Slope pier foundation structure and design method

Abstract

The invention relates to a slope pier foundation structure and a design method, the slope pier foundation structure comprises a rock foundation, a compensation foundation is arranged outside the rock foundation, an expanded foundation is arranged on the rock foundation and the compensation foundation, the compensation foundation comprises a plurality of pile foundations and a bearing platform, and the bearing platform is installed on the pile foundations. The compensation foundation is arranged on the outer side of the slope, the expanded foundation is arranged on the compensation foundation and the rock foundation, the compensation foundation and the rock foundation are combined to jointly provide support for the expanded foundation, under the condition that the stress safety of the bridge foundation is met, deep excavation of a foundation pit is avoided, the mountain excavation amount and the slope protection engineering amount are reduced, and the construction cost is reduced. The problems that in the prior art, when a pier foundation is located on a slope terrain and the geological condition is bedrock geology with high bearing capacity, the pier foundation adopts an expanded foundation, and in order to make the foundation bearing capacity within the full range of the bottom face of the expanded foundation meet the design requirement, the excavation depth of a foundation pit needs to be greatly increased; and therefore, the mountain excavation volume and the slope protection engineering quantity are greatly increased.

Description

Technical Field

[0001] The present application relates to the technical field of bridge engineering, and in particular to a slope bridge pier foundation structure and a design method. Background Art

[0002] At present, the main pier foundation of large-span bridges needs to bear not only the main loads such as the dead load generated by the deadweight of the bridge structure and the live load generated by trains or cars, but also the additional force loads generated by environmental factors such as temperature and wind. The external loads borne by the main pier foundation are often as high as tens of thousands of tons or even hundreds of thousands of tons. The scale of the foundation is very large. For the construction of large-span bridges involving mountains, the pier foundation is located on a slope. When the surface cover layer at the pier is thin and the geological conditions are bedrock geology with a high bearing capacity, it is more economical and reasonable to use an expanded foundation for the pier foundation than a pile foundation.

[0003] In related technologies, expanding the foundation often requires placing the entire bottom surface of the foundation on a bedrock support surface with higher bearing capacity. For a support surface at a certain elevation on a slope, the area close to the inner side of the slope has a higher foundation bearing capacity due to the greater buried depth of the stratum. On the contrary, the area close to the outer side of the slope has a lower buried depth of the stratum and the foundation bearing capacity of the support surface is often poor. In order to make the foundation bearing capacity of the entire range of the expanded foundation bottom surface meet the design requirements, the excavation depth of the foundation pit needs to be greatly increased, resulting in a significant increase in the amount of mountain excavation and slope protection engineering. This not only increases project investment, but also causes greater damage to the mountain environment, and the construction risks of the foundation pit and slope also increase accordingly.

[0004] Therefore, it is necessary to design a new slope pier foundation structure to overcome the above problems. Summary of the Invention

[0005] The present application provides a slope bridge pier foundation structure and design method, which can solve the technical problem in related technologies that when the bridge pier foundation is located on a slope terrain and the geological conditions are bedrock geology with high bearing capacity, the bridge pier foundation adopts an expanded foundation. In order to make the foundation bearing capacity within the entire range of the expanded foundation bottom surface meet the design requirements, the excavation depth of the foundation pit needs to be greatly increased, thereby causing a significant increase in the amount of mountain excavation and slope protection engineering.

[0006] In a first aspect, an embodiment of the present application provides a slope bridge pier foundation structure, which includes a rock foundation, a compensation foundation is provided outside the rock foundation, an expanded foundation is provided on the rock foundation and the compensation foundation, the compensation foundation includes multiple pile foundations and a pedestal, and the pedestal is installed on the multiple pile foundations.

[0007] In a second aspect, an embodiment of the present application provides a design method for a slope bridge pier foundation structure. The design method adopts the above-mentioned slope bridge pier foundation structure and includes the following steps:

[0008] According to the maximum stress σ on the top surface of the rock foundation under the main working condition max-m and minimum stress σ min-m The value range of is used to determine the top surface area of ​​the rock foundation;

[0009] According to the maximum stress σ of the foundation support surface under the main force plus additional force condition max-a and minimum stress σ min-a The value range of is used to determine the area of ​​the foundation support surface and calculate the top surface area of ​​the compensation foundation, where the sum of the top surface area of ​​the rock foundation and the top surface area of ​​the compensation foundation is equal to the area of ​​the foundation support surface;

[0010] According to the top surface area of ​​the compensation foundation and the maximum stress σ of the foundation support surface under the main force plus additional force conditions max-a The total load on the pile top is determined based on the deadweight of the foundation and the pile diameter, number of piles and length of the pile foundation are determined based on the total load of the pile foundation and the geological conditions.

[0011] In combination with the second aspect, in one embodiment, the maximum stress σ on the top surface of the rock foundation under the main working condition is max-m and minimum stress σ min-m The range of values ​​for determining the top surface area of ​​the rock foundation includes:

[0012] According to σ max-m ≤[σ] and σ min-m ≥0 to determine the top surface area of ​​the rock foundation, where [σ] is the allowable bearing capacity of the rock foundation, and the maximum stress σ on the top surface of the rock foundation under the main working condition is max-m The calculation formula is:

[0013]

[0014] The minimum stress σ on the top surface of the rock foundation under the main working condition min-m The calculation formula is:

[0015]

[0016] Where σ max-m is the maximum stress on the top surface of the rock foundation under the main working condition, σ min-m is the minimum stress on the top surface of the rock foundation under the main working condition, N m is the vertical force at the centroid of the top surface of the pier foundation relative to the rock foundation under the main working condition, M xm M is the bending moment along the bridge at the centroid of the top surface of the pier foundation relative to the rock foundation under the main working condition, ym A is the transverse bending moment at the centroid of the top surface of the pier foundation relative to the rock foundation under the main working condition, b is the top surface area of ​​the rock foundation, I xbis the moment of inertia of the top surface of the rock foundation along the bridge direction, I yb is the transverse moment of inertia of the top surface of the rock foundation, x b y is the distance from the stress calculation point to the centroidal axis of the top surface of the rock foundation in the transverse direction of the bridge, b It is the distance from the stress calculation point to the top surface of the rock foundation along the centroid axis of the bridge.

