A method for analyzing the anti-sliding stability of underconsolidated saturated fine-grained tailings dams

Abstract

The present invention discloses a method for analyzing the anti-sliding stability of an under-consolidated saturated fine-grained tailings dam, which belongs to the field of tailings dam stability analysis. The tailings dam is loaded in stages from bottom to top, the consolidation coefficient remains unchanged, and the direction of water seepage is mainly vertical. In combination with the loading and consolidation laws of saturated fine-grained tailings dams, the Terzaghi one-dimensional seepage consolidation theory is modified. It is assumed that the consolidation coefficient remains unchanged during the drainage consolidation process, water seeps vertically or horizontally, and the loading is carried out in stages at a uniform speed. The consolidation degree of the staged loading is calculated layer by layer, and a weighted average is performed according to the staged loading amount to obtain a curve showing the relationship between the consolidation degree and the burial depth. The present invention divides the tailings dam into several vertical strips and analyzes the relationship between the strip consolidation degree and the elevation, thereby determining the spatial function of the shear strength of the under-consolidated tailings, thereby achieving a scientific and effective analysis of the anti-sliding stability of the under-consolidated saturated fine-grained tailings dam.

Description

Technical Field

[0001] The invention relates to the technical field of tailings dam stability analysis, in particular to an anti-sliding stability analysis method for an underconsolidated saturated fine-grained tailings accumulation dam. Background Art

[0002] Tailings particle size is trending towards becoming finer, resulting in higher and faster tailings dams. Quantitative analysis and discussion of the anti-sliding stability calculation methods for tailings dams relative to the tailings dam's rising velocity are becoming increasingly important, especially for saturated fine-grained tailings dams.

[0003] According to an analysis of existing tailings dams in China, the particle gradation of many full tailings has already reached the standard for tailings fine soil, with phosphogypsum and red mud being the two types with the largest discharge volumes. Existing technologies already include research on the drainage, shear resistance, and consolidation characteristics of fine-grained tailings. These include discussions on upstream fine-grained tailings damming issues, research on the calculation and analysis of fine-grained tailings characteristics and stability, research on the relationship between clay content and the physical and mechanical properties of fine-grained tailings, and research on the consolidation characteristics and shear strength of fine-grained tailings. However, none of these research cases analyze the degree of consolidation and its anti-sliding stability based on the saturated fine-grained tailings damming process, and thus fail to systematically explain the relationship between the tailings rise rate and dam stability. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for analyzing the anti-sliding stability of an underconsolidated saturated fine-grained tailings dam to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for analyzing the anti-sliding stability of an underconsolidated saturated fine-grained tailings dam comprises the following steps:

[0007] S1: Divide the tailings dam geological units, divide the tailings dam into several vertical strips and perform horizontal stratification;

[0008] S2: Determine the seepage boundary of each strip and the direction of water seepage;

[0009] S3: Obtain the consolidation coefficient of the tailings dam through consolidation test;

[0010] S4: Based on the effective stress principle and combined with the loading and consolidation laws of saturated fine-grained tailings dams, the Terzaghi one-dimensional seepage consolidation theory is modified: Assuming that the consolidation coefficient remains unchanged during the drainage consolidation process, water seeps vertically or horizontally, and is loaded at a uniform rate in stages, the degree of consolidation U of the staged loading is calculated layer by layer. i,j :

[0011]

[0012] Where: i is the strip number; j is the layer / grade loading number; N i is the number of layered / graded loadings for the i-th block; e is a natural constant; β i is the consolidation parameter of the i-th block dam after completion, in d -1 β i,j is the consolidation parameter of the i-th block during the j-th level loading period, in d -1 ;T i,k T is the end time of loading the kth level of the i-th block, in d; i,k-1 The k-th level loading completion time of the i-th block, in d;

[0013]

[0014] Where: π is the ratio of circumference to circumference; c v is the consolidation coefficient of the dam tailings, in m 2 / d;H i is the maximum drainage distance of the i-th block, in m; H i,j is the average drainage distance of the j-th level loading of the i-th block, in meters;

[0015] S5: Calculate the weighted average degree of consolidation of each layer after the dam is completed

[0016]

[0017] Where: h i,j is the thickness of the j-th layer of the i-th block, in meters;

[0018] S6: Determine the density and shear strength through physical and mechanical tests of various geological units of the tailings dam. Conduct saturated triaxial consolidation undrained shear tests on the tailings to measure the pore water pressure and obtain the effective stress shear strength index.

