Manufacturing method of rock sample for test of heterogeneous rock group in karst area and rock sample for test

Abstract

The invention discloses a manufacturing method of a rock sample for a test of a heterogeneous rock group in a karst area and the rock sample for the test, and relates to the field of geotechnical engineering tests.The method comprises the steps that the corrosion characteristics of the heterogeneous rock group mainly comprising dissolved holes in the karst area are analyzed, and corrosion characteristic parameters are obtained; the corrosion characteristic parameters at least comprise a corrosion rate, a dissolved pore size variation coefficient and a spatial distribution non-uniformity coefficient; preparing a plurality of rock sample unit bodies according to a similarity principle; a plurality of foam particles with various particle sizes are adopted to characterize corrosion holes of the rock mass to be characterized in the heterogeneous rock group, the number and spatial distribution of the foam particles with each particle size are determined according to the corrosion characteristic parameters of the heterogeneous rock group, and the foam particles are prepared from polystyrene; mixing the rock sample unit bodies with the foam particles with the corresponding number, and putting the plurality of rock sample unit bodies mixed with the foam particles into a mold for molding, so as to obtain a rock sample for test; the rock sample for the test has the corrosion characteristic, and the accuracy of the rock sample test in the karst area can be effectively optimized.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical engineering tests, and in particular to a method for preparing a rock sample for a test of a heterogeneous rock group in a karst area and the rock sample for the test. Background Art

[0002] The heterogeneous rock group in the karst area refers to the carbonate rock group divided by taking into account the differences in dissolution characteristics such as the degree of dissolution caused by dissolution, the size of the dissolution structure and the spatial distribution. This type of heterogeneous rock group is distributed in the reservoir area and dam area of ​​the hydropower project constructed in the karst area. Due to the influence of dissolution, the rock mass in this area has obvious heterogeneous characteristics, which plays a decisive role in the mechanical properties of the rock mass in the karst area.

[0003] Rock samples are an important basis for exploring the mechanical properties of rock mass through experimental methods. However, due to the complexity of dissolution and the difficulty of sampling and sample preparation, it is difficult to take and prepare rock samples with specific dissolution characteristics for mechanical testing. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for preparing a rock sample for a karst area heterogeneous rock group test and the rock sample for the test, aiming to solve the above-mentioned problem.

[0005] To achieve the above object, the present invention provides a method for preparing a rock sample for a karst area heterogeneous rock group test, comprising the following steps:

[0006] Step S1, analyzing the dissolution characteristics of a heterogeneous rock group dominated by dissolved pores in a karst area to obtain dissolution characteristic parameters, wherein the dissolution characteristic parameters at least include the dissolution rate, the coefficient of variation of dissolved pore size, and the coefficient of spatial distribution unevenness of the heterogeneous rock group;

[0007] Step S2, preparing a plurality of rock sample units according to a similar principle;

[0008] Step S3, using a plurality of foam particles with various particle sizes to characterize the dissolution pores of the rock mass to be characterized in the heterogeneous rock formation, and determining the number and spatial distribution of foam particles of each particle size according to the dissolution characteristic parameters of the heterogeneous rock formation, wherein the preparation material of the foam particles includes polystyrene;

[0009] Step S4, mixing each of the rock sample units with a corresponding number of foam particles, and placing the multiple rock sample units mixed with the foam particles into a mold for molding, so as to obtain a test rock sample for the rock mass to be characterized.

[0010] Furthermore, the step S1 specifically includes:

[0011] Step S11, selecting a partial area in the karst area as a sampling area;

[0012] Step S12: Conduct geological survey and analysis on the heterogeneous rock group with mainly dissolved pores in the sampling area to determine the dissolution characteristic parameters of the heterogeneous rock group in the sampling area.

[0013] Furthermore, the step S2 specifically includes:

[0014] Step S21, determining similar raw materials of the rock sample unit according to the similarity principle;

[0015] Step S22: using n portions of the similar raw materials to prepare n rock sample units, where n≥2.

[0016] Furthermore, the similar raw materials include at least cement, microsilica powder, quartz sand, iron powder, polycarboxylic acid early strength water reducing agent, defoaming agent and purified water.

