Prediction method and system for crushing strength of rockfill materials considering stress-wetting and drying cycle coupling effect

Abstract

The present invention provides a prediction method and system for the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycle. The method includes: Step S1, obtaining multiple groups of rockfill material samples; Step S2, conducting stress-wet-dry cycle coupling tests on each group of the rockfill material samples under different numbers of wet-dry cycles N and different stresses P; Step S3, conducting crushing tests on each group of the rockfill material samples that have completed the stress-wet-dry cycle coupling tests; Step S4, constructing a prediction model for the crushing strength of rockfill materials considering the coupling influence of stress and the number of wet-dry cycles; Step S5, predicting the crushing strength of the rockfill materials to be predicted under different wet-dry cycles and different stresses. The present invention fully considers the coupling effect of stress and wet-dry cycle on rockfill materials in the actual environment of the rockfill dam, so that more data conforming to the crushing strength of rockfill materials can be predicted.

Description

Technical Field

[0001] The present invention belongs to the technical field of experimental research on geotechnical granular materials, and particularly relates to a prediction method and system for the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycle. Background Art

[0002] In recent years, due to the comprehensive utilization and development needs of water resources, there are many high dam projects under construction or in planning in high-altitude areas. The topographic and geological conditions of the areas where these high dam projects are located are usually very complex, with frequent earthquakes and high intensities, harsh natural environments, and inconvenient transportation. Rockfill dams have the advantages of making full use of local materials, having better adaptability to topographic and geological conditions, lower construction costs, and simple construction methods. Therefore, rockfill dams have become one of the main dam types for hydropower construction in high-altitude areas.

[0003] Up to now, there are a number of 200 - 300m high rockfill dams under construction and proposed construction, such as Shuangjiangkou on the Dadu River, Rumei on the Lancang River, Qizong, Lawa, and Gushui on the Jinsha River. These projects have large construction scales and far-reaching engineering significance. Therefore, it is necessary to accurately evaluate the safety and stability during the operation of high rockfill dams.

[0004] Engineering practices have shown that during the long-term operation of rockfill dams, the physical and mechanical properties of rockfill materials, which are the main dam-building materials, will deteriorate under the influence of various factors, thus directly affecting the overall safety of rockfill dams. Therefore, determining the key factors that affect the physical and mechanical properties of rockfill materials that are more in line with the actual engineering operation environment, and quantitatively determining the relationship between the key factors and the physical and mechanical properties of rockfill materials, so as to provide basic data support for evaluating the overall safety during the operation of rockfill dams, is the key point to be solved at present. Summary of the Invention

[0005] Aiming at the defects existing in the prior art, the present invention provides a prediction method and system for the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycle, which can effectively solve the above problems.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The present invention provides a prediction method for the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycle, including the following steps:

[0008] Step S1, obtaining multiple groups of rockfill material samples;

[0009] Each group of the rockfill material samples includes multiple rockfill material particles; record the particle size d, long axis L, middle axis I, and short axis S of each rockfill material particle; each rockfill material particle in each group of the rockfill material samples has the same rockfill material particle characteristics; wherein, the rockfill material particle characteristics include rockfill material particle size characteristics and rockfill material particle shape characteristics;

[0010] Step S2, perform a stress-wetting and drying cycle coupling test on each group of the rockfill samples under different numbers of wetting and drying cycles N and different stresses P;

[0011] Step S3, perform a crushing test on each group of the rockfill samples that have completed the stress-wetting and drying cycle coupling test in Step S2 to obtain their crushing strength σ; thus, multiple sets of test data are obtained; each set of test data records the corresponding relationship and values of the number of wetting and drying cycles N, the crushing strength σ, and the stress P;

[0012] Step S4, based on the test data obtained in Step S3, study the variation relationship of the crushing strength σ of the rockfill samples with the stress P under different numbers of wetting and drying cycles N, and construct a prediction model for the crushing strength of the rockfill considering the coupling effects of stress and the number of wetting and drying cycles;

[0013] Step S5, use the prediction model for the crushing strength of the rockfill considering the coupling effects of stress and the number of wetting and drying cycles obtained in Step S4 to predict the crushing strength of the rockfill to be predicted under different wetting and drying cycles and different stresses.

[0014] Preferably, Step S1 is specifically as follows:

[0015] Step S1.1, perform a preliminary screening on the rockfill used for the test, and screen out multiple rockfill particles with a particle size d within a set range; use a three-dimensional scanner to obtain and record the shape parameters of each screened rockfill particle, including the major axis L, the intermediate axis I, and the minor axis S;

[0016] Step S1.2, for each screened rockfill particle, calculate the particle size d and the shape characteristic S of each rockfill particle according to the shape parameters (L, I, S) of each rockfill particle I ;

[0017] Step S1.3, according to the particle size d and the shape characteristic S of each screened rockfill particle obtained in Step S1.2 I , further screen all the screened rockfill particles, and screen out the rockfill particles with a particle size d and a shape characteristic S I meeting the test requirements, thereby obtaining rockfill particles with the same rockfill particle characteristics;

[0018] Step S1.4, group the multiple rockfill particles with the same rockfill particle characteristics screened out in Step S1.3, and each group forms one of the rockfill samples.

[0019] Preferably, in Step S1.2, the particle size d of the rockfill particles is calculated using formula (1):

[0020]

[0021] Thus, the particle size d of the rockfill particles is obtained.

