A method for determining the development position of collaborative soil dumping during the demolition of an intermediate bridge

Abstract

The present invention provides a method for determining the collaborative soil dumping development position during the demolition of the intermediate bridge. First, based on the idea of the area microelement of the spatial surface, the bottom area regarding the demolition length of the intermediate bridge and the volume of the dynamically demolished part of the intermediate bridge are solved. Then, according to the Mohr–Coulomb strength criterion and the spatial characteristics during the dynamic demolition of the intermediate bridge, the soil dumping pressure support body is simplified into a prism, a section is cut at the center position of the soil dumping site, and the increment of the slope support effect of this section is calculated. Finally, based on the concept of the collaborative development of the intermediate bridge and the internal soil dumping site, the development length and the soil dumping elevation of the internal soil dumping site are solved. This lays a foundation for effectively solving the difficult problem of slope stability analysis under the conditions of demolishing the intermediate bridge and developing the internal soil dumping site during pit mining; at the same time, it provides a brand-new idea for the landslide prevention and control technology during the demolition of the intermediate bridge, with great scientific significance.

Description

Technical Field

[0001] The present invention belongs to the technical field of open-pit mining, and particularly relates to a method for determining the development position of coordinated waste dumping during the demolition of an intermediate bridge. Background Art

[0002] Waste dumping for slope support is one of the best measures to control the stability of soft-rock open-pit coal mine slopes. Most open-pit coal mines often adopt separate-pit mining in the initial stage of construction or even for a long time, forming an intermediate bridge between adjacent open-pit mines. To recover the coal resources covered by the intermediate bridge, the intermediate bridge needs to be demolished. During the demolition process, the retaining effect of the intermediate bridge on the slope will gradually decrease, and the slope stability will inevitably decrease. Improper handling will lead to large-scale landslides. Waste dumping for slope support can increase the overall anti-sliding force of the slope. Therefore, by means of the coordinated development of intermediate bridge demolition and internal waste dump, the retaining effect of the internal waste dump on the slope can be used to make up for the loss of the retaining effect during the intermediate bridge demolition process, thereby controlling the slope stability.

[0003] However, there is currently no unified understanding of the relationship between the increased anti-sliding force caused by the development of the internal waste dump and the decreased anti-sliding force caused by the demolition of the intermediate bridge. Therefore, it is necessary to establish a quantitative relationship between the two to determine the development position of coordinated waste dumping, and then scientifically guide engineering design, slope treatment, and safety implementation. During the demolition of the intermediate bridge using the existing technology, the slope stability will gradually decrease. When reaching a certain threshold, the slope stability coefficient will be less than the safety reserve coefficient, which does not meet the requirements of safe production. Moreover, the existing technology can only guide the demolition of the intermediate bridge to a certain threshold, that is, just meeting the requirements of the safety reserve coefficient, and cannot guide the continuous demolition of the intermediate bridge until it is completely demolished. Summary of the Invention

[0004] Based on the above problems, the present invention provides a method for determining the development position of coordinated waste dumping during the demolition of an intermediate bridge, including:

[0005] Step 1: Establish a Cartesian rectangular coordinate system at a corner point on one side of the bottom interface of the intermediate bridge to obtain the equation of the inclined base spatial surface Σ and the surface boundary equations y1 and y2 projected on the XOY plane:

[0006]

[0007]

[0008] In the formula, ω represents the base inclination angle; d represents the bottom width of the intermediate bridge; h represents the bridge height of the intermediate bridge; b represents the bridge length of the intermediate bridge; α2 and α3 respectively represent the lower bottom angles on both sides of the intermediate bridge;

[0009] Step 2: Based on the idea of the area microelement of the spatial surface, find the bottom area S corresponding to the demolition length x of the intermediate bridge z of the intermediate bridge z:

[0010]

[0011] Step 3: Calculate the volume V of the dynamically demolished portion of the middle bridge z :

[0012]

[0013] Where α1 represents the bottom angle of the slope along the middle bridge;