[0017] Furthermore, the step S3 specifically includes:

[0018] Step S31, determining the total volume of the foam particles according to the dissolution rate;

[0019] Step S32: determining the number of foam particles and the particle size of each foam particle according to the geological survey and analysis results of the sampling area, and determining the number of foam particles of each particle size in combination with the dissolution rate and the coefficient of variation of the pore size;

[0020] Step S33: determining the number of foam particles of each particle size in each rock sample unit according to the spatial distribution unevenness coefficient.

[0021] Furthermore, the step S31 specifically includes:

[0022] Based on the total volume calculation formula, the total volume of the foam particles is calculated according to the dissolution rate, wherein the total volume calculation formula is:

[0023] V k =V×k;

[0024] Where V k is the total volume of foam particles;

[0025] V is the volume of the rock sample to be characterized;

[0026] k is the dissolution rate.

[0027] Furthermore, the step S32 specifically includes:

[0028] The number of foam particles and the particle size of each foam particle are determined, and the number of foam particles of each particle size is calculated according to a first foam particle number calculation formula, wherein the first foam particle number calculation formula is:

[0029]

[0030] Where Cov is the coefficient of variation of pore size;

[0031] V k is the total volume of multiple foam particles, and V k =V×k, where V is the volume of the rock sample to be characterized and k is the dissolution rate;

[0032] δ is the standard deviation of the particle size of the foam particles;

[0033] μ is the average value of the foam particle size;

[0034] x is the particle size of the foam particles;

[0035] m is the number of foam particles of each particle size.

[0036] Furthermore, the step S33 specifically includes:

[0037] Based on the second foam particle number calculation formula, the number of foam particles of each particle size in each rock sample unit is determined according to the spatial distribution unevenness coefficient, wherein the second foam particle number calculation formula is:

[0038]

[0039] In the formula, u is the spatial distribution unevenness coefficient;

[0040] S0 is the standard deviation of the number of foam particles in n similar raw materials;

[0041] S max is the maximum value of the standard deviation;

[0042] S min is the minimum value of the standard deviation, which is 0;

[0043] a is the number of foam particles of this size in each rock sample unit;

[0044] A is the total number of foam particles of each particle size;

[0045] A / n is the average number of foam particles of each particle size in each rock sample unit.

[0046] Furthermore, the step S4 specifically includes:

[0047] Step S41, stirring and mixing each of the rock sample units and a corresponding number of foam particles;

[0048] Step S42, placing a plurality of rock sample units with the foam particles added thereto into a mold for forming, and covering the surface with a plastic film and allowing the units to stand still;

[0049] Step S43, demoulding and curing to obtain the rock sample for the test.

[0050] The present invention also provides a rock sample for testing heterogeneous rock groups in karst areas, characterized in that the rock sample for testing heterogeneous rock groups in karst areas is prepared using a method for preparing rock samples for testing heterogeneous rock groups in karst areas.

[0051] In the technical solution of the present invention, the test rock sample is prepared by mixing a plurality of rock sample units and a plurality of foam particles with a plurality of particle sizes, wherein the rock sample units are prepared according to a similar principle, and the preparation material of the foam particles includes polystyrene, which is light in weight and small in size, and can meet the requirements of simulating the size of the dissolution pores. Therefore, a plurality of foam particles with a plurality of particle sizes are used to simulate the dissolution pores in the rock mass to be characterized, and the number and spatial distribution of foam particles of each particle size are determined according to the dissolution characteristic parameters of the heterogeneous rock group, that is, the three parameters of dissolution rate, coefficient of variation of dissolution pore size and coefficient of spatial distribution inhomogeneity are used to characterize the dissolution pores. The heterogeneous characteristics caused by the dissolution of heterogeneous rock groups at various stages are quantified. Specifically, the degree of dissolution is characterized by the dissolution rate of the heterogeneous rock group, the size dispersion of the dissolution holes is characterized by the coefficient of variation of the heterogeneous rock group, and the spatial distribution of the dissolution holes is characterized by the coefficient of inhomogeneity of the heterogeneous rock group. The test rock samples prepared in this way have dissolution characteristics, which solves the problem that it is difficult to characterize the dissolution characteristics of heterogeneous rock groups in karst areas and it is difficult to obtain suitable dissolution rock samples for mechanical testing. It can effectively optimize the accuracy of rock sample tests in karst areas and provide a more scientific method for the study of mechanical properties of heterogeneous rock groups in karst areas. In addition, the foam particles used are low in cost, simple to operate, and can be produced in batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0053] Figure 1 A flow chart of an embodiment of a method for preparing a rock sample for a karst area heterogeneous rock group test provided by the present invention;

[0054] Figure 2 for Figure 1 Flow chart of step S1 in FIG.

