Water-rich fire area open pit coal mine side slope safety rock pillar reserving method

Abstract

The invention discloses a water-rich fire area open pit coal mine slope safety rock pillar reserving method, and belongs to the technical field of slope stability evaluation and disaster prevention and control. The method includes the following steps that the geometrical shape, rock stratum distribution and temperature anomaly area data of an open pit coal mine slope are obtained, and a burning area boundary is delimited by combining historical burning records; establishing a slope geologic model of the water-rich fire rock area through the ascertained boundary and water-rich condition of the fire rock area in the slope; and taking the outermost side point of the edge of the burning area as a starting point, reserving a rock pillar, selecting a numerical value of which the stability coefficient is greater than and closest to Fst, and determining the width of the safety flat plate reserved by the corresponding section. According to the method, the stability rule of the side slope is studied, and an important guarantee is provided for safety production of the surface mine containing the burned rock side slope.

Description

Technical Field

[0001] The invention belongs to the technical field of slope stability evaluation and disaster prevention and control, and relates to an open-pit coal mine slope stability analysis method taking into account the influence of a fire zone. Background Art

[0002] Burn zones form due to spontaneous combustion of coal seams or coal combustion during mining. Coal combustion alters the physical and mechanical properties of the rock mass, reducing its strength and changing its structure, significantly impacting slope stability. Burn zones are widespread in many open-pit coal mines in my country, such as those in Xinjiang and Inner Mongolia, creating significant challenges for slope stability management.

[0003] Fire zones are often concentrated in rock fields containing thick, low- to medium-grade metamorphic strata of the Middle and Lower Jurassic systems. After spontaneous combustion, heat diffuses outward, with the primary direction of heat conduction being vertically upward, causing the overlying strata to be thermally baked, forming burned rocks. Horizontally, due to varying degrees of crack density and the presence of both strong and weak fractures, the rock formations become chaotic and fragmented, with collapse and collapse occurring near the strata. The well-developed fracture network of burned rocks provides ample water storage and channels. The water content / richness of burned areas formed after fire is primarily dependent on a variety of factors, including the extent of the burn zone, the degree of fracture development in the burned rock layer, the water-richness of overlying aquifers, and seasonal atmospheric precipitation. The larger the burn zone, the more developed the collapse fractures in the burned rock, and the greater the corresponding water storage space. When fractures extend into overlying aquifers or Quaternary strata, they can be directly recharged from these aquifers or atmospheric precipitation, enriching the rocks with water. The current method is to infer the groundwater reserves at different elevations in the survey area based on the geological task requirements and the distribution of low-resistance anomaly areas in the relevant target layers, combined with geological topography, rock formation occurrence, exposed fracture development, and hydrogeological data. After determining the water-bearing boundary area and the burned rock reserve area, the scope described in the present invention is to set up safety protection rock pillars on the slope without destroying the burned area. At present, there is little research on the method of setting up safety rock pillars on such slopes. Therefore, there is an urgent need for a slope stability analysis method for open-pit coal mines that takes into account the influence of the burned area. Through this method, the stability laws of such slopes are studied, providing important guarantees for the safe production of open-pit mines containing burned rock slopes. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for setting safe rock pillars on the slopes of open-pit coal mines in water-rich fire-burned areas.

[0005] The technical solution adopted by the invention is: a method for setting a safety rock pillar on the slope of an open-pit coal mine in a water-rich fire zone, the technical key points of which are as follows: Step 1: Obtain data on the geometry, rock layer distribution, and temperature anomaly areas of the open-pit coal mine slope. Combined with historical combustion records, the burn zone boundaries are delineated and a database containing the burn zone's spatial location, temperature gradient, and combustion residue distribution is established. By exploring the boundaries and water-rich conditions of the igneous rock area within the slope, a slope geological model of the water-rich igneous rock area is established; Step 2: Divide the established geological model into sections and determine the slope safety reserve coefficient. Based on the two-dimensional section and the upper boundary of the slope, rock pillars of different widths are set starting from the outermost point of the edge of the burned area. The uppermost boundary position and the outermost point of the set rock pillar are connected, and the corresponding slope angle is θ. Step 3, respectively calculating the slope stability coefficients under the conditions of fixing the upper boundary and setting rock pillars of different widths at different angles; Step 4: Determine the safety reserve factor F that meets the conditions st , select the stability coefficient greater than and closest to F st The value of is used to determine the width of the safety flat plate reserved for the corresponding section.

