Hydropower station cement pavement design axle load accumulative action frequency determination method based on transportation volume

Abstract

The invention discloses a transport volume-based method for determining the designed axle load accumulative action times of a cement pavement of a hydropower station. The method comprises the following steps of: calculating the transportation volume of the hydropower station, calculating load stress, calculating temperature stress and designing the axle load accumulative action times. The traffic load characteristics in the hydropower station construction period are considered, a more suitable design method for designing the accumulated axle load action times is provided, and the reliability and scientificity of the design method of the hydropower station cement pavement structure are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of cement pavement design, and in particular relates to a method for determining the cumulative number of axle load actions on a cement pavement design of a hydropower station based on transportation volume. Background Art

[0002] The primary function of cement pavement at a hydropower station is to provide transportation for the station, primarily transporting materials. The axle distribution and load characteristics of vehicles on these pavements differ significantly from those on ordinary roads. The majority of traffic on cement pavements at hydropower stations is concentrated during the construction phase, closely tied to the construction phase, and lacks the characteristic of increasing over time. Current standards cannot accurately calculate the cumulative number of axle loads acting on cement pavements designed for hydropower stations.

[0003] While existing technologies such as Patents 2020115205194 and 2023108356600 disclose methods for calculating the cumulative number of axle load actions, Patent 2020115205194 extrapolates daily traffic volume to annual traffic volume, and then calculates the cumulative equivalent axle loads during the design reference period. However, hydropower station traffic volume is dependent on factors such as construction organization and weather conditions, and daily traffic volume varies significantly between construction sections, making it impossible to extrapolate total traffic volume from daily traffic volume. Patent 2023108356600 refers to the formula in the "Design Specifications for Factory and Mine Roads" when determining the cumulative number of design axle load actions. The axle load conversion index is 11, derived by simplifying the linear fatigue equation and the Miner criterion. This does not consider the effects of different load levels on the degree of pavement damage or the effects of temperature stress on fatigue damage. Given the wide variation in axle loads on hydropower station roads, directly applying the conversion to the power of 11 distorts the results. Moreover, the above patent calculates the load stress according to the formula in Appendix B of the "Highway Cement Concrete Pavement Design Code" JTG D40-2011. The load stress formula in the current highway cement concrete pavement design code is only applicable to 30-140kN for single axle and 80-320kN for double axle. The vehicle load size of the hydropower station exceeds this range, and the calculation results using the load stress formula in the code are distorted.

[0004] In summary, how to determine the cumulative number of axle load actions on the design cement pavement of a hydropower station is a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The main purpose of this invention is to provide a method for determining the cumulative number of axle load actions on a hydropower station cement pavement based on transportation volume. Based on a statistical method for hydropower station transportation volume, the method uses load stress and temperature stress calculation formulas and cement concrete nonlinear fatigue equations to calculate the cumulative number of axle load actions on a hydropower station cement pavement.

[0006] The technical solutions proposed by the present invention are as follows:

[0007] A method for determining the cumulative number of axle load actions on a cement pavement design for a hydropower station based on transportation volume comprises the following steps:

[0008] S1. Traffic statistics of cement roads in hydropower stations

[0009] Calculate the total transportation volume of earthwork G1 and the total transportation volume of concrete G2;

[0010] Then, calculate the required external material and equipment transportation volume G3 and the overall total transportation volume G according to the percentage of the total concrete engineering volume to the total earthwork filling volume. 总 ;

[0011] Finally, the traffic volume K of different vehicles during the construction period is calculated based on the load of different vehicles. i ;

[0012] S2. Calculation of axial load stress and maximum temperature stress

[0013] Determine the structural combination of cement pavement structure, thickness of each structural layer, mechanical parameters of each structural layer material and axle load calculation parameters;

[0014] Calculate the axle load stress of different grades of vehicles based on the proposed cement pavement structure;

[0015] Calculate the maximum temperature stress based on the proposed cement pavement structure;

[0016] S3. Calculation of the cumulative number of times the design axle load acts

[0017] An axle load conversion formula is established based on the nonlinear fatigue equation and Miner's linear cumulative damage criterion, and the axle load stress and maximum temperature stress obtained in step S2 are substituted into the conversion formula to obtain the axle load conversion coefficient;

[0018] According to the axle load conversion coefficient and the traffic volume K obtained in step S1 i , calculate the cumulative number of times the design axle load acts.