[0055] Figure 3 for Figure 1 Flow chart of step S2;

[0056] Figure 4 for Figure 1 Flow chart of step S3;

[0057] Figure 5 for Figure 1 Flow chart of step S4;

[0058] Figure 6 Schematic diagram of the dissolution stages of heterogeneous rock formations.

[0059] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0060] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0062] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0063] The heterogeneous rock group in the karst area refers to the carbonate rock group divided by taking into account the differences in dissolution characteristics such as the degree of dissolution caused by dissolution, the size of the dissolution structure and the spatial distribution. This type of heterogeneous rock group is distributed in the reservoir area and dam area of ​​the hydropower project constructed in the karst area. Due to the influence of dissolution, the rock mass in this area has obvious heterogeneous characteristics, which plays a decisive role in the mechanical properties of the rock mass in the karst area.

[0064] Rock samples are an important basis for exploring the mechanical properties of rock mass through experimental methods. However, due to the complexity of dissolution and the difficulty of sampling and sample preparation, it is difficult to take and prepare rock samples with specific dissolution characteristics for mechanical testing.

[0065] In view of this, the present invention provides a method for preparing rock samples for testing heterogeneous rock groups in karst areas. Figures 1 to 5 The present invention provides a flow chart of a method for preparing rock samples for testing heterogeneous rock groups in karst areas.

[0066] See also Figure 1 The method for preparing the rock sample for the karst area heterogeneous rock group test comprises the following steps:

[0067] Step S1, analyzing the dissolution characteristics of a heterogeneous rock group dominated by dissolved pores in a karst area to obtain dissolution characteristic parameters, wherein the dissolution characteristic parameters at least include the dissolution rate of the heterogeneous rock group, the coefficient of variation of dissolved pore size, and the coefficient of spatial distribution unevenness.

[0068] Step S2, preparing a plurality of rock sample units according to a similar principle;

[0069] Step S3, using a plurality of foam particles with various particle sizes to characterize the dissolution pores of the rock mass to be characterized in the heterogeneous rock formation, and determining the number and spatial distribution of foam particles of each particle size according to the dissolution characteristic parameters of the heterogeneous rock formation, wherein the preparation material of the foam particles includes polystyrene;

[0070] Step S4, mixing each of the rock sample units with a corresponding number of foam particles, and placing the multiple rock sample units mixed with the foam particles into a mold for molding, so as to obtain a test rock sample for the rock mass to be characterized.

[0071] In the technical solution of the present invention, the test rock sample is prepared by mixing a plurality of rock sample units and a plurality of foam particles with a plurality of particle sizes, wherein the rock sample units are prepared according to a similar principle, and the preparation material of the foam particles includes polystyrene, which is light in weight and small in size, and can meet the requirements of simulating the size of the dissolution pores. Therefore, a plurality of foam particles with a plurality of particle sizes are used to simulate the dissolution pores in the rock mass to be characterized, and the number and spatial distribution of foam particles of each particle size are determined according to the dissolution characteristic parameters of the heterogeneous rock group, that is, the three parameters of dissolution rate, coefficient of variation of dissolution pore size and coefficient of spatial distribution inhomogeneity are used to characterize the dissolution pores. The heterogeneous characteristics caused by the dissolution of heterogeneous rock groups at various stages are quantified. Specifically, the degree of dissolution is characterized by the dissolution rate of the heterogeneous rock group, the size dispersion of the dissolution holes is characterized by the coefficient of variation of the heterogeneous rock group, and the spatial distribution of the dissolution holes is characterized by the coefficient of inhomogeneity of the heterogeneous rock group. The test rock samples prepared in this way have dissolution characteristics, which solves the problem that it is difficult to characterize the dissolution characteristics of heterogeneous rock groups in karst areas and it is difficult to obtain suitable dissolution rock samples for mechanical testing. It can effectively optimize the accuracy of rock sample tests in karst areas and provide a more scientific method for the study of mechanical properties of heterogeneous rock groups in karst areas. In addition, the foam particles used are low in cost, simple to operate, and can be produced in batches.

