Multi-stage shear strength calculation method for coal-based solid waste-soil-rock composites

Abstract

This invention discloses a multi-stage shear strength calculation method for coal-based solid waste-soil-rock composites, belonging to the interdisciplinary technical field of geotechnical engineering, geomechanics, and solid waste utilization. The method includes the following steps: obtaining basic physical and mechanical information on the composition and structure of the coal-based solid waste-soil-rock composite; preparing a mixed matrix of solid waste and soil, and preparing interface samples of the matrix and rock; determining the peak shear strength and residual shear strength parameters of the matrix and interface samples using indoor direct shear tests; and calculating the peak and residual shear strength of coal-based solid waste-soil-rock composites with different rock contents based on the macro-micro strength correlation and the shear strength parameters of the matrix and interface. This method only includes two categories: component mechanical parameters and rock volume content, and is general and simple. This invention has broad application prospects in the field of geotechnical reinforcement technology, and also has significant advantages such as resource reuse effects, reduced environmental impact, and improved economic efficiency.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary technical field of geotechnical engineering, geomechanics and solid waste utilization, and in particular relates to a multi-stage shear strength calculation method for coal-based solid waste-soil-rock composites. Background Technology

[0002] Soil-rock mixtures are widely used engineering materials in mining, civil engineering, and geology. Their shear failure is a major factor leading to engineering instability and geological disasters. Although soil-rock mixtures exhibit good engineering properties in some aspects, they often face problems of insufficient strength or poor stability under complex loading conditions. Furthermore, when the moisture content changes, soil-rock mixtures may undergo softening or rheological changes, significantly reducing their strength and increasing safety hazards during engineering operation. To improve the structural stability and shear strength of soil-rock mixtures, artificial modification techniques have emerged. In particular, the development of environmentally friendly and sustainable soil-rock mixture modification technologies has significant economic and ecological benefits. Therefore, a scientific and efficient strength model and calculation method for cemented soil-rock mixtures is a key technical challenge for promoting the modification of soil-rock mixtures from coal-based solid waste.

[0003] However, the existing shear strength models for soil-rock mixtures still have certain limitations, mainly in the following aspects: (1) Existing models usually rely on a large amount of experimental data as basic input to invert model parameters, and their practicality needs to be further improved. (2) There are many undetermined parameters in the model, and the calibration method lacks sufficient mathematical basis. (3) In particular, existing models mainly focus on conventional loose soil-rock mixtures, while the strength composite mechanism of cemented soil-rock mixtures with external additives is complex, and there is a lack of prediction methods for its peak and residual two-stage strength characteristics. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a multi-stage shear strength calculation method for coal-based solid waste-soil-rock composites, thereby resolving the issues present in the prior art.

[0005] To achieve the above objectives, this invention provides a multi-stage shear strength calculation method for coal-based solid waste-soil-rock composites, comprising: To obtain basic information on the composition and structure of coal-based solid waste-soil-rock composites; Based on the basic information of composition and structure, clay and coal-based solid waste slurry were mixed to generate a composite sample of solid waste slurry and fine-grained clay, and a matrix-rock interface sample was obtained at the same time. The peak shear strength and residual shear strength parameters of the composite specimen and the interface specimen were determined based on indoor direct shear tests. The peak shear strength of coal-based solid waste improved soil-rock mixture with different rock contents was obtained based on the macro-micro strength correlation and the peak shear strength parameter. The residual shear strength of coal-based solid waste modified soil-rock mixtures with different rock contents is obtained based on the macro-micro strength correlation and the residual shear strength parameters.

[0006] Preferably, the basic information on the composition and structure of the improved soil-rock mixture based on solid waste includes: the wet density of clay, the composition and water-cement ratio of coal-based solid waste, the mass fraction of coal-based solid waste slurry relative to clay, the density of boulders, the shear strength of the clay-slurry composite matrix, the shear strength of the composite matrix-boulders interface, and the volume content of boulders.

[0007] Preferably, the process of generating a composite sample of solid waste slurry and fine-grained clay, while simultaneously obtaining a matrix-rock interface sample, includes: Select a mold to mix clay and coal-based solid waste slurry to prepare a composite sample of solid waste slurry and fine-grained clay; Core samples were taken from large stones to prepare base-coated stones. The matrix and stones were placed in a mold for composite curing to generate the matrix-stone interface sample.