[0017] In combination with the second aspect, in one embodiment, the maximum stress σ of the foundation support surface under the main force plus additional force working condition is max-a and minimum stress σ min-a The value range of is used to determine the area of ​​the foundation support surface and calculate the top surface area of ​​the compensation foundation, including:

[0018] According to σ max-a ≤[σ] and Determine the area of ​​the foundation support surface, where [σ] is the allowable bearing capacity of the rock foundation, [e] is the allowable eccentricity of the vertical force on the pier foundation relative to the centroid of the foundation support surface, W is the section resistance moment at the edge of the foundation support surface with smaller stress, A is the area of ​​the foundation support surface, N a is the vertical force at the centroid of the pier foundation relative to the foundation support surface under the main force plus additional force working condition, and the maximum stress σ of the foundation support surface under the main force plus additional force working condition max-a The calculation formula is as follows:

[0019]

[0020] The minimum stress σ of the foundation support surface under the main force plus additional force condition min-a The calculation formula is as follows:

[0021]

[0022] Where σ max-a is the maximum stress of the foundation support surface under the main force plus additional force condition, σ min-a is the minimum stress of the foundation support surface under the main force plus additional force condition, N a is the vertical force at the centroid of the pier foundation relative to the foundation support surface under the main force plus additional force condition, M xa M is the bending moment along the bridge at the centroid of the pier foundation relative to the foundation support surface under the main force plus additional force condition, ya is the transverse bending moment of the pier foundation relative to the centroid of the foundation support surface under the main force plus additional force condition, A is the area of ​​the foundation support surface, I x is the moment of inertia of the foundation support surface along the bridge direction, I y is the moment of inertia of the foundation support surface in the transverse direction of the bridge, x is the distance from the stress calculation point to the centroid of the foundation support surface in the transverse direction of the bridge, and y is the distance from the stress calculation point to the centroid of the foundation support surface in the longitudinal direction of the bridge;

[0023] According to A c =AA b Calculate the top surface area of ​​the compensation foundation, where A c To compensate for the top surface area of ​​the foundation, A is the area of ​​the foundation support surface, A b is the top surface area of ​​the rock foundation.

[0024] In combination with the second aspect, in one embodiment, the maximum stress σ of the foundation support surface under the main force plus additional force working condition is calculated based on the top surface area of ​​the compensation foundation. max-a The total load on the pile top is determined based on the deadweight of the pile cap, including:

[0025] The top surface area of ​​the compensation foundation and the maximum stress σ of the foundation support surface under the main force plus additional force conditions are calculated. max-a The total load on the pile top is obtained by substituting the deadweight of the cap into the calculation formula of the total load on the pile top, wherein the calculation formula of the total load on the pile top is as follows:

[0026] N z =A c *σ max-a +G c ,

[0027] Where N z is the total load on the pile top, A c To compensate for the top surface area of ​​the foundation, G c It is the deadweight of the supporting platform.

[0028] In conjunction with the second aspect, in one embodiment, the design method further includes the following steps: determining whether the anti-sliding stability coefficient K of the expanded foundation meets the requirements based on the top surface area of ​​the compensation foundation and the top surface area of ​​the rock foundation, wherein the compensation foundation and the expanded foundation are cast separately, and the calculation formula of the anti-sliding stability coefficient K of the expanded foundation is:

[0029]

[0030] Where, K is the anti-sliding stability coefficient of the expanded foundation, K≥1.3, N is the vertical pressure of the expanded foundation base, H is the horizontal thrust of the expanded foundation base, A c To compensate for the top surface area of ​​the foundation, A b is the top surface area of ​​the rock foundation, A is the area of ​​the foundation support surface, μ c In order to increase the friction coefficient between the bottom surface of the foundation and the top surface of the compensation foundation, μ b To increase the friction coefficient between the bottom surface of the foundation and the top surface of the rock foundation.

[0031] In conjunction with the second aspect, in one embodiment, the design method further comprises the following steps: determining whether the total area of ​​the plurality of pile foundations meets the requirements based on the top surface area of ​​the compensation foundation and the area of ​​the foundation support surface, wherein the total area A of the plurality of pile foundations meets the requirements. z The calculation formula is:

[0032]

[0033] Where A z is the total area of ​​multiple pile foundations, N is the vertical pressure at the base of the expanded foundation, A c To compensate for the top surface area of ​​the foundation, A is the area of ​​the foundation support surface, μ c To expand the friction coefficient between the bottom surface of the foundation and the top surface of the compensating foundation, [τ] is the allowable shear stress of the pile foundation section.

[0034] In conjunction with the second aspect, in one embodiment, the design method further includes the following steps: determining whether the anti-sliding stability coefficient K of the expanded foundation meets the requirements based on the top surface area of ​​the rock foundation and the area of ​​the foundation support surface, wherein the expanded foundation and the compensating foundation are integrally cast, and the calculation formula of the anti-sliding stability coefficient K of the expanded foundation is:

[0035]

[0036] Where, K is the anti-sliding stability coefficient of the expanded foundation, K≥1.3, N is the vertical pressure of the expanded foundation base, H is the horizontal thrust of the expanded foundation base, A b is the top surface area of ​​the rock foundation, A is the area of ​​the foundation support surface, μ b In order to increase the friction coefficient between the bottom surface of the foundation and the top surface of the rock foundation, A z is the total area of ​​multiple pile foundations, and [τ] is the allowable shear stress of the pile foundation section.

