An embedded pile foundation design method for bridges in mountainous areas, along with its storage medium and equipment.

Abstract

This invention discloses a design method, storage medium, and device for embedded pile foundations of bridges in mountainous areas, comprising the following steps: (1) determining the design location and embedding type of the embedded pile foundation based on the mountainous slope topography, and constructing a mechanical model of the embedded pile foundation for bridges in mountainous areas; (2) initially proposing design parameters for the embedded pile foundation based on the embedding type; (3) calculating the lateral pressure P at the potential most unfavorable shear position below the embedded rock layer interface using stress analysis methods; (4) calculating the shear capacity T of the rock mass in the potential most unfavorable shear region below the embedded rock layer interface based on limit equilibrium theory; and (5) determining whether the shear strength T of the rock mass can resist the lateral pressure P. Through stress analysis and limit equilibrium theory, the embedding depth and shear capacity of the rock mass are reasonably determined, ensuring the stability and reliability of the pile foundation under complex terrain conditions.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering technology, and in particular relates to an embedded pile foundation design method for bridges in mountainous areas, as well as a storage medium and device. Background Technology

[0002] The central and western regions of my country are characterized by complex mountainous terrain and rugged landscapes. The ongoing development of these areas has led to the continuous expansion of transportation networks into mountainous regions. Bridges are crucial for these networks to cross valleys, and the load on bridges is ultimately transferred to the ground foundation via pile foundations. Therefore, establishing design methods suitable for bridge foundations in mountainous areas is of great significance for evaluating the safety and stability of transportation engineering projects.

[0003] Currently, there are many types of bridge foundations used in mountainous areas, categorized into shallow foundations (rigid foundations, flexible foundations) and deep foundations (pile foundations, caisson foundations, and box foundations). Currently, pile group foundations are the most widely used in bridge engineering. They consist of a pile cap and several individual piles connected to it, offering advantages such as high bearing capacity, small settlement deformation, and flexible construction techniques (Guizhou Road & Bridge Group Co., Ltd., A Construction Method for Pile Group Foundations of Bridges in Steep Slope Terrain: CN202310946729.7 [P]. 2023-11-07. China Railway Fourth Survey and Design Institute Group Co., Ltd., A Recommended Method for Pile Group Foundations of Railway Bridges: CN202310002297.4 [P]. 2023-05-30.). However, excessively high design standards for pile group foundations lead to significant waste. Especially when setting up bridge piers in steep mountainous terrain, if conventional pile group foundations are still used, the foundation plan dimensions are large, the excavation volume is large, the slope protection engineering is large, the project cost is high, and the environmental damage is significant.

[0004] In the past decade, embedded foundations have been widely used in power transmission towers due to their advantages of significantly reducing mountain excavation and protecting the mountain environment (Zhu Dayu, Huang Dongping, Peng Wenbing. A new type of foundation and construction technology for overhead power line towers and guy wires on rock foundation: CN201510030873.1 [P]. 2015-05-06. Li Yongxiang. Research on the application of rock embedded foundations in 750kV transmission lines [J]. Electric Power Construction, 2009, 30(6): 39-42. Wang Demin, Ruan Shaolin, Liu Changzheng. Research on pull-out test of embedded rock foundation with shallow clay overlying layer [J]. Heilongjiang Electric Power, 2015, 37(1): 49-53.). An embedded foundation refers to a foundation formed by excavating a pit in the ground using blasting, mechanical, or manual methods, inserting a steel reinforcement cage, pouring concrete in layers, and allowing it to cure for a period of time (China Railway Fourth Survey and Design Institute Group Co., Ltd. A Thin-Walled Fully Enclosed Embedded Foundation Suitable for Rock Foundations and Its Construction Method: CN201910712950.X[P]. 2019-11-08.). Compared with conventional pile foundations, embedded foundations have smaller planar dimensions, significantly reducing mountain excavation and protecting the mountain environment. Due to their unique advantages, embedded foundations are particularly valuable in mountainous railway bridge engineering. Researching embedded foundation design methods can promote their application in bridge engineering. However, the application of embedded foundations in bridges is still relatively limited, and corresponding design specifications are lacking in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a design method for embedded pile foundations for bridges in mountainous areas, so as to overcome the environmental damage caused by existing pile group foundations and the inaccuracy of embedded pile foundations in the application of bridges in mountainous areas.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An embedded pile foundation design method for bridges in mountainous areas includes the following steps:

[0008] S1. Based on the mountainous slope topography, determine the design location and embedding type of the bridge embedded pile foundation, and construct a mechanical model of the mountainous bridge embedded pile foundation;

[0009] S2. Based on the embedded type, preliminary design parameters for the embedded pile foundation are proposed, where,

[0010] For vertical embedded pile foundations, the minimum embedded pile length H0 = H1 + H2 + h, and the minimum embedment depth h is determined by the following formula:

[0011]

[0012] M = M0 + F·H1 - M f

[0013]

[0014] In the formula, M is the bending moment at the lower embedment point of the pile foundation; K is the conversion factor for the allowable rock pressure in the horizontal direction based on the rock strata structure, taken as 0.5 to 1.0; R is the saturated uniaxial compressive strength of the rock; M0 is the bending moment at the arch foot of the pile foundation; M f τ is the side friction bending moment of the pile foundation; F is the shear force at the arch foot of the pile foundation; H1 is the length of the side friction section of the pile foundation; τ is the allowable frictional resistance of the rock mass; d is the side length of the pile foundation in the plane of action of the bending moment; θ is the angle between the slope and the vertical direction.

[0015] For an inclined embedded pile foundation with an arch abutment, the minimum embedded depth h is determined by the following formula: H0 = H1 + h, where the minimum embedded length of the pile foundation is H0 = H1 + h.

[0016]

[0017]

[0018] E = K1K2R

[0019] In the formula, h is the embedment depth measured from the lower embedment point of the pile foundation; d is the side length of the pile foundation in the plane of bending moment action; b is the side length of the pile foundation perpendicular to the plane of bending moment action; M0 is the bending moment at the arch foot of the pile foundation; M G Q is the bending moment due to the self-weight of the pile foundation; Q0 is the shear force at the arch foot of the pile foundation; H1 is the length of the friction section of the pile foundation sidewall; G is the self-weight of the pile foundation; θ′ is the angle between the pile foundation and the horizontal plane; Q f K1 is the friction force of the end bearing surface; K2 is the safety factor, which is 0.5; K2 is the conversion factor of the allowable rock pressure in the horizontal direction based on the rock structure, which is 0.5 to 1.0; R is the saturated uniaxial compressive strength of the rock.

[0020] S3. Calculate the lateral pressure P at the most unfavorable shear position below the embedding surface using the stress analysis method at the embedding point:

[0021]

[0022] In the formula, σ is the stress at the embedment point at the lower end of the pile foundation; h x The depth of the shear zone at the most unfavorable location is taken as 1 / 4 of the minimum embedding depth h;

[0023] S4. Based on the limit equilibrium theory, calculate the shear capacity T of the rock mass in the potentially most unfavorable shear zone below the embedded rock layer interface:

[0024] T = SC

[0025] In the formula, S is the area of ​​the shear-resistant zone of the rock mass; C is the design shear strength of the rock mass;

[0026] The shear resistance zone of the rock mass includes a bottom surface and two side surfaces. For vertically embedded pile foundations and arch-abutment inclined pile foundations: the shear capacity of the rock mass in the most unfavorable shear resistance zone is calculated by summing the shear capacities of the bottom surface and the side surfaces, using the following formula:

[0027] T = T1 + T2

[0028] In the formula, T1 is the shear resistance of the rock mass side surface; T2 is the shear resistance of the rock mass bottom surface.