[0014] Step 4: Based on the Mohr-Coulomb strength criterion and the spatial characteristics of the middle bridge during dynamic demolition, calculate the reduction in slope support effect T corresponding to the demolished part of the middle bridge. z :

[0015]

[0016] Where c j is the cohesion of the rock layer of the middle bridge bottom plate; γ z is the weighted bulk density of each rock layer in the middle bridge; is the internal friction angle of the rock layer of the middle bridge bottom plate;

[0017] Step 5: Based on the Mohr-Coulomb strength criterion and considering the spatial characteristics of the internal dump during dynamic development, simplify the dump pressure body into a prism, cut the section at the center of the dump, and calculate the incremental slope support effect T of the dump pressure body. p :

[0018]

[0019] Where x p is the width of soil discharge; c p is the cohesion of the discarded material; p The bulk density of the discarded material; is the internal friction angle of the discarded material; S p is the cross-sectional area of the inner dump; L p The length of the spoil dump to be solved;

[0020] Step 6: Based on the concept of coordinated development of the middle bridge and the inner spoil dump, the T z and T p Mathematical expression to solve the development length L of the spoil dump p :

[0021]

[0022] Furthermore, by controlling the length and width of the dumping site x p , solve the cross-sectional area S of the inner dump p , the cross-sectional area S of the inner dump obtained by calculationp , draw the corresponding cross-section model in CAD software to obtain the minimum waste-dumping elevation.

[0023]

[0024] The beneficial effects of the present invention are as follows:

[0025] The present invention provides a method for determining the collaborative waste-dumping development position during the demolition of the intermediate bridge. By quantitatively characterizing the change in the retaining effect of the intermediate bridge demolition and the development of the internal waste-dumping site on the slope, and establishing a quantitative relationship between the increased anti-sliding force due to the development of the internal waste-dumping site and the decreased anti-sliding force due to the demolition of the intermediate bridge, the solution process for the collaborative waste-dumping development position during the demolition of the intermediate bridge is finally obtained, laying a foundation for effectively solving the problem of slope stability analysis under the conditions of demolishing the intermediate bridge and developing the internal waste-dumping site during pit mining; at the same time, it provides a new idea for the landslide prevention and control technology during the demolition of the intermediate bridge, with great scientific significance. The expected results of the invention can also be extended to the collaborative design of the intermediate bridge and the waste-dumping site during the mining process of adjacent open-pit coal mines, having broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a diagram of the spatial form and stress state of the intermediate bridge and the internal waste-dumping site of the present invention.

[0027] Figure 2 It is a calculation schematic diagram of the intermediate bridge and the internal waste-dumping site of the present invention, where (a) is a plan schematic diagram of the collaborative development of the intermediate bridge demolition and the internal waste-dumping site; (b) is a sectional view along 1-1'; (c) is a schematic diagram of the spatial geometric elements of the demolished part of the intermediate bridge.

[0028] Figure 3 It is a typical geological sectional view of the present invention.

[0029] Figure 4 It is a schematic diagram of the waste-dumping pressure-supporting section when the waste-dumping elevation is +932m of the present invention.

[0030] Figure 5 It is the development length L of the waste-dumping site of the present invention p = 240m, which is a plan schematic diagram of the waste-dumping pressure-supporting.

[0031] Figure 6 It is the development length L of the waste-dumping site of the present invention p = 500m, and when the waste-dumping width is 40m, it is a plan schematic diagram of the waste-dumping pressure-supporting.

[0032] Figure 7 It is a schematic diagram of the waste-dumping pressure-supporting section when the waste-dumping elevation is +920m of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The invention will be further described below with reference to the accompanying drawings and specific implementation examples.

[0034] Affected by the specifications of mining and transportation equipment and the formation conditions, the spatial form of the demolished intermediate bridge and the coordinated dumping pressure support is generally an irregular polyhedron. During the demolition of the intermediate bridge, its retaining effect on the non-working side will inevitably gradually weaken, and the development of the inner dump is equivalent to offsetting the weakening of the retaining effect. Based on the analysis of the stress state of the intermediate bridge and the inner dump during the coordinated development process, in order to facilitate the quantitative analysis of the retaining effect, the slope angle is used to replace the complex multi-step combination, and the mechanical model of the intermediate bridge demolition and inner dump development process is further simplified, as shown in the figure below. Figure 1 shown.