[0037] In conjunction with the second aspect, in one embodiment, the design method further includes the following steps: determining whether the thickness of the cap meets the requirements based on the pile diameter and the center distance between adjacent pile foundations, wherein the thickness T of the cap is calculated as follows:

[0038]

[0039] Where T is the thickness of the cap, S is the center distance between adjacent pile foundations, and d is the diameter of the pile foundation.

[0040] In combination with the second aspect, in one embodiment, the ratio of the center distance S between adjacent pile foundations to the pile foundation diameter d is greater than or equal to 2.

[0041] The beneficial effects of the technical solutions provided in the embodiments of the present application include:

[0042] By setting up a compensation foundation on the outside of the slope and an extended foundation on the compensation foundation and the rock foundation, the compensation foundation and the rock foundation together provide support for the extended foundation. Under the condition of ensuring the stress safety of the bridge foundation, deep excavation of the foundation pit is avoided, the amount of mountain excavation and the amount of slope protection engineering are reduced, and the technical problem in related technologies that when the pier foundation is located on a slope and the geological conditions are bedrock geology with high bearing capacity, the pier foundation adopts an extended foundation. In order to make the foundation bearing capacity within the entire range of the bottom surface of the expanded foundation meet the design requirements, the foundation pit excavation depth needs to be greatly increased, thereby causing a significant increase in the amount of mountain excavation and slope protection engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0044] Figure 1 A side view of a slope bridge pier foundation structure provided in an embodiment of the present application;

[0045] Figure 2 A top view of the rock foundation and compensation foundation provided in an embodiment of the present application;

[0046] Figure 3 for Figure 2 Cross-sectional view of AA;

[0047] Figure 4 A schematic diagram of the structure of the compensation foundation and the expanded foundation provided in the embodiment of the present application;

[0048] Figure 5 A bottom view of the compensating foundation and the expanded foundation provided in an embodiment of the present application.

[0049] In the figure: 1. Rock foundation; 2. Compensating foundation; 21. Pile foundation; 22. Capping platform; 3. Expanded foundation; 4. Bridge pier. DETAILED DESCRIPTION

[0050] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 this application.

[0051] The embodiments of the present application provide a slope bridge pier foundation structure and design method, which can solve the technical problem that when the bridge pier foundation is located on a slope terrain and the geological conditions are bedrock geology with high bearing capacity, the bridge pier foundation adopts an expanded foundation. In order to make the foundation bearing capacity within the entire range of the expanded foundation bottom surface meet the design requirements, the foundation pit excavation depth needs to be greatly increased, thereby causing a significant increase in the amount of mountain excavation and slope protection engineering.

[0052] See also Figure 1 、 Figure 4 and Figure 5 As shown, an embodiment of the present application provides a slope pier foundation structure, which includes a rock foundation 1, a compensation foundation 2 is provided outside the rock foundation 1, an expanded foundation 3 is provided on the rock foundation 1 and the compensation foundation 2, and the compensation foundation 2 includes multiple pile foundations 21 and a pedestal 22, and the pedestal 22 is installed on the multiple pile foundations 21.

[0053] In this embodiment, a plurality of the pile foundations 21 are inserted into the bedrock, and the plurality of the pile foundations 21 are arranged in an area with low foundation bearing capacity on the outside of the slope in combination with the topography. The cap 22 can be set to an L shape in combination with the plane arrangement of the plurality of the pile foundations 21. The plurality of the pile foundations 21 are set in the bottom area of ​​the cap 22, and the cap 22 is surrounded by the outside of the rock foundation 1. A pier 4 is cast on the expanded foundation 3. The expanded foundation 3 and the compensation foundation 2 can be cast separately or integrally. The plurality of the pile foundations 21 are set far away On one side away from the slope, a plurality of pile foundations 21 and the pedestal 22 are cast integrally, the top surface of the compensation foundation 2 and the top surface of the rock foundation 1 can be set flush, the top surface of the compensation foundation 2 and the top surface of the rock foundation 1 form a complete foundation supporting surface, the expanded foundation 3 is set on the foundation supporting surface, and the compensation foundation 2 and the rock foundation 1 are combined to provide support for the expanded foundation 3. Under the condition of meeting the stress safety of the bridge foundation, the deep excavation of the foundation pit is avoided, and the amount of mountain excavation and the amount of slope protection engineering are reduced.

[0054] This embodiment sets the compensation foundation 2 on the outside of the slope, and sets the expanded foundation 3 on the compensation foundation 2 and the rock foundation 1. The compensation foundation 2 and the rock foundation 1 are combined to provide support for the expanded foundation 3. Under the condition of ensuring the stress safety of the bridge foundation, deep excavation of the foundation pit is avoided, and the amount of mountain excavation and slope protection engineering is reduced. This solves the technical problem in the related art that when the pier foundation is located on a slope and the geological conditions are bedrock geology with high bearing capacity, the pier foundation adopts an expanded foundation. In order to make the foundation bearing capacity within the entire range of the bottom surface of the expanded foundation meet the design requirements, the foundation pit excavation depth needs to be greatly increased, thereby causing a significant increase in the amount of mountain excavation and slope protection engineering.

