Multi-stage shear strength calculation method for coal-based solid waste-soil-stone complex

Abstract

The invention discloses a multi-stage shear strength calculation method of a coal-based solid waste-soil-stone complex, and belongs to the cross technical field of geotechnical engineering, geomechanics and solid waste utilization, and the method comprises the following steps: obtaining basic physical and mechanical information of composition and structure of the prepared coal-based solid waste-soil-stone complex; preparing a mixed matrix of the solid waste and the soil body, and preparing an interface sample of the matrix and the block stone; determining a peak shear strength parameter and a residual shear strength parameter of a matrix and an interface sample by virtue of an indoor direct shear test; calculating peak values and residual shear strength of the coal-based solid waste-soil-stone composites with different block stone contents on the basis of a macro-micro strength correlation formula and the shear strength parameters of the matrix and the interface; the method only comprises two types of component mechanical parameters and block stone volume content, and has generality and simplicity. The method has a wide application prospect in the technical field of rock-soil reinforcement, and has the advantages of remarkable resource recycling effect, reduction of environmental influence, improvement of economic efficiency and the like.

Description

Technical Field

[0001] The present invention belongs to the cross-technical field of geotechnical engineering, geomechanics and solid waste utilization, and in particular relates to a multi-stage shear strength calculation method for a coal-based solid waste-soil-stone complex. Background Art

[0002] Soil-rock mixture is an engineering material widely used in mining, civil engineering and geology. Its shear failure is one of the main factors leading to engineering instability and geological disasters. Although soil-rock mixture exhibits good engineering properties in some aspects, it often faces the problem of insufficient strength or poor stability under complex loading conditions. In addition, when the moisture content changes, the soil-rock mixture may undergo softening or rheology, significantly reducing its strength, thereby increasing the safety hazards in engineering operation. In order to improve the structural stability and shear strength of soil-rock mixture, artificial improvement technology has emerged. In particular, the research and development of environmentally friendly and sustainable soil-rock mixture modification technology has significant economic and ecological benefits. Therefore, a scientific and efficient strength model and calculation method of cemented soil-rock mixture is a key technical difficulty in promoting coal-based solid waste to improve soil-rock mixture.

[0003] However, the existing shear strength models of soil-rock mixtures still have certain limitations, which are mainly reflected in the following aspects: (1) The existing models usually rely on a large amount of test data as the basic input to invert the 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, the 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 dual-stage strength characteristics. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a multi-stage shear strength calculation method for coal-based solid waste-soil-stone composites to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides a method for calculating the multi-stage shear strength of a coal-based solid waste-soil-stone composite, comprising:

[0006] Obtain basic information on the composition and structure of coal-based solid waste-soil-rock complex;

[0007] Based on the basic information of the composition and structure, clay and coal-based solid waste slurry are mixed to generate a composite sample of solid waste slurry and fine-grained clay, and a matrix-rock interface sample is obtained at the same time;

[0008] Determine the peak shear strength parameters and residual shear strength parameters of the composite sample and the interface sample based on an indoor direct shear test;

[0009] Based on the macro-micro strength correlation formula and the peak shear strength parameter, the peak shear strength of the coal-based solid waste-improved soil-rock mixture with different block rock contents is obtained;

[0010] Based on the macro-micro strength correlation formula and the residual shear strength parameter, the residual shear strength of the soil-rock mixture improved by coal-based solid waste with different block stone contents is obtained.

[0011] Preferably, the basic information on the composition and structure of the coal-based solid waste improved soil-rock mixture includes: wet density of clay, composition of coal-based solid waste and water-cement ratio, mass fraction of coal-based solid waste slurry relative to clay, rock density, shear strength of clay-slurry composite matrix, shear strength of composite matrix-rock interface and volume content of rock.

[0012] Preferably, the process of generating a composite sample of solid waste slurry and fine-grained clay and simultaneously obtaining a matrix-rock interface sample comprises:

[0013] Select a mold, mix clay and coal-based solid waste slurry, and prepare a composite sample of solid waste slurry and fine-grained clay;

[0014] The large block of stone is processed and cored to prepare the base-surface block of stone, and the matrix and the block of stone are placed in a mold for composite curing to generate the matrix-block of stone interface sample.

[0015] Preferably, the expression for obtaining the peak shear strength parameter is:

[0016] τ m =c m +σ·tanφ m ;

[0017] τ i =c i +σ·tanφ i ;

[0018] Among them, τ m is the peak shear strength of the reinforced matrix, c m is the normal stress of the reinforced matrix, σ is the cohesion, φ m is the peak internal friction angle of the reinforced matrix, τ i is the peak shear strength of the matrix-rock interface, c i is the normal stress at the matrix-rock contact interface, φ i is the peak internal friction angle of the matrix-rock contact interface.

