impermeability and can effectively prevent water from penetrating into the inner bottom surface of the ditch body 210.

[0157] As a specific example, the cross section of the water collection well 30 is in a square shape. In other embodiments, those skilled in the art can also set the cross section of the water collection well 30 to other shapes according to actual needs.

[0158] Furthermore, the cross section of the drainage hole 40 is any one of a rectangular, circular, and horseshoe shape. Those skilled in the art can flexibly select according to actual needs.

[0159] As a specific example, the side wall slope ratio of the trench body 210 is set to 3:1.

[0160] As a preferred example, the water permeable pipe 230 is a PVC water permeable pipe 230 with a diameter of 300 mm.

[0161] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent structure or equivalent process transformation made by using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the protection scope of the present invention.

Claims

1. A design method for a gravity anchor suitable for complex mountainous terrain, characterized in that: The following steps are involved: S1, determining the basic minimum size of the anchor according to the principle of minimizing the volume of the anchor and minimizing the amount of foundation pit excavation, and obtaining the current design structure of the anchor; S2, calculating the anti-slip safety factor and the anti-overturning safety factor of the current design structure of the anchor in the area, and determining whether the anti-slip safety factor is greater than a first preset threshold, and determining whether the anti-overturning safety factor is greater than a second preset threshold. If not, proceed to steps S31 to S34; if yes, proceed to step S35; S31, when either the anti-slip safety factor is greater than a first preset threshold value or the anti-overturning safety factor is greater than a second preset threshold value is not established, it is determined that the current design structure of the anchor does not meet the design requirements, and drainage design is performed on the area where the anchor is located to lower the groundwater level in the area where the anchor is located; S32, obtaining the design water level of the anchor in the area where it is located, and determining whether the design water level is lower than or equal to the minimum design elevation of the anchor; S33, when the design water level is lower than or equal to the minimum design elevation of the anchor, increase the volume of the anchor according to a preset volume increment, and then return to step S2; S34, when the designed water level is higher than the minimum elevation of the anchor base, continue to perform drainage design on the area where the anchor is located, so that the groundwater level in the area where the anchor is located continues to drop, and then return to step S2; S35, determining whether the current design structure of the anchor meets the design requirements.

2. The design method of gravity anchorage suitable for complex mountainous terrain according to claim 1 is characterized in that: The step S1 specifically includes the following steps: Establishing an overall bridge model, and calculating the sum of the tensions of the main cables according to the overall bridge model; Calculate the required anchor weight based on the sum of the tension of the main cables; Obtaining the anchoring mode of the main cable strand, and preliminarily determining the minimum size of the front anchor chamber and the minimum size of the rear anchor chamber according to the anchoring mode of the main cable strand and the weight of the anchor; wherein the anchor comprises an anchor body, a first multi-stage toothed step for preventing the anchor body from sliding in the transverse direction of the bridge, and a second multi-stage toothed step for preventing the anchor body from sliding in the longitudinal direction of the bridge, and a front anchor chamber and a rear anchor chamber are formed inside the anchor body, and the rear anchor chamber and the front anchor chamber are arranged correspondingly; Obtaining the rock layer distribution data and the bearing capacity data of the bearing layer in the area where the anchor is located, and determining the minimum burial depth of the anchor body according to the rock layer distribution data, the bearing capacity data of the bearing layer and the weight of the anchor; The number of the first multi-level tooth ridges, the number of the second multi-level tooth ridges, the height of each first multi-level tooth ridge and the height of each second multi-level tooth ridge are determined based on the principle of minimum volume and minimum foundation pit excavation.

3. The design method of gravity anchorage suitable for complex mountainous terrain according to claim 2 is characterized in that: The anchor body includes an anchor block and a loose-cable saddle pier foundation, the loose-cable saddle pier foundation includes a first part with a flat bottom surface and a second part with the first multi-stage tooth ridges arranged on the bottom surface, the anchor block includes a third part with a flat bottom surface and a fourth part with the second multi-stage tooth ridges arranged on the bottom surface, and the number of the first multi-stage tooth ridges is the same as the number of the second multi-stage tooth ridges.

