A method for calculating the uplift force of a power transmission line reinforced slab foundation

Abstract

This invention relates to the field of power technology and discloses a method for calculating the uplift force on a reinforced slab foundation for transmission lines. This method employs the principle of friction reinforcement and the soil weight method, combined with soil mechanics theory and elasticity theory, to calculate the uplift force of the slab foundation under the combined action of reinforcement and backfill. This invention addresses the problem of the lack of suitable methods for calculating uplift force on reinforced slab foundations in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of power technology, specifically a method for calculating pull-out force on a reinforced plate foundation for a transmission line. Background Technology

[0002] Transmission lines often cross desert areas, and due to the loose sandy soil of the desert, slab foundations are a commonly used foundation type. Reinforced slab foundations have been tested in transmission lines, and the tests show that reinforced slab foundations can significantly improve the uplift bearing capacity of slab foundations and have a good effect on windbreak and sand fixation. However, there is currently no suitable method for calculating the uplift force on reinforced slab foundations. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, this invention provides a method for calculating pull-out force on reinforced plate foundations for power transmission lines, solving the problem of the lack of a suitable method for calculating pull-out force on reinforced plate foundations in the prior art.

[0004] The technical solution adopted by the present invention to solve the above problems is:

[0005] A method for calculating the uplift force on a reinforced slab foundation for power transmission lines is proposed. This method employs the principle of friction reinforcement and the soil weight method, combined with soil mechanics theory and elasticity theory, to calculate the uplift force of the slab foundation under the combined action of reinforcement and backfill soil.

[0006] As a preferred technical solution, if dF>dT, the reinforcement remains stable; where dF represents the total frictional force generated between the soil and the reinforcement on the slab foundation, and dT represents the tensile force on the reinforcement.

[0007] As a preferred technical solution, dT = T1 - T2, dF = 2σfbdl; where dT represents the tensile force caused by the tie in the micro-unit segment, T1 represents the force on the left section of the tie, T2 represents the force on the right section of the tie, σ represents the normal stress pressing down on the tie, f represents the friction coefficient between the tie and the soil, b represents the width of the tie, and dl represents the length of the anchorage section of the tie.

[0008] As a preferred technical solution, when h>h c When h ≤ h, the failure shape of the soil is a combination of an inverted frustum and a column connected to each other; when h ≤ h c At that time, the failure shape of the soil is frustum-shaped; where h represents the depth of the slab foundation, h c This indicates the critical burial depth for extraction on a slab foundation.

[0009] As a preferred technical solution, T U =γ E (G U1 +T U2 +T U3) / K1+G / K2; where, T U G represents the standard value of the pull-out bearing capacity of a slab foundation. U1 T represents the self-weight of the soil within the uplift influence range. U2 T represents the pull-out resistance of the geogrid laid on the surface of the slab foundation. U3 G represents the pull-out resistance generated by the geogrid laid between the ground surface and the slab foundation surface; K1 represents the design safety factor related to the foundation resistance; K2 represents the design safety factor related to the foundation's self-weight; γ represents the tensile strength of the geogrid laid between the ground surface and the slab foundation surface. E This represents the influence coefficient of horizontal force.

[0010] As a preferred technical solution, when h>h c hour,

[0011]

[0012] Where γ represents the weighting intensity of the soil above the bottom surface of the slab foundation, h c The value represents the critical depth of burial for the slab foundation, h represents the burial depth of the slab foundation, B represents the width of the slab foundation, α represents the upward burial angle, and V0 represents the volume of the slab foundation within the burial depth h.

[0013] As a preferred technical solution, when h≤h c hour,

[0014]

[0015] Where γ represents the weighting intensity of the soil above the bottom surface of the slab foundation, h c The value represents the critical depth of burial for the slab foundation, h represents the burial depth of the slab foundation, B represents the width of the slab foundation, α represents the upward burial angle, and V0 represents the volume of the slab foundation within the burial depth h.

[0016] As a preferred technical solution, T U2 = (c1+γdtanφ1)A1(sinθ+cosθtanφ); where c1 represents the interfacial cohesion between the reinforced aeolian sand and the geogrid, γ represents the weight of the soil above the bottom of the slab foundation, φ1 represents the interfacial friction angle between the aeolian sand and the geogrid, A1 represents the area of ​​the reinforcement outside the fracture surface of the first layer of reinforcement, θ represents the geogrid pull-up angle, d represents the burial depth of the first layer of reinforcement, and φ represents the friction angle of the reinforced aeolian sand.

[0017] As a preferred technical solution, T U3= (c1+γd1 tanφ1)A2(sinθ+cosθtanφ); where c1 represents the interfacial cohesion between the reinforced aeolian sand and the geogrid, γ represents the weight of the soil above the bottom of the slab foundation, φ1 represents the interfacial friction angle between the reinforced aeolian sand and the geogrid, A2 represents the area of ​​the reinforcement outside the fracture surface of the second layer of reinforcement, θ represents the geogrid pull-up angle, and d1 represents the embedment depth of the second layer of reinforcement.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) This invention can take into account the contribution of reinforcement to the uplift bearing capacity of square base plate foundation, and proposes a calculation method for the uplift bearing capacity of reinforced soil composite foundation. It can give full play to the joint effect of reinforcement and soil, improve the uplift bearing capacity of reinforced slab foundation, and has high economic value.

