A method for calculating the bearing capacity of a vertical anchoring cylinder anchoring structure

Abstract

This invention relates to a method for calculating the bearing capacity of a vertical anchoring cylinder anchoring structure in the field of foundation pit and slope protection engineering. The main steps include: a) determining point D, the point of equal earth pressure on both sides of the retaining pile; b) calculating the theoretical straight sliding surface AD ​​of the soil passing through point D; c) determining the theoretical straight sliding surface OF of the passive zone outside the pit, passing through the intersection line between the ground surface and the retaining pile (or wall), and determining the intersection line E between the OF surface and the AD surface or the excavation face; determining the theoretical straight sliding surface DC of the passive zone outside the pit, passing through point D; d) calculating the passive earth pressure p at point F. pFk Calculate the passive earth pressure p along line E. pEk ; use p pFk As the soil resistance of section CD, the soil resistance above line E and below point C is taken as 0. The soil resistance of sections EF and FD is calculated according to a linear distribution to determine the bearing capacity of the anchoring cylinder. This invention uses a graphical method to calculate the bearing capacity of the anchoring cylinder, which solves the problem of calculating the bearing capacity of the anchoring cylinder under excavation conditions, which is difficult to determine through experiments. The calculation speed is fast and the accuracy is high.

Description

A method for calculating the bearing capacity of a vertical anchoring cylinder anchorage structure Technical Field

[0001] This invention relates to a method for calculating the bearing capacity of a vertical anchoring cylinder anchoring structure in the field of foundation pit and slope protection engineering. Background Technology

[0002] Utilizing deep soil to provide tensile bearing capacity is an important design and construction method used in civil and hydraulic engineering. Its main applications include anchor bolt technology, anchor plate technology, pull-out foundations, anchors, and other foundation forms requiring tensile bearing capacity in foundation pit and slope engineering. The core idea of ​​anchor bolt technology is to drive a slender rod into deep soil and rock, providing tensile bearing capacity through the connection between the rod, the anchor body, and the soil and rock, and transmitting it through the rod. Anchor bolt technology is fast to construct and inexpensive, making it widely used in civil and hydraulic engineering. Anchor bolts primarily provide pull-out bearing capacity through side friction; however, there is also the technique of enlarged-hole anchor bolts, which involves designing an enlarged-hole section within the anchor bolt to provide some end resistance as part of the pull-out bearing capacity. However, anchor bolt technology has the following problems: (1) Anchor bolts require anchoring soil layers with high bearing capacity, which makes them difficult to use in soft soil; (2) Anchor bolts require a large area of ​​underground space, which limits the application of anchor bolt technology. Although various recyclable anchor bolts have been developed, they still have problems such as large temporary underground space occupation, low recycling rate, small construction space for recycling operations, difficult recycling construction, and high cost, which limit the application of anchor bolts in many engineering projects. In order to improve the bearing capacity of anchor bolts, plate-shaped components are pre-embedded in backfill soil, and tensile members are used to transfer the pull-out bearing capacity provided by the plate-shaped components. In civil engineering, this is called an anchor plate structure. The anchor plate structure has high bearing capacity, but the tensile members and the anchor plate need to be connected and buried in the soil. Therefore, it is generally only applicable in backfill soil. In addition, pull-out piles mainly use the friction between the soil and the pile body to provide pull-out bearing capacity. Various forms of enlarged-base pull-out piles use enlarged heads to improve the pull-out bearing capacity of pull-out piles, but the utilization of the pull-out bearing capacity of deep soil is still insufficient. How to better utilize the uplift bearing potential of deep rock or soil, how to completely eliminate useless solid residues in the rock or soil after construction, purify underground space, and realize the recycling and reuse of solid materials have significant engineering practical significance and environmental benefits. Furthermore, the field of geotechnical anchoring engineering requires providing enormous horizontal or oblique tensile forces, such as anchors for suspension bridges, anti-overturning and anti-sliding of tall structures, and anti-sliding and anti-overturning of dams. Providing anchoring structures with high reliability, large anchoring force, and low cost has broad application prospects in the field of geotechnical anchoring engineering. In 2021, the inventors proposed an anchoring cylinder anchoring structure (patent application number: 2021106762672), and proposed the construction and construction method of the anchoring cylinder anchoring structure.This type of anchoring tube anchoring structure comprises five parts: the anchored component, the anchoring tube, the tension member, the anchored component connection, and the anchoring tube connection. The anchored component is the component requiring tensile force. The anchoring tube is a hollow tubular component that provides the construction working surface for the anchoring tube connection. The tension member is a component with tensile bearing capacity, embedded in rock or soil, with one end connected to the anchored component and the other end connected to the anchoring tube. The anchoring tube is located in the rock or soil and provides the anchoring force. The tension member passes through the sidewall of the anchoring tube and extends to the hollow part of the anchoring tube. The anchored component connection is a component or combination of components that firmly connects the tension member and the anchored component. The anchoring tube connection is a component or combination of components that firmly connects the tension member and the anchoring tube. Vertical anchoring tube anchoring structures are a commonly used structural form, referring to anchoring tube anchoring structures where the anchoring tube is placed vertically in rock or soil. The calculation of the bearing capacity of this type of anchoring structure is directly related to engineering safety and cost, and currently there are no practically usable research results. For example, in foundation pit support, when the anchoring cylinder provides the anchoring bearing capacity, the foundation pit is in an excavated state, and the anchoring cylinder is located in the soil slope outside the foundation pit. The bearing mechanism is complex, and many factors influence the support force provided by the soil and rock mass, including the properties and distribution of the foundation soil, the influence of foundation pit excavation and retaining components, and the interaction between the anchoring cylinder components and the soil and rock mass. It is particularly important to emphasize that the influence of foundation pit excavation and soil unloading on the vertical anchoring cylinder anchoring structure in foundation pit support, which has a significant impact on the anchoring cylinder bearing capacity, is difficult to determine through experiments. Therefore, theoretical calculation and analysis are even more important. Summary of the Invention