[0022] Preferably, in step S1.2, the shape characteristic S of the rockfill particles is obtained by using formula (2). I ;

[0023]

[0024] In step S1.3, the rockfill particles with the shape characteristic S I between 0.6 and 0.8 are screened out. The rockfill particles with the shape characteristic S I between 0.6 and 0.8 are specifically flat.

[0025] Preferably, in step S1.3, the difference in the particle size d of the screened rockfill particles does not exceed 10%; in step S1.4, the number of rockfill particles in the rockfill sample is not less than 30 and they have the same lithology.

[0026] Preferably, step S2 is specifically as follows:

[0027] For each group of the rockfill samples, they are layered and placed into the barrel of the stress-dry-wet cycle coupling test device. Moreover, the dry density of the rockfill particles filled in each layer is 1.05 times that of the rockfill particles in the layer below, so as to ensure that each rockfill particle is evenly stressed during the stress-dry-wet cycle coupling test. After the filling is completed, the stress-dry-wet cycle coupling test is carried out under different dry-wet cycle numbers N and different stresses P.

[0028] Preferably, step S3 is specifically as follows:

[0029] Step S3.1: Place each group of the rockfill samples that have completed the stress-dry-wet cycle coupling test described in step S2 on the lower loading plate of the crushing test device, and make the axis direction of the short axis S of the rockfill particles in each group of the rockfill samples parallel to the upper and lower loading plates of the crushing test device;

[0030] Step S3.2: Conduct a crushing test by using the crushing test device, record the load F when the rockfill sample is crushed, and calculate the crushing strength σ of the rockfill sample;

[0031] Step S3.3: Record the corresponding relationship and values of the dry-wet cycle number N, the crushing strength σ, and the stress P to form test data.

[0032] Preferably, step S3.2 is specifically as follows:

[0033] The crushing strength σ of the rockfill sample is obtained by using formula (3):

[0034]

[0035] Thus, the crushing strength σ of the rockfill sample is obtained.

[0036] Preferably, step S4 is specifically as follows:

[0037] Step S4.1, assume that the number of wet-dry cycles N in the test is designed with n values, which are respectively: N1, N2,..., N n ;

[0038] Step S4.2, when the number of wet-dry cycles N = N i , where i = 1, 2,..., n, the variation relationship equation of the crushing strength σ of the rockfill sample shown in formula (4) with respect to the stress P is obtained:

[0039] σ = a i + b i P (4)

[0040] where a i , b i are the values of the correlation coefficient a and the value of the correlation coefficient b when the number of wet-dry cycles N = N i ;

[0041] Since the number of wet-dry cycles N is designed with n values, the variation relationship equation set of the crushing strength σ of the rockfill sample shown in formula (5) with respect to the stress P is obtained:

[0042]

[0043] Step S4.3, therefore, for the n values N1, N2,..., N n of the number of wet-dry cycles N, n values of the correlation coefficient a are correspondingly obtained, which are respectively: a1, a2,..., a n ; n values of the correlation coefficient b are correspondingly obtained, which are respectively: b1, b2,..., b n ;

[0044] Step S4.4, based on the relationship obtained in step S4.3, analyze the correlation relationship between the correlation coefficient a and the number of wet-dry cycles N to obtain the correlation relationship equation shown in formula (6); analyze the correlation relationship between the correlation coefficient b and the number of wet-dry cycles N to obtain the correlation relationship equation shown in formula (7);

[0045] a = αln(-βln(N)) (6)

[0046]

[0047] where: α, β, γ, η are all the values of the fitting coefficients in the correlation relationship equation;

[0048] Step S4.5. Thus, a broken strength change model of the rockfill considering the coupled influence of stress and the number of wet-dry cycles as shown in formula (8) is constructed:

[0049]

[0050] Thus, a prediction model of the broken strength of the rockfill considering the coupled influence of stress and the number of wet-dry cycles is obtained.

[0051] The present invention also provides a system for implementing the prediction method of the broken strength of the rockfill considering the stress-wet-dry cycle coupling effect, including:

[0052] A preprocessing module, configured to preprocess and group the rockfill particles to obtain multiple groups of rockfill samples;

[0053] A coupling and crushing test module, configured to perform stress-wet-dry cycle coupling tests on each group of rockfill samples processed by the preprocessing module under different numbers of wet-dry cycles N and different stresses P, and perform crushing tests on each group of the rockfill samples that have completed the stress-wet-dry cycle coupling tests to obtain their broken strength σ; thereby obtaining multiple sets of test data; each set of test data records the corresponding relationship and values of the number of wet-dry cycles N, the broken strength σ, and the stress P;

[0054] A prediction model construction module, configured to study the variation relationship of the broken strength σ of the rockfill samples with the stress P under different numbers of wet-dry cycles N according to the test data, and construct a prediction model of the broken strength of the rockfill considering the coupled influence of stress and the number of wet-dry cycles;

[0055] A broken strength prediction module, configured to use the prediction model of the broken strength of the rockfill considering the coupled influence of stress and the number of wet-dry cycles to predict the broken strength of the rockfill to be predicted under different wet-dry cycles and different stresses.