[0019] Specifically, the calculation expression of the axle load conversion coefficient is:

[0020]

[0021] Among them, N s is the maximum number of fatigue actions under the design axle load, N ij The maximum number of fatigue actions of the j-th axle load of the i-th vehicle, D s is the fatigue damage under any axial load, D i is the fatigue damage of the i-th vehicle under the j-th axle load, σ ps is the design axial load stress, σ pi is the load stress on the j-th axle of the i-th vehicle, σt is the maximum temperature stress, f r is the flexural strength of cement concrete.

[0022] Specifically, the calculation formula for axial load stress is:

[0023]

[0024] Where: D c is the cross-sectional bending stiffness of the surface plate; D b is the cross-sectional bending stiffness of the base plate; P is the uniaxial load; is the moment distribution coefficient; M c is the bending moment coefficient of the surface plate; h c is the thickness of the cement surface layer.

[0025] Specifically, the maximum temperature stress calculation formula is:

[0026]

[0027] Where: α c is the linear expansion coefficient of concrete; E c h is the elastic modulus of the surface material; c is the thickness of cement surface layer; T g is the maximum temperature gradient; B L is the temperature stress coefficient of the comprehensive temperature warping stress and internal stress.

[0028] Specifically, the calculation formula for the cumulative number of axle load actions is:

[0029]

[0030] Among them, η1 is the lateral distribution coefficient of the vehicle wheel track; η2 is the lane allocation coefficient; n is the number of vehicle types; and m is the number of vehicle axles.

[0031] Specifically, the traffic volume K i The expression is:

[0032]

[0033] Where: C i is the vehicle transport volume allocation coefficient; K i载重 Rated load of the vehicle.

[0034] Specifically, the material mechanical parameters of each structural layer are the elastic modulus and Poisson's ratio of each structural layer, and the axle load calculation parameters are the single axle axle weight of vehicles of different grades and the equivalent load radius of the wheel load on one side.

[0035] Specifically, D c 、D bThe calculation refers to Section B.2.2-3 of the Highway Cement Concrete Pavement Design Specification JTG 3340-202*. Compared with the prior art, the present invention has the following advantages:

[0036] 1. The present invention calculates the traffic volume of different levels of vehicles during the construction of a hydropower station through the transportation volume during the construction of the hydropower station, which can accurately reflect the traffic characteristics during the construction of the hydropower station and more accurately calculate the overall traffic volume of the hydropower station.

[0037] 2. In the part of load stress calculation, the present invention refers to the calculation method of the new draft for comments to obtain a load stress calculation formula that takes into account the equivalent load radius of the wheel load on one side. The axle load conversion result is more in line with the actual working conditions.

[0038] 3. The present invention adopts nonlinear fatigue equation to convert axle load, which can reflect the difference in the degree of damage to the pavement caused by different levels of load, making the calculation of the cumulative number of times the design axle load acts more accurate, improving and supplementing the design of cement pavement thickness of hydropower stations, and playing a role in improving and beneficially supplementing the current specifications. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0040] 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] See also Figure 1 A method for determining the cumulative number of axle load actions on cement pavement design for a hydropower station based on transportation volume includes the following steps:

[0042] S1. Traffic statistics of cement roads in hydropower stations

[0043] First, calculate the total transportation volume of earthwork G1 and the total transportation volume of concrete G2;

[0044] G1=V1ρ1

[0045] G2=V2ρ2

[0046] Where: V1 is the total earthwork volume, m 3 ; ρ1 is the loose density of earth and rock, t / m 3 ; V2 is the total concrete volume, m 3 ; ρ2 is the density of concrete, t / m 3 ;

[0047] Then, calculate the required external material and equipment transportation volume G3 and the total transportation volume G according to the percentage of the total concrete engineering volume to the total earthwork filling volume. 总 as follows;

[0048] G3=V2D

[0049] G 总 =G 1+ G 2+ G3

[0050] Where: D is per 1m 3 Transportation volume of external materials and equipment required for concrete, t / m 3 ; V1 and V2 are obtained according to the design of the hydropower station.

[0051] Finally, the traffic volume K of different vehicles during the construction period is calculated based on the load of different vehicles. i as follows;

[0052]

[0053] Where: C i is the vehicle transport volume allocation coefficient; K i载重 is the rated load of the vehicle, t / vehicle.

