A method for calculating the overturning resistance of a foundation pole with assembled foundation

Abstract

The application relates to a calculation method of overturning resistance of a power pole with a fabricated foundation, and belongs to the technical field of power grid operation and maintenance, which comprises the following steps: 1, obtaining data of a power pole body and calculating the overturning resistance limit bearing capacity F1 of the power pole body; 2, obtaining data of a fabricated foundation and calculating the overturning resistance limit bearing capacity F2 of the fabricated foundation; and 3, calculating the overturning resistance limit bearing capacity F of the whole power pole body and fabricated foundation according to F1, F2 and the respective interaction coefficients of F1 and F2. The application provides a scientific reference for the power pole with the fabricated foundation and can assist the design of the power pole with the fabricated foundation.

Description

Technical Field

[0001] The invention relates to a method for calculating the anti-overturning bearing capacity of an electric pole with an assembled foundation, and belongs to the technical field of power grid operation and maintenance. Background Art

[0002] Power poles can collapse or tip over in extreme weather conditions, such as typhoons. These can cause serious power outages, such as short circuits and power outages, and cause significant inconvenience to people. The collapse of power poles on both sides of roads also hinders traffic.

[0003] To prevent poles from tipping over or collapsing in extreme weather due to insufficient bearing capacity, which could cause immeasurable damage to the power grid, the current solution is to install prefabricated foundations at the bottom of the poles to increase their stability and anti-tipover strength. However, research on the anti-tipover bearing capacity of poles with prefabricated foundations has not yet been conducted.

[0004] A Chinese invention patent with publication number CN105488732A discloses a method for calculating the collapse load of power towers against disaster weather. The specific steps include collecting data on the power towers' resistance to natural disasters at construction sites, constructing an extreme value distribution function, calculating the minimum load of the power towers against disasters, the total load against natural disasters, and selecting data.

[0005] In the calculation steps of the above reference example, the supporting effect of the prefabricated foundation on the pole is not taken into account. Therefore, the calculation of the anti-overturning bearing capacity of the pole with a prefabricated foundation is inaccurate and the error is large. It cannot provide a reference for the pole with a prefabricated foundation, so it is urgently needed to be improved. Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the present invention designs a method for calculating the anti-overturning bearing capacity of an electric pole with an assembled foundation, which provides a scientific reference for the electric pole with an assembled foundation and can assist in the design of the electric pole with an assembled foundation.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for calculating the anti-overturning bearing capacity of an electric pole with an assembled foundation comprises the following steps:

[0009] Step 1: Obtain the data of the pole body and calculate the anti-overturning ultimate bearing capacity F1 of the pole body;

[0010] Step 2: Obtain the data of the prefabricated foundation and calculate the ultimate anti-overturning bearing capacity F2 of the prefabricated foundation;

[0011] Step 3, calculating the overturning resistance ultimate bearing capacity F of the whole of the electric pole body and the assembled foundation according to F1, F2 and the interaction coefficient corresponding to each of F1 and F2.

[0012] Further, in the step 1, assuming that the soil reaches the limit equilibrium state, then

[0013] wherein m is the soil parameter pressure;

[0014] b0 = bk0, wherein b is the actual width of the electric pole body, and k0 is a space increase coefficient;

[0015] h t is the buried depth of the electric pole body;

[0016] wherein H0 is the distance from the action point of the horizontal force of the upper end part of the electric pole body on the design ground surface;

[0017]

[0018] Further, in the step 2, the assembled foundation comprises a pile cap and a plurality of pile foundations vertically fixed at the bottom end of the pile cap and buried underground, then F2 = nη h R ha , wherein n is the number of piles, R ha is the characteristic value of the horizontal bearing capacity of a single pile, and η h is an effect comprehensive coefficient.

[0019] Further, the calculation formula of the effect comprehensive coefficient η h is as follows:

[0020] η h = η i η r + η b + η l ;

[0021] η i is the mutual influence effect coefficient of the pile foundation;

[0022] η r is the top constraint effect coefficient of the pile foundation;

[0023] η l is the lateral soil horizontal resistance effect coefficient of the pile cap;

[0024] η b is the bottom friction effect coefficient of the pile cap.