[0029] S5. Determine whether the shear capacity T of the rock mass in the most unfavorable shear zone below the embedment surface is greater than the lateral pressure P at the most unfavorable shear position below the embedment surface; if T≥P, then determine the embedded pile length H=H0; if T<P, then assume that the embedment surface is moved down by 0.5m, that is, increase the embedded pile length H to H0+0.5m, and repeat steps S2-S5.

[0030] In step S2, for the inclined embedded pile foundation of the arch abutment, M0 and Q0 are given by the design load in the code, M G G and Q f The calculation formula is as follows:

[0031] Q f =fbd

[0032] G=ρgbdH1

[0033]

[0034] In the formula, f is the allowable skin friction between the pile foundation concrete and the rock; ρ is the density of the pile foundation concrete; and g is the acceleration due to gravity.

[0035] In step S4, for vertically embedded pile foundations, the calculation formulas for the shear resistance T1 of the rock mass side surface and the shear resistance T2 of the rock mass bottom surface are as follows:

[0036]

[0037] T2=[a+(a+h x tanθ)tanα](a+h x tanθ)τ

[0038] a=(H0-h)tanθ-d

[0039] In the formula, α is the rock mass friction angle; a is the horizontal distance from the lower end of the pile embedment point to the slope surface; l is the horizontal distance from the most unfavorable embedment point to the slope surface; H0 is the minimum length of the embedded pile; h x The depth of the shear zone at the most unfavorable location is taken as 1 / 4 of the minimum embedment depth h, and θ is the angle between the slope and the vertical direction.

[0040] For inclined embedded pile foundations with arch abutments, the formulas for calculating the shear capacity T1 of the rock mass side surface and the shear capacity T2 of the rock mass bottom surface are as follows:

[0041]

[0042] T2=f·(b+ltanα)l

[0043]

[0044] l=h x cosθ′+a+h x sinθ′tanθ′l=h x cosθ′+a+h x sinθ′tanθ′

[0045] In the formula, α is the rock mass friction angle; a is the horizontal distance from the lower end of the pile embedment point to the slope surface; l is the horizontal distance from the most unfavorable embedment point to the slope surface; H1 is the length of the friction section of the pile foundation sidewall; θ′ is the angle between the pile foundation and the horizontal plane; h x The depth of the shear zone at the most unfavorable location is taken as 1 / 4 of the minimum embedding depth h.

[0046] The steps in step S5 include:

[0047] S51. If T is not less than P, then determine the length of the embedded pile foundation H = H0;

[0048] S52. If T is less than P, increase the embedded pile length H by H0 + 0.5m. Assuming the embedded surface shifts down by 0.5m, repeat step S2, correcting the embedded point bending moment value M and the minimum embedded depth h. Determine the new embedded surface position based on the minimum embedded depth h. Determine the width of the rock edge on the free face based on the new embedded surface position. a Calculate the length H1 of the sidewall constraint section; repeat step S3 to calculate the lateral pressure P at the most unfavorable location below the embedment surface; repeat step S4 to calculate the shear capacity T of the rock mass in the most unfavorable area below the embedment surface; if T is not less than P, determine the embedded pile length H = H0 + 0.5m; if T is less than P, continue to increase the embedded pile length H until T is not less than P.

[0049] In another aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the embedded pile foundation design method for mountain bridges.

[0050] In another aspect, the present invention provides a computer device including a memory, a processor, and a computer program, the computer program being stored in the memory and configured to be executable by the processor, wherein the processor, when executing the computer program, implements the steps in the embedded pile foundation design method for mountain bridges.