[0003] The purpose of this invention is to provide a method for calculating the bearing capacity of a vertical anchoring tube anchoring structure. This method can take into account the influence of the free surface and the excavation surface on its bearing capacity, and can calculate the bearing capacity of the vertical anchoring tube more accurately. It is particularly suitable for foundation pit support engineering calculations.

[0004] The method for calculating the bearing capacity of this type of vertical anchoring cylinder anchoring structure includes the following steps:

[0005] a) Based on the excavation depth of the foundation pit and the physical and mechanical characteristics of the soil layers, calculate the active earth pressure on the outside of the foundation pit and the passive earth pressure on the inside of the foundation pit, and determine the location and depth of the equal value point (marked as point D) of the earth pressure on both sides of the retaining pile (or wall).

[0006] b) Calculate the theoretical straight sliding surface of the soil (marked as AD surface) at the isopleth point (point D) determined in step a) without considering the effect of retaining piles (or walls);

[0007] c) When the anchor cylinder moves from the outside of the pit into the pit, it passes through the theoretical straight sliding surface of the passive zone outside the pit (marked as OF surface) that intersects the ground surface with the retaining pile (or wall), and marks the intersection of the OF surface and the anchor cylinder as point F. Determine the angle between the OF surface and the horizontal plane, and determine the intersection line of the OF surface with the AD surface or excavation face determined in step b). Mark the position of the intersection line as line E. When the anchor cylinder moves from the outside of the pit into the pit, it passes through the equipotential point (point D) determined in step a). Mark the theoretical straight sliding surface of the passive zone outside the pit (marked as DC surface) that intersects the DC surface with the anchor cylinder as point C.