[0056] The prediction method and system of the broken strength of the rockfill considering the stress-wet-dry cycle coupling effect provided by the present invention have the following advantages:

[0057] The present invention provides a prediction method and system of the broken strength of the rockfill considering the stress-wet-dry cycle coupling effect, which fully considers the influence of the stress-wet-dry cycle coupling effect on the broken strength of the rockfill, accurately predicts data that is more in line with the actual broken strength of the rockfill in actual engineering, and provides a reference for predicting the change of the broken strength of the rockfill for building a dam during the operation of an actual rockfill dam project under the influence of the cyclic change of the reservoir water level and the self-weight of the dam body. Description of the Drawings

[0058] Figure 1Flow chart of the prediction method for the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycles provided by the present invention;

[0059] Figure 2 Graph showing the variation relationship between the crushing strength σ of rockfill materials and the stress P under different numbers of wet-dry cycles N provided by the embodiments of the present invention;

[0060] Figure 3 Graph showing the correlation relationship between the fitting coefficient a and the number of wet-dry cycles N provided by the embodiments of the present invention;

[0061] Figure 4 Graph showing the correlation relationship between the fitting coefficient b and the number of wet-dry cycles N provided by the embodiments of the present invention;

[0062] Figure 5 Surface graph showing the variation of the crushing strength σ of rockfill materials with the number of wet-dry cycles N and the stress P provided by the embodiments of the present invention;

[0063] Figure 6 Typical load-displacement curve graph obtained from the stress-wet-dry cycle coupling test of rockfill materials after experiencing 20, 32, and 40 wet-dry cycles and coupling a stress P of 1.5 MPa provided by the embodiments of the present invention. Detailed implementation manners

[0064] In order to make the technical problems, technical solutions, and beneficial effects solved by the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0065] The present invention provides a prediction method and system for the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycles, fully considering the influence of the stress-wet-dry cycle coupling effect on the crushing strength of rockfill materials, accurately predicting data that is more in line with the actual crushing strength of rockfill materials in actual projects, and providing a reference for predicting the change of the crushing strength of the rockfill materials for building dams in actual rockfill dam projects under the influence of the cyclic change of the reservoir water level and the self-weight of the dam body during operation.

[0066] Specifically, the inventors have found through research that during the long-term operation of the rockfill dam, during the water storage and operation stages, the water level of the reservoir will fluctuate periodically between the dead water level and the normal water storage level. The rockfill materials inside the upstream rockfill area are therefore subject to the dry-wet cycle, and under the action of the dam body's own weight, they are also subject to the continuous action of external stress. The dry-wet cycle and the action of external stress will cause the physical and mechanical properties of the rockfill materials, such as shear strength and deformation modulus, to deteriorate significantly, thereby causing the rockfill dam to deform incoordinated and excessively, leading to cracks on the dam top and instability of the dam slope. The dry-wet cycle and the action of external stress will change the physical and mechanical properties of the rockfill materials, which is specifically manifested in that when the external stress increases, the rockfill materials are more likely to break. At the same time, under the action of the dry-wet cycle, the crushing strength of the rockfill materials will decrease.

[0067] Therefore, combined with the characteristics of the long-term operating environment of rockfill dams, it is determined that the effects of dry-wet cycles and external stress are key factors affecting the physical and mechanical properties of rockfill materials. The present invention studies the changes in the physical and mechanical properties of rockfill materials after dry-wet cycles and external stresses, and predicts and determines the crushing strength of rockfill materials after an unknown number of dry-wet cycles and unknown stresses through a limited number of test data, thereby providing a reference for predicting the changes in the physical and mechanical properties of rockfill materials for actual rockfill dam projects under the influence of reservoir water level cycles and the deadweight of the dam body during operation.

[0068] like Figure 1 As shown, the present invention provides a method for predicting the crushing strength of rockfill materials considering the stress-dry-wet cycle coupling effect, comprising the following steps:

[0069] Step S1, obtaining multiple groups of rockfill material samples;

[0070] Each group of rockfill material samples includes a plurality of rockfill material particles; the particle size d, the major axis L, the median axis I and the minor axis S of each rockfill material particle are recorded; each rockfill material particle in each group of rockfill material samples has the same rockfill material particle characteristics; wherein the rockfill material particle characteristics include the rockfill material particle size characteristics and the rockfill material particle shape characteristics;

[0071] Step S1 is specifically as follows:

[0072] Step S1.1, preliminarily screening the rockfill material for the test, screening out a plurality of rockfill material particles with a particle size d within a set range; using a three-dimensional scanner to obtain and record shape parameters of each rockfill material particle after screening, including a major axis L, a middle axis I, and a minor axis S;

[0073] Step S1.2, for each rockfill particle after screening, according to the shape parameters (L, I, S) of each rockfill particle, calculate the particle size d and shape feature S of each rockfill particle I ;

[0074] In the present invention, the particle size d of the rockfill particles is calculated by using formula (1):

[0075]

[0076] Thus, the particle size d of the rockfill particles is obtained.

[0077] The shape characteristic S of the rockfill particles is obtained by using formula (2) I ;

[0078]

[0079] Step S1.3: According to the particle size d and the shape characteristic S of each sieved rockfill particle obtained in step S1.2 I , all the sieved rockfill particles are further screened to select the rockfill particles with the particle size d and the shape characteristic S I meeting the test requirements, thereby obtaining rockfill particles with the same rockfill particle characteristics;

[0080] As an example, the rockfill particles with the shape characteristic S I between 0.6 and 0.8 are selected. The rockfill particles meeting the shape characteristic S I between 0.6 and 0.8 are specifically flat. The particle size d is between 20 and 22 mm, and the difference in the particle size d does not exceed 10%;

[0081] Step S1.4: Group the multiple rockfill particles with the same rockfill particle characteristics screened in step S1.3, and each group forms one of the rockfill samples.