[0055] See also Figure 1-3As shown, an embodiment of the present application provides a design method for a slope bridge pier foundation structure. The design method adopts the above-mentioned slope bridge pier foundation structure and includes the following steps:

[0056] S1: Maximum stress σ on the top surface of rock foundation 1 under the main working condition max-m and minimum stress σ min-m The value range of is used to determine the top surface area of ​​the rock foundation 1.

[0057] S2: Maximum stress σ on the foundation support surface under the main force plus additional force conditions max-a and minimum stress σ min-a The value range of is used to determine the area of ​​the foundation support surface and calculate the top surface area of ​​the compensation foundation 2, where the sum of the top surface area of ​​the rock foundation 1 and the top surface area of ​​the compensation foundation 2 is equal to the area of ​​the foundation support surface.

[0058] S3: Based on the top surface area of ​​the compensation foundation 2 and the maximum stress σ of the foundation support surface under the main force plus additional force working condition max-a The total load on the pile top is determined by the deadweight of the bearing platform 22, and the pile diameter, number of piles and pile length of the pile foundation 21 are determined according to the total load of the pile foundation 21 and the geological conditions.

[0059] In this embodiment, according to the maximum stress σ on the top surface of the rock foundation 1 under the main working condition, max-m and minimum stress σ min-m The value range of the rock foundation 1 is determined by the top surface area, and the maximum stress σ of the foundation support surface under the main force plus additional force working condition is calculated. max-a and minimum stress σ min-a The value range of is used to determine the area of ​​the foundation support surface. The top surface area of ​​the rock foundation 1 and the area of ​​the foundation support surface can be used to calculate the top surface area of ​​the compensation foundation 2. Then, according to the top surface area of ​​the compensation foundation 2 and the maximum stress σ of the foundation support surface under the main force plus additional force working condition, max-a The total load on the pile top is determined by the weight of the pile cap 22 and the deadweight of the pile cap 22. The total load on the pile top is calculated as follows:

[0060] N z =A c *σ max-a +G c ,

[0061] Where N z is the total load on the pile top, A c To compensate for the top surface area of ​​foundation 2, G c is the deadweight of the cap 22. Then, according to the total load on the pile top and the geological conditions, the pile diameter, number of piles and pile length of the pile foundation 21 can be determined according to the conventional bridge foundation design method.

[0062] Furthermore, in some embodiments, the maximum stress σ on the top surface of the rock foundation 1 under the main working condition is max-m and minimum stress σ min-m The value range of , which determines the top surface area of ​​the rock foundation 1, includes:

[0063] According to σ max-m ≤[σ] and σ min-m ≥0 to determine the top surface area of ​​the rock foundation 1, where [σ] is the allowable bearing capacity of the rock foundation 1, and the maximum stress σ on the top surface of the rock foundation 1 under the main working condition is max-m The calculation formula is:

[0064]

[0065] The minimum stress σ on the top surface of the rock foundation 1 under the main working condition is min-m The calculation formula is:

[0066]

[0067] Where σ max-m is the maximum stress on the top surface of rock foundation 1 under the main working condition, σ min-m is the minimum stress on the top surface of rock foundation 1 under the main working condition, N m is the vertical force at the centroid of the top surface of the pier foundation relative to the rock foundation 1 under the main working condition, M xm is the bending moment along the bridge at the centroid of the top surface of the pier foundation relative to the rock foundation 1 under the main working condition, M ym is the transverse bending moment of the pier foundation relative to the top centroid of the rock foundation 1 under the main working condition, A b is the top surface area of ​​rock foundation 1, I xb is the moment of inertia of the top surface of rock foundation 1 along the bridge direction, I yb is the transverse moment of inertia of the top surface of rock foundation 1, x b y is the distance from the stress calculation point to the centroidal axis of the top surface of the rock foundation in the transverse direction of the bridge, b It is the distance from the stress calculation point to the top surface of the rock foundation along the centroid axis of the bridge.

[0068] In this embodiment, the maximum stress σ on the top surface of the rock foundation 1 under the main working condition is max-m The calculation formula and the minimum stress σ on the top surface of the rock foundation 1 under the main working condition min-m Substitute the calculation formula into σ max-m ≤[σ] and σ min-m≥0, the top surface area of ​​the rock foundation 1 can be determined. According to the top surface area of ​​the rock foundation 1 and the distribution of rock layers in geological survey, the design elevation of the top surface of the rock foundation 1 is determined to ensure that the top surface of the rock foundation 1 meets the bearing capacity requirements and the top surface area of ​​the rock foundation 1 is greater than or equal to the area required by the design. Under the main working condition, the vertical force N of the pier foundation relative to the top surface centroid of the rock foundation 1 m , the bending moment M along the bridge at the centroid of the top surface of the pier foundation relative to the rock foundation 1 under the main working condition xm , Under the main working condition, the transverse bending moment M of the pier foundation at the top centroid relative to the rock foundation 1 ym The moment of inertia I of the top surface of the rock foundation 1 along the bridge direction can be obtained through calculation and analysis of the bridge superstructure. xb , the transverse moment of inertia I of the top surface of rock foundation 1 yb , the distance x from the stress calculation point to the centroidal axis of the top surface of the rock foundation in the transverse direction of the bridge b And the distance y from the stress calculation point to the top surface of the rock foundation along the bridge centroid axis b It can be obtained through geometric calculation. The reference rectangular coordinate system takes the centroid of the top surface of the rock foundation 1 as the origin, the x-axis along the bridge direction, and the y-axis across the bridge direction. The top surface area of ​​the rock foundation 1 is determined according to the main working conditions. This can avoid excessive uneven settlement and deformation of the foundation support surface under long-term daily operating loads due to the vertical stiffness difference between the compensation foundation 2 and the rock foundation 1, thereby causing cracks in the foundation structure.