[0008] Preferably, the expression for obtaining the peak shear strength parameter is: ; ; in, To reinforce the peak shear strength of the matrix, To reinforce the normal stress of the matrix, For cohesion, To reinforce the peak internal friction angle of the matrix, The peak shear strength at the matrix-rock interface. The normal stress at the matrix-block interface, It represents the peak internal friction angle at the matrix-rock contact interface.

[0009] Preferably, the expression for obtaining the residual shear strength parameter is: ; ; in, and The residual internal friction angle between the matrix and the interface. and This represents the residual shear strength of the matrix and the interface.

[0010] Preferably, the expression for obtaining the peak shear strength of coal-based solid waste improved soil-rock mixture with different rock contents is: ; in, VBP represents the peak shear strength of the cemented soil-rock mixture, and VBP represents the volume fraction of the rock.

[0011] Preferably, the expression for obtaining the residual shear strength of coal-based solid waste improved soil-rock mixture with different rock contents is: ; in, The residual shear strength of the cemented soil-rock mixture. The residual strength of the matrix taking into account structural effects; The geometric parameters of the shear failure surface of the constructed cemented soil-rock mixture are: Let π be the mathematical constant pi, and arccos be the inverse cosine function.

[0012] Compared with the prior art, the present invention has the following advantages and technical effects: First, the two-stage shear strength calculation model and method for soil-rock mixtures created in this invention fills the technical gap in existing research on the prediction of shear strength of modified soil-rock mixtures from solid waste. Second, the content of this invention has significant improvements compared with the prior art: (1) The improved technical feature is that, compared with the existing technology for predicting the shear strength of conventional soil-rock mixtures, the content of this invention considers the special mechanical process of externally added curing agents; (2) The improved technical method is that the composite material mechanics method is used to define the structural parameters of solid waste slurry-soil-rock mixtures, and the proposed soil-rock mixture shear strength calculation model and method is general, with few model parameters and corresponding physical meanings; (3) The improved technical advancement is that the proposed strength correlation fully considers the general coupling process of component mechanics and structural parameters, and the implementation of this invention only requires indoor testing of component mechanics parameters. Attached Figure Description

[0013] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart of the multi-stage shear strength calculation method for coal-based solid waste-soil-rock composite according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the verification of peak intensity prediction in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the verification of residual strength prediction in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the verification of multi-stage strength prediction of coal-based solid waste-soil-rock composite in an embodiment of the present invention. Detailed Implementation

[0014] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0015] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0016] Example 1 like Figure 1 As shown in the figure, this embodiment provides a flowchart of a multi-stage shear strength calculation method for coal-based solid waste-soil-rock composites, including: To obtain basic information on the composition and structure of coal-based solid waste-soil-rock composites; Based on the basic information of composition and structure, clay and coal-based solid waste slurry were mixed to generate a composite matrix sample of solid waste slurry and fine-grained clay, and an interface sample of matrix-rock was obtained at the same time. The peak shear strength and residual shear strength parameters of the matrix sample and the interface sample were determined based on indoor direct shear tests. The peak shear strength of coal-based solid waste improved soil-rock mixture with different rock contents was obtained based on the macro-micro strength correlation and the peak shear strength parameter. The residual shear strength of coal-based solid waste modified soil-rock mixtures with different rock contents is obtained based on the macro-micro strength correlation and the residual shear strength parameters.

[0017] Specifically: (1) Determine the basic information on the composition and structure of the coal-based solid waste-soil-rock composite.

[0018] Coal-based solid waste slurry is used as an external admixture, and the soil-rock mixture (a mixture of clay and boulders) is used as the reinforced medium. The wet density of the clay, the composition and water-cement ratio of the coal-based solid waste, the mass fraction of the coal-based solid waste slurry relative to the clay, and the density of the boulders are the basic physical parameters of the components. The shear strength of the clay-slurry composite matrix and the shear strength of the composite matrix-boulders interface are the basic mechanical parameters of the components. The volumetric boulders content (VBP) can be converted from boulders mass and used as a structural control parameter.

[0019] (2) Select a suitable mold to mix clay and coal-based solid waste slurry, and prepare a composite sample (matrix) of solid waste slurry and fine clay in the laboratory. At the same time, process large stones to obtain cores to prepare base-covered stones. Place the matrix and stones in the mold for composite curing, as a matrix-stone interface sample.

[0020] When preparing the above-mentioned samples, the same component parameters as those of the coal-based solid waste modified soil-rock mixture must be used, including the wet density of the clay, the slurry properties of the coal-based solid waste slurry, and its mass fraction in the clay.