[0082] For example, the number of rockfill particles in each group of rockfill samples is not less than 30 and the lithology is the same.

[0083] Step S2: Perform a stress-wetting and drying cycle coupling test on each group of the rockfill samples under different numbers of wetting and drying cycles N and different stresses P;

[0084] Step S2 is specifically as follows:

[0085] For each group of the rockfill material samples, they are placed layer by layer into the cylinder of the stress-wetting and drying cycle coupling test device. For example, they are placed in 5 layers into the cylinder of the stress-wetting and drying cycle coupling test device. And, in order to make the rockfill material samples as uniform as possible and the stress on each rockfill particle more balanced during the stress-wetting and drying cycle coupling test, the dry density of the rockfill particles filled in each layer is 1.05 times that of the rockfill particles in the layer below it, so as to ensure that when the stress-wetting and drying cycle coupling test is carried out, the stress on each rockfill particle is balanced; after the filling is completed, the stress-wetting and drying cycle coupling test is carried out under different numbers of wetting and drying cycles N and different stresses P.

[0086] When carrying out the stress-wetting and drying cycle coupling test, the setting of the stress P needs to meet the requirement of being less than 50% of the crushing strength of the rockfill particles in the natural state, so as to ensure that all rockfill particles do not break during the stress-wetting and drying cycle coupling test. As an embodiment, the stress P is set to be less than 4 MPa.

[0087] Step S3: Conduct a crushing test on each group of the rockfill material samples that have completed the stress-wetting and drying cycle coupling test described in Step S2 to obtain their crushing strength σ; thus, multiple sets of test data are obtained; each set of test data records the corresponding relationship and values of the number of wetting and drying cycles N, the crushing strength σ, and the stress P.

[0088] Step S3 is specifically as follows:

[0089] Step S3.1: Place each group of the rockfill material samples that have completed the stress-wetting and drying cycle coupling test described in Step S2 on the lower loading plate of the crushing test device, and make the axis direction of the short axis S of the rockfill particles in each group of the rockfill material samples parallel to the upper and lower loading plates of the crushing test device.

[0090] Step S3.2: Conduct a crushing test using the crushing test device, record the load F when the rockfill material sample breaks, and use formula (3) to obtain the crushing strength σ of the rockfill material sample:

[0091]

[0092] Thus, the crushing strength σ of the rockfill material sample is obtained.

[0093] Step S3.3: Record the corresponding relationship and values of the number of wetting and drying cycles N, the crushing strength σ, and the stress P to form test data.

[0094] Step S4: According to the test data obtained in Step S3, study the variation relationship of the crushing strength σ of the rockfill material sample with the stress P under different numbers of wetting and drying cycles N, and construct a prediction model for the crushing strength of the rockfill considering the coupling effects of stress and the number of wetting and drying cycles.

[0095] Step S4 is specifically as follows:

[0096] Step S4.1: Assume that there are n designed values for the number of wet-dry cycles N in the experiment, which are: N1, N2,..., N n ;

[0097] Step S4.2: When the number of wet-dry cycles N = N i , where i = 1, 2,..., n, the variation relationship equation of the crushing strength σ of the rockfill sample with the stress P shown in formula (4) is obtained:

[0098] σ = a i + b i P (4)

[0099] where a i , b i are the values of the correlation coefficient a and the value of the correlation coefficient b when the number of wet-dry cycles N = N i ;

[0100] Since there are n designed values for the number of wet-dry cycles N, the variation relationship equation set of the crushing strength σ of the rockfill sample with the stress P shown in formula (5) is obtained:

[0101]

[0102] Step S4.3: Therefore, for the n values N1, N2,..., N n of the number of wet-dry cycles N, n values of the correlation coefficient a are correspondingly obtained, which are: a1, a2,..., a n ; correspondingly, n values of the correlation coefficient b are obtained, which are: b1, b2,..., b n ;

[0103] Step S4.4: Based on the relationship obtained in Step S4.3, analyze the correlation between the correlation coefficient a and the number of wet-dry cycles N to obtain the correlation relationship equation shown in formula (6); analyze the correlation between the correlation coefficient b and the number of wet-dry cycles N to obtain the correlation relationship equation shown in formula (7);

[0104] a = αln(-βln(N)) (6)

[0105]

[0106] where: α, β, γ, η are all the values of the fitting coefficients in the correlation relationship equation;

[0107] Step S4.5: Thus, the variation model of the crushing strength of the rockfill considering the coupled influence of stress and the number of wet-dry cycles shown in formula (8) is constructed:

[0108]

[0109] Thus, a prediction model for the crushing strength of rockfill materials considering the coupled effects of stress and the number of wet-dry cycles is obtained.

[0110] Step S5: Using the prediction model for the crushing strength of rockfill materials considering the coupled effects of stress and the number of wet-dry cycles obtained in Step S4, predict the crushing strength of the rockfill materials to be predicted under different wet-dry cycles and different stresses.

[0111] The following introduces an embodiment:

[0112] Step S1: Obtain multiple groups of rockfill material samples.