[0019] Preferably, the expression for obtaining the residual shear strength parameter is:

[0020] τ rm =σtanφ rm;

[0021] τ ri =σtanφ ri ;

[0022] Among them, φ rm and φ ri is the residual internal friction angle between the matrix and the interface, τ rm and τ ri is the residual shear strength of the matrix and the interface.

[0023] Preferably, the expression for obtaining the peak shear strength of the coal-based solid waste-improved soil-rock mixture with different rock content is:

[0024]

[0025] Among them, τ bim-p is the peak shear strength of cemented soil-rock mixture, and VBP represents the volume content of block rock.

[0026] Preferably, the expression for obtaining the residual shear strength of the soil-rock mixture improved by coal-based solid waste with different rock content is:

[0027] τ bim-r =(1-VBP)τ αm ;

[0028] Among them, τ bim-r is the residual shear strength of cemented soil-rock mixture, τ αm is the residual strength of the matrix considering the structural effect;

[0029] τ αm =σtan(φ rm +α)

[0030] α is the geometric parameter of the shear failure surface of the constructed cemented soil-rock mixture:

[0031]

[0032] π is the circumference of a circle, and arccos is the inverse cosine function.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] First, the two-stage shear strength calculation model and method of soil-rock mixture created by the present invention fills the technical gap in the existing research on the prediction of shear strength of solid waste improved soil-rock mixture. Secondly, the content of the present invention has obvious improvements compared with the existing technology: (1) The technical feature of the improvement is that compared with the existing shear strength prediction technology for conventional soil-rock mixture, the content of the present invention takes into account the special mechanical process of the external curing agent (2) The improved technical method is that the composite material mechanics method is used to determine the structural parameters of the solid waste slurry-soil-rock mixture, and the proposed soil-rock mixture shear strength calculation model and method are general, with few model parameters and corresponding physical meanings; (3) The technical advancement of the improvement is that the proposed strength correlation formula fully considers the general coupling process of component mechanics and structural parameters, and the implementation of the content of the present invention only requires indoor testing of the component mechanical parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0036] Figure 1 This is a flow chart of a method for calculating the multi-stage shear strength of a coal-based solid waste-soil-rock composite according to an embodiment of the present invention;

[0037] Figure 2 A schematic diagram for verifying the peak intensity prediction of an embodiment of the present invention;

[0038] Figure 3 A schematic diagram for verifying the residual strength prediction of an embodiment of the present invention;

[0039] Figure 4 It is a schematic diagram for verifying the multi-stage strength prediction of the coal-based solid waste-soil-rock composite according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0041] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0042] Embodiment 1

[0043] like Figure 1As shown, this embodiment provides a process of a multi-stage shear strength calculation method for a coal-based solid waste-soil-stone composite, including:

[0044] Obtain basic information on the composition and structure of coal-based solid waste-soil-rock complex;

[0045] Based on the basic information of the composition and structure, clay and coal-based solid waste slurry are mixed to generate a composite matrix sample of solid waste slurry and fine-grained clay, and a matrix-rock interface sample is obtained at the same time;

[0046] Determine the peak shear strength parameters and residual shear strength parameters of the matrix sample and the interface sample based on an indoor direct shear test;

[0047] Based on the macro-micro strength correlation formula and the peak shear strength parameter, the peak shear strength of the coal-based solid waste-improved soil-rock mixture with different block rock contents is obtained;

[0048] Based on the macro-micro strength correlation formula and the residual shear strength parameter, the residual shear strength of the soil-rock mixture improved by coal-based solid waste with different block stone contents is obtained.

[0049] Specifically:

[0050] (1) Determine the basic information on the composition and structure of the coal-based solid waste-soil-rock complex.

[0051] Coal-based solid waste slurry is the external admixture medium, and the soil-rock mixture is the reinforced medium (a mixture of clay and block stone). The wet density of clay, the composition of coal-based solid waste and the water-binder ratio, the mass fraction of coal-based solid waste slurry relative to clay, and the block stone density 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-block stone interface are the basic mechanical parameters of the components. The volume content of block stone (VBP) can be converted into a structural control parameter by the block stone mass.

[0052] (2) Select a suitable mold, mix the clay and coal-based solid waste slurry, and prepare a composite sample (matrix) of solid waste slurry and fine clay indoors. At the same time, core the large block stone to prepare the base-covered block stone, place the matrix and block stone in the mold for composite curing, and use it as the matrix-block stone interface sample.

[0053] When preparing the above-mentioned samples, the same component parameters as those of the coal-based solid waste-improved soil-rock mixture must be used, including the wet density of clay, the slurry properties of the coal-based solid waste slurry, and its mass fraction in the clay.