[0008] d) Calculate the passive earth pressure at the depth of point F determined in step c), denoted as p. pFk The passive earth pressure at the depth location of line E determined in step c) is denoted as p. pEk ;

[0009] e) The passive earth pressure p at the depth of point F calculated in step d) pFk The soil resistance acting on the anchoring cylinder from the depth of point C determined in step c) to the depth of point D determined in step a) is represented by the passive earth pressure p at the depth of point F. pFk As the minuend, the quotient obtained by dividing the depth difference between points D and F by the depth difference between point D and line E is then multiplied by the passive earth pressure p at the depth position of line E calculated in step d). pEk As a subtraction factor, the calculated difference is taken as the resistance of the foundation soil acting on the anchor tube at point F. The resistance of the foundation soil acting on the anchor tube at depths above and below the E line and depths below the C point is taken as zero. The resistance of the foundation soil acting on the anchor tube between the E line and point F, and between point F and point D, is calculated according to a linear distribution. The ultimate bearing capacity of the anchor tube is calculated through the resistance of the foundation soil acting on the anchor tube.

[0010] In the above-mentioned method for calculating the bearing capacity of the vertical anchoring tube anchorage structure, in step e), when the calculated ultimate bearing capacity of the anchoring tube is greater than the anchoring tube bearing capacity determined by the vertical pull-out bearing capacity limit of the anchoring tube, the anchoring tube bearing capacity calculated by the vertical pull-out bearing capacity of the anchoring tube is used as the ultimate bearing capacity of the anchoring tube.

[0011] In the above-mentioned method for calculating the bearing capacity of the vertical anchoring tube anchoring structure, in steps b) and c), for stratified soil foundations, the equivalent internal friction angle of the soil is used for calculation. The value of the equivalent internal friction angle is taken as the internal friction angle of each relevant soil layer weighted by thickness.

[0012] The present invention provides a method for calculating the bearing capacity of vertical anchoring tubes under excavation conditions. This method addresses the challenge of calculating the bearing capacity of vertical anchoring tubes under excavation conditions. Through multi-step theoretical analysis, a practical method for calculating the bearing capacity of vertical anchoring tubes is proposed. This method solves the problem of calculating and analyzing the bearing capacity of anchoring tubes when it is difficult to directly determine the bearing capacity through experiments under excavation conditions. The method is fast, reliable, and accurate, and has been verified through foundation pit excavation practice. Attached Figure Description

[0013] Figure 1 is a force analysis diagram of the vertical anchoring cylinder anchoring structure in the foundation pit support under the ultimate bearing state in an embodiment of the present invention;

[0014] Figure 2 is a simplified diagram of the calculation of the horizontal bearing capacity of a single cylinder using the pressure diffusion angle method under conditions without the group cylinder effect, according to an embodiment of the present invention.

[0015] Figure 3 is a simplified diagram of the calculation of the horizontal bearing capacity of a single cylinder under the pressure diffusion angle method under the condition of generating a group of cylinders in an embodiment of the present invention.

[0016] Figure 4 is a plan view of the anchor cylinder foundation pit support used in an embodiment of the present invention;

[0017] Figure 5 is a cross-sectional view of the anchor cylinder foundation pit support used in an embodiment of the present invention;

[0018] Figure 6 is a scene diagram (photo) of anchor cylinder foundation pit support used in an embodiment of the present invention;

[0019] Figure 7 is a graph showing the monitoring results of the horizontal displacement of each depth of the anchor cylinder relative to the top in the anchor cylinder foundation pit support of an embodiment of the present invention.

[0020] Figure 8 shows the results of horizontal displacement monitoring of deep soil in the foundation pit supported by the anchor cylinder in one embodiment of the present invention. Detailed Implementation

[0021] Explanation of reference numerals in the attached drawings: 1-Anchoring cylinder; 2-Anchored component; 3-Tension component; 4-Theoretical straight sliding surface of the active zone outside the pit; 5-Theoretical straight sliding surface of the passive zone inside the pit; 6-Anchoring cylinder connection; 7-Anchored component connection.