[0072] It should be noted that when analyzing and summarizing the heterogeneity of heterogeneous rock groups dominated by solution pores in karst areas, the inventors divided the dissolution evolution process into three stages and clarified the dissolution characteristics of each stage, specifically:

[0073] Inhomogeneous rock groups are affected by dense structural surfaces, and water is easily accumulated on the layers and joints and fissures. The rock mass is constantly eroded and dissolved by pore water and fissure water, causing the soluble substances in the rock to be continuously dissolved. Figure 6 (a), when groundwater infiltrates into the rock formation, karst dissolution occurs first near the structural surface, forming a large number of holes with small diameters. At this time, the degree of dissolution is small, the size difference of the dissolution holes is small, and the distribution is relatively uneven. In the middle stage of dissolution (such as Figure 6 As the dissolution continues, groundwater flows along the structural surface of the soluble rock and continuously dissolves and erodes it, forming a large number of holes with smaller diameters. In addition, the holes with smaller diameters in the early stage of dissolution continue to grow larger. At this time, the size difference of the dissolution holes becomes larger, but the distribution is more uniform. In the later stage of dissolution (such as Figure 6 As shown in (c), as karstification progresses, the dissolution pores continue to grow larger. At this time, the size difference of the dissolution pores is the largest and the distribution is the most uniform.

[0074] Therefore, the inventors used three indicators, namely, dissolution rate, coefficient of variation of dissolved pore size and coefficient of spatial distribution inhomogeneity, to characterize and quantify the heterogeneous characteristics caused by dissolution at each stage.

[0075] It should also be noted that in the present invention, by using foam particles with different particle sizes, the simulated pore size has variability and meets the actual sample preparation requirements. In addition, the shape of the foam particles is a regular circle. If foam particles of different particle sizes are mixed when purchased, they can be screened and separated using a stainless steel round hole sieve.

[0076] For further information, see Figure 2 , the step S1 specifically includes:

[0077] Step S11, selecting a partial area in the karst area as a sampling area.

[0078] In this step, the sampling area is an area representative of dissolution in the karst area.

[0079] Step S12: Conduct geological survey and analysis on the heterogeneous rock group with mainly dissolved pores in the sampling area to determine the dissolution characteristic parameters of the heterogeneous rock group in the sampling area.

[0080] In this step, a statistical window is set for the sampling area, and the dissolution characteristics of the heterogeneous rock group mainly composed of dissolved pores in the statistical window are analyzed to obtain the dissolution characteristic parameters.

[0081] For details, please refer to Figure 3 , the step S2 specifically includes:

[0082] Step S21: Determine similar raw materials of the rock sample unit according to the similarity principle.

[0083] Specifically, the similar raw materials include at least cement, microsilica fume, quartz sand, iron powder, polycarboxylic acid early strength water reducing agent, defoaming agent and purified water. Furthermore, the ratio of cement, microsilica fume, quartz sand, iron powder, polycarboxylic acid early strength water reducing agent, defoaming agent and purified water is 250:32.5:200:62.5:0.75:0.75:70, wherein the quartz sand contains quartz sand of different sizes, and the ratio is 70-100 (mesh): 40-70 (mesh): 26-40 (mesh): 8-16 (mesh) = 1:6:8:5.

[0084] It should be noted that if the similar raw materials contain too much water, the foam particles will float when they are subsequently added, so the proportion of water must be strictly controlled; in addition, the polycarboxylic acid early strength water reducer must be added to the water.

[0085] Step S22: using n portions of the similar raw materials to prepare n rock sample units, where n≥2.

[0086] In this step, the amount of each similar raw material can prepare at least 1 / n test rock sample. More specifically, in one embodiment of the present invention, the amount of n similar raw materials can prepare at least 1.5 test rock samples. In this way, it can be ensured that the similar raw materials after loss are still sufficient to prepare one test rock sample.

[0087] It should be noted that, considering the small volume of the experimental rock sample, the volume of each of the n rock sample units into which it is divided is also small. In order to ensure that each subsequent rock sample unit can completely wrap its corresponding number of foam particles, 3-4 rock sample units are generally prepared.

