A method for water conservation treatment of slope combustion-altered rock in an open coal mine

Abstract

The application relates to the technical field of coal mine water-preserved mining, and discloses a method for water-preserved treatment of burned and altered rock of a slope of an open-pit coal mine, which comprises the following steps: constructing a probe drill hole at an upper step corresponding to a water gushing point of a slope, obtaining the boundary and vertical distance of burned and altered rock under the water gushing point, and classifying and defining; lowering a detection device into the probe drill hole to obtain an image, determining the direction of a water-conducting fracture, and dividing the water-conducting channel into different types; performing target design of a grouting drill hole according to the channel type and the position of the burned and altered rock, arranging vertical or inclined grouting drill holes at the intersection of steps, limiting the safe vertical distance between the slope bottom line and the drill hole; injecting grouting materials by adopting a descending sectional grouting process, taking the double control of orifice pressure and flow as the end standard of grouting, and consolidating to form a curtain for cutting off the water-conducting channel; and extracting a core of a test hole to combine with geophysical prospecting data to evaluate the effect, so that the method can accurately intercept the water-conducting channel, avoid water resource waste and slope landslide, and prevent the step from being split and leaking due to blind grouting.

Description

Technical Field

[0001] This application relates to the field of water-conserving mining technology in coal mines, specifically a method for water-conserving treatment of burnt rock slopes in open-pit coal mines. Background Technology

[0002] In some shallow coal seams in western my country's mining areas, spontaneous combustion is severe. After the surrounding rock is baked, its internal structure is reconstructed, exhibiting physical characteristics of reduced mechanical strength and increased porosity. It possesses abundant water-conducting and water-storing space, forming highly water-rich igneous rock aquifers. During the stripping process in open-pit coal mines, water from these igneous rock aquifers can easily gush out in large quantities from the bottom of the slope through fissures. Currently, the conventional treatment for water gushing from the bottom of open-pit coal mine slopes is to collect it and discharge it to a collection pool at the bottom of the pit and pump it to the surface. This passive drainage method results in a serious waste of groundwater resources. Some mining areas have tried to use traditional vertical drilling grouting curtains for seepage prevention, but traditional vertical straight hole grouting is mainly used to intercept the lateral recharge of groundwater flow fields at a distance. It cannot adapt to the complex and variable water-conducting channels inside the igneous rock on the slope, and it is difficult to effectively intercept and seal the concentrated water gushing points at the bottom of the open-pit coal mine slopes.

[0003] Due to the lack of targeted near-end interception measures, the mudstone at the bottom of the slope is constantly soaked by water, making it extremely prone to weathering and disintegration, leading to serious mining disasters such as large-scale slope spalling and landslides. Traditional treatment solutions also include the use of excavation and trenching curtain walls, but this approach not only has a long construction period and high treatment costs, but also this large-scale mechanical excavation operation can easily cause serious secondary physical disturbances to the already weathered and fragile slope toe, thus increasing the safety risk of slope instability.

[0004] Burnt rock itself has special engineering geological properties with extremely high porosity and fragile rock strata mechanical structure. When carrying out conventional grouting operations in the existing technology, due to the lack of a dynamic grouting control mechanism for burnt rock strata, blind construction is very likely to cause transverse splitting inside the slope steps due to excessive grouting pressure, or cause a large amount of ineffective leakage of grout along coarse pores and cracks. This makes it difficult for the grouting material to effectively solidify in the designated area, making it difficult to form a water-blocking curtain that cuts off the supply path, and ultimately the water retention and treatment effect at the water inflow point does not meet expectations. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a method for water retention and treatment of burnt rock on open-pit coal mine slopes. This method solves the technical problems of serious waste of groundwater resources caused by traditional passive drainage, difficulty in effectively intercepting complex water channels by single vertical straight hole grouting, easy occurrence of slope spalling and landslide disasters due to long-term soaking of mudstone at the bottom of the slope, and easy occurrence of slope step splitting and ineffective grout leakage due to blind pressure in conventional grouting processes.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] This application provides a method for water retention and treatment of sintered rock on open-pit coal mine slopes, comprising the following steps: conducting physical exploration operations on the upper bench corresponding to the water inflow point on the side of the open-pit coal mine slope; obtaining the physical boundary position of the sintered rock below the water inflow point and the vertical distance between the sintered rock and the side bench through exploration boreholes; classifying and defining the location of the sintered rock based on the relative spatial relationship between the sintered rock and the water inflow point; lowering an in-hole detection device into the exploration borehole to obtain internal stratum image data; comprehensively determining the direction of the water-conducting fractures between the water inflow point and the sintered rock based on the lithological characteristics of the strata revealed by the exploration borehole; and delineating the water-conducting channels based on the differences in the direction of the water-conducting fractures. Different types are classified; grouting boreholes are designed with specific targets based on the type of water-conducting channel and the location of the calcined rock, determining the borehole opening position, borehole inclination angle, borehole depth, casing length, and borehole diameter; a downward segmented grouting process is used to inject grouting material into the grouting borehole, and the grouting completion standard is controlled by both orifice pressure and flow rate indicators, consolidating inside the rock strata to form a curtain that cuts off the water-conducting channel; inspection holes are constructed and core samples are extracted from the inspection holes, and the water retention effect of the water inflow point is evaluated by the core recovery rate, the completeness of core fracture filling, the unit water absorption rate of the pressure test of the inspection hole, and the distribution of the water-rich abnormal zone above the grouting section.