[0113] Step S1.1: Conduct a preliminary screening on the rockfill materials for the test, and screen out the rockfill material particles with a particle size d of 20 - 30 mm; use a three-dimensional scanner to obtain and record the shape parameters of each screened rockfill material particle, including the long axis L, the middle axis I, and the short axis S.

[0114] Step S1.2: For each screened rockfill material particle, calculate the particle size d and the shape characteristic S of each rockfill material particle according to the shape parameters (L, I, S) of each rockfill material particle. I ;

[0115] Step S1.3: According to the particle size d and the shape characteristic S of each screened rockfill material particle I , further screen all the screened rockfill material particles, and screen out the flat rockfill material particles with a shape characteristic S I between 0.6 and 0.8, a particle size d between 20 and 22 mm, and the difference in particle size d not exceeding 10%.

[0116] Step S1.4: Group the multiple rockfill material particles with the same rockfill material particle characteristics screened out, and divide them into 16 groups. The number of rockfill material particles in each group of rockfill material samples is 32 and they have the same lithology.

[0117] Step S2: Conduct a stress-wet-dry cycle coupling test on each group of the rockfill material samples under different numbers of wet-dry cycles N and different stresses P.

[0118] In this embodiment, the number of wet-dry cycles N is set to 0, 8, 16, and 24 times; the stress P is set to 0, 0.5, 1, and 2 MPa, so as to conduct an orthogonal test on 16 groups of rockfill material samples.

[0119] Step S3: Conduct a crushing test on the 16 groups of rockfill material samples that have completed the stress-wet-dry cycle coupling test.

[0120] Specifically, for each group of rockfill samples after the stress-wetting and drying cycle coupling test with a given stress P and the number of wetting and drying cycles N, a crushing test is carried out. The displacement loading method is used for quasi-static loading until the rockfill is crushed, and the loading speed is controlled at 0.002 mm / s to prevent crushing caused by dynamic effects. Record the load F when the rockfill sample is crushed, and use formula (3) to obtain the crushing strength σ of the rockfill sample.

[0121] The test data are shown in Table 1:

[0122] Table 1 Summary of the crushing strength of rockfill samples

[0123]

[0124]

[0125] Step S4. Based on the test data obtained from Table 1, study the variation relationship between the crushing strength σ of the rockfill sample and the stress P under different numbers of wetting and drying cycles N, and construct a prediction model for the crushing strength of the rockfill considering the coupled effects of stress and the number of wetting and drying cycles;

[0126] Step S4.1. In the test, a total of 4 values of the number of wetting and drying cycles N are designed, which are 0, 8, 16, and 24 times respectively;

[0127] Step S4.2. Under each number of wetting and drying cycles N, plot the variation relationship curve of the crushing strength σ with the stress P in the coordinate system, as Figure 2 shown, so as to obtain the variation relationship equation:

[0128] σ = a i + b i P (4)

[0129] where: i = 1, 2, 3, 4, a i , b i are the values of the correlation coefficient a and the correlation coefficient b when the number of wetting and drying cycles N is 0, 8, 16, and 24;

[0130] Step S4.3. In this embodiment, the 4 values of the correlation coefficient a are determined to be 8.508, 7.488, 6.933, and 6.684 respectively, and the 4 values of the correlation coefficient b are -0.023, -0.301, -0.455, and -0.440 respectively.

[0131] Step S4.4. Analyze the correlation relationship between the correlation coefficient a and the number of wetting and drying cycles N to obtain Figure 3 the correlation relationship curve between the correlation coefficient a and the number of wetting and drying cycles N as shown. Analyze the correlation relationship between the correlation coefficient b and the number of wetting and drying cycles N to obtain Figure 4The correlation curve between the correlation coefficient b and the number of wet-dry cycles N shown

[0132] For Figure 3 and Figure 4 analysis is carried out to obtain the correlation equation between the correlation coefficient a and the number of wet-dry cycles N: a = αln(-βln(N)); and the correlation equation between the correlation coefficient b and the number of wet-dry cycles N: In this embodiment, the values of the fitting coefficients α, β, γ, η are determined to be -1.900, -0.009, 1.903, -0.1 respectively.

[0133] Therefore, a = -1.9ln(0.009ln(N)),

[0134] Step S4.5, construct a variation model of the crushing strength of rockfill considering the coupled influence of stress and the number of wet-dry cycles:

[0135] Substitute the values of the fitting coefficients α, β, γ, η into the variation model of the crushing strength of rockfill, and the final prediction model of the crushing strength of rockfill considering the coupled influence of stress and the number of wet-dry cycles is obtained as:

[0136]

[0137] As Figure 5 shown, draw the variation surface of the crushing strength σ of rockfill with the number of wet-dry cycles N and stress P. The crushing strength σ of rockfill under any number of wet-dry cycles N and any stress P can be determined and predicted through this surface.

[0138] Step S5, use the obtained prediction model of the crushing strength of rockfill considering the coupled influence of stress and the number of wet-dry cycles to predict the crushing strength of the rockfill to be predicted under different wet-dry cycles and different stresses.