[0019] S7: The spatial function of the internal friction angle of each block of the tailings dam is established by the layered average consolidation degree and the corresponding elevation:

[0020]

[0021] Where: is the spatial function of the friction angle within the i-th block, in degrees; is the internal friction angle of the normal consolidation effective stress of the dam tailings, in degrees; is the average degree of consolidation at the elevation z position of the i-th block;

[0022] S8: For strips with an average consolidation degree of 100% on the dam surface, the position of the seepage line is determined according to the steady seepage analysis. For strips with an average consolidation degree of less than 100%, the seepage line is located on the dam surface.

[0023] S9: Based on the limit equilibrium method, search for sliding arc surfaces of arbitrary shapes, perform anti-sliding stability calculations, and obtain the minimum value of the stability coefficient, which is the corresponding sliding arc surface.

[0024] Furthermore, the concentration of tailings entering the storage is 25%, particles smaller than 0.075mm account for 80%, and the clay content is 15%.

[0025] Furthermore, the tailings dam geological unit divided in S1 includes the tailings accumulation dam, initial dam and dam foundation.

[0026] Furthermore, the tailings dam is built by raising it upstream by 50m, with an average outer slope ratio of 1:5 and a rising speed of 0.007 to 0.036m / d.

[0027] Furthermore, the initial dam is located at the foot of the downstream slope and is filled with weathered slate. The bearing layer of the dam foundation is strongly weathered slate, and the dam height is 30m.

[0028] Furthermore, the dam foundation is located below the tailings accumulation dam and the initial dam, with a slope of 8%, and is composed of slate with different degrees of weathering from top to bottom.

[0029] Furthermore, the seepage line in S8 is determined by the initial dam and the tailings dam near the initial dam according to the steady seepage analysis, and the seepage line of the remaining parts of the tailings dam is located on the dam surface.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The anti-sliding stability analysis method of underconsolidated saturated fine-grained tailings dam of the present invention is based on the effective stress principle and the seepage consolidation theory of Terzaghi. The whole method has clear ideas, clear concepts, reasonable assumptions and simple steps.

[0032] 2. The anti-sliding stability analysis method of the under-consolidated saturated fine-grained tailings dam of the present invention determines the spatial function of the effective stress internal friction angle by strip and block through seepage consolidation analysis, thereby realizing the anti-sliding stability calculation of the under-consolidated saturated fine-grained tailings dam.

[0033] 3. The anti-sliding stability analysis method of the under-consolidated saturated fine-grained tailings dam of the present invention can realize quantitative calculation and analysis of the anti-sliding stability coefficient of the saturated fine-grained tailings dam corresponding to the rising speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a cross-sectional diagram of the geological unit division of the upstream fine-grained tailings dam of the wet tailings pond of the present invention;

[0035] Figure 2 This is a schematic diagram of the strip division and layering of the tailings dam of the present invention;

[0036] Figure 3 Schematic diagram of the seepage consolidation analysis model for graded constant velocity loading during dam-building according to the present invention;

[0037] Figure 4 It is the technical roadmap of the method of the present invention. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] like Figure 4 As shown, an embodiment of the present invention provides a method for analyzing the anti-sliding stability of an underconsolidated saturated fine-grained tailings dam, comprising the following steps:

[0040] S1: Divide the tailings dam geological unit into tailings accumulation dam, initial dam, and dam foundation, such as Figure 1 As shown: the concentration of tailings entering the storage is 25%, particles less than 0.075mm account for 80%, and the clay content is 15%; the upstream height of the tailings dam is 50m, the average external slope ratio of the stacking is 1:5.0, the rising speed is 0.007-0.036m / d, and the service life is 12 years; the initial dam is located at the foot of the downstream slope, filled with weathered slate, the dam foundation bearing layer is strongly weathered slate, and the dam height is 30m; the dam foundation is located below the tailings dam and the initial dam, with a slope of 8%, and slate of different degrees of weathering from top to bottom; the initial dam and the tailings dam near the initial dam determine the infiltration line according to the stable seepage analysis, and the infiltration line of the remaining parts of the tailings dam is located on the dam surface; based on this, the tailings dam is divided into 10 vertical strips in this embodiment, and the horizontal layer thickness of the tailings dam is 5m, as shown Figure 2 As shown;

[0041] S2: Determine the seepage boundary and water seepage direction of each strip. For strips 1 to 3, the outer slope of the tailings dam and the inner slope of the initial dam are both drainage boundaries. The average drainage distance H i,j for Figure 3 The maximum drainage distance is divided by 2; for strips 4 to 10, the outer slope of the tailings dam is the drainage boundary, and the average drainage distance H i,j like Figure 3 As shown;

[0042] S3: Obtain the consolidation coefficient c of the tailings dam through consolidation test v ;

[0043] S4: Based on the effective stress principle and combined with the loading and consolidation laws of saturated fine-grained tailings dams, the Terzaghi one-dimensional seepage consolidation theory is modified: Assuming that the consolidation coefficient remains unchanged during the drainage consolidation process, water seeps vertically or horizontally, and is loaded at a graded uniform rate, the analysis model is as follows: Figure 3 As shown, the degree of consolidation U of the graded loading is calculated layer by layer. i,j :

[0044]

[0045] Where: i is the strip number; j is the layer / grade loading number; N i is the number of layered / graded loadings for the i-th block; e is a natural constant; β i is the consolidation parameter of the i-th block dam after completion, in d -1 β i,j is the consolidation parameter of the i-th block during the j-th level loading period, in d -1 ;T i,k T is the end time of loading the kth level of the i-th block, in d; i,k-1 The k-th level loading completion time of the i-th block, in d;

[0046]

[0047] Where: π is the ratio of circumference to circumference; c v is the consolidation coefficient of the dam tailings, in m 2 / d;H i is the maximum drainage distance of the i-th block, in m; H i,j is the average drainage distance of the j-th level loading of the i-th block, in meters;

[0048] S5: Calculate the weighted average degree of consolidation of each layer after the dam is completed

[0049]

[0050] Where: h i,j is the thickness of the j-th layer of the i-th block, in meters;

[0051] S6: Through physical and mechanical tests on the geological units of the tailings dam, the density and shear strength are determined. Saturated triaxial consolidation undrained shear tests are conducted on the tailings to measure the pore water pressure, and the effective stress shear strength index is obtained, as shown in the following table:

[0052]

[0053] S7: The spatial function of the internal friction angle of each block of the tailings dam is established by the layered average consolidation degree and the corresponding elevation:

[0054]

[0055] Where: is the spatial function of the friction angle within the i-th block, in degrees; is the internal friction angle of the normal consolidation effective stress of the dam tailings, in degrees; is the average degree of consolidation at the z position of the i-th block, as shown in the following table:

[0056]

[0057]

[0058] S8: For strips with an average consolidation degree of 100% on the dam surface, the position of the seepage line is determined according to the steady seepage analysis. For strips with an average consolidation degree of less than 100%, the seepage line is located on the dam surface.

[0059] S9: Based on the limit equilibrium method, considering the hydrostatic pressure, search for sliding arc surfaces of arbitrary shapes, perform anti-sliding stability calculations, and obtain the minimum stability coefficient, that is, the corresponding sliding arc surface, such as Figure 1 shown.

[0060] To sum up: Based on the existing research on fine-grained tailings dam technology, the present invention develops a method for calculating the anti-sliding stability of tailings dams corresponding to the rising velocity of the tailings dam, according to the effective stress principle and the basic theory of seepage consolidation, combined with the loading and consolidation laws of tailings dams, especially for saturated fine-grained tailings dams, to achieve a scientific and effective analysis of the anti-sliding stability of under-consolidated saturated fine-grained tailings dams.