[0088] For details, please refer to Figure 4 , the step S3 specifically includes:

[0089] Step S31, determining the total volume of the foam particles according to the dissolution rate.

[0090] It should be noted that the dissolution rate is the ratio of the volume of dissolved particles in the heterogeneous rock group to the total volume of the heterogeneous rock group, that is, the ratio of the volume of foam particles to the volume of the rock mass to be characterized.

[0091] Therefore, further, the step S31 specifically includes:

[0092] Based on the total volume calculation formula, the total volume of the foam particles is calculated according to the dissolution rate, wherein the total volume calculation formula is:

[0093] V k =V×k; (1)

[0094] In formula (1), V k is the total volume of foam particles;

[0095] V is the volume of the rock sample to be characterized;

[0096] k is the dissolution rate.

[0097] Step S32: determine the number of foam particles and the particle size of each foam particle according to the geological survey and analysis results of the sampling area, and determine the number of foam particles of each particle size in combination with the dissolution rate and the coefficient of variation of the pore size.

[0098] In this step, based on the results of geological survey and analysis of the heterogeneous rock group in the sampling area, the number of foam particles and the particle size of each foam particle are determined according to the conditions of the dissolution holes in the rock mass to be characterized.

[0099] It should be noted that the coefficient of variation Cov of the pore size refers to the size dispersion of the dissolution pores. The larger the coefficient of variation Cov of the pore size, the greater the dispersion of the pores. The smaller the coefficient of variation Cov of the pore size, the smaller the dispersion of the pores.

[0100] Furthermore, the step S32 specifically includes:

[0101] The number of foam particles and the particle size of each foam particle are determined, and the number of foam particles of each particle size is calculated according to a first foam particle number calculation formula, wherein the first foam particle number calculation formula is:

[0102]

[0103] In formula (2), Cov is the coefficient of variation of pore size;

[0104] V k is the total volume of multiple foam particles, and V k =V×k, where V is the volume of the rock sample to be characterized and k is the dissolution rate;

[0105] δ is the standard deviation of the particle size of the foam particles;

[0106] μ is the average value of the foam particle size;

[0107] x is the particle size of the foam particles;

[0108] m is the number of foam particles of each particle size.

[0109] Specifically, in this step, a calculation calculator for estimating the dissolution rate k and the coefficient of variation of the pore size Cov is established in Excel according to the calculation formula for the number of the first foam particles. After the specific particle size of the foam particles and the number of each particle size are input, the dissolution rate k and the coefficient of variation of the pore size Cov in this case can be obtained. Therefore, by continuously changing the number of foam particles of each particle size, the dissolution rate k (error 0.1%) and the coefficient of variation of the pore size Cov (error 0.001) that best conform to the known values ​​can be obtained.

[0110] It should be noted that since the number of foam particles is an integer, it is often difficult to obtain a dissolution rate k and a coefficient of variation Cov of pore size that fully meet the requirements during estimation. Therefore, a set of data that best fits the known dissolution rate k and the coefficient of variation Cov of pore size can be selected for sample preparation.

[0111] Step S33: determining the number of foam particles of each particle size in each rock sample unit according to the spatial distribution unevenness coefficient.

[0112] In this step, the spatial distribution unevenness coefficient u is determined according to the standard deviation of the foam particles in the n rock sample units. First, the standard deviation of the foam particles in the n rock sample units is calculated, and then the spatial distribution unevenness coefficient u is obtained by homogenizing the standard deviation. The smaller the spatial distribution unevenness coefficient u, the better the uniformity of the pore distribution. The larger the spatial distribution unevenness coefficient u, the worse the uniformity of the pore distribution. Figure 3 ).

[0113] Furthermore, the step S33 specifically includes:

[0114] Based on the second foam particle number calculation formula, the number of foam particles of each particle size in each rock sample unit is determined according to the spatial distribution unevenness coefficient, wherein the second foam particle number calculation formula is:

[0115]

[0116] In formula (3), u is the spatial distribution unevenness coefficient;

[0117] S0 is the standard deviation of the number of foam particles in n similar raw materials;

[0118] S max is the maximum value of the standard deviation;

[0119] S min is the minimum value of the standard deviation, which is 0;

[0120] a is the number of foam particles of this size in each rock sample unit;

[0121] A is the total number of foam particles of each particle size;

[0122] A / n is the average number of foam particles of each particle size in each rock sample unit.