[0025] Further, when the pile cap is placed on the ground surface and the lateral surface of the pile cap is not covered with soil, the bottom friction effect coefficient η bη is the lateral soil horizontal resistance effect coefficient of the pile foundation l .

[0026] η is the mutual influence effect coefficient of the pile foundation i The calculation formula of η is as follows:

[0027]

[0028] S a / d is the ratio of the center distance of the pile foundation along the horizontal load action direction to the pile diameter of the pile foundation;

[0029] n1 is the number of piles in each row of the pile foundation along the horizontal load action direction;

[0030] n2 is the number of piles in each row of the pile foundation along the vertical direction of the horizontal load action direction.

[0031] Further, the calculation formula of the characteristic value R ha of the horizontal bearing capacity of the single pile is as follows:

[0032]

[0033] EI is the bending stiffness of the pile foundation;

[0034] α is the pile-soil deformation coefficient of the pile foundation;

[0035] v x is the horizontal displacement coefficient of the pile top of the pile foundation;

[0036] χ oa is the allowable value of the horizontal displacement of the pile top of the pile foundation.

[0037] Further, when the bending stiffness of the pile body of the pile foundation controls the value of χ oa , the calculation formula of χ oa is as follows:

[0038] Further, in step 3, the calculation formula of F is as follows: F = 0.8k1F1+0.6k2k3k4F2;

[0039] The interaction coefficient includes:

[0040] k1 is the factor of the influence of the pile length of the pile foundation on the bearing capacity of the pole body;

[0041] k2 is the influence factor of the influence of the pile length of the pile foundation on the bearing capacity of the fabricated foundation;

[0042] k3 is the influence factor of the influence of the embedded depth of the pole body on the bearing capacity of the fabricated foundation;

[0043] K4 is an influence factor of the influence of the size increase of the pile cap on the bearing capacity of the fabricated foundation.

[0044] Further, in the step 1, S j The following formula needs to be met:

[0045] S j ≥γ f S0, and M j ≥γ f H0S0;

[0046] Wherein M j is the limit overturning moment of the pole body;

[0047] γ f is an additional partial coefficient;

[0048] S0 is the horizontal force of the pole body on the ground end part.

[0049] Compared with the prior art, the present application has the following characteristics and beneficial effects:

[0050] The present application simplifies the bearing capacity of the fabricated foundation pole into two bearing parts by calculating the overturning limit bearing capacity of the pole body and the fabricated foundation, takes the stress of the soil around the pole body reaching the limit state as the standard, carries out the corresponding calculation and research, and finally obtains the limit bearing capacity of the pole with the fabricated foundation through correction, which is high in accuracy, good in applicability, meets the engineering requirements, embodies the accuracy and applicability of the calculation method, and is used for the overturning bearing capacity calculation of the pole with the fabricated foundation, and provides corresponding technical support for the new type of foundation. DETAILED DESCRIPTION

[0051] The present application will be described in more detail below in combination with embodiments.

[0052] The overturning bearing capacity calculation method of the pole with the fabricated foundation in the embodiment comprises the following steps:

[0053] Step 1, obtaining the data of the pole body and calculating the overturning limit bearing capacity F1 of the pole body;

[0054] Step 2, obtaining the data of the fabricated foundation and calculating the overturning limit bearing capacity F2 of the fabricated foundation;

[0055] Step 3, calculating the overturning limit bearing capacity F of the whole pole body and fabricated foundation according to F1, F2 and the respective interaction coefficients of F1 and F2.

[0056] Specifically, in step 1, it is assumed that the soil reaches the limit equilibrium state, then

[0057] Wherein, m is the soil parameter pressure;

[0058] b0=bk0, wherein b is the actual width of the pole body, and k0 is a space increase coefficient;

[0059] h t is the buried depth of the pole body;

[0060] Wherein H0 is the distance from the point of action of the horizontal force of the upper end part of the pole body on the ground to the design ground;

[0061] Wherein θ is determined by the equation ;

[0062] Meanwhile, θ can also be valued by Table 1 as follows.