[0061] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for analyzing the anti-sliding stability of an underconsolidated saturated fine-grained tailings dam, characterized in that: The following steps are involved: S1: Divide the tailings dam geological units, divide the tailings dam into several vertical strips and perform horizontal stratification; S2: Determine the seepage boundary of each strip and the direction of water seepage; S3: Obtain the consolidation coefficient of the tailings dam through consolidation test; S4: Based on the effective stress principle and combined with the loading and consolidation laws of saturated fine-grained tailings dams, the Terzaghi one-dimensional seepage consolidation theory is modified: Assuming that the consolidation coefficient remains unchanged during the drainage consolidation process, water seeps vertically or horizontally, and is loaded at a uniform rate in stages, the degree of consolidation U of the staged loading is calculated layer by layer. i,j : Where: i is the strip number; j is the layer / grade loading number; N i is the number of layered / graded loadings for the i-th block; e is a natural constant; β i is the consolidation parameter of the i-th block dam after completion, in d -1 ; β i,j is the consolidation parameter of the i-th block during the j-th level loading period, in d -1 ; T i,k T is the end time of loading the kth level of the i-th block, in d; i,k-1 The k-th level loading completion time of the i-th block, in d; Where: π is the ratio of circumference to circumference; c v is the consolidation coefficient of the dam tailings, in m 2 / d;H i is the maximum drainage distance of the i-th block, in m; H i,j is the average drainage distance of the j-th level loading of the i-th block, in meters; S5: Calculate the weighted average degree of consolidation of each layer after the dam is completed Where: h i,j is the thickness of the j-th layer of the i-th block, in meters; S6: Determine the density and shear strength through physical and mechanical tests of various geological units of the tailings dam. Conduct saturated triaxial consolidation undrained shear tests on the tailings to measure the pore water pressure and obtain the effective stress shear strength index. S7: The spatial function of the internal friction angle of each block of the tailings dam is established by the layered average consolidation degree and the corresponding elevation: Where: is the spatial function of the friction angle within the i-th block, in degrees; is the internal friction angle of the normal consolidation effective stress of the dam tailings, in degrees; is the average degree of consolidation at the elevation z position of the i-th block; S8: For strips with an average consolidation degree of 100% on the dam surface, the position of the seepage line is determined according to the steady seepage analysis. For strips with an average consolidation degree of less than 100%, the seepage line is located on the dam surface. S9: Based on the limit equilibrium method, search for sliding arc surfaces of arbitrary shapes, perform anti-sliding stability calculations, and obtain the minimum value of the stability coefficient, which is the corresponding sliding arc surface.

2. The anti-sliding stability analysis method for an underconsolidated saturated fine-grained tailings dam according to claim 1, characterized in that: The concentration of tailings entering the storage is 25%, particles smaller than 0.075mm account for 80%, and the clay content is 15%.

3. The anti-sliding stability analysis method for an underconsolidated saturated fine-grained tailings dam according to claim 1, characterized in that: The tailings dam geological unit divided in S1 includes tailings accumulation dam, initial dam and dam foundation.

4. The anti-sliding stability analysis method for an underconsolidated saturated fine-grained tailings dam according to claim 3, characterized in that: The tailings dam is built by raising the pile by 50m upstream, with an average outer slope ratio of 1:5 and a rising speed of 0.007 to 0.036m / d.

5. The anti-sliding stability analysis method for an underconsolidated saturated fine-grained tailings dam according to claim 3, characterized in that: The initial dam is located at the foot of the downstream slope and is built with weathered slate. The bearing layer of the dam foundation is strongly weathered slate and the dam height is 30m.

6. The anti-sliding stability analysis method for an underconsolidated saturated fine-grained tailings dam according to claim 3, characterized in that: The dam foundation is located below the tailings accumulation dam and the initial dam, has a slope of 8%, and is composed of slate with different degrees of weathering from top to bottom.

7. The anti-sliding stability analysis method for an underconsolidated saturated fine-grained tailings dam according to claim 3, characterized in that: The seepage line in S8 is determined by the initial dam and the tailings dam near the initial dam according to the steady seepage analysis. The seepage line of the rest of the tailings dam is located on the dam surface.

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