[0006] Furthermore, in step 4, select the stability coefficient that is greater than and closest to F st The numerical method is as follows: according to the initial safety distance L, the corresponding slope angle is obtained and the slope stability coefficient is calculated; the safety distance L is increased, the corresponding slope angle is obtained, and the calculated slope stability coefficient increases until the slope safety reserve coefficient F is obtained. st The optimal safety distance L n , the corresponding slope angle is θ n .

[0007] The beneficial effects of the present invention are as follows: the method for setting up safe rock pillars on the slopes of open-pit coal mines in water-rich burnt areas obtains data on the geometric form, rock layer distribution and temperature anomaly areas of the open-pit coal mine slopes, and delineates the boundaries of the burnt areas in combination with historical combustion records; a geological model of the slope of the water-rich burnt rock area is established by exploring the boundaries and water-rich conditions of the burnt rock area in the slope; a rock pillar is set up starting from the outermost point on the edge of the burnt area, and a rock pillar with a stability coefficient greater than and closest to F is selected. st The value of is used to determine the width of the safety plate left in the corresponding section. This method studies the stability of the slope and provides an important guarantee for the safe production of open-pit mines with igneous rock slopes. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0009] Figure 1 Schematic diagram of the steps for setting up a rock pillar for safety protection on a water-rich fire-burned rock slope according to an embodiment of the present invention; Figure 2 This is a cross-sectional location diagram of the water-bearing igneous rock area ascertained by geophysical exploration in an embodiment of the present invention; Figure 3 This is a cross-sectional position diagram of the slope of the water-bearing igneous rock area in an embodiment of the present invention; Figure 4 This is a position diagram for calculating and analyzing the slope profile of the water-bearing igneous rock area in an embodiment of the present invention; Explanation of the serial numbers in the figure: 1 to the boundary slope, 2 burned rock, 3 burned rock boundary, 4 other original rock, 5 safety rock column width L6, angle θ corresponding to the safety rock column width L. DETAILED DESCRIPTION

[0010] To make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the following Figures 1-4 The present invention is further described in detail with reference to the accompanying drawings and specific embodiments.

[0011] The present embodiment adopts a method for setting a safety rock pillar on the slope of an open-pit coal mine in a water-rich fire zone, comprising the following steps: Step 1: Use 3D laser scanning, drill core sampling, and infrared thermal imaging to obtain data on the geometric shape, rock layer distribution, and temperature anomaly areas of the open-pit coal mine slope. Combined with historical combustion records, the boundaries of the burn zone are delineated, and a database containing the spatial location of the burn zone, temperature gradient, and distribution of combustion residues is established. By exploring the boundaries and water-rich conditions of the burned rock area within the slope, a slope geological model of the water-rich burned rock area is established.

[0012] Step 2: Divide the established geological model into sections and determine the slope safety reserve factor according to relevant specifications. Based on the two-dimensional section and on the premise that the upper part of the slope reaches the boundary, rock pillars of different widths are set starting from the outermost point of the edge of the burned area. The connection between the uppermost boundary position and the outermost point of the rock pillar is connected. The corresponding slope angle is θ. Step 3: Calculate the slope stability coefficients for different angles when the upper boundary is fixed and rock pillars of different widths are left. Step 4: List the regularity between the stability coefficient and the width of different rock pillars (corresponding to different angles), see Table 1. According to the slope conditions of the mine fire area and the open-pit mining design specification "Design Specification for Open-pit Mines in Coal Industry" GB50197-2015, determine the safety reserve factor F that meets the conditions. st , select the stability coefficient greater than and closest to F st The value of is used to determine the width of the safety plate reserved for the corresponding section; (5) During construction, when mining near the protected rock pillar area, water exploration and drainage projects should be carried out in advance.

[0013] The present invention focuses on the setting of the safety distance L in the figure, that is, under the condition that the surface boundary is fixed, as the width L of the protective rock pillar increases, the corresponding slope angle θ will become smaller, such as Figure 1 , the angle θ1 corresponding to the width of the safety rock column L1, the angle θ2 corresponding to the width of the safety rock column L2, ... and so on, through the comprehensive trial calculation of different safety distances L (corresponding to different angles), the slope stability coefficient is calculated respectively. As the safety distance L increases, the corresponding slope angle will become gentler, and the slope stability coefficient will increase, and finally the slope safety reserve coefficient F is obtained. st The optimal safety distance L n , which corresponds to a slope angle θ n After the determination, during the mining process, it is necessary to combine the use of water exploration and drainage drilling. The main purpose is to explore water before mining, to prevent the error in the boundary of water-rich igneous rock, which will lead to water outflow, reduce the stability of the slope, and affect mining.