[0008] Furthermore, the physical exploration operation includes conducting exploratory boreholes and extracting rock cores for measurement; the exploratory boreholes are arranged on the upper step, and the horizontal distance between the exploratory borehole position and the slope crest line is not greater than a set horizontal distance; a casing is installed at the borehole opening, and the installation length of the casing is calculated and determined based on hydrostatic pressure parameters; the classification is divided into two categories: igneous rock below the water inflow point and igneous rock on the side.

[0009] Furthermore, the borehole detection device includes borehole television; based on the difference in the direction of the water-conducting fracture, the water-conducting channel is divided into a transverse channel, a longitudinal channel, and a combined transverse and longitudinal channel.

[0010] Furthermore, the targeted design of grouting boreholes based on the type of water channel and the location of the calcined rock includes: constructing vertical or inclined grouting boreholes on the side steps towards the water channel as grouting boreholes, with at least two rows of grouting boreholes arranged, the row spacing between adjacent rows of grouting boreholes not greater than a set row spacing, the planar projection spacing between the grouting boreholes not greater than a set projection spacing, and the rows of grouting boreholes arranged in a crisscross pattern.

[0011] Furthermore, under the condition that the igneous rock location is below the water inflow point: when the water guiding channel is a transverse channel, the grouting borehole adopts the vertical grouting borehole, and the distance between the opening position of the vertical grouting borehole and the slope crest line is not greater than a first set distance. The casing length of the vertical grouting borehole is calculated and determined based on the hydrostatic pressure. When the water guiding channel is a vertical channel or a combined longitudinal and transverse channel, the grouting borehole adopts the inclined grouting borehole, and the distance between the opening position of the inclined grouting borehole and the slope crest line is not less than a second set distance. The casing length of the inclined grouting borehole is calculated by combining the borehole inclination angle and the hydrostatic pressure. The vertical distance between the slope bottom line and the inclined grouting borehole is calculated by combining the borehole inclination angle, the vertical distance between the steps, the slope angle, and the distance between the opening position of the inclined grouting borehole and the slope crest line. It is determined that the vertical distance between the slope bottom line and the inclined grouting borehole is not less than a set safety distance.

[0012] Furthermore, under the condition that the igneous rock location is the lateral igneous rock: when the distance between the lateral igneous rock boundary and the slope crest line is greater than a first set distance, the grouting borehole adopts the vertical grouting borehole, and the distance between the opening position of the vertical grouting borehole and the slope crest line is not greater than the first set distance. The casing length of the vertical grouting borehole is calculated and determined based on hydrostatic pressure. When the distance between the lateral igneous rock boundary and the slope crest line is less than the first set distance or the lateral igneous rock is located below the sidewall, the grouting borehole adopts the inclined grouting borehole, and the distance between the opening position of the inclined grouting borehole and the slope crest line is not less than a second set distance. The casing length of the inclined grouting borehole is calculated by combining the borehole inclination angle and hydrostatic pressure. The vertical distance between the slope bottom line and the inclined grouting borehole is calculated by combining the borehole inclination angle, the vertical distance between the steps, the slope angle, and the distance between the opening position of the inclined grouting borehole and the slope crest line. It is determined that the vertical distance between the slope bottom line and the inclined grouting borehole is not less than a set safety distance.