[0021] (3) Using indoor direct shear tests, the shear strength parameters of the matrix and interface specimens were determined, where the peak shear strength was described by the following formula: , , , These represent peak shear strength, normal stress, cohesion, and peak internal friction angle, respectively. The subscripts m and i represent the reinforced matrix and the matrix-rock contact interface, respectively.

[0022] The residual shear strength of the matrix and interface is and : and This represents the residual internal friction angle between the matrix and the interface.

[0023] (3) Based on the proposed macro-micro strength correlation, the peak shear strength of the coal-based solid waste improved soil-rock mixture with different rock contents is calculated based on equations (1) and (2): VBP represents the peak shear strength of the cemented soil-rock mixture, and VBP represents the volume fraction of the rock.

[0024] (4) Based on the proposed macro-micro strength correlation, the residual shear strength of coal-based solid waste improved soil-rock mixture with different rock contents is calculated as follows: It represents the residual shear strength of the cemented soil-rock mixture. To account for the residual strength of the matrix and interface considering structural effects, the following formula is used for calculation based on equations (3) and (4): in, The geometric parameters of the shear failure surface of the constructed cemented soil-rock mixture are calculated using the following formula: Let π be the mathematical constant pi, and arccos be the inverse cosine function.

[0025] Example 2 This embodiment provides a verification example of a multi-stage shear strength calculation method for coal-based solid waste-soil-rock composites, including: (1) In this example, the basic information on the composition and structure of the coal-based solid waste-soil-rock composite is as follows: The coal-based solid waste solidification solution comprises multi-source cementing materials, water, and an alkaline activator. The multi-source cementing materials include silicate cement, slag, and fly ash in a mass ratio of 3:3:2. The mass ratio of the aqueous solution to the multi-source cementing materials is 1.0. The solid content of the alkaline activating solution is approximately 20% of the mass ratio of the multi-source cementing materials.

[0026] The selected silicate cement has a fineness greater than 300 (m). 2 / kg), which is Po 42.5 silicate cement; the selected fly ash is grade I fly ash; the selected slag is S95 slag powder with a flow ratio >95%. The alkali activation solution is a water glass solution prepared with added sodium hydroxide, with a modulus of 2.0.

[0027] The soil and rock parameters are as follows: the wet density of clay is 1.8 g / cm³. 3 The solid content of the coal-based solid waste solidification solution was 20% of the clay mass; the boulders were broken limestone with a particle size between 5-30 mm. VBP selected 0%, 10%, 20%, and 30% for a total of 4 groups.

[0028] (2) Select a suitable mold and prepare the above-mentioned coal-based solid waste-soil-stone mixture. In addition, keep the properties and ratio of the coal-based solid waste solidification solution and clay unchanged, and keep the solid content ratio of the coal-based solid waste solidification and clay at 20% to obtain a clay-slurry composite matrix sample. At the same time, use this matrix to prepare an interface sample by combining it with cored stones. Tests were carried out on the matrix and interface samples, and the peak and residual shear strength parameters of the matrix and interface were obtained by fitting with equation (1-4). ).

[0029] In the implementation plan, the mold is cylindrical with a radius r = 5.64 cm, a height h = 10 cm, and a volume V = 999.33 cm³. 3 The shear area S = 99.88 cm² 2 .

[0030] (3) VBP is 10%, 20%, and 30% respectively, which will determine the peak intensity of the matrix and the interface, i.e., the parameter. Substituting into equation (5), VBP is 0%, 10%, 20%, and 30% respectively, the peak shear strength of the coal-based solid waste cemented soil-rock mixture is calculated.

[0031] (4) VBP is 10%, 20%, and 30% respectively, and the residual strength parameter of the matrix is... Substitute into equation (6), where the undetermined parameter The parameters are calculated from equation (7). It is calculated from equation (8).

[0032] Through the above steps, the evolution of peak and residual shear strength of the soil-rock mixture after the addition of the prepared coal-based solid waste solution can be accurately calculated. To verify the correctness of this technical method, indoor tests were conducted on cemented soil-rock mixtures with different rock contents in step (1). The test pressure was 0 kPa, 50 kPa, 100 kPa, and 200 kPa, a total of four stress levels, including peak and residual shear strength, with a total of 32 sets of indoor experimental test values. The comparison between the test results and the model calculation results is shown in [link to model calculation]. Figure 2-3 The test values ​​and predicted values ​​show a very good agreement, which fully demonstrates the effectiveness of the present invention.