[0139] Furthermore, verify the prediction model of the crushing strength of rockfill proposed by the present invention:

[0140] Carry out stress-wet-dry cycle coupling tests with 20, 32, and 40 wet-dry cycle numbers N for rockfill samples with the same particle size range of rockfill particles, and couple the stress P to 1.5 MPa; then carry out crushing tests, and the typical load-displacement curve obtained is as Figure 6As shown, the displacement is the distance that the loading plate moves when the rockfill sample is broken. When the loading plate moves a certain displacement, the rockfill sample will break, so as to obtain the load F when the rockfill sample is broken. Then, according to formula (3), the crushing strength σ of the rockfill sample is obtained. Finally, when the measured stress P is 1.5 MPa, the crushing strengths σ of the rockfill after 20, 32, and 40 wet-dry cycles are 6.466 MPa, 5.593 MPa, and 5.217 MPa respectively.

[0141] Using the rockfill crushing strength prediction model of the present invention, directly predicting the rockfill samples with the same range of rockfill particle sizes, the crushing strengths σ of the rockfill after 20, 32, and 40 wet-dry cycles under the condition that the stress is 1.5 MPa are 6.697 MPa, 5.822 MPa, and 5.654 MPa respectively.

[0142] It can be seen that the error between the crushing strength σ predicted by the present invention and the crushing strength σ obtained from the test measured data is less than 8%, indicating that the method of the present invention is in good agreement with the actual results.

[0143] The present invention also provides a system for realizing the prediction method of the crushing strength of rockfill considering the coupling effect of stress-wet-dry cycle, which is used to automatically realize the prediction method of the crushing strength of rockfill considering the coupling effect of stress-wet-dry cycle provided by the present invention, including:

[0144] A pretreatment module, which is used to pretreat and group the rockfill particles to obtain multiple groups of rockfill samples;

[0145] Specifically, the pretreatment module can execute the content described in step S1 above, preliminarily screen the rockfill used for the test, obtain its shape parameters of the preliminarily screened rockfill by using a three-dimensional scanner, and calculate the particle size d and shape feature S of each rockfill particle according to the shape parameters I ; screen out the rockfill particles with the same rockfill particle characteristics; wherein, the rockfill particle characteristics are the rockfill particles with the particle size d being approximately the same and the shape being flat; group the multiple rockfill particles with the same rockfill particle characteristics screened out, and each group forms a rockfill sample.

[0146] A coupling and crushing test module, which is used to conduct stress-wet-dry cycle coupling tests on each group of rockfill samples processed by the pretreatment module under different numbers of wet-dry cycles N and different stresses P, and conduct crushing tests on each group of the rockfill samples that have completed the stress-wet-dry cycle coupling tests to obtain their crushing strengths σ; thus obtaining multiple sets of test data; each set of test data records the corresponding relationship and values of the number of wet-dry cycles N, the crushing strength σ, and the stress P;

[0147] Specifically, the coupling and crushing test module can execute the content described in steps S2 and S3 above, and put the groups of rockfill samples screened by the pretreatment module into the stress-wetting and drying cycle coupling test device in batches to conduct stress-wetting and drying cycle coupling tests under different numbers of wetting and drying cycles N and different stresses P; take out the rockfill samples after the stress-wetting and drying cycle coupling tests with the established number of wetting and drying cycles N and the established stress P from the stress-wetting and drying cycle coupling test device, conduct crushing tests on each group of rockfill samples, and determine the crushing strength σ of the rockfill samples.

[0148] The prediction model construction module is used to study the variation relationship of the crushing strength σ of the rockfill samples with the stress P under different numbers of wetting and drying cycles N according to the test data, and construct a prediction model for the crushing strength of the rockfill considering the coupling effects of stress and the number of wetting and drying cycles.

[0149] The prediction model construction module can execute the content described in step S4 above, and establish the variation relationship equation of the crushing strength σ of the rockfill samples with the stress P: σ = a i + b i P; where a i , b i are the values of the correlation coefficient a and the correlation coefficient b when the number of wetting and drying cycles N = N i ; construct the correlation relationship equation between the correlation coefficient a and the number of wetting and drying cycles N: a = αln(-βln(N)); construct the correlation relationship equation between the correlation coefficient b and the number of wetting and drying cycles N: where: α, β, γ, η are all the values of the fitting coefficients in the correlation relationship equation;

[0150] Finally, construct a variation model for the crushing strength of the rockfill considering the coupling effects of stress and the number of wetting and drying cycles:

[0151] The crushing strength prediction module is used to predict the crushing strength of the rockfill to be predicted under different wetting and drying cycles and different stresses by using the prediction model for the crushing strength of the rockfill considering the coupling effects of stress and the number of wetting and drying cycles.

[0152] The crushing strength prediction module can execute the content described in step S5 above, and predict the crushing strength of the rockfill to be predicted under different wetting and drying cycles and different stresses.

[0153] Furthermore, it can also include an input display module and a control module:

[0154] The input display module is used to receive the control instructions input by the operator, and display the input, output, and intermediate processing data of the corresponding module in the form of text, list, static or dynamic trend charts according to the control instructions.

[0155] A control module, which is communicatively connected to a preprocessing module, a coupling and crushing test module, a prediction model construction module, a crushing strength prediction module, and an input display module, controls the operation of each module.

[0156] The prediction method and system for the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycle provided by the present invention have the following characteristics:

[0157] (1) The prediction method and system for the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycle involved in the present invention first propose a prediction model for the crushing strength of rockfill materials considering the coupling influence of stress and wet-dry cycle. By substituting the data obtained from the test into this model to determine the values of each parameter, the final prediction model can be obtained.