[0013] Furthermore, the targeted design of the grouting borehole also includes: after the construction of the inclined grouting borehole for the treatment of the step above the water inflow point is completed, if there is residual water inflow, a supplementary grouting inclined hole is designed on the step below; the supplementary grouting inclined hole and the inclined grouting borehole of the step above intersect in space to form a cross water-blocking curtain, and the vertical distance between the bottom line of the slope and the supplementary grouting inclined hole is not less than a set safety distance.

[0014] Furthermore, the method of injecting grouting material into the grouting borehole using a downward segmented grouting process includes: grouting in alternating layers or segments from top to bottom; conducting a water pressure test before grouting, grouting under conditions where the water pressure is greater than or equal to a set water pressure, and preparing the grouting material according to the results of the water pressure test; the grouting material is mainly cement slurry, and water glass, quick-setting agent, and sawdust are added to the cement slurry when encountering water inrush points or grout leakage from step cracks.

[0015] Furthermore, the dual control of orifice pressure and flow rate indicators for grouting termination criteria includes: selecting the smaller value between the tensile strength of the grouting rock layer and the water pressure of the calcined rock as the grouting termination pressure; using an injection rate per meter not exceeding a set injection rate and a grouting duration reaching a set time as the grouting termination flow rate indicator; and stopping the next section of construction if the previous section does not reach the grouting termination pressure and the grouting termination flow rate indicator.

[0016] Furthermore, the construction inspection holes and the extraction of core samples from the inspection holes include: the inspection holes are divided into two types: vertical inspection holes and oblique inspection holes. The vertical inspection holes are arranged above the main water-conducting channel sealing section, and the oblique inspection holes are arranged between the grouting boreholes; the degree of complete filling of the core fractures is determined by taking core samples from the same stratum of the exploratory boreholes and the grouting boreholes and using computed tomography to test the degree of reduction in porosity; and the absence of water-rich anomalies in the upper part of the grouting section is detected by high-density electrical resistivity tomography.

[0017] This application provides a method for water retention treatment of scorched rock on open-pit coal mine slopes. It has the following beneficial effects: 1. This application clarifies the boundary location of the calcined rock by implementing physical exploration operations and lowering in-hole detection equipment, and classifies the water diversion channels into transverse, longitudinal, and combined transverse and longitudinal types. Then, it matches the corresponding vertical grouting boreholes or inclined grouting boreholes for targeted design. This targeted classification and targeted hole layout structure overcomes the technical defects of traditional single vertical hole grouting, which is difficult to effectively intercept water inflow at the bottom of the slope. It can accurately cut off the water supply path at the bottom of the open-pit coal mine slope, and avoid the loss and waste of groundwater resources caused by long-term direct discharge into the foundation pit.

[0018] 2. In the targeted design stage of grouting boreholes, this application comprehensively incorporates spatial geometric parameters such as borehole inclination angle, vertical distance between steps, and slope angle, sets a safety distance limit logic between the slope bottom line and the vertical distance of the grouting borehole, and uses multiple rows of grouting boreholes to form a cross-water-blocking curtain in space. This design not only blocks the long-term soaking and weathering of mudstone at the bottom of the slope by complex groundwater flow from the source, greatly reducing the risk of man-made disasters such as slope slab collapse and landslides in the mining area, but also avoids secondary physical disturbances to the toe of the fragile slope caused by drilling and grouting activities.

[0019] 3. This application adopts a down-flow segmented grouting process. Before grouting construction, a water pressure test is performed to dynamically adjust the grouting material. The smaller value between the tensile strength of the grouting rock layer and the water pressure of the igneous rock is strictly selected as the grouting end pressure control standard. This dual pressure and flow control mechanism is highly consistent with the physical and geological characteristics of the igneous rock, which has high porosity and low mechanical strength. It effectively prevents the problem of step transverse splitting and ineffective leakage of grout caused by excessive grouting pressure, and ensures the quality of the water-blocking curtain consolidation in the stratum. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method in this application; Figure 2 This is a schematic diagram of the borehole design for water retention treatment of calcined rock below the water inflow point in this application; Figure 3 This is a schematic diagram of the borehole design for water retention treatment of calcined rock on the side of the water inflow point in this application. Figure 4 This is a schematic diagram of the planar projection of the inclined hole arrangement in this application. Detailed Implementation