[0022] As an embodiment of the present invention, the method for calculating the bearing capacity of the vertical anchoring cylinder anchoring structure of the present invention is described below with reference to Figures 1 to 8. In this embodiment, a practical application case of anchoring cylinder foundation pit support is first introduced. The composition of the foundation soil and the main conventional physical and mechanical properties of the application case are shown in Table 1. φ1220×12×14500 steel pipes are used as anchoring cylinders and driven into the soil using the vibration method. The plan layout of the anchoring cylinder support foundation pit is shown in Figure 4, and the cross-sectional view is shown in Figure 5. The anchoring cylinder foundation pit support described in this embodiment was implemented starting in October 2021 and can be divided into the following five stages: the first stage is to tension the tension members under the condition that the foundation pit is filled with water up to the bottom of the waist beam; the second stage is to remove the two steel supports set before the installation of the anchoring cylinder; the third stage is to drain the water filled into the foundation pit; the fourth stage is to fill the foundation pit with water again and backfill; the fifth stage is to drain the water filled into the foundation pit again. The duration of each stage and the observation results of the anchoring cylinder and the foundation pit deformation are shown in Table 2. The deformation of the anchoring cylinder at each stage is shown in Figure 7. The monitoring values ​​of the lateral displacement of the deep soil in the foundation pit are shown in Figure 8.

[0023] Table 1. Distribution of Main Foundation Soil Layers and Conventional Physical and Mechanical Properties of Anchored Pit Support Site

[0024]

[0025] The following describes the specific implementation steps of the method for calculating the bearing capacity of the vertical anchoring structure of the present invention, based on the above-mentioned case of anchoring cylinder foundation pit support.

[0026] First, under plane strain conditions and with sufficient vertical tensile bearing capacity of the anchoring cylinder, the stress analysis of the vertical anchoring structure in the foundation pit support under the ultimate bearing state is shown in Figure 1. Based on the foundation pit depth of 6m and the distribution and main physical and mechanical characteristics of the foundation soil (see Table 1 above), the active earth pressure on the outside of the foundation pit and the passive earth pressure on the inside of the foundation pit can be calculated according to the current standard "Technical Specification for Foundation Pit Support" (JGJ120-2012). This determines the location and depth of the isopleth point D on both sides of the retaining pile (or wall). Simultaneously, the depth and other parameters of each point shown in Figure 1 can be calculated. The calculation results are shown in Table 3.

[0027] Table 2 Monitoring Results of Anchored Pit Support (Positive values ​​are for the inside of the pit)

[0028]

[0029] Second, calculate the theoretical straight sliding surface, that is, determine the angle (45° - ψ) between the AD surface and the vertical plane as shown in Figure 1. m / 2), where ψ m Let ψ be the internal friction angle of a homogeneous soil layer. For stratified soils, ψm The value is taken as the equivalent internal friction angle (°) of each soil layer above point D, weighted by thickness. In this embodiment, ψ m The calculated value is 30.58°, as shown in Table 3.

[0030] Table 3. Calculation of Passive Earth Pressure under Plane Strain Conditions in Case Studies of Anchored Pit Support.

[0031]

[0032] Third, determine the theoretical straight sliding surface OF of the passive zone outside the pit, which passes through the intersection of the ground surface and the retaining pile (or wall) when the anchoring cylinder moves from the outside of the pit into the pit. That is, determine the angle between the OF surface and the horizontal plane as shown in Figure 1 (45° - ψ). m / 2), point F is located on the intersection line of the anchoring cylinder and the OF surface, determine the position of the intersection line E between the OF surface and the AD surface; determine the theoretical straight sliding surface DC of the passive zone outside the pit passing through point D, that is, determine the angle (45° + ψ) between the DC surface and the vertical plane as shown in Figure 1. m / 2), ψ m The method for obtaining the value is the same as in step b). OF / / DC. In this step, referring to Figure 1, the depth calculation value Z of points C, D, E, and F is determined using a graphical method for the two anchor cylinders used in the anchor cylinder foundation pit support on the east and west sides, as shown in Figures 4 to 6. C Z D Z E Z F The calculated values ​​are shown in Table 3.