[0054] S2. Calculation of axial load stress and temperature stress

[0055] First, determine the structural combination of the cement pavement structure, the thickness of each structural layer, the mechanical parameters of each structural layer material (including elastic modulus and Poisson's ratio) and axle load calculation parameters (including single-axle axle weight of different grades of vehicles and equivalent load radius of one side wheel load).

[0056] Next, the axle load stress of vehicles of different grades is calculated based on the proposed cement pavement structure. The calculation formula is:

[0057]

[0058] Where: D c is the cross-sectional bending stiffness of the surface layer, MPa·m 3 ;D b is the cross-sectional bending stiffness of the base plate, MPa·m 3 ; P is the axle load, MN; is the moment distribution coefficient; M c is the bending moment coefficient of the surface plate; h c is the thickness of cement surface layer, m;

[0059] Finally, the maximum temperature stress is calculated based on the proposed cement pavement structure using the following formula:

[0060]

[0061] Where: α c is the linear expansion coefficient of concrete; E c is the elastic modulus of the surface material, MPa; h c is the thickness of cement surface layer, m; T g is the maximum temperature gradient, °C; B L is the temperature stress coefficient of the comprehensive temperature warping stress and internal stress.

[0062] S3. Calculation of the cumulative number of times the design axle load acts

[0063] First, the axle load conversion formula is established based on the nonlinear fatigue equation and Miner's linear cumulative damage criterion, and the axle load conversion coefficient is calculated as follows:

[0064]

[0065] Among them, N s is the maximum number of fatigue actions under the design axle load, N ij is the maximum fatigue action times of the j-th axle load of the i-th vehicle, D s is the fatigue damage under any axial load, D ij is the fatigue damage of the i-th vehicle under the j-th axle load, σ ps is the design axial load stress, σ pij is the load stress of the jth axle load of the i-th vehicle, σ t is the maximum temperature stress, f r is the flexural strength of cement concrete, which is 5MPa.

[0066] Next, the cumulative number of times the design axle load acts is calculated as follows:

[0067]

[0068] Among them, η1 is the lateral distribution coefficient of the vehicle wheel track, which is 0.5-0.65 for a single lane and 0.4-0.5 for a double lane; η2 is the lane allocation coefficient, which is 1 for a single lane and 0.5 for a double lane; n is the number of vehicle types; m is the number of vehicle axles.

[0069] Specifically, D c 、D b The calculation method refers to B.2.2-3 of the "Highway Cement Concrete Pavement Design Specification" (Draft for Comments JTG3340-202*), as follows:

[0070]

[0071] Among them, E c is the elastic modulus of the surface layer, MPa; hc is the thickness of the surface layer, m; v c is the Poisson's ratio of the surface material; E b is the elastic modulus of the base plate, MPa; h b is the thickness of the base plate, m; v b is the Poisson's ratio of the surface material.

[0072] Specifically, The calculation method refers to B.2.2-2 of the "Highway Cement Concrete Pavement Design Specification" (Draft for Comments JTG 3340-202*), as follows:

[0073]

[0074] Among them, k v is the vertical spring coefficient between the double-layer plates with interlayer conditions, MN / m; k v0 is the vertical spring coefficient between double-layer plates without interlayer, MN / m;

[0075] Specifically, M c Calculate according to the following formula:

[0076]

[0077] Where a is the equivalent load radius of the wheel load on one side, m, refer to Table 5.5.2 of the "Design Code for Factory and Mine Roads" GBJ 22-1987; r g To calculate the equivalent relative stiffness radius of the double-layer plate under load stress, mm, the calculation method refers to B.2.3-3 in the "Highway Cement Concrete Pavement Design Code" (Draft for Comments JTG 3340-202*).

[0078] Specifically, g The equivalent relative stiffness radius is calculated as follows:

[0079]

[0080] Among them, E t , equivalent rebound modulus of the bottom foundation, MPa; v t is the Poisson's ratio of the slab foundation.

[0081] Specifically, the equivalent rebound modulus of the slab foundation is calculated as follows:

[0082]

[0083] α=0.86+0.26ln h x

[0084]

[0085] Where E0 is the rebound modulus of the roadbed top, MPa; α is the regression coefficient related to the total thickness of the granular layer; E x is the equivalent rebound modulus of the granular layer, MPa; h x is the total thickness of the granular layer, m; w, the number of granular layers; E y is the rebound modulus of the yth granular layer, MPa; h y is the thickness of the yth granular layer, m.

[0086] Specifically, α c is the linear expansion coefficient of concrete; T g is the maximum temperature gradient, ℃, determined by referring to Table E.0.3-2 and Table 3.0.10 in the Code for Design of Highway Cement Concrete Pavement JTG D40-2011.