[0069] In the specific design process of the top surface area of ​​the rock foundation 1, an initial value can be set for the top surface area of ​​the rock foundation 1. The initial top surface area A of the rock foundation 1 can be obtained by geometric calculation. b , the initial top surface moment of inertia of rock foundation 1 along the bridge direction I xb , the initial top surface transverse moment of inertia of rock foundation 1 I yb , the initial distance x from the stress calculation point to the centroid axis of the top surface of the rock foundation in the transverse direction of the bridge b , the initial distance y from the stress calculation point to the top surface of the rock foundation along the bridge centroid axis b , substitute each parameter into the maximum stress σ on the top surface of the rock foundation 1 under the main working condition max-m and minimum stress σ min-m The calculation formula for σ is max-m and σ min-n , and then check σ max-m and σ min-m Whether σ is satisfied max-m ≤[σ] and σ min-m ≥0, if the initial top surface area of ​​the rock foundation 1 is too small, then the top surface area of ​​the rock foundation 1 should be appropriately increased and recalculated until σ max-m and σ min-m Satisfy σ max-m≤[σ] and σ min-m ≥0, and keep the basic safety margin within 10%.

[0070] Furthermore, in some embodiments, the maximum stress σ of the foundation support surface under the main force plus additional force working condition is max-a and minimum stress σ min-a The value range of , determines the area of ​​the foundation support surface and calculates the top surface area of ​​the compensation foundation 2, including:

[0071] Step 1: According to σ max-a ≤[σ] and Determine the area of ​​the foundation support surface, where [σ] is the allowable bearing capacity of the rock foundation 1, [e] is the allowable eccentricity of the vertical force on the pier foundation relative to the centroid of the foundation support surface, W is the section resistance moment at the edge of the foundation support surface with smaller stress, A is the area of ​​the foundation support surface, N a is the vertical force at the centroid of the pier foundation relative to the foundation support surface under the main force plus additional force working condition, and the maximum stress σ of the foundation support surface under the main force plus additional force working condition max-a The calculation formula is as follows:

[0072]

[0073] The minimum stress σ of the foundation support surface under the main force plus additional force condition min-a The calculation formula is as follows:

[0074]

[0075] Where σ max-a is the maximum stress of the foundation support surface under the main force plus additional force condition, σ min-a is the minimum stress of the foundation support surface under the main force plus additional force condition, N a is the vertical force at the centroid of the pier foundation relative to the foundation support surface under the main force plus additional force condition, M xa M is the bending moment along the bridge at the centroid of the pier foundation relative to the foundation support surface under the main force plus additional force condition, ya is the transverse bending moment of the pier foundation relative to the centroid of the foundation support surface under the main force plus additional force condition, A is the area of ​​the foundation support surface, I x is the moment of inertia of the foundation support surface along the bridge direction, I y is the moment of inertia of the foundation support surface in the transverse direction of the bridge, x is the distance from the stress calculation point to the centroidal axis of the foundation support surface in the transverse direction of the bridge, and y is the distance from the stress calculation point to the centroidal axis of the foundation support surface in the longitudinal direction of the bridge.

[0076] Step 2: According to A c =AA b Calculate the top surface area of ​​the compensation foundation 2, where A cTo compensate for the top surface area of ​​foundation 2, A is the area of ​​the foundation support surface, A b is the top surface area of ​​the rock foundation 1.

[0077] In this embodiment, the maximum stress σ of the foundation support surface under the main force plus additional force working condition is max-a The calculation formula and the minimum stress σ of the foundation support surface under the main force plus additional force condition min-a Substitute the calculation formula into σ max-a ≤[σ] and The area of ​​the foundation support surface can be determined, where the top surface of the rock foundation 1 and the top surface of the compensation foundation 2 together constitute the foundation support surface. The area of ​​the foundation support surface is equal to the plane size required for the expansion foundation 3. Under the main force plus additional force working condition, the vertical force N of the pier foundation relative to the centroid of the foundation support surface is a , the bending moment M along the bridge direction at the centroid of the pier foundation relative to the foundation support surface under the main force plus additional force condition xa , the transverse bending moment M of the pier foundation relative to the centroid of the foundation support surface under the main force plus additional force condition ya The moment of inertia of the foundation support surface along the bridge direction I can be obtained through bridge structure calculation and analysis. x , the transverse moment of inertia of the foundation support surface I y The distance x from the stress calculation point to the centroidal axis of the foundation support surface in the transverse direction of the bridge, and the distance y from the stress calculation point to the centroidal axis of the foundation support surface in the longitudinal direction of the bridge can be obtained by geometric calculation. The reference rectangular coordinate system takes the centroid of the foundation support surface as the origin, the longitudinal direction of the bridge as the x-axis, and the transverse direction of the bridge as the y-axis. The area of ​​the foundation support surface and the top surface area of ​​the compensation foundation 2 are determined according to the main force plus additional force conditions, which can ensure the stability of the foundation support surface and the force safety of the foundation structure under extreme load conditions such as storms, huge waves, cold waves, and high temperatures.

[0078] In the process of designing the area of ​​the foundation support surface, an initial value can be set for the foundation support surface first, and the initial area A of the foundation support surface and the initial moment of inertia I of the foundation support surface along the bridge direction can be obtained through geometric calculation. x , the initial transverse moment of inertia of the foundation support surface I y , the initial distance x from the stress calculation point to the centroid of the foundation support surface in the transverse direction of the bridge, the initial distance y from the stress calculation point to the centroid of the foundation support surface in the longitudinal direction of the bridge, and substitute these parameters into the maximum stress σ of the foundation support surface under the main force plus additional force condition. max-a and minimum stress σ min-a The calculation formula for σ is max-a and σ min-a , and then check σ max-a and σ min-a Whether σ is satisfied max-a ≤[σ] and If the initial area of ​​the foundation support surface is too small, the area of ​​the foundation support surface should be appropriately increased and recalculated until σ max-a and σ min-a Satisfy σ max-a ≤[σ] and And keep the basic safety margin within 10%.