[0123] Specifically, in this step, a spatial distribution unevenness coefficient u estimation calculator is established in Excel according to the second foam particle number calculation formula, and the number of foam particles of one particle size in each rock sample unit is calculated each time. After determining the number of similar raw materials, i.e., the number of rock sample units, the spatial distribution unevenness coefficient u in this case will be obtained by inputting the number of foam particles in each rock sample unit. By continuously changing the number of foam particles in each rock sample unit, the spatial distribution unevenness coefficient u (error 0.001) that best matches the known spatial distribution unevenness coefficient can be obtained. Repeat the above operation until the number of foam particles of all particle sizes in each rock sample unit is obtained.

[0124] It should be noted that since the number of foam particles in each rock sample unit is an integer, it is often difficult to obtain a spatial distribution unevenness coefficient u that fully meets the requirements during estimation. Therefore, a set of data that best fits the known spatial distribution unevenness coefficient u can be selected for sample preparation.

[0125] It should also be noted that the spatial distribution unevenness coefficient u is obtained according to the above formula (3) based on the number of foam particles of a certain particle size in different rock sample units, and the spatial distribution unevenness coefficient u obtained according to the above formula (3) for the number of foam particles of each particle size in different rock sample units is the same.

[0126] For details, please refer to Figure 5 , the step S4 specifically includes:

[0127] Step S41, stirring and mixing each of the rock sample units and a corresponding number of foam particles.

[0128] In this step, the foam particles are completely wrapped by the rock sample unit body. A corresponding number of foam particles are added to each rock sample unit body, thereby preparing test rock samples with different uniformity levels.

[0129] It should be noted that in order to keep the spatial distribution unevenness coefficient u unchanged, when adding foam particles, the n rock sample units are sorted in order of the number of foam particles as at least the first rock sample unit, the second rock sample unit, ..., the nth rock sample unit, then the portion with the most foam particles of each particle size is added to the first rock sample unit, and correspondingly, the portion with the second most foam particles of each particle size is added to the second rock sample unit, and so on, and the portion with the least foam particles of each particle size is added to the nth rock sample unit.

[0130] Step S42: placing a plurality of rock sample units with the foam particles added thereto into a mold for forming, and covering the surface with a plastic film and allowing the units to stand.

[0131] More specifically, based on the above-mentioned embodiment of "n portions of the similar raw materials are capable of preparing at least 1.5 test rock samples", a combination of n rock sample units can obtain 1.5 test rock samples. Therefore, 1 / n of the test rock samples are selected from each of the rock sample units as a molded body, and it is ensured that the foam particles in each of the rock sample units are mixed in the molded body, and then the molded body is placed in a mold for molding, and the surface is covered with a plastic film and allowed to stand.

[0132] Step S43, demoulding and curing to obtain the rock sample for the test.

[0133] Specifically, the method for preparing rock samples for heterogeneous rock group tests in karst areas provided by the present invention is specifically described through the following specific embodiments.

[0134] In a specific embodiment, the method for preparing rock samples for testing heterogeneous rock groups in karst areas comprises the following specific steps:

[0135] Step S1, selecting an area representative of dissolution in the karst area as a sampling area, setting a statistical window for the sampling area, and analyzing the dissolution characteristics of the heterogeneous rock group dominated by dissolved pores in the statistical window to obtain the dissolution characteristic parameters, and determining that the dissolution rate k is 4%, the coefficient of variation Cov of dissolved pore size is 0.46, and the coefficient of spatial distribution unevenness u is 0.4.

[0136] Step S2, according to the similarity principle, determine that the similar raw materials of the rock sample unit body include cement, microsilica powder, quartz sand, iron powder, polycarboxylic acid early strength water reducing agent, defoaming agent and pure water, and the ratio of cement, microsilica powder, quartz sand, iron powder, polycarboxylic acid early strength water reducing agent, defoaming agent and pure water is 250:32.5:200:62.5:0.75:0.75:70, and the quartz sand contains quartz sand of different sizes, and the ratio is 70-100 (mesh): 40-70 (mesh): 26-40 (mesh): 8-16 (mesh) = 1:6:8:5. Then use 3 portions of the similar raw materials to prepare 3 rock sample units,

[0137] Step S3: first, based on the total volume calculation formula, calculate the total volume of the foam particles according to the dissolution rate, that is, V k =V×k=196.35cm 3 ×4%=7.854cm 3 .