[0020] (2) It can effectively reduce the size of slab foundations, save materials, and improve the economic benefits of the project.

[0021] (3) It can reduce the excavation disturbance range, which is beneficial to environmental protection and at the same time gives full play to the windproof and sand-fixing effect of the reinforcing material. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a failure model for a reinforced soil composite.

[0023] Figure 2 for Figure 1 One of the magnified views of a section;

[0024] Figure 3 for Figure 1 The second enlarged view of a part. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0026] Example 1

[0027] like Figures 1 to 3 As shown, this invention adopts the principle of friction reinforcement and combines classical soil mechanics theory and elasticity theory to propose a method for calculating the pull-out force of reinforced soil slab foundations, taking into account the pull-out force of the slab foundation under the combined action of reinforcement and backfill soil.

[0028] 1) Friction reinforcement principle

[0029] Failure model of reinforced soil composite such as Figure 1 As shown.

[0030] The length of the anchorage section of the reinforcing bar is dl. The force on the left section of the reinforcing bar is T1, and the force on the right section is T2. The normal stress pressing down on the reinforcing bar is σ. Neglect the weight of the reinforcing bar and the weight of the soil in the micro-unit segment. Let the coefficient of friction between the reinforcing bar and the soil be f, and let b be the width of the reinforcing bar. Let the tensile force induced by the reinforcing bar in this micro-unit segment be dT.

[0031] dT=T1-T2 (1)

[0032] Let dF be the total frictional force generated between the soil and the tie rod on this infinitesimal element segment, then we have:

[0033] dF=2σfbdl (2)

[0034] dT = T1 - T2, dF = 2σfbdl; where T1 represents the force on the left section of the tie bar, T2 represents the force on the right section of the tie bar, σ represents the normal stress pressing down on the tie bar, f represents the friction coefficient between the tie bar and the soil, b represents the width of the tie bar, dl represents the length of the anchorage section of the tie bar, dF represents the total friction force generated between the soil and the tie bar on the slab foundation, and dT represents the tensile force on the tie bar.

[0035] Based on the force analysis of this micro-element, it can be seen that if dF > dT, there will be no mutual displacement between the reinforcement and soil, and the reinforcement will remain stable, meaning it will not be pulled out. This indicates that the slab foundation under the combined action of reinforcement and soil can remain stable; in other words, the horizontal force of the soil is overcome by the frictional force between the reinforcement and soil, and the micro-element remains stable. Conversely, it cannot remain stable if dF > dT.

[0036] 2) Calculation of ultimate uplift bearing capacity

[0037] When h>h c =1.5B, where h is the depth of the foundation slab, and B is the width of the foundation slab; the failure shape of the soil is a combination of a frustum and a column, with a depth of h. c The following damaged soil mass is columnar in shape, with an approximate square shape at the base, h c The junction between the point and the inverted cone is approximately circular; the burial depth h c The above soil failure mode is approximately frustum-shaped. When h ≤ h c At that time, the failure shape of the soil is frustum-shaped. For example... Figure 1 As shown.

[0038] The pull-out resistance of reinforced sandy soil should be equal to the sum of the vertical projection of the soil's self-weight, the shear capacity of its lateral surfaces, and the pull-out resistance of each layer of geogrid. Under the ultimate pull-out displacement of the foundation slab, the total frictional force generated at the geogrid-soil interface forms an angle θ with the horizontal plane. The vertical decomposition of this total frictional force directly constitutes part of the pull-out resistance, while the horizontal decomposition forms a horizontal constraint on the soil, increasing its shear resistance. Based on this integration, the following theoretical calculation formula is obtained:

[0039] T U =γ E (G U1 +T U2 +T U3 ) / K1+G / K2; where, T U G represents the standard value of the pull-out bearing capacity of a slab foundation. U1 T represents the self-weight of the soil within the uplift influence range. U2 T represents the pull-out resistance of the geogrid laid on the surface of the slab foundation. U3 G represents the pull-out resistance generated by the geogrid laid between the ground surface and the slab foundation surface; K1 represents the design safety factor related to the foundation resistance; K2 represents the design safety factor related to the foundation's self-weight; γ represents the tensile strength of the geogrid laid between the ground surface and the slab foundation surface. E This represents the influence coefficient of horizontal force.

[0040] 1) When h>h c hour,

[0041] 2) When h ≤ h c hour,

[0042] 3) Wherein, γ represents the weight of the soil above the bottom surface of the slab foundation (kN / m). 3 ), h c The critical burial depth (m) for slab foundations is generally expressed as h. c =1.5B, where h represents the depth of the slab foundation (m), B represents the width of the slab foundation (m), α represents the upward angle (°), and V0 represents the volume of the slab foundation within the depth h (m³). 3 ).