[0051] Beneficial Effects: The embedded pile foundation design method for bridge pile foundations in mountainous areas designed in this invention can effectively solve the problems of high engineering cost, large excavation volume, and serious environmental damage associated with traditional pile group foundations in mountainous bridge engineering. By introducing the embedded pile foundation design method, based on stress analysis and limit equilibrium theory, the embedment depth of the pile foundation and the shear resistance of the rock mass are rationally determined, ensuring the stability and reliability of the pile foundation under complex terrain conditions. Furthermore, this method significantly reduces the planar dimensions of the pile foundation and the amount of construction excavation, reduces the demand for slope protection engineering, optimizes engineering costs, and minimizes the impact on the ecological environment of mountainous areas, demonstrating high engineering application value and promising prospects for promotion. Attached Figure Description

[0052] Figure 1 Elevation layout diagram of a bridge in a mountainous area;

[0053] Figure 2 This is a schematic diagram of the overall shear failure of the rock mass at the pile tip of a vertical pile foundation.

[0054] Figure 3 A schematic diagram of the overall shear failure of the rock mass at the pile tip of the inclined pile foundation with arch seat;

[0055] Figure 4 This is a schematic diagram of stress distribution; Detailed Implementation

[0056] The method of the present invention will be further described in detail below with reference to engineering examples, in order to enable those skilled in the art to have a more detailed understanding and knowledge of the method of the present invention. The following embodiments should not be construed as limiting the scope of protection of the present invention in any way.

[0057] An embedded pile foundation design method for bridges in mountainous areas includes the following steps:

[0058] S1. Based on the mountainous slope topography, determine the design location and embedment type of the bridge embedded pile foundation, and construct a mechanical model of the mountainous bridge embedded pile foundation. Specifically, this includes the following steps:

[0059] S11. Conduct detailed topographic mapping and survey of the mountainous area where the bridge is located. The elevation layout of the bridge in the mountainous area is shown in the figure below. Figure 1 As shown, the slope, aspect, geomorphological features and geological conditions of the slope are analyzed to identify geological defects that affect the stability of the structure, including: potential unstable areas and faults, fissures, etc.

[0060] S12. Bridge Site Selection and Design Location Determination: Based on the "Specifications for Design of Highway Bridge and Culvert Foundations" (JTG D63-2007), and according to the results of topographic analysis, and by evaluating the height difference of the bridge site, the bearing capacity of the foundation and the properties of the rock mass, a suitable bridge site and pile foundation installation points are selected to ensure that the design site can provide sufficient bearing capacity and stability.

[0061] S13. Mechanical Model Construction: After determining the design location, a mechanical model of the embedded pile foundation-rock mass system is constructed based on the actual terrain conditions and the selected embedded type. This model should reflect the interaction between the pile foundation and the surrounding rock mass, including parameters such as load distribution, pile embedment depth, lateral pressure on the rock mass, and shear strength. Embedded types include: vertical pile foundations and arch-supported inclined embedded pile foundations. A schematic diagram of the overall shear failure of the rock mass at the pile tip of a vertical pile foundation is shown below. Figure 2 As shown, H1 is the length of the friction section of the pile foundation sidewall, that is, the embedment depth between the upper and lower embedment points of the pile foundation embedded in the slope; H2 is the embedment depth between the lower embedment point of the pile foundation embedded in the slope and the lower embedment point of the pile foundation; h is the embedment depth measured from the lower embedment point of the pile foundation; h x The depth of the shear zone at the most unfavorable location is taken as 1 / 4 of the minimum embedment depth h; a is the horizontal distance from the embedment point at the bottom of the pile foundation to the slope surface; the embedment point is equivalent to the fixed point: the fixed point of the pile foundation is the position where the superstructure has no relative displacement or rotation relative to the substructure; d is the side length of the pile foundation in the plane of bending moment action; b is the side length of the pile foundation perpendicular to the plane of bending moment action; θ is the angle between the slope and the vertical direction; H2 = H0 - h - H1; l is the horizontal distance from the most unfavorable point of the embedded surface to the slope surface, i.e. Figure 2 The horizontal distance from the slope side to the slope surface of the pile foundation at the left shear plane; α is the rock friction angle; M0 is the bending moment at the pile foundation arch foot; F is the shear force at the pile foundation arch foot; P is the lateral pressure at the most unfavorable shear resistance position below the pile foundation embedment surface.