[0138] Then three kinds of foam particles with different particle sizes were selected for sample preparation, and the particle sizes of the foam particles were 0.2 cm, 0.4 cm and 0.6 cm respectively.

[0139] Then, the number of foam particles of each particle size is calculated according to the first foam particle number calculation formula, that is:

[0140]

[0141] Specifically, according to the above formula, a calculator for estimating the dissolution rate k and the coefficient of variation Cov was established in Excel, as shown in Table 1 below. The specific particle sizes of the foam particles, 0.2, 0.4 and 0.6, were entered in the table, and then the number of each foam particle was continuously changed until the most consistent known dissolution rate k (error 0.1%) and coefficient of variation Cov of pore size (error 0.001) were obtained. By estimation, 370 foam particles with a particle size of 0.2 cm, 70 foam particles with a particle size of 0.4 cm, and 35 foam particles with a particle size of 0.6 cm were obtained.

[0142] Table 1

[0143]

[0144]

[0145] Based on the second foam particle quantity calculation formula, the quantity of foam particles of three particle sizes in each rock sample unit is determined according to the spatial distribution unevenness coefficient, that is:

[0146]

[0147] Specifically, according to the above formula, a spatial distribution unevenness coefficient u estimation calculator is established in Excel, as shown in Table 2 below, and the number of foam particles of one particle size in each rock sample unit is calculated each time. After determining the number of similar raw materials, that is, the number of rock sample units, the spatial distribution unevenness coefficient u in this case will be obtained by inputting the number of foam particles in each rock sample unit. By continuously changing the number of foam particles in each rock sample unit, the spatial distribution unevenness coefficient u (error 0.001) that best matches the known spatial distribution unevenness coefficient can be obtained. Repeat the above operation until the number of foam particles of all particle sizes in each rock sample unit is obtained.

[0148] Table 3

[0149]

[0150]

[0151]

[0152] Step S4, add 219 of the 0.2 cm foam particles, 44 of the 0.4 cm foam particles, and 20 of the 0.6 cm foam particles to the same rock sample unit and stir and mix, add 96 of the 0.2 cm foam particles, 30 of the 0.4 cm foam particles, and 11 of the 0.6 cm foam particles to another rock sample unit and stir and mix, add 5 ...55 of the 0.2 cm foam particles, 44 of the 0.4 cm foam particles, and 20 of the 0.6 cm foam particles to the same rock sample unit and stir and mix, 16 portions of 4 cm foam particles and 4 portions of 0.6 cm foam particles are added to another rock sample unit and stirred to mix; then the three rock sample units with the foam particles are placed in a mold for molding, and the surface is covered with a plastic film and allowed to stand for 24 hours in a room at a temperature of 20°C ± 2°C and a relative humidity greater than 50%; then the mold is removed and placed in a standard concrete curing room at a temperature of 20°C ± 2°C and a relative humidity of 95±5% for 28 days of curing to obtain the test rock sample.

[0153] The present invention also provides a rock sample for testing heterogeneous rock groups in karst areas. The rock sample for testing heterogeneous rock groups in karst areas is prepared by the method for preparing the rock sample for testing heterogeneous rock groups in karst areas described above.

[0154] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing rock samples for testing heterogeneous rock groups in karst areas, characterized in that: The following steps are involved: Step S1, analyzing the dissolution characteristics of a heterogeneous rock group dominated by dissolved pores in a karst area to obtain dissolution characteristic parameters, wherein the dissolution characteristic parameters at least include the dissolution rate, the coefficient of variation of dissolved pore size, and the coefficient of spatial distribution unevenness of the heterogeneous rock group; Step S2, preparing a plurality of rock sample units according to a similar principle; Step S3, using a plurality of foam particles with various particle sizes to characterize the dissolution pores of the rock mass to be characterized in the heterogeneous rock formation, and determining the number and spatial distribution of foam particles of each particle size according to the dissolution characteristic parameters of the heterogeneous rock formation, wherein the preparation material of the foam particles includes polystyrene; Step S4, mixing each of the rock sample units with a corresponding number of foam particles, and placing the multiple rock sample units mixed with the foam particles into a mold for molding, so as to obtain a test rock sample for the rock mass to be characterized.