[0035] Through mechanical analysis, the middle bridge demolition body (developed inner dumping ground) is subjected to the non-working thrust F and its own gravity W. z (W p ) and the support force of the bottom interface N z (N P ) and shear resistance T z (T p ) role, such as Figure 1 As shown. Obviously, the size of the retaining effect is determined by the size of the bottom interface shear resistance T. Based on the expression of shear strength, it can be seen that for the demolished part of the middle bridge bottom interface shear resistance T z The size of is determined by its spatial form and the properties of the bottom rock layer, and the shear resistance T of the bottom interface of the developed internal dump is p The size of is determined by its spatial form and the mechanical index of the discarded materials. Based on the Mohr-Coulomb shear strength criterion, it can be seen that the loss of the retaining effect during the demolition of the middle bridge and the increase in the retaining effect of the corresponding inner dump are related to their spatial form parameters α1, α2, α3, ω, d, h, b, x1, L p Among them, α1, α2, α3, and ω are the slope inclination, bottom angle under the strike, and base inclination along the middle bridge, respectively; d, h, b, and x z 、L p and L are the bottom width of the middle bridge, bridge height, bridge length, demolition length of the middle bridge, development length of the spoil dump and total length of the mining pit, respectively, in m.

[0036] In this example, the southern slope of an open-pit coal mine is used as an example. The normal operating parameters for the stope are a flat plate width of 40m, a slope angle of 70°, and a step height of 12m. The operating parameters for the spoil dump are a flat plate width of 80m, a slope angle of 33°, and a step height of 24m. The southern slope has a dip angle of 5-8° and is composed of Quaternary and Tertiary systems, mudstone, and coal. Weak layers exist on the coal seam floor, and the slope lacks major faults, making it a typical down-dipping soft rock slope. The slope experienced two major landslides on September 10, 2010, and May 16, 2011, resulting in the upper portion being primarily composed of loose soil formed by the sliding of discarded materials, mudstone, and other materials.

[0037] In this embodiment, a typical geological section is as shown in Figure 3 , and the physical and mechanical indexes of each rock and soil mass are shown in Table 1.

[0038] Table 1 Physical and mechanical indexes of rock and soil mass

[0039]

[0040] By demolishing the middle bridge, the coal resources overlaid by the middle bridge are mined back to the maximum extent. When the demolished length x of the middle bridge z is 200 m, the slope stability coefficient is 1.20, which just meets the requirement of the safety reserve coefficient; if the middle bridge is continuously demolished, the slope stability coefficient will be less than 1.20, not meeting the requirement of the safety reserve coefficient. To ensure the safe production of the mine and the stable continuation of production capacity, the slope stability is controlled to meet the safety production requirements by the method of coordinating the waste rock disposal and the demolition of the middle bridge, that is, controlling the slope stability coefficient to be greater than or equal to the safety reserve coefficient of 1.20. It should be noted that the internal waste dump develops from west to east.

[0041] A method for determining the coordinated waste rock disposal development position during the demolition of the middle bridge includes the following steps:

[0042] Step 1: Since the change amount of the retaining effect of the middle bridge during the demolition process and the internal waste dump during the corresponding development process on the slope is related to their spatial form parameters, therefore, combining the relative spatial position relationship between the middle bridge and the internal waste dump, a Cartesian rectangular coordinate system is established at a corner point on one side of the bottom interface of the middle bridge, as shown in Figure 2 . The equation of the inclined base spatial surface Σ and the surface boundary equations y1 and y2 projected on the XOY plane can be obtained.