[0062] A schematic diagram of the overall shear failure of the rock mass at the pile tip of an inclined embedded pile foundation with an arch seat is shown below. Figure 3 As shown; the pile foundation is perpendicular to the slope surface, H1 is the length along the pile foundation between the slope surface and the lower embedment point of the pile foundation; h is the embedment depth measured from the lower embedment point of the pile foundation; h x The depth of the shear zone at the most unfavorable location is taken as 1 / 4 of the minimum embedment depth h; a is the horizontal distance from the lower embedment point of the pile foundation to the slope surface; d is the side length of the pile foundation in the plane of bending moment action; b is the side length of the pile foundation perpendicular to the plane of bending moment action; l is the horizontal distance from the most unfavorable embedment point to the slope surface, i.e. Figure 3The horizontal distance from the slope side to the slope surface of the pile foundation at the left shear plane; α is the rock friction angle; θ is the angle between the pile foundation and the horizontal plane; M0 is the bending moment at the pile foundation arch foot; Q0 is the shear force at the pile foundation arch foot; P is the lateral pressure at the most unfavorable shear resistance position below the pile embedment surface; G is the self-weight of the pile foundation; M G Q is the bending moment due to the self-weight of the pile foundation; f The end bearing friction force refers to the friction force generated between the bottom (end) of the pile foundation and the contact surface with the soil.

[0063] S14. Environmental and Engineering Feasibility Assessment: During the model construction process, an engineering feasibility analysis is conducted in conjunction with the mountainous environmental conditions to ensure that the selected location will not affect the safety of construction and operation due to unfavorable geological factors or environmental limitations.

[0064] S2. Based on the embedded type, preliminary design parameters for the embedded pile foundation are proposed, where,

[0065] For vertical embedded pile foundations, the minimum embedded pile length H0 = H1 + H2 + h, and the minimum embedment depth h is determined by the following formula:

[0066]

[0067] M = M0 + F·H1 - M f (2)

[0068]

[0069] In the formula, M is the bending moment at the lower embedment point of the pile foundation; K is the conversion factor for the allowable rock pressure in the horizontal direction based on the rock strata structure, taken as 0.5 to 1.0; R is the saturated uniaxial compressive strength of the rock; M0 is the bending moment at the arch foot of the pile foundation; M f τ is the side friction bending moment of the pile foundation; F is the shear force at the arch foot of the pile foundation; H1 is the length of the side friction section of the pile foundation; τ is the allowable frictional resistance of the rock mass; d is the side length of the pile foundation in the plane of bending moment action;

[0070] For an inclined embedded pile foundation with an arch abutment, the minimum embedded depth h is determined by the following formula: H0 = H1 + h, where the minimum embedded length of the pile foundation is H0 = H1 + h.

[0071]

[0072] E=K1K2R (8)

[0073] In the formula, h is the embedment depth measured from the lower embedment point of the pile foundation; d is the side length of the pile foundation in the plane of bending moment action; b is the side length of the pile foundation perpendicular to the plane of bending moment action; M0 is the bending moment at the arch foot of the pile foundation; M G Q is the bending moment due to the self-weight of the pile foundation; Q0 is the shear force at the arch foot of the pile foundation; H1 is the length of the friction section of the pile foundation sidewall; G is the self-weight of the pile foundation; θ′ is the angle between the slope and the vertical direction; Q fK1 is the friction force of the end bearing surface; K2 is the safety factor, which is 0.5; K2 is the conversion factor of the allowable rock pressure in the horizontal direction based on the rock structure, which is 0.5 to 1.0; R is the saturated uniaxial compressive strength of the rock.

[0074] Specifically, M0 and Q0 are given by the design loads in the specification, M G G and Q f The calculation formula is as follows:

[0075] Q f =fbd (9)

[0076] G=ρgbdH1 (10)

[0077]

[0078] In the formula, f is the allowable skin friction between the pile foundation concrete and the rock; ρ is the density of the pile foundation concrete; and g is the acceleration due to gravity.