[0054] (3) The shear strength parameters of the matrix and interface samples were determined by indoor direct shear test, where the peak shear strength was described by the following formula:

[0055] τ m =cm +σ·tanφ m (1)

[0056] τ i =c i +σ·tanφ i (2)

[0057] τ, σ, c, φ represent the peak shear strength, normal stress, cohesion and peak internal friction angle, respectively. The subscripts m and i represent the reinforced matrix and matrix-rock contact interface, respectively.

[0058] The residual shear strength of the matrix and the interface is τ rm and τ ri :

[0059] τ rm =σtanφ rm (3)

[0060] τ ri =σtanφ ri (4)

[0061] φ rm and φ ri is the residual internal friction angle between the matrix and the interface.

[0062] (3) Based on the proposed macro-micro strength correlation formula, the peak shear strength of coal-based solid waste-improved soil-rock mixture with different rock content is calculated based on formulas (1) and (2):

[0063]

[0064] τ bim-p is the peak shear strength of cemented soil-rock mixture, and VBP represents the volume content of block rock.

[0065] (4) Based on the proposed macro-micro strength correlation formula, the residual shear strength of the soil-rock mixture improved by coal-based solid waste with different rock content is calculated as follows:

[0066] τ bim-r =τ αm · (6)

[0067] τ bim-r is the residual shear strength of cemented soil-rock mixture. αm In order to consider the matrix and interface residual strength of the structural effect, the following formula is used based on formula (3) and (4):

[0068] τ αm =σtan(φ rm +α) (7)

[0069] Among them, α is the geometric parameter of the shear failure surface of the cemented soil-rock mixture constructed, which is calculated using the following formula:

[0070]

[0071] π is the circumference of a circle, and arccos is the inverse cosine function.

[0072] Embodiment 2

[0073] This embodiment provides a verification example of a multi-stage shear strength calculation method for a coal-based solid waste-soil-rock composite, including:

[0074] (1) In this example, the basic information on the composition and structure of the coal-based solid waste-soil-rock complex is as follows:

[0075] The coal-based solid waste solidification solution includes multi-source cementitious materials, water, and alkali activator. The multi-source cementitious materials include silicate cement, slag, and fly ash, and the mass ratio thereof is 3:3:2. The mass ratio of the aqueous solution to the multi-source cementitious materials is 1.0. The mass ratio of the solid content of the alkali-activated solution to the multi-source cementitious materials is about 20%.

[0076] The selected silicate cement fineness is greater than 300 (m 2 / kg), which is Po 42.5 silicate cement; the selected fly ash is first-class fly ash; the selected slag is S95 slag powder, and the flow ratio is>95%. The alkali-activated solution is a water glass solution prepared by adding sodium hydroxide, and the modulus is 2.0.

[0077] Soil and stone parameters are: the wet density of clay is 1.8g / cm 3 The solid content of coal-based solid waste solidification solution and the mass ratio of clay is 20%; the block stone is broken limestone with a particle size between 5-30mm. VBP selected 4 groups of 0%, 10%, 20% and 30%.

[0078] (2) Select a suitable mold and prepare the above-mentioned coal-based solid waste-soil-stone mixture. In addition, the properties and proportions of the coal-based solid waste solidification solution and clay are kept unchanged, and the solid content ratio of the coal-based solid waste solidification and clay is still maintained at 20%, so as to obtain a clay-slurry composite matrix sample. At the same time, the matrix is ​​composited with the core block stone to prepare the interface sample. Tests are carried out on the matrix and interface samples, and the peak and residual shear strength parameters (c m φ m φ rm c i φ i ).

[0079] In the embodiment, the mold is cylindrical with a radius r = 5.64 cm, a height h = 10 cm, and a volume V = 999.33 cm3 , shear surface area S = 99.88 cm 2 .

[0080] (3) VBP is 10%, 20%, and 30% respectively. The peak intensity of the matrix and the interface, i.e., the parameter c m φ m c i φ i Substituting into formula (5), VBP is 0%, 10%, 20% and 30% respectively, and the peak shear strength of the coal-based solid waste cemented soil-rock mixture is calculated.

[0081] (4) VBP is 10%, 20%, and 30% respectively, and the residual strength parameter φ of the matrix is rm Substitute into equation (6), where the unknown parameter τ αm It is calculated by formula (7), and parameter α is calculated by formula (8).

[0082] Through the above steps, the peak and residual shear strength evolution results of the soil-rock mixture after adding the configured coal-based solid waste solution can be accurately calculated. In order to verify the correctness of the technical method, indoor tests were carried out on the cemented soil-rock mixture with different block stone contents in step (1). The test pressure was 0kPa, 50kPa, 100kPa, and 200kPa, a total of four stress levels, including peak and residual shear strength, with a total of 32 sets of indoor experimental test values. Comparison of test results and model calculation results can be seen in Figure 2-3 , the test value and the predicted value have a very good consistency, which fully demonstrates the effectiveness of the content of the present invention.