[0079] Furthermore, in some embodiments, the maximum stress σ of the foundation support surface under the main force plus additional force working condition is calculated based on the top surface area of ​​the compensation foundation 2. max-a and the deadweight of the cap 22 to determine the total load on the pile top, including:

[0080] The top surface area of ​​the compensation foundation 2 and the maximum stress σ of the foundation support surface under the main force plus additional force condition are calculated. max-a The weight of the cap 22 is substituted into the calculation formula of the total load on the pile top to obtain the total load on the pile top, wherein the calculation formula of the total load on the pile top is as follows:

[0081] N z =A c *σ max-a +G c ,

[0082] Where N z is the total load on the pile top, A c To compensate for the top surface area of ​​foundation 2, G c is the deadweight of the platform 22.

[0083] In this embodiment, the sum of the top surface load of the compensation foundation 2 and the deadweight of the cap 22 is equal to the total load on the pile top. c , the maximum stress σ of the foundation support surface under the main force plus additional force condition max-a And the deadweight G of the platform 22 c Substitute the calculation formula of the total load on the pile top into the total load on the pile top N z According to the total load of the pile foundation and the geological conditions, the pile diameter, number of piles and pile length of the pile foundation 21 can be determined according to the conventional design method of the bridge foundation.

[0084] Furthermore, in some embodiments, the design method further includes the following steps: determining whether the anti-sliding stability coefficient K of the expanded foundation 3 meets the requirements based on the top surface area of ​​the compensation foundation 2 and the top surface area of ​​the rock foundation 1, wherein the compensation foundation 2 and the expanded foundation 3 are cast separately, and the calculation formula of the anti-sliding stability coefficient K of the expanded foundation 3 is:

[0085]

[0086] Where, K is the anti-sliding stability coefficient of the expanded foundation 3, K≥1.3, N is the vertical pressure of the expanded foundation base, H is the horizontal thrust of the expanded foundation base, A c To compensate for the top surface area of ​​foundation 2, A b is the top surface area of ​​the rock foundation 1, A is the area of ​​the foundation support surface, μ c In order to increase the friction coefficient between the bottom surface of the foundation and the top surface of the compensation foundation, μ b To increase the friction coefficient between the bottom surface of the foundation and the top surface of the rock foundation.

[0087] In this embodiment, the top surface area A of the foundation 2 is compensated. c and the top surface area A of rock foundation 1 b Substitute into the calculation formula of the anti-sliding stability system K of the expanded foundation 3, where the expanded foundation base vertical pressure N and the expanded foundation base horizontal thrust H can be obtained through bridge structure calculation and analysis, and the friction coefficient μ between the bottom surface of the expanded foundation and the top surface of the compensation foundation is c And the friction coefficient μ between the bottom surface of the foundation and the top surface of the rock foundation b It can be obtained by consulting the design specifications or on-site tests. If the anti-sliding stability coefficient K of the expanded foundation 3 is greater than or equal to 1.3, there is no need to adjust the structural dimensions of the expanded foundation 3. If the anti-sliding stability coefficient K of the expanded foundation 3 is less than 1.3, the self-weight of the expanded foundation is increased by adjusting the thickness of the expanded foundation 3 to increase the vertical pressure N of the expanded foundation base until the anti-sliding stability coefficient K of the expanded foundation 3 is greater than or equal to 1.3.

[0088] Furthermore, in some embodiments, the design method further comprises the following steps: determining whether the total area of ​​the plurality of pile foundations 21 meets the requirements based on the top surface area of ​​the compensation foundation 2 and the area of ​​the foundation support surface, wherein the total area A of the plurality of pile foundations 21 is z The calculation formula is:

[0089]

[0090] Where A z is the total area of ​​the pile foundations 21, N is the vertical pressure at the base of the expanded foundation, A c To compensate for the top surface area of ​​foundation 2, A is the area of ​​the foundation support surface, μ c To expand the friction coefficient between the bottom surface of the foundation and the top surface of the compensating foundation, [τ] is the allowable shear stress of the pile foundation section.

[0091] In this embodiment, the top surface area A of the foundation 2 is compensated. c Substitute the total area A of the plurality of pile foundations 21 into the area A of the foundation support surface. zThe calculation formula is: where the vertical pressure N of the expanded foundation base can be obtained through bridge structure calculation and analysis, and the friction coefficient μ between the bottom surface of the expanded foundation and the top surface of the compensation foundation is c The allowable shear stress [τ] of the pile foundation section can be obtained by consulting the design specifications or field tests, and the total area A of the multiple pile foundations 21 can be obtained by consulting the design specifications according to the concrete strength grade used in the pile foundation 21. z It can be calculated by the pile diameter and the number of piles. If the total area A of the pile foundation 21 is z If the requirements are met, there is no need to adjust the pile diameter and the number of piles. If the total area of ​​the multiple pile foundations 21 does not meet the requirements, the pile diameter and the number of piles need to be adjusted until the total area of ​​the multiple pile foundations 21 meets the requirements.