[0043]

[0044]

[0045] Step 2: Based on the idea of the spatial surface area microelement, the bottom area S with respect to the demolished length x of the middle bridge z is obtained: z :

[0046]

[0047] where

[0048] Step 3: The dynamically demolished part of the middle bridge is an irregular hexahedron with a volume of V z , which can be obtained by subtracting regular geometric bodies:

[0049]

[0050] in,

[0051] Step 4: Based on the Mohr–Coulomb strength criterion and the spatial characteristics of the dynamic removal process of the intermediate bridge, the reduction in the slope support effect caused by the removal of the intermediate bridge can be obtained:

[0052]

[0053] Where c j is the cohesion of the rock layer (weak layer) of the middle bridge bottom plate, kPa; γ z is the weighted density of each rock layer in the middle bridge, kN / m 3 ; is the internal friction angle of the rock layer (weak layer) of the middle bridge bottom plate, °.

[0054] Step 5: Based on the Mohr-Coulomb strength criterion and considering the spatial characteristics of the internal dump during its dynamic development, the dump pressure body is simplified into a prism. A 1-1' section is selected at the center of the dump to analyze the incremental slope support effect:

[0055]

[0056] Where x p is the width of soil discharge, m; c p is the cohesive force of the discarded material, kPa; γ p is the bulk density of the discarded material, kN / m 3 ; is the internal friction angle of the discarded material, °; S p is the cross-sectional area of the inner dump, m 2 .

[0057] Step 6: The removal of the middle bridge will inevitably weaken the retaining effect of the slope, and the lost retaining effect can be compensated by draining the soil and pressing the slope, thereby achieving the purpose of controlling the slope stability. z and T p From the mathematical expression, it can be seen that under the condition that the physical and mechanical parameters of the rock and soil mass and the dump elevation are known, the variation of the retaining effect is only related to the morphological parameters of the intermediate bridge and the dump. Based on the synergistic concept of the retaining effect of the intermediate bridge and the inner dump, the T z and T p Mathematical expression (let T z =T p ), the development length L of the spoil dump can be solved p :

[0058]

[0059] Similarly, control the length of the dump site L p And soil discharge width xp It is also possible to solve the cross-sectional area S of the internal waste dump p :

[0060]

[0061] The cross-sectional area S of the internal waste dump obtained through calculation p , draw the corresponding cross-section model in CAD software to obtain the minimum waste dumping elevation

[0062] For a specific mine, the mining operation parameters, the base dip angle ω, the spatial form parameters of the intermediate bridge, and the lithology of each stratum can all be regarded as known quantities. Then, the equation of the inclined base spatial surface Σ and the surface boundary equations: y1, y2 can be obtained. If the demolition length x of the intermediate bridge is clear z , the bottom area S can be obtained z and the volume V of the demolished part of the intermediate bridge z , thereby obtaining the reduction amount of the slope retaining effect caused by the demolition of the intermediate bridge. By clarifying the planned waste dumping elevation and mining operation parameters, the cross-sectional area S of the internal waste dump can be obtained through cad software p , based on matlab and the development length L of the waste dump p Mathematical expression, the development length L of the waste dump can be obtained p , similarly, by clarifying the planned development length L of the waste dump p and the waste dumping width x p , through the cross-sectional area S of the internal waste dump p Mathematical expression, the cross-sectional area of the internal waste dump can be obtained, and then the waste dumping elevation threshold can be obtained

[0063] In this embodiment, the lower bottom angles α1 and α of the intermediate bridge along the slope dip and strike 2,3 are both 43°, the base dip angle is 5°, the bottom width d, the bridge height h, the bridge length b, and the total length L of the mining pit of the intermediate bridge are 130m, 40m, 260m, and 1200m respectively

[0064] Combined with the relative spatial position relationship between the intermediate bridge and the internal waste dump, a Cartesian rectangular coordinate system is established at a corner point on one side of the bottom interface of the intermediate bridge, and the equation of the inclined base spatial surface Σ can be obtained

[0065]

[0066] Surface boundary equations: y1, y2

[0067]

[0068] If the demolition length x of the intermediate bridge z is 160m, the bottom area S can be calculated z :

[0069]

[0070] The dynamically demolished part of the middle bridge is an irregular hexahedron with a volume of:

[0071]

[0072] It is planned to dump soil to elevation +932m, and the cross-sectional area S of the internal dump site can be calculated z and the dump width x p are 883.7367m 2 , 30m respectively, as Figure 4 shown.