[0033] Example 3 This embodiment supplements a verification case of a multi-stage shear strength calculation method for coal-based solid waste-soil-rock composites, including the following information: The raw materials were the same as in Example 2, except that the mass ratio of solid content in the coal-based solid waste solution and clay was changed to 30%, and the VBP was 27%. Due to the increased dosage of the curing agent and the change in VBP, the overall performance of the coal-based solid waste-soil-rock composite in this case differed from that in Example 2. Indoor tests were conducted at 0-200 kPa to test the curing and improvement effect of the soil-rock mixture and to verify the method, resulting in a total of 8 sets of experimental values.

[0034] This case study follows the basic steps of Implementation Example 2, where the peak and residual shear strength parameters of the matrix and interface under the new variables were obtained. These parameters were used as component input parameters, with VBP=27% substituted into calculation formula (5-8) for calculation. It can be seen that, under varying slurry ratios and boulders content, the implementation of this invention still largely matches the experimental results (see...). Figure 4 By using only experimental test results of the matrix and interface as input parameters, the strength of soil-rock mixtures under different VBP conditions can be predicted, demonstrating the generality and practicality of the core method of this invention.

[0035] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for calculating the multi-stage shear strength of a coal-based solid waste-soil-rock composite, characterized in that, Includes the following steps: To obtain basic physical and mechanical information on the composition and structure of coal-based solid waste-soil-rock composites; Based on the basic information of composition and structure, clay and coal-based solid waste slurry are mixed to generate a composite sample (matrix) of solid waste slurry and fine-grained clay, and at the same time, a matrix-rock interface sample is obtained. Based on indoor direct shear tests, the peak shear strength parameters and residual shear strength parameters of the matrix sample and the interface sample were determined. The peak shear strength of coal-based solid waste-soil-rock composites with different rock contents was obtained based on the macro-micro strength correlation and the peak shear strength parameter. The residual shear strength of coal-based solid waste-soil-rock composites with different rock contents was obtained based on the macro-micro strength correlation and the residual shear strength parameters. The expression for obtaining the residual shear strength parameter is: ； ； in, and The residual internal friction angle between the matrix and the interface. and The residual shear strength of the matrix and interface. It is cohesive force; The expression for obtaining the peak shear strength of coal-based solid waste improved soil-rock mixture with different rock contents is as follows: ； in, VBP represents the peak shear strength of the cemented soil-rock mixture, where VBP represents the volume fraction of the boulders. To reinforce the peak shear strength of the matrix; The expression for obtaining the residual shear strength of coal-based solid waste improved soil-rock mixture with different rock contents is as follows: ； in, The residual shear strength of the cemented soil-rock mixture. The residual strength of the matrix taking into account structural effects; ； The geometric parameters of the shear failure surface of the constructed cemented soil-rock mixture are: ； Let π be the mathematical constant pi, and arccos be the inverse cosine function.

2. The method for calculating the multi-stage shear strength of a coal-based solid waste-soil-rock composite according to claim 1, characterized in that, The basic information on the composition and structure of the improved soil-rock mixture based on solid waste includes: the wet density of clay, the composition and water-cement ratio of coal-based solid waste, the mass fraction of coal-based solid waste slurry relative to clay, the density of boulders, the shear strength of the clay-slurry composite matrix, the shear strength of the composite matrix-boulders interface, and the volume content of boulders.

3. The method for calculating the multi-stage shear strength of a coal-based solid waste-soil-rock composite according to claim 1, characterized in that, The process of generating a composite sample of solid waste slurry and fine-grained clay, and simultaneously obtaining a matrix-rock interface sample, includes: Select a mold to mix, sample, and cure the remolded clay and coal-based solid waste slurry to prepare a composite sample of solid waste slurry and fine-grained clay; Core samples were taken from large stones to prepare base-coated stones. The matrix and stones were placed in a mold for composite curing to generate the matrix-stone interface sample.

4. The method for calculating the multi-stage shear strength of a coal-based solid waste-soil-rock composite according to claim 1, characterized in that, The expression for obtaining the peak shear strength parameter is: ； ； in, To reinforce the normal stress of the matrix, To reinforce the peak internal friction angle of the matrix, The peak shear strength at the matrix-rock interface. The normal stress at the matrix-block interface, It represents the peak internal friction angle at the matrix-rock contact interface.

Images