[0021] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0022] Please see Figure 1 This application provides a method for water retention treatment of burnt rock on open-pit coal mine slopes, including the following main implementation steps: S100. Boundary Exploration and Location Classification of Burned Rock Below Side Bench: Burned rock below side bench refers to the unexposed burned rock aquifer located below the bench after the open-pit coal mine has been stripped. In this step, based on existing data on the extent of the burned area, physical exploration is conducted on the upper bench corresponding to the side bench water inflow point. The physical exploration specifically includes drilling exploratory boreholes and core extraction measurements. Exploratory boreholes are located on the upper bench corresponding to the side bench water inflow point, with the borehole location no more than 10m horizontally from the slope crest line. A casing is installed at the borehole opening, and measurements are taken based on hydrostatic pressure parameters. The installation length of the casing is calculated and determined; the physical boundary position of the igneous rock below the water inflow point and the vertical distance between the igneous rock and the side steps are obtained through borehole measurement data; after obtaining the spatial position parameters, the location of the igneous rock is classified and defined according to the relative spatial relationship between the igneous rock and the water inflow point, specifically divided into two categories: igneous rock below the water inflow point and igneous rock on the side; for the selection of drilling rigs and conventional coring techniques for exploratory borehole construction operations, those skilled in the art can conventionally select according to the hardness of the formation on site. The borehole implementation process is a well-known technology in this field and will not be described in detail here.

[0023] S200, Identification and Classification of Water Conduits for Water Inflow at the Bottom of Side Slope: Water conduits are fissure channels connecting the rock strata where the water inflow point is located with the water body inside the igneous rock. After the exploratory borehole is completed, borehole television is lowered into the exploratory borehole to obtain image data of the strata. Based on the obtained borehole images, the distribution characteristics of geological fissures in the lateral and vertical directions are observed and statistically analyzed. Combined with the lithological characteristics of the strata exposed by the borehole, the direction of the water-conducting fissures between the water inflow point and the igneous rock is comprehensively determined. Based on the differences in the direction of the water-conducting fissures, the water conduits are classified into lateral type, longitudinal type, and combined lateral and longitudinal type.

[0024] S300, targeted design of boreholes for water retention treatment on slope bottom and side slope: Based on the water channel type determined by S200 and the spatial location of the burnt rock defined by S100, targeted design of grouting boreholes is carried out. Targeted design parameters include borehole opening position, borehole inclination angle, borehole depth, casing length, and borehole diameter. Vertical or inclined grouting boreholes are constructed on the steps to guide the water channel, with no less than 2 rows of boreholes, row spacing no greater than 2m, and borehole planar projection spacing no greater than 3m, arranged in a cross pattern. Adapted borehole spatial morphology is adopted for different types of water channel. Taking the longitudinal and transverse composite channel water retention treatment inclined borehole as an example, the specific length of the casing and the safe vertical distance between the slope bottom line and the inclined borehole are comprehensively calculated and determined by combining physical parameters such as borehole inclination angle, vertical distance between steps, slope angle, hydrostatic pressure, and the distance between the borehole opening position and the slope top line.

[0025] For the S400 water retention treatment borehole curtain grouting construction, a downward segmented grouting process is adopted to inject grouting material into the treatment boreholes arranged in S300. The downward segmented grouting is carried out from top to bottom in layers or alternating segments, with a segment length of 5 to 10m. A water pressure test is carried out before grouting. Grouting is carried out when the water pressure is greater than or equal to 3m³ / h, and grouting material is prepared according to the water pressure test results. The grouting material is mainly cement grout. When encountering water inflow points and grout leakage from step cracks, water glass, quick-setting agent and sawdust are added. The grouting completion standard adopts dual control of borehole pressure and flow rate index, and finally solidifies inside the rock strata to form a curtain that cuts off the water conduction channel.

[0026] The evaluation of the water retention treatment effect of the S500 slope bottom water inflow point mainly examines the actual effect of the water retention treatment. The test indicators include a core recovery rate of over 90%, complete filling of core fissures, a water absorption rate of less than 0.01 L / (min·m·m) per unit of pressure test in the test hole, no water-rich abnormal zone in the upper part of the grouting section detected by high-density electrical resistivity tomography, and complete sealing of the water inflow point without water discharge. Complete filling of core fissures means that core samples are taken from the same stratum as the exploratory boreholes and grouting treatment boreholes, and the porosity is reduced by more than 90% after treatment by CT scanning. Test holes are divided into two categories: vertical holes and inclined holes. For the operation of high-density electrical resistivity tomography instruments and image processing of CT scans, those skilled in the art can use conventional commercial equipment. The test process is a well-known technology in this field and will not be described in detail here.