[0073] The development length L of the dump site p (as Figure 5 shown):

[0074]

[0075] If the above other conditions remain unchanged, the planned development length L of the dump site p is 500m and the dump width is 40m. As Figure 6 shown, the corresponding cross-sectional area S of the internal dump site can be solved p :

[0076]

[0077] Drawing the model in CAD software shows that when dumping soil to +920m, the cross-sectional area of the internal dump site is 486.374m 2 >308.597m 2 , so the dump elevation can be determined as +920m, as Figure 7 shown.

Claims

1. A method for determining the collaborative soil discharge development position during the demolition of an intermediate bridge, characterized in that, Including: Step 1: Establish a Cartesian rectangular coordinate system at a corner point on one side of the middle bridge bottom interface, obtaining the equation of the inclined base spatial surface Σ and the surface boundary equations y1 and y2 projected onto the XOY plane; The equation of the inclined base spatial surface Σ and the surface boundary equations y1 and y2 projected onto the XOY plane are specifically expressed as: ； ； In the formula, ω represents the base inclination angle; d represents the bottom width of the middle bridge; h represents the bridge height of the middle bridge; b represents the bridge length of the middle bridge; α2 and α3 respectively represent the lower bottom angles on both sides of the middle bridge; Step 2: Based on the idea of the differential element of the spatial curved surface area, find the demolition length x of the middle bridge z The corresponding bottom area S z ; Step 3: Calculate the volume V of the dynamically demolished part of the intermediate bridge z ; Step 4: Calculate the reduction amount of slope retaining effect corresponding to the demolished part of the middle bridge according to the Mohr-Coulomb strength criterion and the spatial characteristics during the dynamic demolition process of the middle bridge ; Step 5: Based on the Mohr-Coulomb strength criterion and considering the spatial characteristics during the dynamic development process of the inner waste dump, simplify the waste dump rib-pressing body into a prism, cut a section at the center position of the waste dump, and calculate the incremental retaining effect of the waste dump rib-pressing body on the slope ; Step 6: Based on the concept of the coordinated development of the intermediate bridge and the inner waste dump, establish mathematical expressions for T z and T p , and solve for the development length L of the waste dump p .

2. The method for determining the collaborative soil discharging development position during the demolition of the intermediate bridge according to claim 1, wherein Regarding the demolition length x of the intermediate bridge in step 2 z The bottom area S z is expressed as: 。 3. The method for determining the collaborative soil discharging development position during the removal of the intermediate bridge according to claim 2, wherein The volume V of the dynamic demolition part of the intermediate bridge in step 3 z is expressed as: ； In the formula, α1 represents the lower bottom angle of the middle bridge along the slope tendency.

4. The method for determining the collaborative soil dumping development position during the demolition of the intermediate bridge according to claim 3, wherein The reduction in the slope retaining effect corresponding to the part of the intermediate bridge demolished in Step 4 It is expressed as: ； In the formula, is the cohesion of the intermediate bridge floor rock stratum; is the weighted unit weight of each rock stratum of the intermediate bridge; is the internal friction angle of the intermediate bridge floor rock stratum.

5. The method for determining the collaborative soil discharge development position during the removal of the intermediate bridge according to claim 4, wherein The increment of the retaining effect of the waste-dumping rib on the slope in Step 5 It is expressed as: ； In the formula, is the waste dumping width; is the cohesion of the waste materials; is the unit weight of the waste materials; is the internal friction angle of the waste materials; S p is the cross-sectional area of the internal waste dump; is the development length of the waste dump to be solved.

6. The method for determining the collaborative soil discharge development position during the removal of the intermediate bridge according to claim 5, characterized in that, The development length L of the waste dump in step 6 p is expressed as: ； In the formula, is the total length of the quarry pit.

7. The method for determining the collaborative soil dumping development position during the demolition of the intermediate bridge according to claim 6, characterized in that, By controlling the development length of the waste dump and the waste dumping width x p to solve the cross-sectional area S of the internal waste dump p : 。

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