[0083] Embodiment 3

[0084] This example adds a verification case of a multi-stage shear strength calculation method for a coal-based solid waste-soil-rock composite, and the information includes:

[0085] The raw materials are the same as those in Example 2, except that the solid content mass ratio of the coal-based solid waste solution and clay is changed to 30%, and the VBP is 27%. Due to the increase in the amount of curing agent and the change in VBP, the overall performance of the coal-based solid waste-soil-stone composite in this case is different from that in Example 2. Indoor tests were carried out to test the curing improvement effect of the soil-stone mixture and verify the method at 0-200 kPa, with a total of 8 sets of experimental values.

[0086] The implementation of this case refers to the basic steps of implementation example 2, in which the peak and residual shear strength parameters of the matrix and interface under the new variables are obtained, and the above parameters are used as component input parameters, VBP = 27% is substituted into the calculation formula (5-8) for calculation. It can be seen that under the changed slurry ratio and block stone content, the implementation content of the present invention is still basically consistent with the test results (see Figure 4). Using only the experimental test results of the matrix and the interface as input parameters, the strength of the soil-rock mixture under different VBPs can be predicted, which illustrates the generality and practicality of the core method of the present invention.

[0087] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection 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: The following steps are involved: Obtain basic physical and mechanical information on the composition and structure of the prepared coal-based solid waste-soil-rock composite; Based on the basic information of the 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 a matrix-rock interface sample is obtained at the same time; Based on an indoor direct shear test, peak shear strength parameters and residual shear strength parameters of the matrix sample and the interface sample are measured; Based on the macro-micro strength correlation formula and the peak shear strength parameter, the peak shear strength of the coal-based solid waste-soil-stone composite with different rock content is obtained; The residual shear strength of coal-based solid waste-soil-stone composites with different block rock contents is obtained based on the macro-micro strength correlation formula and the residual shear strength parameter.

2. The multi-stage shear strength calculation method of the coal-based solid waste-soil-rock composite according to claim 1 is characterized in that: The basic information on the composition and structure of the coal-based solid waste improved soil-rock mixture 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 the block stone, the shear strength of the clay-slurry composite matrix, the shear strength of the composite matrix-block stone interface and the volume content of the block stone.

3. The multi-stage shear strength calculation method of the coal-based solid waste-soil-rock composite according to claim 1 is 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 comprises: Select a mold, mix, sample and cure the reshaped clay and coal-based solid waste slurry, and prepare a composite sample of the solid waste slurry and fine-grained clay; The large block of stone is processed and cored to prepare the base-surface block of stone, and the matrix and the block of stone are placed in a mold for composite curing to generate the matrix-block of stone interface sample.

4. The multi-stage shear strength calculation method of the coal-based solid waste-soil-rock composite according to claim 1, characterized in that: The expression for obtaining the peak shear strength parameter is: t m =c m +σ·tanφ m ; t i =c i +σ·tanφ i ; Among them, τ m is the peak shear strength of the reinforced matrix, c m is the normal stress of the reinforced matrix, σ is the cohesion, φ m is the peak internal friction angle of the reinforced matrix, τ i is the peak shear strength of the matrix-rock interface, c i is the normal stress at the matrix-rock contact interface, φ i is the peak internal friction angle of the matrix-rock contact interface.

5. The multi-stage shear strength calculation method of the coal-based solid waste-soil-rock composite according to claim 1 is characterized in that: The expression for obtaining the residual shear strength parameter is: t rm =stanφ rm ; t ri =stanφ ri ; Among them, φ rm and φ ri is the residual internal friction angle between the matrix and the interface, τ rm and τ ri is the residual shear strength of the matrix and the interface.

6. The multi-stage shear strength calculation method of the coal-based solid waste-soil-rock composite according to claim 1, characterized in that: The expression for obtaining the peak shear strength of the coal-based solid waste-improved soil-rock mixture with different block rock contents is: Among them, τ bim-p is the peak shear strength of cemented soil-rock mixture, and VBP represents the volume content of rock.

7. The multi-stage shear strength calculation method of the coal-based solid waste-soil-rock composite according to claim 1, characterized in that: The expression for obtaining the residual shear strength of the soil-rock mixture improved by coal-based solid waste with different block rock contents is: t bim-r =(1-VBP)τ αm ; Among them, τ bim-r is the residual shear strength of cemented soil-rock mixture, τ αm is the residual strength of the matrix considering the structural effect; t αm =σtan(φ rm +a); α is the geometric parameter of the shear failure surface of the constructed cemented soil-rock mixture: π is the circumference of a circle, and arccos is the inverse cosine function.

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