[0027] In one embodiment of this application, the specific implementation process of the exploration and location classification of the burnt rock boundary under the side step in step S100 is described in detail. The exploration and classification process is implemented through the following sub-steps.

[0028] S110. Based on the exploration of the original area of ​​the fire zone, exploratory boreholes shall be constructed on the upper step corresponding to the water inflow point on the side slope. The horizontal distance between the exploratory borehole location and the top line of the slope shall not exceed 10m. For the selection of drilling rigs and drilling technology for exploratory borehole construction, those skilled in the art can select according to the properties of the rock strata and geological conditions on site. Exploratory borehole construction is a well-known technology in this field and will not be described in detail here.

[0029] S120. Install a casing at the opening of the exploratory borehole, the casing length being... In the formula, For hydrostatic pressure, Not greater than The largest integer.

[0030] S130, the sintered rock below the side bench is a water-bearing sintered rock located below the bench after the open-pit coal mine has been stripped. The boundary of the sintered rock below the water inflow point and the vertical distance between the sintered rock and the bench were determined by exploratory drilling.

[0031] S140. Based on the relative position of the igneous rock and the water inflow point, the location of the igneous rock is divided into two categories: igneous rock below the water inflow point and igneous rock to the side of the water inflow point.

[0032] In one embodiment of this application, the specific implementation process of identifying and classifying the water-conducting channels at the bottom of the side slope in step S200 is described in detail. The identification and classification process is implemented through the following sub-steps.

[0033] S210, the water-conducting channel at the bottom of the side slope is a fracture channel connecting the rock strata at the water-bearing point at the bottom of the side slope with the igneous rock. After the exploratory borehole is completed, a borehole television is lowered into the exploratory borehole to observe and acquire image data inside the exploratory borehole. For the equipment layout and image acquisition operation of the borehole television, those skilled in the art can use conventional borehole detection equipment. The equipment layout and image acquisition operation are well-known technologies in this field and will not be described in detail here.

[0034] S220. Analyze the distribution characteristics of fractures in the horizontal and vertical directions in the image data obtained from borehole television, and combine them with the lithological characteristics of the strata exposed by the exploration borehole to comprehensively determine the direction of the water-conducting fractures between the water inflow point and the pyromorphic rock.

[0035] S230. Based on the comprehensive judgment of the water inflow point and the direction of the water-conducting fractures between the burnt rocks, the water-conducting channels are divided into transverse, longitudinal, and combined transverse and longitudinal types.

[0036] In one embodiment of this application, the specific implementation process of the targeted design of the borehole for water retention treatment at the bottom of the side slope in step S300 is described in detail. The targeted design process of the borehole for water retention treatment is implemented through the following sub-steps.

[0037] S310, see appendix Figure 4 , Figure 4 This is a schematic planar projection of the inclined hole arrangement according to an embodiment of this application; the targeted design parameters for water retention treatment drilling include the borehole opening position, borehole inclination angle, borehole depth, casing length, and borehole diameter; depending on the type of water guide channel, vertical or inclined grouting boreholes are constructed on the side steps to guide the water guide channel, with at least two rows of grouting boreholes arranged, and the row spacing is as follows: Spacing between grouting boreholes (planar projection) not exceeding 2m The length should not exceed 3m, and the grouting boreholes in each row should be arranged in a crisscross pattern.

[0038] S320, see appendix Figure 2 , Figure 2 This is a schematic diagram of the borehole design for water retention treatment of igneous rock below a water inflow point according to an embodiment of this application; for igneous rock below a water inflow point, water retention treatment borehole designs are carried out according to the type of water guiding channel, specifically divided into design schemes for transverse channels, vertical channels and longitudinal-transverse composite channels for igneous rock below.

[0039] S321. For the transverse channel of the burnt rock below, vertical boreholes should be used for water retention treatment, with exploratory boreholes also serving as treatment boreholes; the distance between the vertical borehole opening position and the slope crest line... Not exceeding 10m; a sleeve is installed at the opening of the vertical hole, with a sleeve length of [missing information]. In the formula, For hydrostatic pressure, Not greater than The largest integer.