[0087] Specifically, B L The temperature stress coefficient for the comprehensive temperature warping stress and internal stress is calculated with reference to B.3.3 of the "Highway Cement Concrete Pavement Design Code" JTG D40-2011 as follows:

[0088]

[0089] Where, L is the length of the surface plate, m; r g is the equivalent relative stiffness radius of the double-layer plate when calculating load stress, m; h c is the thickness of the surface layer, m; E c is the elastic modulus of the surface layer, MPa; h c is the thickness of the surface layer, m; E b is the elastic modulus of the base plate, MPa; h b is the thickness of the base plate, m; D c is the cross-sectional bending stiffness of the surface layer, MPa·m 3 ;D b is the cross-sectional bending stiffness of the base plate, MPa·m 3 ξ is a parameter related to the double-layer plate structure; r β is the interlayer contact condition parameter, m; k n , vertical contact stiffness between the surface layer and the base layer, MPa / m.

[0090] The technical solution of the present invention is further described by taking the cement pavement structure of a hydropower station as an example. The following specific examples further describe the present invention, but do not limit the scope of protection of the present invention.

[0091] S1. Statistics of cement road transportation volume at hydropower stations

[0092] First, determine the total earthwork transportation volume, total earthwork filling volume, total concrete transportation volume, loose density of earthwork, and concrete density of the hydropower station (Table 1); 1m 3 Transportation volume of external concrete materials and equipment (Table 2).

[0093] Table 1 Transport volume and density of hydropower stations

[0094] <![CDATA[Total earthwork volume (m 3 )]]> 2536000 <![CDATA[Total volume of concrete (m 3 )]]> 753000 Percentage of total concrete transport volume to total earth and rock filling volume 15％ <![CDATA[Loose density of earth and rock (t / m 3 )]]> 2.3 <![CDATA[Concrete density (t / m 3 )]]> 2.4

[0095] Table 2 1m 3 Transportation volume of external concrete materials and equipment

[0096]

[0097] The total transportation volume of earth and stone, the total transportation volume of concrete, the transportation volume of external materials and equipment, and the total transportation volume are calculated.

[0098] G1=V1ρ1=5832800t

[0099] G2=V2ρ2=1807200t

[0100] G3=V2D=692760t

[0101] G 总 =G 1+ G 2+ G3=8332760t

[0102] There are two main types of vehicles during the construction of the water station: 1载重 15t), Qi-40 vehicle load (K 2载重 The traffic volume of the two types of vehicles during the construction period was calculated based on the design load of the rear axle of the Qi-30 vehicle (Table 3).

[0103] Table 3 Traffic volume of each axle of different grades of vehicles

[0104]

[0105]

[0106] S2. Calculation of load stress and temperature stress

[0107] First, determine the structural combination of the cement pavement structure, the thickness of each structural layer, the mechanical parameters of the materials of each structural layer, and the axle load calculation parameters.

[0108] The mechanical parameters of the materials of each structural layer are determined according to the "Highway Cement Concrete Pavement Design Code" JTG D40-2011 (see Table 4); the axle load calculation parameters can be determined according to the "Factory and Mine Road Design Code" GBJ 22-1987 (Table 5).

[0109] Table 4 Pavement structure and material mechanical parameter values

[0110] Structural layer Elastic modulus (MPa) Poisson's ratio μ Thickness (m) Cement concrete surface layer 31000 0.15 0.28 Cement stabilized gravel base 2000 0.25 0.3 Graded crushed stone subbase 250 0.35 0.25 roadbed 50 0.4 —

[0111] Table 5 Axle load calculation parameters

[0112]

[0113] Next, the load stresses of different axles of the two vehicles were calculated (Table 6).

[0114]

[0115] α=0.26ln(h x )+0.86=0.26×ln(0.2)+0.86=0.499

[0116]

[0117]

[0118] Table 6 Bending moment coefficient and load stress of surface plate at different axes

[0119]

[0120] Next, the location of the hydropower station is Zone IV. According to Table E.0.3-2 and Table 3.0.10 in the "Highway Cement Concrete Pavement Design Code" JTG D40-2011, T g The temperature is 92℃ / m, the linear expansion coefficient of concrete is 0.000007, and the maximum temperature stress of the pavement structure is calculated with reference to the current specifications.