[0033] Fourth, the passive earth pressure p from the ground surface to section F can be calculated according to the "Technical Specification for Foundation Pit Support" (JGJ120-2012). pFk passive earth pressure p from the surface to section E pEk In this embodiment, for the anchoring cylinders used on the east and west sides, the calculation results of the passive earth pressure at point F and point E are shown in Table 3. The passive earth pressure at the ground surface is 0, so it can be considered that the earth pressure between the ground surface and point F and between the ground surface and point E are linearly distributed. Thus, the passive earth pressure distribution of the two segments is determined, completing the fourth step and proceeding to the fifth step.

[0034] Fifth, for homogeneous soil, as shown in Figure 1, the resultant passive earth pressure between points F and C is only proportional to the depth. Therefore, the passive earth pressure distribution on the anchoring cylinder in section FC is equal, as shown in Figure 1. The passive earth pressure acting on the anchoring cylinder is generated by the combined action of the stable slope ABCD and the unstable slope OAD, as shown in Figure 1. The distribution ratio of the two is linearly related to the length of the theoretical slip surface. Point D is entirely generated by the stable slope. The passive earth pressure acting on the anchoring cylinder should deduct the portion transmitted to the retaining piles (or walls) by the sliding slope. The remaining portion can be used as the limit value of the horizontal bearing capacity of the anchoring cylinder. That is, the resultant force of the earth pressure in the filling portion shown in Figure 1 is the maximum effective horizontal bearing capacity of the anchoring cylinder. In this embodiment, the passive earth pressure acting on the portion below point C on the anchoring cylinder is also beneficial to improving the bearing capacity of the anchoring cylinder and can be used as a safety reserve. The bearing capacity of the anchoring cylinder is transmitted obliquely to the retaining piles (or walls) by the tension member. The anchoring cylinder also needs to meet the requirements of vertical pull-out bearing capacity. For the portion below point H, the reduction in bearing capacity caused by the active earth pressure on the side of the anchor cylinder facing away from the foundation pit needs to be considered. For foundation pit support engineering, the retaining piles (or walls), anchor cylinder, and the soil and rock mass between them should be treated as a whole for calculations on anti-sliding, anti-overturning, pit bottom heave, and overall stability. The inclination angle and distribution of tension members also have a significant impact on the bearing capacity of the anchor cylinder. In this embodiment, as shown in Figure 1, the distance between the anchor cylinder and the retaining piles (or walls) is crucial to the bearing capacity of the anchor cylinder; the bearing capacity of shallow soil layers can be ignored, and sufficient anchor cylinder embedment depth is necessary. For anchor cylinders in silt, silty soil, and fill, the angle between the theoretical straight slip surface and the vertical plane should be appropriately increased, and it is advisable to utilize deeper, higher-strength soil layers to provide horizontal bearing capacity. According to Figure 1, the resultant force point of the tension member (3) on the side of the retaining pile (or wall) should preferably be near the resultant force point of the active earth pressure acting on the retaining pile (or wall) in the OD section. The resultant force point on the side of the anchor tube can be set near the resultant force point of the active and passive earth pressure acting above point C of the anchor tube, thereby determining the inclination angle of the tension member. Multiple tension members can be set. According to Figure 1, when designing the anchor tube support structure, the horizontal distance between the anchor tube and the retaining pile (or wall) should first be determined according to the site conditions. Under the condition that the site allows, the horizontal distance should be large enough. Since the cost of tension members is relatively low, a larger horizontal distance can reduce the design depth of the anchor tube and save engineering costs. In this step, the calculation of the bearing capacity of a single anchor tube includes two parts: the calculation of the ultimate horizontal bearing capacity of a single tube and the calculation of the vertical pull-out bearing capacity of a single tube. Among them, the calculation of the ultimate horizontal bearing capacity of a single cylinder can take the DO surface and OB surface shown in Figure 1 as free surfaces. For sandy soil layers, the stress diffusion angle method can be used for estimation, that is, refer to Figure 2 and Figure 1, and use formula (1) for calculation.