[0158] (2) The prediction model for the crushing strength of rockfill materials considering the coupling influence of stress and the number of wet-dry cycles proposed by the present invention can predict the crushing strength of rockfill materials under any stress and the number of wet-dry cycles. The prediction result is more in line with the actual situation, can accurately quantify the influence of the number of cycles and stress on the crushing strength of rockfill materials, and provides reliable data for the change of the crushing strength of the rockfill materials for the dam construction of an actual rockfill dam project under the influence of the cyclic change of the reservoir water level and the self-weight of the dam body during operation. For example, it is used to determine the crushing strength of the rockfill materials for the dam construction of a core wall rockfill dam after experiencing the coupling action of the cyclic rise and fall of the reservoir water level and the self-weight of the dam body.

[0159] (3) The present invention only needs to conduct stress-wet-dry cycle coupling tests on a small amount of rockfill materials under different stresses and different numbers of wet-dry cycles, and conduct crushing tests on the rockfill materials after the stress-wet-dry cycle coupling action. The requirements for test equipment are low, the number of tests is small, the operation is simple, it can effectively save test materials and test time, and improve work efficiency.

[0160] (4) The solution of the present invention is particularly applicable to the design stage of rockfill dam projects.

[0161] Specifically, in the engineering design stage of the rockfill dam, by using the method of the present invention, first, a rockfill sample that meets certain particle characteristics of the rockfill for testing is determined. Then, a stress-wet-dry cycle coupling test and a crushing strength test are carried out on the rockfill sample to obtain a prediction model for the crushing strength of the rockfill considering the coupling effects of stress and the number of wet-dry cycles. Through the obtained prediction model for the crushing strength of the rockfill, the crushing strength of the rockfill under different wet-dry cycles and different stresses is predicted, and it is judged whether the crushing strength of the rockfill meets the engineering design requirements of the rockfill dam. If it meets the requirements, it is recommended to use the rockfill sample that meets the particle characteristics of the current rockfill for dam construction. If it does not meet the requirements, the specific data of the particle characteristics of the rockfill sample is replaced, and the prediction of the crushing strength is carried out again in a loop until a rockfill sample with a crushing strength that meets the engineering design requirements of the rockfill dam is obtained, and it is used to guide the dam construction. Therefore, the solution provided by the present invention can provide reference data for the selection of the rockfill sample in the engineering design stage of the rockfill dam and guide the screening of the rockfill particles used for dam construction.

[0162] The above embodiments are merely illustrative examples of the technical solutions of the present invention. The prediction method and system for the crushing strength of the rockfill considering the stress-wet-dry cycle coupling effect involved in the present invention are not limited solely to the content described in the above embodiments, but are subject to the scope defined by the claims. Any modification, supplement, or equivalent replacement made by those skilled in the art to which the present invention pertains on the basis of this embodiment is within the scope protected by the claims of the present invention.

Claims

1. A prediction method for the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycles, characterized in that, It includes the following steps: Step S1, obtaining multiple groups of rockfill material samples; Each group of the rockfill material samples includes multiple rockfill material particles; recording the particle size d, long axis L, middle axis I, and short axis S of each rockfill material particle; each rockfill material particle in each group of the rockfill material samples has the same rockfill material particle characteristics; wherein, the rockfill material particle characteristics include rockfill material particle size characteristics and rockfill material particle shape characteristics; Specifically, step S1 is as follows: Step S1.1, preliminarily screening the rockfill material for the test, screening out multiple rockfill material particles with the particle size d within the set range; using a three-dimensional scanner to obtain and record the shape parameters of each rockfill material particle after screening, including the long axis L, middle axis I, and short axis S; Step S1.2: For each rockfill aggregate particle after screening, based on the shape parameters (L, I, S) of each rockfill aggregate particle, calculate the particle size d and shape characteristic S of each rockfill aggregate particle I ; In step S1.2, using formula (1), calculating to obtain the particle size d of the rockfill material particle: Thus, the particle size d of the rockfill material particle is obtained; Step S1.

3. According to the particle size d and shape feature S of each screened rockfill particle obtained in step S1.2 I , further screen all the screened rockfill particles, and screen out the rockfill particles with particle size d and shape feature S I that meet the test requirements, thereby obtaining rockfill particles with the same rockfill particle characteristics; Step S1.4, grouping the multiple rockfill material particles with the same rockfill material particle characteristics screened out in step S1.3, and each group forms one of the rockfill material samples; Step S2, conducting a stress-dry-wet cycle coupling test on each group of the rockfill material samples under different dry-wet cycle numbers N and different stresses P; Step S3, conducting a crushing test on each group of the rockfill material samples that have completed the stress-dry-wet cycle coupling test in step S2, obtaining its crushing strength σ; thus, multiple sets of test data are obtained; each set of test data records the corresponding relationship and values of the dry-wet cycle number N, crushing strength σ, and stress P; Step S4, based on the test data obtained in step S3, studying the variation relationship of the crushing strength σ of the rockfill material samples with the stress P under different dry-wet cycle numbers N, and constructing a prediction model for the crushing strength of the rockfill material considering the coupled influence of stress and dry-wet cycle number; Step S5, using the prediction model for the crushing strength of the rockfill material considering the coupled influence of stress and dry-wet cycle number obtained in step S4, predicting the crushing strength of the rockfill material to be predicted under different dry-wet cycles and different stresses.