[0040] S322. For both vertical and longitudinal-transverse composite channels in the lower calcined rock, inclined boreholes are used for water retention treatment; the distance between the inclined borehole opening position and the slope top line... Not less than 15m; a sleeve is installed at the opening of the inclined hole, and the sleeve length is... And not less than 5m; the distance between the end of the casing and the vertical passage is not less than 10m, and the distance between the casing orifice flange and the step is... The diameter is 20 to 30 cm; the plane projection of the inclined hole passes through the water inflow point, and the vertical distance between the bottom line of the slope and the inclined hole is 20 to 30 cm. m, where, The drilling angle is... The vertical distance between the steps, For the slope angle, It is the hydrostatic pressure.

[0041] S330, see appendix Figure 3 , Figure 3 This is a schematic diagram of the borehole design for water retention treatment of flammable rock on the side of a water inflow point according to an embodiment of this application; for flammable rock on the side, the design is based on the distance between the boundary of the flammable rock on the side and the top of the slope. The size relationship is used to design the drilling for water retention treatment.

[0042] S331, when the distance between the lateral burnt rock boundary and the slope crest line For depths greater than 10m, vertical boreholes are used for water retention treatment, with exploratory boreholes also serving as treatment boreholes; the distance between the vertical borehole opening and the slope crest line... Not exceeding 10m; a sleeve is installed at the opening of the vertical hole, with a sleeve length of [missing information]. In the formula, For hydrostatic pressure, Not greater than The largest integer.

[0043] S332, when the distance between the lateral burnt rock boundary and the slope crest line When the depth is less than 10m or the lateral burnt rock is located below the slope flank, inclined boreholes should be used for water retention treatment; the distance between the inclined borehole opening position and the slope crest line should be... Not less than 15m; a sleeve is installed at the opening of the inclined hole, and the sleeve length is... And not less than 5m; the distance between the flange of the casing orifice and the step The diameter is 20 to 30 cm; the plane projection of the inclined hole passes through the water inflow point, and the vertical distance between the bottom line of the slope and the inclined hole is 20 to 30 cm. m, where, The drilling angle is... The vertical distance between the steps, For the slope angle, It is the hydrostatic pressure.

[0044] S340. When residual water seepage exists after the completion of the inclined hole construction on the upper step of the water seepage point, a supplementary grouting inclined hole shall be designed on the lower step. The supplementary grouting inclined hole designed on the lower step shall intersect the upper inclined hole in space to form a V-shaped curtain, and the vertical distance between the bottom line of the slope and the supplementary grouting inclined hole shall not be less than 20m. For the specific drilling rig positioning and angle adjustment operations based on the aforementioned parameters, those skilled in the art can perform them in conjunction with the on-site equipment manual. The drilling equipment adjustment operation is a well-known technology in this field and will not be described in detail here.

[0045] In one embodiment of this application, the specific implementation process of the water-retaining treatment borehole curtain grouting construction in step S400 is described in detail. The water-retaining treatment borehole curtain grouting construction process is implemented through the following sub-steps.

[0046] S410. The grouting for water retention treatment adopts a downward segmented grouting process, grouting is carried out in layers or alternating segments from top to bottom, with a segment length of 5 to 10m; a water pressure test is carried out before grouting, and grouting is carried out when the water pressure is greater than or equal to 3m³ / h, and the grouting material is prepared according to the water pressure test results; for the specific operation of the water pressure test and the connection of the test pipeline, those skilled in the art can use conventional hydrogeological exploration equipment to achieve it, and the operation of the water pressure test is a well-known technology in this field, and will not be described in detail here.

[0047] S420, the grouting material for water retention treatment is mainly cement grout; when encountering grout leakage at water inflow points and grout leakage from step cracks, water glass, quick-setting agent and sawdust are added.

[0048] In the S430 water retention treatment drilling segmented grouting, the hole should be swept and the next segment grouting should be carried out at least 12 hours after the completion of the upper segment pure cement grouting; if water glass and quick-setting agents and other chemical materials are added, the time can be shortened to 4 to 8 hours before the next segment grouting.

[0049] S440. The end pressure of grouting in water-retaining treatment boreholes is determined by combining the tensile strength of the grouting rock layer and the water pressure of the sintered rock. The smaller value between the tensile strength of the grouting rock layer and the water pressure of the sintered rock is selected as the end pressure of grouting. Generally, the end pressure of the borehole should not exceed 0.2 MPa. The end pressure of the borehole can be adjusted and determined during the grouting construction process. If the final pressure is not reached, grouting should continue or the borehole should be swept and re-grouted.