[0063] η θ μ η·μ η θ μ η·μ 0.10 0.784 82.9 8.3 5.00 0.720 11.8 59.1 0.25 0.774 41.3 10.4 6.00 0.718 11.6 69.0 0.50 0.761 25.3 12.7 7.00 0.716 11.3 79.0 1.00 0.746 17.7 17.7 8.00 0.715 11.2 89.2 2.00 0.732 14.1 28.1 9.00 0.714 11.0 99.3 3.00 0.725 12.6 37.8 10.00 0.713 11.0 109.1 4.00 0.722 13.1 48.5

[0064] Table 1

[0065] Meanwhile, S j needs to meet the following formula requirements:

[0066] S j ≥γ f S0, and M j ≥γ f H0S o ;

[0067] Wherein M j is the ultimate overturning moment of the pole body;

[0068] γ f is an additional partial coefficient;

[0069] S0 is the horizontal force of the upper end part of the pole body on the ground.

[0070] Further, in step 2, the fabricated foundation includes a pile cap and a plurality of pile foundations vertically fixed at the bottom end of the pile cap and buried in the ground, then F2=nη h R ha , wherein n is the number of piles, if n=1, it is a single pile, and if n≥2, it is a group pile, R ha is the characteristic value of the horizontal bearing capacity of a single pile, η h is an effect comprehensive coefficient, η h reacts the interaction between the pile cap and the pile foundation and the soil.

[0071] In this embodiment, the type of pile foundation is a steel pile, a precast pile, or a reinforced ratio of no less than 0.65% cast-in-place pile.

[0072] Further, the effect comprehensive coefficient η hThe calculation formula of η

[0073] η h = η i η r + η b + η l ;

[0074] η i is the mutual influence effect coefficient of the pile foundation;

[0075] η r is the constraint effect coefficient of the top of the pile foundation;

[0076] η l is the lateral soil horizontal resistance effect coefficient of the pile cap;

[0077] η b is the bottom friction effect coefficient of the pile cap.

[0078] In particular, in actual application, the pile cap is placed on the ground surface and the side of the pile cap is not covered with soil, and the bottom friction effect coefficient η b of the pile cap and the lateral soil horizontal resistance effect coefficient η l of the pile cap can be ignored, and only the influence of η i and η r is considered.

[0079] Further, the calculation formula of the mutual influence effect coefficient η i of the pile foundation is as follows:

[0080]

[0081] wherein S a / d is the ratio of the center distance of the pile foundation to the pile diameter along the horizontal load action direction;

[0082] n1 is the number of piles in each row of pile foundations along the horizontal load action direction;

[0083] n2 is the number of piles in each row of pile foundations along the vertical direction of the horizontal load action.

[0084] Specifically, the constraint of the pile top in the pile cap has two states of free and embedded, the free state can make the bending moment of the pile top of the pile foundation zero and the horizontal displacement slightly large, and the embedded state can make the horizontal displacement of the pile cap small and the bending moment of the pile top of the pile foundation slightly large.

[0085] Therefore, the values of η r according to displacement control and bending control are shown in Table 2 as follows:

[0086] converted depth αh 2.4 2.6 2.8 3.0 3.5 ≥4.0 displacement control 2.58 2.34 2.20 2.13 2.07 2.05 intensity control 1.44 1.57 1.71 1.82 2.00 2.07

[0087] Table 2

[0088] Further, the single-pile horizontal bearing capacity characteristic value R ba is calculated by the formula:

[0089]

[0090] EI is the pile body bending stiffness of the pile foundation;

[0091] α is the pile-soil deformation coefficient of the pile foundation;

[0092] v x is the pile top horizontal displacement coefficient of the pile foundation;

[0093] Specifically, v x may be selected according to Table 3 as follows:

[0094]

[0095] Table 3

[0096] χ oa is the pile top horizontal displacement allowable value of the pile foundation, and the displacement control χ oa of the pile foundation is taken.

[0097] Further, χ oa has two control standards, which are the displacement of the pile foundation and the bending strength of the pile foundation, and when the bending strength of the pile body of the pile foundation is taken to control the value of χ oa , the calculation formula of χ oa is:

[0098] In particular, in Table 2 and Table 3, the conversion depth αh is the pile length conversion depth of the pile foundation, and specifically is:

[0099]

[0100] b p is the calculation width of the pile foundation;

[0101] m is the proportional coefficient of the foundation coefficient along the depth, kN / m 4 ;

[0102] h is the pile length of the pile foundation.