2. The prediction method of the crushing strength of rockfill materials considering the stress-wetting and drying cycle coupling effect according to claim 1, characterized in that In step S1.2, the shape characteristic S of the rockfill particles is obtained by using formula (2). I ; In step S1.3, the shape feature S is screened out I The rockfill particles between 0.6 and 0.8 conform to the shape feature S I The rockfill particles between 0.6 and 0.8 are specifically flat 3. The prediction method for the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycles according to claim 1, wherein In step S1.3, the difference in the particle size d of the screened rockfill material particles does not exceed 10%; in step S1.4, the number of rockfill material particles in the rockfill material sample is not less than 30 and they have the same lithology.

4. The prediction method of the crushing strength of rockfill materials considering the stress-wet-dry cycle coupling effect according to claim 1, characterized in that Specifically, step S2 is as follows: For each group of the rockfill material samples, layering them into the cylinder of the stress-dry-wet cycle coupling test device, and moreover, the dry density of the rockfill material particles filled in each layer is 1.05 times that of the rockfill material particles in the layer below, so as to ensure that when conducting the stress-dry-wet cycle coupling test, each rockfill material particle is evenly stressed; after the filling is completed, conduct the stress-dry-wet cycle coupling test under different dry-wet cycle numbers N and different stresses P.

5. The prediction method of the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycles according to claim 1, characterized in that, Specifically, step S3 is as follows: Step S3.1, placing each group of the rockfill material samples that have completed the stress-dry-wet cycle coupling test in step S2 on the lower loading plate of the crushing test device, and making the axis direction of the short axis S of the rockfill material particles in each group of the rockfill material samples parallel to the upper and lower loading plates of the crushing test device; Step S3.2: Conduct a crushing test using a crushing test device, record the load F when the rockfill sample is crushed, and calculate the crushing strength σ of the rockfill sample; Step S3.3: Record the corresponding relationship and values of the number of wet-dry cycles N, the crushing strength σ, and the stress P to form test data.

6. The prediction method for the crushing strength of rockfill materials considering the stress-wet-dry cycle coupling effect according to claim 5, characterized in that Specifically, Step S3.2 is as follows: Using Equation (3), obtain the crushing strength σ of the rockfill sample: Thus, the crushing strength σ of the rockfill sample is obtained.

7. The prediction method of the crushing strength of rockfill materials considering the coupling effect of stress and wet-dry cycles according to claim 1, characterized in that Specifically, Step S4 is as follows: Step S4.1: Assume that in the test, the number of wet-dry cycles N is designed with n values, which are respectively: N1, N2,..., N n ; Step S4.2, when the number of wet-dry cycles N = N i , where i = 1, 2,..., n, the variation relationship equation of the crushing strength σ of the rockfill sample shown in formula (4) with respect to the stress P is obtained: σ = a i + b i P(4) Among them, a i , b i are the values of the correlation coefficient a and the correlation coefficient b when the number of wet-dry cycles N = N i ; Since the number of wet-dry cycles N is designed with n values in total, the following system of equations showing the variation relationship of the crushing strength σ of the rockfill sample with the stress P as shown in Equation (5) is obtained: Step S4.

3. Therefore, for the n values N1, N2,..., N of the number of wet-dry cycles N, n , n values of the correlation coefficient a are correspondingly obtained, which are respectively: a1, a2,..., a n ; n values of the correlation coefficient b are correspondingly obtained, which are respectively: b1, b2,..., b n ; Step S4.4: Based on the relationship obtained in Step S4.3, analyze the correlation relationship between the correlation coefficient a and the number of wet-dry cycles N to obtain the correlation equation as shown in Equation (6); analyze the correlation relationship between the correlation coefficient b and the number of wet-dry cycles N to obtain the correlation equation as shown in Equation (7); a = αln(-βln(N)) (6) where: α, β, γ, η are all the values of the fitting coefficients in the correlation equation; Step S4.5: Thus, construct a variation model of the rockfill crushing strength considering the coupled influence of stress and the number of wet-dry cycles as shown in Equation (8): Thus, a prediction model of the rockfill crushing strength considering the coupled influence of stress and the number of wet-dry cycles is obtained.

8. A system for implementing the prediction method of the crushing strength of rockfill materials considering the stress-wetting and drying cycle coupling effect as described in any one of claims 1 to 7, characterized in that, It includes: A pretreatment module for preprocessing and grouping the rockfill particles to obtain multiple groups of rockfill samples; A coupling and crushing test module for conducting a stress-wet-dry cycle coupling test on each group of rockfill samples processed by the pretreatment module under different numbers of wet-dry cycles N and different stresses P, and conducting a crushing test on each group of the rockfill samples that have completed the stress-wet-dry cycle coupling test to obtain their crushing strength σ; thereby obtaining multiple sets of test data; each set of test data records the corresponding relationship and values of the number of wet-dry cycles N, the crushing strength σ, and the stress P; A prediction model construction module for studying the variation relationship of the crushing strength σ of the rockfill sample with the stress P under different numbers of wet-dry cycles N according to the test data, and constructing a prediction model of the rockfill crushing strength considering the coupled influence of stress and the number of wet-dry cycles; A crushing strength prediction module for predicting the crushing strength of the rockfill to be predicted under different wet-dry cycles and different stresses using the prediction model of the rockfill crushing strength considering the coupled influence of stress and the number of wet-dry cycles.

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