[0043] T U2 = (c1 + γdtanφ1)A1(sinθ + cosθtanφ); where c1 represents the interfacial cohesion between the reinforced aeolian sand and the geogrid (kPa), and γ represents the weight of the soil above the bottom of the slab foundation (kN / m). 3 φ1 represents the interfacial friction angle (°) between aeolian sand and geogrid, and A1 represents the area of ​​the reinforcement outside the fracture surface of the first layer of reinforcement (m²). 2), θ represents the geogrid pull-out angle (°), d represents the embedment depth of the first layer of reinforcement (m), and φ represents the soil friction angle (°).

[0044] T U3 = (c1 + γd1tanφ1)A2(sinθ + cosθtanφ); where c1 represents the interfacial cohesion between the reinforced aeolian sand and the geogrid (kPa), and γ represents the weight of the soil above the bottom of the slab foundation (kN / m). 3 φ1 represents the interfacial friction angle (°) between the reinforced aeolian sand and the geogrid, and A2 represents the area of ​​the reinforcement material outside the fracture surface of the second layer of reinforcement (m²). 2 ), θ represents the geogrid pull-out angle (°), and d1 represents the embedment depth of the second layer of reinforcement (m).

[0045] As described above, the present invention can be implemented well.

[0046] All features disclosed in all embodiments of this specification, or steps in all methods or processes implied in the disclosure, may be combined and / or extended or replaced in any way, except for mutually exclusive features and / or steps.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for calculating pull-out force on a reinforced plate foundation for a transmission line, characterized in that, Using the principle of friction reinforcement and the soil weight method, combined with soil mechanics theory and elasticity theory, the uplift force of the slab foundation under the combined action of reinforcement and backfill soil is calculated. ， ； in, This represents the total frictional force generated between the soil and the tie rods on the slab foundation. This indicates the tensile force acting on the reinforcing bars. This indicates that the left section of the tie rod is under stress. This indicates the force on the right section of the tie rod. This represents the normal stress that holds the tie rod in place. This represents the coefficient of friction between the tie rod and the soil. Indicates the width of the reinforcing strip. Indicates the length of the reinforcement anchorage section; like > Then the reinforcing steel remains stable; when > When the soil fails, the failure shape is a combination of an inverted frustum and a column connected together; when ≤ At that time, the failure shape of the soil was a frustum-shaped cone; among which, Indicates the depth of burial on the slab foundation. Indicates the critical burial depth for extraction on a slab foundation; ； in, This indicates the standard value of the pull-out bearing capacity on a slab foundation. This represents the self-weight of the soil within the area affected by the uplift. This indicates the pull-out resistance of the geogrid laid on the surface of the slab foundation. This indicates the pull-out resistance of the geogrid laid between the ground surface and the surface of the slab foundation. This indicates the self-weight of the slab foundation. This represents the design safety factor related to foundation resistance. This indicates the design safety factor related to the foundation's self-weight. This represents the influence coefficient of horizontal force.

2. The method for calculating pull-out force on a reinforced plate foundation for a transmission line according to claim 1, characterized in that, when > hour, ; in, This indicates the weighting of the soil above the bottom surface of the slab foundation. This indicates the critical burial depth for extraction on a slab foundation. Indicates the depth of burial on the slab foundation. Indicates the width of the slab foundation. Indicates an upward angle. express Volume of buried inner slab foundation.

3. The method for calculating pull-out force on a reinforced plate foundation for a transmission line according to claim 1, characterized in that, when ≤ hour, ; in, This indicates the weighting of the soil above the bottom surface of the slab foundation. This indicates the critical burial depth for extraction on a slab foundation. Indicates the depth of burial on the slab foundation. Indicates the width of the slab foundation. Indicates an upward angle. express Volume of buried inner slab foundation.

4. The method for calculating pull-out force on a reinforced plate foundation for a transmission line according to claim 1, characterized in that, ;in, This indicates the interfacial cohesion between reinforced aeolian sand and geogrid. This indicates the weighting of the soil above the bottom surface of the slab foundation. This represents the interfacial friction angle between aeolian sand and geogrid. This represents the area of ​​the reinforcement material outside the fracture surface of the first layer of reinforcement. Indicates the pull-up angle of the geogrid. Indicates the embedment depth of the first layer of reinforcing material. This represents the friction angle of reinforced aeolian sand.

5. The method for calculating pull-out force on a reinforced plate foundation for a transmission line according to claim 1, characterized in that, ;in, This indicates the interfacial cohesion between reinforced aeolian sand and geogrid. This indicates the weighting of the soil above the bottom surface of the slab foundation. This represents the interfacial friction angle between reinforced aeolian sand and geogrid. This indicates the area of ​​the reinforcement outside the fracture surface of the second layer of reinforcement. Indicates the pull-up angle of the geogrid. This indicates the embedment depth of the second layer of reinforcing material.

Images