[0103] Further, in step 3, the calculation formula of F is: F = 0.8k1F1+0.6k2k3k4F2;

[0104] The interaction coefficient includes:

[0105] k1 is the factor of the influence of the pile length of the pile foundation on the bearing capacity of the electric pole body;

[0106] k2 is an influence factor of the pile length of the pile foundation on the bearing capacity of the fabricated foundation;

[0107] k3 is an influence factor of the embedded depth of the pole body on the bearing capacity of the fabricated foundation;

[0108] k4 is an influence factor of the size increase of the pile cap on the bearing capacity of the fabricated foundation;

[0109] Specifically, as shown in Table 4, the interaction coefficient is valued by numerical simulation:

[0110]

[0111] Table 4.

[0112] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the term "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above-mentioned term in the present application can be understood according to the specific circumstances.

[0113] Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

Claims

1. A method for calculating the anti-overturning bearing capacity of an electric pole with an assembled foundation, characterized by: The steps include: Step 1: Obtain the data of the pole body and calculate the anti-overturning ultimate bearing capacity F1 of the pole body; Step 2: Obtain the data of the prefabricated foundation and calculate the ultimate anti-overturning bearing capacity F2 of the prefabricated foundation; Step 3: Calculate the anti-overturning ultimate bearing capacity F of the pole body and the assembled foundation as a whole based on F1, F2 and the interaction coefficients corresponding to F1 and F2; In step 1, it is assumed that the soil has reached the limit equilibrium state. ; Where m is the soil parameter pressure; ,in is the actual width of the pole body, is the space enlargement coefficient; is the buried depth of the pole body; ,in It is the distance from the point of action of the horizontal force on the upper end of the pole body to the designed ground; ； In step 2, the assembled foundation includes a cap and a plurality of pile foundations vertically fixed to the bottom of the cap and buried underground. ,in, is the number of piles, is the characteristic value of the horizontal bearing capacity of a single pile, is the comprehensive effect coefficient; The comprehensive effect coefficient The calculation formula is: is the mutual influence effect coefficient of pile foundation; is the constraint effect coefficient of the pile foundation top; is the horizontal resistance effect coefficient of the lateral soil of the cap; is the friction effect coefficient of the bottom surface of the cap; The mutual influence effect coefficient of the pile foundation The calculation formula is: ； in, is the ratio of the center distance of the pile foundation along the direction of horizontal load to the pile diameter of the pile foundation; is the number of piles in each row of pile foundation along the direction of horizontal load action; is the number of piles in each row of pile foundation along the direction perpendicular to the horizontal load; In step 3, the calculation formula of F is: ; The interaction coefficients include: is the factor that affects the pile length of the pile foundation on the bearing capacity of the pole body; is the influencing factor of the pile length on the bearing capacity of the prefabricated foundation; is the influencing factor of the buried depth of the pole body on the bearing capacity of the prefabricated foundation; It is the influencing factor of the increase of the cap size on the bearing capacity of the prefabricated foundation.

2. The method for calculating the anti-overturning bearing capacity of an assembled foundation pole according to claim 1 is characterized in that: When the cap is placed on the ground and the side of the cap is not covered with soil, the friction effect coefficient of the cap bottom is ignored. and the horizontal resistance effect coefficient of the lateral soil of the cap .

3. The method for calculating the anti-overturning bearing capacity of a pole with an assembled foundation according to claim 1 is characterized in that: The characteristic value of the horizontal bearing capacity of a single pile The calculation formula is: ； in, is the bending stiffness of the pile body of the pile foundation; is the pile-soil deformation coefficient of the pile foundation; is the horizontal displacement coefficient of the pile top of the pile foundation; It is the allowable value of horizontal displacement of pile top in pile foundation.

4. The method for calculating the anti-overturning bearing capacity of a pole with an assembled foundation according to claim 3 is characterized in that: When the bending strength of the pile foundation is controlled When the value of The calculation formula is: .

5. The method for calculating the anti-overturning bearing capacity of an assembled foundation pole according to claim 1 is characterized in that: In the step 1, The following formula must be met: ； in is the ultimate overturning moment of the pole body; is the additional partial coefficient; It is the horizontal force acting on the upper part of the pole body on the ground.

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