[0079] S3. Calculate the lateral pressure P at the most unfavorable shear position below the embedding surface based on the embedding point stress:

[0080]

[0081] In the formula, σ is the stress at the embedment point at the lower end of the pile foundation; h x The depth of the shear zone at the most unfavorable location is taken as 1 / 4 of the minimum embedding depth h;

[0082] S4. Based on the limit equilibrium theory, calculate the shear capacity T of the rock mass in the potentially most unfavorable shear zone below the embedded rock layer interface:

[0083] T = SC (14)

[0084] In the formula, S is the area of ​​the shear-resistant zone of the rock mass; C is the design shear strength of the rock mass;

[0085] The shear resistance zone of the rock mass includes a bottom surface and two side surfaces. For vertically embedded pile foundations and arch-abutment inclined pile foundations, the shear capacity of the rock mass in the most unfavorable shear resistance zone is calculated by summing the shear capacities of the bottom and side surfaces.

[0086] For vertically embedded pile foundations, the calculation formulas for the shear capacity T1 of the rock mass side surface and the shear capacity T2 of the rock mass bottom surface are as follows:

[0087] T = T1 + T2 (15)

[0088]

[0089] T2=[a+(a+h x tanθ)tanα](a+h x tanθ)τ (17)

[0090] a=(H0-h)tanθ-d (18)

[0091] In the formula, T1 is the shear resistance of the rock mass side surface; T2 is the shear resistance of the rock mass bottom surface; α is the rock mass friction angle; a is the horizontal distance from the lower embedment point of the pile foundation to the slope surface; l is the horizontal distance from the most unfavorable embedment point to the slope surface; H0 is the minimum length of the embedded pile foundation; h x The depth of the shear zone at the most unfavorable location is taken as 1 / 4 of the minimum embedment depth h; τ is the allowable skin friction of the rock mass, obtained from geological exploration data; θ is the angle between the slope and the vertical direction.

[0092] For an inclined embedded pile foundation with an arch abutment, the formula for calculating the shear capacity T of the rock mass in the potentially most unfavorable shear zone below the embedded rock interface is as follows:

[0093] T = T1 + T2 (19)

[0094]

[0095] T2=f·(b+ltanα)l (21)

[0096]

[0097] l=h x cosθ′+a+h x sinθ′tanθ′l=h x cosθ′+a+h x sinθ′tanθ′ (23)

[0098] In the formula, α is the rock mass friction angle; a is the horizontal distance from the lower end of the pile embedment point to the slope surface; l is the horizontal distance from the most unfavorable embedment point to the slope surface; H1 is the length of the friction section of the pile foundation sidewall; θ′ is the angle between the pile foundation and the horizontal plane; h x The depth of the shear zone at the most unfavorable location is taken as 1 / 4 of the minimum embedding depth h.

[0099] S5. Determine whether the shear capacity T of the rock mass in the most unfavorable shear resistance zone below the embedment surface is greater than the lateral pressure P at the most unfavorable shear resistance position below the embedment surface;

[0100] S51. If T≥P, then determine the length of the embedded pile foundation H=H0;

[0101] S52. If T < P, increase the embedded pile length H to H0 + 0.5m. Assuming the embedded surface moves down 0.5m, repeat step S2, correct the embedded point bending moment value M and the minimum embedded depth h, and determine the new embedded surface position based on the minimum embedded depth h. Based on the new embedded surface position, determine the width a of the free face rock edge and the length H1 of the sidewall constraint section. Repeat step S3 to calculate the lateral pressure P at the most unfavorable shear position below the embedded surface. Repeat step S4 to calculate the shear capacity T of the rock mass in the most unfavorable range below the embedded surface. If T is not less than P, determine the embedded pile length H = H0 + 0.5m. If T is less than P, continue to increase the embedded pile length H until T is not less than P.