[0035]

[0036] In the formula:

[0037] N axk - Horizontal component of the ultimate bearing capacity of the vertical anchoring cylinder;

[0038] p pzk Passive earth pressure acting on the anchor cylinder under plane strain conditions at depth -z;

[0039] p azk Active earth pressure acting on the anchoring cylinder under plane strain conditions at depth -z;

[0040] d - Diameter of the anchoring cylinder;

[0041] L z The horizontal distance between the central axis of the anchoring cylinder at depth -z and the theoretically calculated straight sliding surface;

[0042] θ - Ground stress diffusion angle.

[0043] As can be seen from Figure 2 and Equation (1), when the anchoring cylinder spacing D is less than (d+2L) z When tanθ), a group tube effect will occur, which will prevent the horizontal bearing capacity of a single tube from being fully utilized. When the anchor tubes overlap each other, they will reach the planar state shown in Figure 1.

[0044] Based on Table 1 and Figure 2, the calculated values ​​of the ultimate horizontal bearing capacity of a single cylinder are shown in Table 4.

[0045] As shown in Table 4, the calculation of the ultimate horizontal bearing capacity of a single cylinder is of guiding significance for the design calculation of vertical anchoring cylinder anchoring structures. Once the location and embedment depth of the single cylinder are determined, the ultimate horizontal bearing capacity of the single cylinder can be calculated, and the influence of the group cylinder effect can be considered in conjunction with Figure 3. By matching the depth of the resultant force application point with the setting depth of the anchoring cylinder connection, and then verifying the vertical pull-out bearing capacity of the single cylinder of the anchoring cylinder, and considering an appropriate safety factor, the main design calculation contents of the anchoring cylinder anchoring structure can be completed.

[0046] In the fifth step of this embodiment, when determining the ultimate bearing capacity of a single cylinder, the limit of its ultimate vertical uplift bearing capacity should also be considered. When calculating the ultimate vertical uplift bearing capacity of the single cylinder, the normal soil pressure acting on the sidewall of the anchored cylinder is p on the side near the foundation pit. pzk When active earth pressure is used on the side away from the foundation pit, the hydrostatic pressure should be deducted during the calculation. Formula (2) can be used for calculation.

[0047]

[0048] In the formula:

[0049] μ - the friction coefficient between the anchoring cylinder and the soil, which can be taken from Section 7.1;

[0050] c p - The bonding strength between the anchoring cylinder and the soil can be determined with reference to Section 7.1;

[0051] p 0k The remaining part of the static earth pressure at depth -z after deducting the hydrostatic pressure.

[0052] z T - Anchoring cylinder bottom burial depth;

[0053] G c -Weight of the anchor cylinder (minus buoyancy);

[0054] The meanings of the other symbols are the same as before.

[0055] In the fifth step of this embodiment, the most reasonable design scheme can be determined by calculating the optimal horizontal inclination angle of the tension member.

[0056] From equations (1) and (2), the optimal horizontal inclination angle of the tension member can be calculated according to equation (3).

[0057]

[0058] In the formula:

[0059] α max -Optimal horizontal tilt angle for tension members;

[0060] The meanings of the other symbols are the same as before.

[0061] The ultimate vertical pull-out bearing capacity of the single tube and the optimal horizontal inclination angle of the tension member calculated according to equations (2) and (3) are shown in Table 4.

[0062] Table 4 Calculated values ​​of single-tube bearing capacity in anchored tube foundation pit support

[0063]

[0064] In the fifth step of this embodiment, the bearing capacity calculation of the vertical anchoring cylinder anchoring structure can be completed by the following method.

[0065] As shown in Table 4, to fully utilize the single-tube bearing capacity, the anchoring tube connection should be moved down to the depth of the resultant force of the ultimate horizontal bearing capacity, and the wainscoting should be moved down to make the tension member consistent with the calculated value of the ideal horizontal inclination angle. Alternatively, the depth of the anchoring tube can be increased to improve its vertical pull-out bearing capacity. In this embodiment, the west anchoring tube experienced an upward pull-out of approximately 4 mm relative to the ground surface. During loading, the back soil surface anchored on the west side developed a separation crack at the ground surface, with a crack width of approximately 7 mm. The east anchoring tube did not exhibit the above problem. According to the monitoring results, the horizontal bearing capacity provided by the anchoring tube in actual use is 848 kN. The ultimate bearing capacity value of the anchoring tube calculated according to the method of this invention is close to the measured value. Detailed calculation comparison is shown in Table 5.