4. The design method of gravity anchorage suitable for complex mountainous terrain according to claim 3 is characterized in that: The calculation of the anti-slip safety factor of the current design structure of the anchor in the area in step S2 specifically includes the following steps: S21, using the formula Obtaining the anti-slip force of the anchor ;in, , G v is the weight of the anchor, G a is the weight of the backfill soil of the anchor pit, N is the sum of the vertical loads of the approach bridge piers set at the top of the anchor, T is the sum of the tension of the main cable, θ is the angle between the main cable and the horizontal plane, S 总 is the anchor base area, The friction angle of the basement rock, c is the cohesion of the basement rock, is the anchor base stress; represents the number of units of the first part divided according to the number of stages of the first multi-stage tooth ridge, represents the number of units in the second part divided according to the number of levels of the first multi-level tooth ridge, Indicates the number of units in the third part divided according to the number of levels of the second multi-level tooth ridge, Indicates the number of units in the fourth part divided according to the number of stages of the second multi-stage tooth ridge; F 浮 is the buoyancy of the anchor caused by groundwater; is the friction angle of the basement rock layer of the ith unit, is the cohesion of the basement rock layer of the ith unit, is the anchor base area corresponding to the i-th unit; S22, using the formula Determine the sliding force on the anchor caused by the sum of the tension of the main cables ; S23, using the formula Calculate the anti-slip safety factor of the current design of the anchor in the area .

5. The design method of gravity anchorage suitable for complex mountainous terrain according to claim 4 is characterized in that: The anti-overturning safety factor in step S2 is obtained by the following steps: S200, using the formula Calculate the anti-overturning safety factor of the current design configuration of the anchor in the area where it is located ;in, Indicates the number of units divided by the anchorage. Indicates the number of units into which the anchor pit backfill soil is divided. Indicates the number of units divided into the approach bridge piers, G vi is the weight of the anchor unit, G aj is the weight of the anchor pit backfill unit, N k is the vertical load of the approach bridge pier unit, d vi is the distance between the ith anchor unit and the rotation axis, d aj is the distance between the jth anchor pit backfill unit and the rotation axis, d Nk is the distance between the kth approach bridge pier unit and the rotation axis, d 浮 is the distance between the buoyancy of the anchor caused by groundwater and the rotation axis, d T The vertical distance from the rotation axis under the action of the sum of the tension of the main cables; among them, the front toe line of the base of the anchor body is the rotation axis, and the anti-overturning moment The overturning moment is the sum of the weight of the anchor, the weight of the backfill soil of the anchor foundation pit, and the vertical load of the approach bridge set on the top of the anchor on the rotation axis. It is the sum of the tension of the main cable and the sum of the moments generated by the buoyancy generated by the groundwater on the rotating shaft.

6. The design method of gravity anchorage suitable for complex mountainous terrain according to claim 5 is characterized in that: The first preset threshold and the second preset threshold are both 2.

0.

7. The design method of gravity anchorage suitable for complex mountainous terrain according to claim 5 is characterized in that: The step S31 specifically includes the following steps: When both of the anti-slip safety factor being less than or equal to the first preset threshold and the anti-overturning safety factor being greater than the second preset threshold are established at the same time, the anti-slip safety factor is calculated by inverse calculation according to the formula in step S21 and the formula in step S23. Buoyancy equal to the first preset threshold ; Design drainage holes to drain the area where the anchor is located: according to Calculate the target water level to which the groundwater level needs to be lowered, obtain the current groundwater level, and determine the depth of the anchor pit water level drop based on the current groundwater level and the target water level; Using formula Obtain the water inflow of the anchor pit ; where k is the permeability coefficient, H is the thickness of the phreatic aquifer, and s is the water level drop of the anchor pit. is the precipitation influence radius, r0 is the equivalent radius of the foundation pit; According to the water inflow of the anchor pit Determining drainage hole flow ; According to the drainage hole flow Calculate the effective cross-sectional area A of the drainage hole.

8. The design method of gravity anchorage suitable for complex mountainous terrain according to claim 7 is characterized in that: The step S31 specifically includes the following steps: When both of the anti-slip safety factor being greater than the first preset threshold and the anti-rollover safety factor being less than or equal to the second preset threshold are established at the same time, the anti-rollover safety factor is calculated by inverse calculation according to the formula in step S200. The buoyancy equal to the second preset threshold ; Design drainage holes to drain the area where the anchor is located: according to Calculate the target water level to which the groundwater level needs to be lowered, obtain the current groundwater level, and determine the depth of the anchor pit water level drop based on the current groundwater level and the target water level; Using formula Obtain the water inflow of the anchor pit ; According to the water inflow of the anchor pit Determining drainage hole flow ; According to the drainage hole flow Calculate the effective cross-sectional area A of the drainage hole.

9. The design method of gravity anchorage suitable for complex mountainous terrain according to claim 7 is characterized in that: The steps are based on the drainage hole flow The calculation of the effective cross-sectional area A of the drainage hole specifically includes the following steps: According to the hydraulic calculation formula , calculate the effective cross-sectional area A of the drainage hole; where, is the flow rate, , R is the hydraulic radius, , n is the roughness coefficient of the drainage hole wall, is the wetted perimeter of the drainage hole, and i is the longitudinal slope of the drainage hole.

10. The design method of gravity anchorage suitable for complex mountainous terrain according to claim 7, characterized in that: The drainage hole flow The water inflow of anchor pit 2~3 times of.

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