[0092] Furthermore, in some embodiments, the design method further includes the following steps: determining whether the anti-sliding stability coefficient K of the expanded foundation 3 meets the requirements based on the top surface area of ​​the rock foundation 1 and the area of ​​the foundation support surface, wherein the expanded foundation 3 and the compensation foundation 2 are integrally cast and formed, and the calculation formula of the anti-sliding stability coefficient K of the expanded foundation 3 is:

[0093]

[0094] Where, K is the anti-sliding stability coefficient of the expanded foundation 3, K≥1.3, N is the vertical pressure of the expanded foundation base, H is the horizontal thrust of the expanded foundation base, A b is the top surface area of ​​the rock foundation 1, A is the area of ​​the foundation support surface, μ b In order to increase the friction coefficient between the bottom surface of the foundation and the top surface of the rock foundation, A z is the total area of ​​the piles 21, and [τ] is the allowable shear stress of the pile cross section.

[0095] In this embodiment, the top surface area A of the rock foundation 1 is b and the area A of the foundation support surface are substituted into the calculation formula of the anti-sliding stability system K of the expanded foundation 3, where the vertical pressure N of the expanded foundation base and the horizontal thrust H of the expanded foundation base can be obtained through bridge structure calculation and analysis, and the friction coefficient μ between the bottom surface of the expanded foundation and the top surface of the rock foundation can be obtained. b The allowable shear stress [τ] of the pile foundation section can be obtained by consulting the design specifications or field tests, and the total area A of the multiple pile foundations 21 can be obtained by consulting the design specifications according to the concrete strength grade used in the pile foundation 21. zIt can be calculated through the pile diameter and the number of piles. If the anti-sliding stability coefficient K of the expanded foundation 3 is greater than or equal to 1.3, there is no need to adjust the structural dimensions of the expanded foundation 3. If the anti-sliding stability coefficient K of the expanded foundation 3 is less than 1.3, the thickness of the expanded foundation 3 is adjusted to increase the self-weight of the expanded foundation, so as to increase the vertical pressure N of the expanded foundation base until the anti-sliding stability coefficient K of the expanded foundation 3 is greater than or equal to 1.3.

[0096] Further, see Figure 1 As shown, in some embodiments, the design method further includes the following steps: determining whether the thickness of the cap 22 meets the requirements based on the pile diameter and the center distance between adjacent pile foundations, wherein the calculation formula of the thickness T of the cap 22 is:

[0097]

[0098] Where T is the thickness of the cap 22, S is the center distance between adjacent pile foundations, and d is the diameter of the pile foundation.

[0099] In this embodiment, the center distance S of adjacent pile foundations and the pile foundation diameter d are substituted into the calculation formula of the thickness T of the cap 22. If the thickness T of the cap 22 meets the requirements, there is no need to adjust the thickness T of the cap 22. If the thickness T of the cap 22 does not meet the requirements, it is necessary to adjust the thickness T of the cap 22 until the thickness T of the cap 22 meets the requirements.

[0100] Further, see Figure 1 As shown, in some embodiments, the ratio of the center distance S of adjacent pile foundations to the pile foundation diameter d is greater than or equal to 2.

[0101] In the description of this application, it should be noted that the terms "upper" and "lower" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0102] It should be noted that, in this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0103] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A slope bridge pier foundation structure, characterized in that: It includes a rock foundation, a compensation foundation is arranged outside the rock foundation, an expanded foundation is arranged on the rock foundation and the compensation foundation, the compensation foundation includes multiple pile foundations and a bearing platform, and the bearing platform is installed on the multiple pile foundations.

2. A design method for a slope bridge pier foundation structure, using the slope bridge pier foundation structure according to claim 1, characterized in that: The design method comprises the following steps: According to the maximum stress σ on the top surface of the rock foundation under the main working condition max-m and minimum stress σ min-m The value range of is used to determine the top surface area of ​​the rock foundation; According to the maximum stress σ of the foundation support surface under the main force plus additional force condition max-a and minimum stress σ min-a The value range of is used to determine the area of ​​the foundation support surface and calculate the top surface area of ​​the compensation foundation, where the sum of the top surface area of ​​the rock foundation and the top surface area of ​​the compensation foundation is equal to the area of ​​the foundation support surface; According to the top surface area of ​​the compensation foundation and the maximum stress σ of the foundation support surface under the main force plus additional force conditions max-a The total load on the pile top is determined based on the deadweight of the foundation and the pile diameter, number of piles and length of the pile foundation are determined based on the total load of the pile foundation and the geological conditions.

3. The design method according to claim 2, wherein: The maximum stress σ on the top surface of the rock foundation under the main working condition max-m and minimum stress σ min-m The range of values ​​for determining the top surface area of ​​the rock foundation includes: According to σ max-m ≤[σ] and σ min-m ≥0 to determine the top surface area of ​​the rock foundation, where [σ] is the allowable bearing capacity of the rock foundation, and the maximum stress σ on the top surface of the rock foundation under the main working condition is max-m The calculation formula is: The minimum stress σ on the top surface of the rock foundation under the main working condition min-m The calculation formula is: Where σ max-m is the maximum stress on the top surface of the rock foundation under the main working condition, σ min-m is the minimum stress on the top surface of the rock foundation under the main working condition, N m is the vertical force at the centroid of the top surface of the pier foundation relative to the rock foundation under the main working condition, M xm M is the bending moment along the bridge at the centroid of the top surface of the pier foundation relative to the rock foundation under the main working condition, ym A is the transverse bending moment at the centroid of the top surface of the pier foundation relative to the rock foundation under the main working condition, b is the top surface area of ​​the rock foundation, I xb is the moment of inertia of the top surface of the rock foundation along the bridge direction, I yb is the transverse moment of inertia of the top surface of the rock foundation, x b y is the distance from the stress calculation point to the centroidal axis of the top surface of the rock foundation in the transverse direction of the bridge, b It is the distance from the stress calculation point to the top surface of the rock foundation along the centroid axis of the bridge.