[0102] Furthermore, to facilitate the application of the embedded pile foundation design method for mountain bridges in the preferred embodiment, a computer-readable storage medium and a computer device are also provided in the preferred embodiment. The computer-readable storage medium in the preferred embodiment stores a computer program, which, when executed by a processor, implements the steps in the aforementioned embedded pile foundation design method for mountain bridges. Correspondingly, the computer device includes a memory, a processor, and a computer program; wherein the computer program is stored in the memory and configured to be executable by the processor, and the processor, when executing the computer program, implements the steps in the aforementioned embedded pile foundation design method for mountain bridges.

[0103] Example 1

[0104] Taking the vertical embedded pile foundation of a railway bridge in a mountainous area as an example, the calculation parameters are as follows:

[0105] Pile foundation dimensions: b = 3m, d = 8.5m, H0 = 20m;

[0106] Rock mass parameters: τ = 12 MPa, friction angle α = 38°;

[0107] Slope gradient: 45°;

[0108] Design loads: M0 = 6388 kN·m, Q = 1224 kN.

[0109] By simultaneously solving equations (1), (2), and (3) in step S2, the minimum embedding depth h is obtained as 9.0 m; substituting the calculated result of h into equations (12) and (13) in step S3, the lateral pressure P of the pile foundation at the most unfavorable shear position is obtained as 1661.0 kN; substituting the calculated result of h into equations (15), (16), (17), and (18) in step S4, the shear resistance capacity T of the rock mass in the most unfavorable shear area is obtained as 1889.7 kN; comparing the lateral pressure of the embedded pile foundation with the shear resistance capacity of the rock mass in the shear area, it is determined that P = 1661.0 kN < T = 1889.7 kN, so the designed size H0 of the vertical embedded pile foundation meets the design requirements.

[0110] Embodiment 2

[0111] Taking a mountain railway bridge arch seat inclined embedded pile foundation selected for research as an example, the calculation parameters are as follows:

[0112] Pile foundation parameters: b = 22 m, d = 8 m, H0 = 22 m, gravity density ρ = 25 kN / m 3 ;

[0113] Rock mass parameters: f = 0.25 MPa, friction angle α = 38°, safety factor K1 = 0.5, rock allowable pressure conversion factor K2 = 2, rock saturated uniaxial compressive strength R = 20 MPa;

[0114] Design loads: M0 = 10262 kN·m, Q = 1788 kN; <​​​​​​​

Claims

1. A method for designing embedded pile foundations for bridges in mountainous areas, characterized in that, Includes the following steps: S1. Based on the mountainous slope topography, determine the design location and embedding type of the bridge embedded pile foundation, and construct a mechanical model of the embedded pile foundation for mountainous bridges; S2. Based on the embedded type, initially propose design parameters for the embedded pile foundation; determine the minimum embedment depth h based on the embedded type of the bridge embedded pile foundation. This refers to the length of the friction section of the pile foundation sidewall; S3. Calculate the lateral pressure P at the most unfavorable shear position below the embedding surface using the stress analysis method at the embedding point: In the formula, This refers to the stress at the embedment point from the lower end of the pile foundation; The depth of the shear zone at the most unfavorable location is taken as 1 / 4 of the minimum embedding depth h; The length of the pile foundation side perpendicular to the plane of bending moment action; This is the bending moment at the lower embedment point of the pile foundation; S4. Based on the limit equilibrium theory, calculate the shear capacity T of the rock mass in the potentially most unfavorable shear zone below the embedded rock layer interface: S5. Determine whether the shear capacity T of the rock mass in the most unfavorable shear zone below the embedment surface is greater than the lateral pressure P at the most unfavorable shear position below the embedment surface; If T≥P, then the length of the embedded pile foundation is determined to be H=H0; If T < P, then assume the embedment surface shifts down by 0.5m, which increases the embedded pile length H by H0 + 0.5m, and repeat steps S2-S5; Step S2 includes the following steps: If the embedded type is an arch-supported inclined embedded pile foundation, the minimum embedded depth h is determined by the following formula: H0 = H1 + h. In the formula, h is the embedment depth calculated from the embedment point at the lower end of the pile foundation; The length of the pile foundation side in the plane of bending moment action; The length of the pile foundation side perpendicular to the plane of bending moment action; This refers to the bending moment at the arch foot of the pile foundation; The bending moment is the self-weight of the pile foundation; H1 represents the shear force at the arch foot of the pile foundation; H1 is the length of the friction section of the pile foundation sidewall. For the self-weight of the pile foundation; The angle between the pile foundation and the horizontal plane; For the friction force of the bearing surface; For safety, a factor of 0.5 is used; The conversion factor for the allowable rock pressure in the horizontal direction based on the rock strata structure is taken as 0.5 to 1.0; M represents the saturated uniaxial compressive strength of the rock; M0 and Q0 are given by the design load in the code, M G G and Q f The calculation formula is as follows: In the formula, This refers to the allowable skin friction between the pile foundation concrete and the rock. The density of the pile foundation concrete; This is the acceleration due to gravity.