[0066] Table 5 Comparison of calculated and measured values ​​of vertical pull-out bearing capacity of single-tube anchored foundation pit support.

[0067]

[0068]

[0069] As shown in Table 4, in this embodiment, the horizontal bearing capacity of the anchor tube has not been fully utilized, but the vertical bearing capacity is close to the calculated limit value. In the experiment, the anchor tube was observed to be slightly pulled up and rise above the ground surface. This also shows that the anchor tube calculation theory and method introduced in this section have important engineering reference value.

[0070] This patent includes, but is not limited to, other similar methods that can be used by those skilled in the art.

Claims

1. A method for calculating the bearing capacity of a vertical anchoring cylinder anchorage structure, comprising the following steps: a) Based on the excavation depth and the physical and mechanical characteristics of the soil layers, calculate the active earth pressure on the outside of the excavation pit and the passive earth pressure on the inside of the excavation pit, and determine the location and depth of the isopleth point (marked as point D) of the earth pressure on both sides of the retaining piles (or walls); b) Calculate the theoretical linear sliding surface of the soil (marked as surface AD) passing through the isopleth point (point D) determined in step a) without considering the action of the retaining piles (or walls); c) Determine the location of the anchoring cylinder outside the pit that crosses the intersection line between the ground surface and the retaining piles (or walls) when it moves from the outside of the pit into the pit. The passive zone theoretical straight sliding surface (marked as OF surface) is determined, and the intersection of OF surface and anchor cylinder is marked as point F. The angle between OF surface and horizontal plane is determined, and the intersection line between OF surface and AD surface or excavation surface determined in step b) is determined. The position of the intersection line is marked as line E. When the anchor cylinder moves from outside the pit into the pit, the passive zone theoretical straight sliding surface (marked as DC surface) outside the pit passes through the isopleth point (point D) determined in step a) is determined, and the intersection of sliding surface DC surface and anchor cylinder is marked as point C. d) Calculate the passive earth pressure at the depth of point F determined in step c), denoted as p. pFk The passive earth pressure at the depth location of line E determined in step c) is denoted as p. pEk e) The passive earth pressure p at the depth of point F calculated in step d) pFk The soil resistance acting on the anchoring cylinder from the depth of point C determined in step c) to the depth of point D determined in step a) is represented by the passive earth pressure p at the depth of point F. pFk As the minuend, the quotient obtained by dividing the depth difference between points D and F by the depth difference between point D and line E is then multiplied by the passive earth pressure p at the depth position of line E calculated in step d). pEk As a subtraction factor, the calculated difference is taken as the resistance of the foundation soil acting on the anchor tube at point F. The resistance of the foundation soil acting on the anchor tube at depths above and below the E line and depths below the C point is taken as zero. The resistance of the foundation soil acting on the anchor tube between the E line and point F, and between point F and point D, is calculated according to a linear distribution. The ultimate bearing capacity of the anchor tube is calculated through the resistance of the foundation soil acting on the anchor tube.

2. The method for calculating the bearing capacity of the vertical anchoring cylinder anchorage structure according to claim 1, characterized in that... In step e) above, when the calculated ultimate bearing capacity of the anchor tube is greater than the anchor tube bearing capacity determined by the vertical pull-out bearing capacity, the anchor tube bearing capacity calculated by the vertical pull-out bearing capacity is used as the ultimate bearing capacity of the anchor tube.

3. The method for calculating the bearing capacity of the vertical anchoring cylinder anchorage structure according to claim 1, characterized in that... In steps b) and c) above, for stratified soil foundations, the equivalent soil internal friction angle is used for calculation. The value of the equivalent soil internal friction angle is taken as the internal friction angle of each relevant soil layer weighted by thickness.

Images