4. The design method according to claim 3, wherein: The maximum stress σ of the foundation support surface under the main force plus additional force working condition max-a and minimum stress σ min-a The value range of is used to determine the area of ​​the foundation support surface and calculate the top surface area of ​​the compensation foundation, including: According to σ max-a ≤[σ] and Determine the area of ​​the foundation support surface, where [σ] is the allowable bearing capacity of the rock foundation, [e] is the allowable eccentricity of the vertical force on the pier foundation relative to the centroid of the foundation support surface, W is the section resistance moment at the edge of the foundation support surface with smaller stress, A is the area of ​​the foundation support surface, N a is the vertical force at the centroid of the pier foundation relative to the foundation support surface under the main force plus additional force working condition, and the maximum stress σ of the foundation support surface under the main force plus additional force working condition max-a The calculation formula is as follows: The minimum stress σ of the foundation support surface under the main force and additional force conditions min-a The calculation formula is as follows: Where σ max-a is the maximum stress of the foundation support surface under the main force plus additional force condition, σ min-a is the minimum stress of the foundation support surface under the main force plus additional force condition, N a is the vertical force at the centroid of the pier foundation relative to the foundation support surface under the main force plus additional force condition, M xa M is the bending moment along the bridge at the centroid of the pier foundation relative to the foundation support surface under the main force plus additional force condition, ya is the transverse bending moment of the pier foundation relative to the centroid of the foundation support surface under the main force plus additional force condition, A is the area of ​​the foundation support surface, I x is the moment of inertia of the foundation support surface along the bridge direction, I y is the moment of inertia of the foundation support surface in the transverse direction of the bridge, x is the distance from the stress calculation point to the centroid of the foundation support surface in the transverse direction of the bridge, and y is the distance from the stress calculation point to the centroid of the foundation support surface in the longitudinal direction of the bridge; According to A c =AA b Calculate the top surface area of ​​the compensation foundation, where A c To compensate for the top surface area of ​​the foundation, A is the area of ​​the foundation support surface, A b is the top surface area of ​​the rock foundation.

5. The design method according to claim 4, wherein: The maximum stress σ of the foundation support surface under the main force plus additional force working condition is calculated based on the top surface area of ​​the compensation foundation. max-a The total load on the pile top is determined based on the deadweight of the pile cap, including: The top surface area of ​​the compensation foundation and the maximum stress σ of the foundation support surface under the main force plus additional force conditions are calculated. max-a The total load on the pile top is obtained by substituting the deadweight of the cap into the calculation formula of the total load on the pile top, wherein the calculation formula of the total load on the pile top is as follows: N z =A c *s max-a +G c , Where N z is the total load on the pile top, A c To compensate for the top surface area of ​​the foundation, G c It is the deadweight of the supporting platform.

6. The design method according to claim 4, wherein: The design method further includes the following steps: determining whether the anti-sliding stability coefficient K of the expanded foundation meets the requirements based on the top surface area of ​​the compensation foundation and the top surface area of ​​the rock foundation, wherein the compensation foundation and the expanded foundation are cast separately, and the calculation formula of the anti-sliding stability coefficient K of the expanded foundation is: Where, K is the anti-sliding stability coefficient of the expanded foundation, K≥1.3, N is the vertical pressure of the expanded foundation base, H is the horizontal thrust of the expanded foundation base, A c To compensate for the top surface area of ​​the foundation, A b is the top surface area of ​​the rock foundation, A is the area of ​​the foundation support surface, μ c In order to increase the friction coefficient between the bottom surface of the foundation and the top surface of the compensation foundation, μ b To increase the friction coefficient between the bottom surface of the foundation and the top surface of the rock foundation.

7. The design method according to claim 4, wherein: The design method further comprises the following steps: determining whether the total area of ​​the plurality of pile foundations meets the requirements according to the top surface area of ​​the compensation foundation and the area of ​​the foundation support surface, wherein the total area A of the plurality of pile foundations meets the requirements. z The calculation formula is: Where A z is the total area of ​​multiple pile foundations, N is the vertical pressure at the base of the expanded foundation, A c To compensate for the top surface area of ​​the foundation, A is the area of ​​the foundation support surface, μ c To expand the friction coefficient between the bottom surface of the foundation and the top surface of the compensating foundation, [τ] is the allowable shear stress of the pile foundation section.

8. The design method according to claim 4, wherein: The design method further includes the following steps: determining whether the anti-sliding stability coefficient K of the expanded foundation meets the requirements based on the top surface area of ​​the rock foundation and the area of ​​the foundation support surface, wherein the expanded foundation and the compensating foundation are integrally cast and formed, and the calculation formula of the anti-sliding stability coefficient K of the expanded foundation is: Where, K is the anti-sliding stability coefficient of the expanded foundation, K≥1.3, N is the vertical pressure of the expanded foundation base, H is the horizontal thrust of the expanded foundation base, A b is the top surface area of ​​the rock foundation, A is the area of ​​the foundation support surface, μ b In order to increase the friction coefficient between the bottom surface of the foundation and the top surface of the rock foundation, A z is the total area of ​​multiple pile foundations, and [τ] is the allowable shear stress of the pile foundation section.

9. The design method according to claim 2, wherein: The design method further includes the following steps: determining whether the thickness of the cap meets the requirements based on the pile diameter and the center distance between adjacent pile foundations, wherein the thickness T of the cap is calculated as follows: Where T is the thickness of the cap, S is the center distance between adjacent pile foundations, and d is the diameter of the pile foundation.

10. The design method according to claim 9, wherein: The ratio of the center distance S between adjacent pile foundations to the pile foundation diameter d is greater than or equal to 2.

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