2. The embedded pile foundation design method for mountain bridges according to claim 1, characterized in that, In step S4 In the formula, This refers to the shear resistance of the rock mass's side surface. This refers to the shear resistance of the bottom surface of the rock mass.

3. The embedded pile foundation design method for mountain bridges according to claim 2, characterized in that, For an inclined embedded pile foundation with an arch abutment, the calculation formulas for the shear capacity T1 of the rock mass side surface and the shear capacity T2 of the rock mass bottom surface are as follows: In the formula, The angle of friction of the rock mass; The horizontal distance from the lower embedment point of the pile foundation to the slope surface; H1 is the horizontal distance from the most unfavorable point of the embedded surface to the slope surface; H1 is the length of the friction section of the pile foundation sidewall. The angle between the pile foundation and the horizontal plane; The depth of the shear zone at the most unfavorable location is determined by taking a value that is 1 / 4 of the minimum embedding depth h; In the formula, This represents the area of ​​the shear-resistant zone of the rock mass. Design shear strength for the rock mass; The shear resistance zone of the rock mass includes a bottom surface and two side surfaces. For vertically embedded pile foundations and arch-abutment inclined pile foundations: the shear capacity of the rock mass in the most unfavorable shear resistance zone is calculated by summing the shear capacities of the bottom surface and the side surfaces, using the following formula: In the formula, This refers to the shear resistance of the rock mass's side surface. This refers to the shear resistance of the bottom surface of the rock mass.

4. The embedded pile foundation design method for mountain bridges according to claim 1, characterized in that, The steps in step S5 include: S51. If T is not less than P, then determine the length of the embedded pile foundation. ; S52. If T is less than P, then increase the length H of the embedded pile foundation as follows: Assuming the embedding surface shifts downward by 0.5m, repeat step S2, correcting the fixed-point bending moment value M and the minimum embedding depth h. Determine the new embedding surface position based on the minimum embedding depth h; determine the width of the rock edge on the free face based on the new embedding surface position. and the length of the sidewall constraint section Repeat step S3 to calculate the lateral pressure P at the most unfavorable location below the embedment surface; repeat step S4 to calculate the shear capacity T of the rock mass within the most unfavorable range below the embedment surface; if T is not less than P, then determine the embedded pile length H = If T is less than P, then continue to increase the length H of the embedded pile until T is not less than P.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps in the embedded pile foundation design method for mountain bridges according to any one of claims 1 to 4.

6. A computer device comprising a memory, a processor, and a computer program, characterized in that, The computer program is stored in a memory and configured to be executed by a processor, and when the processor executes the computer program, it implements the steps in the embedded pile foundation design method for mountain bridges according to any one of claims 1 to 4.

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