2. The method for preparing rock samples for karst area heterogeneous rock group testing according to claim 1, characterized in that: The step S1 specifically includes: Step S11, selecting a partial area in the karst area as a sampling area; Step S12: Conduct geological survey and analysis on the heterogeneous rock group with mainly dissolved pores in the sampling area to determine the dissolution characteristic parameters of the heterogeneous rock group in the sampling area.

3. The method for preparing rock samples for testing heterogeneous rock groups in karst areas according to claim 1, characterized in that: The step S2 specifically includes: Step S21, determining similar raw materials of the rock sample unit according to the similarity principle; Step S22: using n portions of the similar raw materials to prepare n rock sample units, where n≥2.

4. The method for preparing rock samples for testing heterogeneous rock groups in karst areas according to claim 3, characterized in that: The similar raw materials include at least cement, microsilica powder, quartz sand, iron powder, polycarboxylic acid early strength water reducing agent, defoaming agent and purified water.

5. The method for preparing rock samples for testing heterogeneous rock groups in karst areas according to claim 3, characterized in that: The step S3 specifically includes: Step S31, determining the total volume of the foam particles according to the dissolution rate; Step S32: determining the number of foam particles and the particle size of each foam particle according to the geological survey and analysis results of the sampling area, and determining the number of foam particles of each particle size in combination with the dissolution rate and the coefficient of variation of the pore size; Step S33: determining the number of foam particles of each particle size in each rock sample unit according to the spatial distribution unevenness coefficient.

6. The method for preparing rock samples for testing heterogeneous rock groups in karst areas according to claim 5, characterized in that: The step S31 specifically includes: Based on the total volume calculation formula, the total volume of the foam particles is calculated according to the dissolution rate, wherein the total volume calculation formula is: In k =V×k; Where V k is the total volume of foam particles; V is the volume of the rock sample to be characterized; k is the dissolution rate.

7. The method for preparing rock samples for testing heterogeneous rock groups in karst areas according to claim 5, characterized in that: The step S32 specifically includes: The number of foam particles and the particle size of each foam particle are determined, and the number of foam particles of each particle size is calculated according to a first foam particle number calculation formula, wherein the first foam particle number calculation formula is: Where Cov is the coefficient of variation of pore size; V k is the total volume of multiple foam particles, and V k =V×k, where V is the volume of the rock sample to be characterized and k is the dissolution rate; δ is the standard deviation of the particle size of the foam particles; μ is the average value of the foam particle size; x is the particle size of the foam particles; m is the number of foam particles of each particle size.

8. The method for preparing rock samples for testing heterogeneous rock groups in karst areas according to claim 5, characterized in that: The step S33 specifically includes: Based on the second foam particle number calculation formula, the number of foam particles of each particle size in each rock sample unit is determined according to the spatial distribution unevenness coefficient, wherein the second foam particle number calculation formula is: In the formula, u is the spatial distribution unevenness coefficient; S0 is the standard deviation of the number of foam particles in n similar raw materials; S max is the maximum value of the standard deviation; S min is the minimum value of the standard deviation, which is 0; a is the number of foam particles of this size in each rock sample unit; A is the total number of foam particles of each particle size; A / n is the average number of foam particles of each particle size in each rock sample unit.

9. The method for preparing rock samples for testing heterogeneous rock groups in karst areas according to claim 5, characterized in that: The step S4 specifically includes: Step S41, stirring and mixing each of the rock sample units and a corresponding number of foam particles; Step S42, placing a plurality of rock sample units with the foam particles added thereto into a mold for forming, and covering the surface with a plastic film and allowing the units to stand; Step S43, demoulding and curing to obtain the rock sample for the test.

10. A rock sample for testing heterogeneous rock formations in karst areas, characterized in that: The rock sample for karst area heterogeneous rock group test is prepared by the method for preparing the rock sample for karst area heterogeneous rock group test as described in any one of claims 1-9.

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