Method for analyzing anti-sliding stability of under-consolidated saturated fine-grain tailing fill dam

Abstract

The invention discloses a method for analyzing the anti-sliding stability of an under-consolidation saturated fine grain tailing fill dam, and belongs to the field of tailing dam stability analysis. The method comprises the following steps: carrying out graded loading on a tailing fill dam from bottom to top, keeping a consolidation coefficient unchanged, mainly adopting a vertical seepage direction of water, correcting a Taisha foundation one-dimensional seepage consolidation theory in combination with a saturated fine grain tailing fill dam loading and consolidation rule, assuming that the consolidation coefficient is unchanged and water vertically or horizontally seeps in a seepage drainage consolidation process, and carrying out graded constant-speed loading, so as to obtain a consolidation consolidation result; and hierarchically calculating the consolidation degree of graded loading, and carrying out weighted averaging according to the graded loading amount to obtain a relation curve of the consolidation degree and the burial depth. According to the method, the tailing fill dam is divided into a plurality of vertical strips, and the relationship between the consolidation degree and the elevation of the strips is analyzed, so that the spatial function of the shear strength of the under-consolidated tailings is determined, and the anti-sliding stability of the under-consolidated saturated fine-grain tailing fill dam is scientifically and effectively analyzed.

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] According to data from the China Mining Association, by the end of 2017, the stock of tailings in my country was 19.5 billion tons, and it will increase by 1 billion tons every year. According to statistics in 2020, the number of tailings ponds in my country is close to 8,000. The particle size of tailings has a trend of becoming finer and finer, and the tailings dams are getting higher and higher, and the rising speed is getting faster and faster. Quantitative analysis and discussion of the calculation method of the anti-sliding stability of tailings dams corresponding to the rising speed of tailings dams is becoming more and more important, especially for saturated fine-grained tailings dams.

[0003] According to the analysis of the existing tailings ponds in China, many tailings particle gradations have reached the standard of tailings powder soil, among which phosphogypsum and red mud are the two types with the largest discharge volume. There are cases in the prior art that study the characteristics of fine-grained tailings such as seepage, shear resistance, and consolidation, including the discussion of the problem of upstream fine-grained tailings damming, the study of fine-grained tailings characteristics and stability calculation analysis, the study of clay content and the physical and mechanical properties of fine-grained tailings, and the study of the consolidation characteristics and shear strength of fine-grained tailings. However, none of the above research cases analyzed the degree of consolidation and its anti-sliding stability based on the saturated fine-grained tailings damming process, and thus could not systematically explain the relationship between the tailings rising speed and the stability of the dam. Summary of the invention

[0004] The object 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-mentioned 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 geological units of the tailings dam into several vertical strips and perform horizontal stratification;

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

[0009] S3: The consolidation coefficient of the tailings dam is obtained through consolidation test;

[0010] S4: Based on the effective stress principle and 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 the loading is graded and uniform, the consolidation degree U of the graded loading is calculated layer by layer ij :

[0011]

[0012] Where: i is the strip number; j is the layered / graded 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 after the dam is completed, in d -1 β i,j is the consolidation parameter of the i-th block during the j-th loading period, in d -1 ; T i,k is the end time of loading the kth level of the i-th block, in d; T i,k-1 is the end time of loading the kth level of the i-th block, in d;

[0013]

[0014] Where: π is the ratio of circumference to diameter; 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 ith 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 m;

[0018] S6: Determine the gravity 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 dam 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 strip of the tailings dam is established by the average consolidation degree of each layer and the corresponding elevation:

[0020]

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

[0022] S8: For strips with an average consolidation degree of 100% on the dam surface, the position of the infiltration line is determined according to the stable seepage analysis. For strips with an average consolidation degree of less than 100% on the dam surface, the infiltration 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 0.075 mm account for 80%, and the clay content is 15%.

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

[0026] Furthermore, the tailings dam is built by upstream heightening 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 built 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 slate with different degrees of weathering from top to bottom.

[0029] Furthermore, the infiltration 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 infiltration line of the rest 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 the under-consolidated saturated fine-grained tailings dam of the present invention is based on the effective stress principle and the Terzaghi seepage consolidation theory. 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 strips and blocks 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 It is a cross-sectional diagram of geological unit division of the upstream fine-grained tailings dam of the wet tailings pond of the present invention;

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

[0036] Figure 3 It is a schematic diagram of the seepage consolidation analysis model of graded isovelocity loading during dam-building of the present invention;

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

[0038] 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.

[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 geological units of tailings dam 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 bearing layer of the dam foundation 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 slates 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, such as 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 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 consolidation degree U of the graded loading is calculated layer by layer. ij :

[0044]

[0045] Where: i is the strip number; j is the layered / graded 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 after the dam is completed, in d -1 β i,j is the consolidation parameter of the i-th block during the j-th loading period, in d -1 ; T i,k is the end time of loading the kth level of the i-th block, in d; T i,k-1 is the end time of loading the kth level of the i-th block, in d;

[0046]

[0047] Where: π is the ratio of circumference to diameter; 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 ith 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,jis the thickness of the j-th layer of the i-th block, in m;

[0051] S6: Through physical and mechanical tests of various geological units of the tailings dam, the gravity and shear strength are determined. The saturated triaxial consolidation undrained shear test of the pore water pressure is carried out on the tailings of the dam to obtain the effective stress shear strength index, as shown in the following table:

[0052]

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

[0054]

[0055] Where: is the spatial function of the internal friction angle of the i-th block, in degrees; is the internal friction angle of normal consolidation effective stress of dam tailings, in degrees; is the average consolidation degree at the i-th block elevation z position, 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 infiltration line is determined according to the stable seepage analysis. For strips with an average consolidation degree of less than 100% on the dam surface, the infiltration line is located on the dam surface.

[0059] S9: Based on the limit equilibrium method, considering the hydrostatic pressure, searching for sliding arc surfaces of arbitrary shapes, calculating the anti-sliding stability, and obtaining 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 speed of tailings dams, 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 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 implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope 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 geological units of the tailings dam into several vertical strips and perform horizontal stratification; S2: Determine the seepage boundary of each strip and the water seepage direction; S3: The consolidation coefficient of the tailings dam is obtained through consolidation test; S4: Based on the effective stress principle and 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 the loading is graded and uniform, the consolidation degree U of the graded loading is calculated layer by layer ij : Where: i is the strip number; j is the layered / graded 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 after the dam is completed, in d -1 ; β i,j is the consolidation parameter of the i-th block during the j-th loading period, in d -1 ; T i,k is the end time of loading the kth level of the i-th block, in d; T i,k-1 is the end time of loading the kth level of the i-th block, in d; Where: π is the circumference of a circle; 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 ith 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 m; S6: Determine the gravity 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 dam 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 strip of the tailings dam is established by the average consolidation degree of each layer and the corresponding elevation: Where: is the spatial function of the internal friction angle of the i-th block, in degrees; is the internal friction angle of normal consolidation effective stress of dam tailings, in degrees; is the average degree of consolidation at the i-th block elevation position z; S8: For strips with an average consolidation degree of 100% on the dam surface, the position of the infiltration line is determined according to the stable seepage analysis. For strips with an average consolidation degree of less than 100% on the dam surface, the infiltration 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 of 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 0.075 mm account for 80%, and the clay content is 15%.

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

4. The anti-sliding stability analysis method of an underconsolidated saturated fine-grained tailings dam according to claim 3 is characterized by: The tailings dam is built by upstream heightening by 50m, 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 of 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 of an under-consolidated 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, with a slope of 8%, and is slate with different degrees of weathering from top to bottom.

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

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