[0014] Table 1 Analysis of the width of safety rock pillars Width of safety rock pillar (m) / corresponding slope angle (°) <![CDATA[L1]]> <![CDATA[L2]]> <![CDATA[L3]]> <![CDATA[L4]]> <![CDATA[L5]]> Stability coefficient <![CDATA[FS1]]> <![CDATA[FS2]]> <![CDATA[FS3]]> <![CDATA[FS4]]> <![CDATA[FS5]]> Example:

[0015] The burned rock on the north side of an open-pit mine in Xinjiang contains water and is bedding-type. Analysis of existing data indicates that the main sources of groundwater recharge are atmospheric precipitation and long-distance runoff. The burned rock itself has well-developed pores and fissures, which are likely to form groundwater channels.

[0016] 1. Through geophysical exploration, the distribution of water in the burned area was determined. See the cross-sectional diagram for details. Figure 3 ; 2. By establishing a geological model, cutting sections, and establishing a slope geological model for analysis, the analysis section shows Figure 3 and 4 , based on the open pit rock mine design specifications and on-site actual conditions, the safety factor is determined to be 1.3; 3. The final decision was made that the principle of this project was to not exploit the water-bearing areas of burned rock. Through comprehensive calculations of different widths of protective rock pillars and different slope angles, the initial width of the protective rock pillars could be set to zero. At this point, the corresponding slope angles could be measured using CAD software. The widths of the different protective rock pillars and the corresponding slope angles were recorded, and the safety and stability coefficients were calculated. The calculation results are shown in Table 2: Table 2 Orthogonal analysis table of safety plate width and slope angle to boundary Safety rock column width / m corresponding angle / ° 25 30 35 40 45 30 1.267 1.284 1.302 1.356 1.385 It was finally decided to retain a 35m protective rock column according to the B5 rock top and the slope angle was 30°, which was greater than and closest to the safety stability factor of 1.3.

[0017] At this time, the construction is carried out with the optimal engineering parameters. Before actual construction, the water content must be explored first. The calculation results are shown in Figure 4 .

[0018] 4. The burned rock area is rich in water, and the water-rich area of ​​the burned rock is heterogeneous. There is a certain error in the theoretical estimation of the water-bearing boundary line. The water-bearing boundary line is actually a water-bearing storage zone. The water-richness and permeability gradually weaken as it moves away from the burned water-rich area. Therefore, vertical drilling can be adopted on the vertical section, with a drilling footage of about 50m, an advance detection distance of 60m, and a drilling spacing of 10~20m. That is, during the stripping work of the mining pit, water exploration and drainage work needs to be carried out when it is 60m away from the water-bearing boundary.

[0019] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for setting up a safety rock pillar on the slope of an open-pit coal mine in a water-rich fire zone, characterized in that: The following steps are involved: Step 1: Obtain data on the geometry, rock layer distribution, and temperature anomaly areas of the open-pit coal mine slope. Combined with historical combustion records, the burn zone boundaries are delineated and a database containing the burn zone's spatial location, temperature gradient, and combustion residue distribution is established. By exploring the boundaries and water-rich conditions of the igneous rock area within the slope, a slope geological model of the water-rich igneous rock area is established; Step 2: Divide the established geological model into sections and determine the slope safety reserve coefficient. Based on the two-dimensional section and the upper boundary of the slope, rock pillars of different widths are set starting from the outermost point of the edge of the burned area. The uppermost boundary position and the outermost point of the set rock pillar are connected, and the corresponding slope angle is θ. Step 3, respectively calculating the slope stability coefficients under the conditions of fixing the upper boundary and setting rock pillars of different widths at different angles; Step 4: Determine the safety reserve factor F that meets the conditions st , select the stability coefficient greater than and closest to F st The value of is used to determine the width of the safety flat plate reserved for the corresponding section.

2. A method for laying safety rock pillars on the slope of an open-pit coal mine in a water-rich fire zone according to claim 1, characterized in that: In step 4, select the stability coefficient that is greater than and closest to F st The numerical method is as follows: according to the initial safety distance L, the corresponding slope angle is obtained and the slope stability coefficient is calculated; the safety distance L is increased, the corresponding slope angle is obtained, and the calculated slope stability coefficient increases until the slope safety reserve coefficient F is obtained. st The optimal safety distance L n , the corresponding slope angle is θ n .

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