[0121]

[0122]

[0123] S3. Calculation of the cumulative number of times the design axle load acts

[0124] First, the axle load conversion factor is calculated based on the load stress and maximum temperature stress calculated in S2 (Table 7).

[0125] Table 7 Axle load conversion factors

[0126]

[0127] The cumulative number of times the design axle load acts is calculated.

[0128]

[0129] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed above in terms of preferred embodiments, this is not intended to limit the present invention. Therefore, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical solution of the present invention and are based on the technical essence of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for determining the cumulative number of axle load actions on a cement pavement design for a hydropower station based on transportation volume, characterized in that: The steps include: S1. Traffic statistics of cement roads in hydropower stations Calculate the total transportation volume of earthwork G1 and the total transportation volume of concrete G2; Then, calculate the required external material and equipment transportation volume G3 and the overall total transportation volume G according to the percentage of the total concrete engineering volume to the total earthwork filling volume. 总 ; Finally, the traffic volume K of different vehicles during the construction period is calculated based on the load of different vehicles. i ; S2. Calculation of axial load stress and maximum temperature stress Determine the structural combination of cement pavement structure, thickness of each structural layer, mechanical parameters of each structural layer material and axle load calculation parameters; Calculate the axle load stress of different grades of vehicles based on the proposed cement pavement structure; Calculate the maximum temperature stress based on the proposed cement pavement structure; S3. Calculation of the cumulative number of times the design axle load acts The axle load conversion formula is established based on the nonlinear fatigue equation and Miner linear cumulative damage criterion, and the axle load stress and maximum temperature stress obtained in step S2 are substituted into the conversion formula to obtain the axle load conversion coefficient; based on the axle load conversion coefficient and the traffic volume K obtained in step S1, i , calculate the cumulative number of times the design axle load acts.

2. The method for determining the cumulative number of axle load actions on a cement pavement designed for a hydropower station according to claim 1, characterized in that: The calculation expression of axle load conversion factor is: Among them, N s is the maximum number of fatigue actions under the design axle load, N ij The maximum number of fatigue actions of the j-th axle load of the i-th vehicle, D s is the fatigue damage under any axial load, D ij is the fatigue damage of the i-th vehicle under the j-th axle load, σ ps is the design axial load stress, σ pij is the load stress of the jth axle load of the i-th vehicle, σ t is the maximum temperature stress, f r is the flexural strength of cement concrete.

3. The method for determining the cumulative number of axle load actions on a cement pavement designed for a hydropower station according to claim 2, characterized in that: The calculation formula for axial load stress is: Where: D c is the cross-sectional bending stiffness of the surface plate; D b is the cross-sectional bending stiffness of the base plate; P is the uniaxial load; is the moment distribution coefficient; M c is the bending moment coefficient of the surface plate; h c is the thickness of the cement surface layer.

4. The method for determining the cumulative number of axle load actions on a cement pavement designed for a hydropower station according to claim 3, characterized in that: The maximum temperature stress calculation formula is: Where: α c is the linear expansion coefficient of concrete; E c h is the elastic modulus of the surface material; c is the thickness of cement surface layer; T g is the maximum temperature gradient; B L is the temperature stress coefficient of the comprehensive temperature warping stress and internal stress.

5. The method for determining the cumulative number of axle load actions on a cement pavement designed for a hydropower station according to claim 4, characterized in that: The calculation formula for the cumulative number of axle load actions is: Among them, η1 is the lateral distribution coefficient of the vehicle wheelbase, η2 is the lane distribution coefficient, n is the number of vehicle types, and m is the number of vehicle axles.

6. The method for determining the cumulative number of axle load actions on a cement pavement designed for a hydropower station according to any one of claims 1 to 5, characterized in that: Traffic volume K i The expression is: Where: C i is the vehicle transport volume allocation coefficient, K i载重 Rated load for different grades of vehicles.

7. The method for determining the cumulative number of axle load actions on a cement pavement designed for a hydropower station according to claim 6, characterized in that: The mechanical parameters of the materials of each structural layer are the elastic modulus and Poisson's ratio of each structural layer, and the axle load calculation parameters are the single axle weight of vehicles of different grades and the equivalent load radius of the wheel load on one side.

8. The method for determining the cumulative number of axle load actions on a cement pavement designed for a hydropower station according to claim 6, characterized in that: D c 、D b The calculation refers to Section B.2.2-3 of the Highway Cement Concrete Pavement Design Specification JTG 3340-202*.

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