[0050] For S450, the grouting flow rate at the end of the water retention treatment drilling is no more than 1L / min per meter, and the grouting must last for more than 30 minutes; the next section of construction shall not be carried out if the grouting end standard of the previous section has not been met.

[0051] In one embodiment of this application, the specific implementation process of evaluating the water conservation effect of the water inflow point at the bottom of the side slope in step S500 is described in detail. The evaluation process of the water conservation effect is implemented through the following sub-steps.

[0052] S510. Inspection holes are divided into two categories: vertical holes and inclined holes. The number of inspection holes shall not be less than 10% of the total grouting treatment holes, and the drilling spacing shall be 10 to 20m. Vertical inspection holes shall be arranged above the main water diversion channel blocking section, and inclined inspection holes shall be arranged between grouting holes.

[0053] S520, complete core fracture filling refers to the process of taking core samples from the same stratum as the exploratory borehole and the grouting treatment borehole, and then performing CT scan testing to test the reduction of porosity by more than 90% after treatment. For the specific equipment operation and image processing of CT scan testing, those skilled in the art can use conventional non-destructive testing equipment. CT scan testing operation is a well-known technology in this field and will not be described in detail here.

[0054] S530, the evaluation of the water retention treatment effect of the water inflow point mainly includes the core recovery rate of the test hole reaching more than 90%, the core fractures being completely filled, the water absorption rate of the test hole pressure test unit being less than 0.01L / (min·m·m), the absence of water-rich anomaly zone in the upper part of the grouting section of the high-density electrical resistivity tomography detection, and the complete sealing of the water inflow point without water discharge; for the specific equipment layout and data extraction of high-density electrical resistivity tomography detection, those skilled in the art can use conventional geophysical exploration equipment to achieve this. The operation of high-density electrical resistivity tomography detection is a well-known technology in this field and will not be described in detail here.

[0055] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for water retention treatment of burnt rock on open-pit coal mine slopes, characterized in that, Includes the following steps: S100. Conduct physical exploration operations on the upper step corresponding to the water inflow point on the side slope of the open-pit coal mine. Obtain the physical boundary position of the igneous rock below the water inflow point and the vertical distance between the igneous rock and the side slope step through construction exploration drilling. Classify and define the position of the igneous rock according to the relative spatial relationship between the igneous rock and the water inflow point. S200. Lower an in-hole detection device into the exploration borehole to obtain internal formation image data, and combine the lithological characteristics of the formation revealed by the exploration borehole to comprehensively determine the direction of the water-conducting fracture between the water inflow point and the igneous rock, and classify the water-conducting channels into different types based on the differences in the direction of the water-conducting fracture. S300. Based on the type of water channel and the location of the calcined rock, perform targeted design of grouting boreholes, and determine the borehole opening position, borehole inclination angle, borehole depth, casing length and borehole diameter of the grouting boreholes. S400: The grouting material is injected into the grouting borehole using a down-flow segmented grouting process, and the grouting end standard is controlled by both borehole pressure and flow rate indicators, and the grouting material is solidified inside the rock strata to form a curtain that cuts off the water-conducting channel. S500, construct inspection holes and extract rock cores from the inspection holes. The water retention and treatment effect of the water inflow point is evaluated by the rock core recovery rate, the degree of rock core fracture filling, the water absorption rate of the unit water pressure test of the inspection hole, and the distribution of the abnormal water-rich area in the upper part of the grouting section.

2. The method for water retention treatment of burnt rock on open-pit coal mine slopes according to claim 1, characterized in that, The exploratory boreholes are arranged on the upper step, and the horizontal distance between the location of the exploratory boreholes and the top of the slope is no greater than a set horizontal distance. The casing is installed at the borehole opening during exploration. The installation length of the casing is calculated and determined based on hydrostatic pressure parameters. The calculation formula is as follows: ,in, This refers to the installation length of the sleeve. Not greater than The largest integer, It is the hydrostatic pressure; The classification is divided into two categories: igneous rocks below the water inrush point and igneous rocks on the side.

3. The method for water retention treatment of burnt rock on open-pit coal mine slopes according to claim 1, characterized in that, The in-hole detection equipment includes a borehole television; Based on the difference in the direction of the water-conducting fissures, the water-conducting channels are divided into transverse channels, longitudinal channels, and combined transverse and longitudinal channels.

4. The method for water retention treatment of burnt rock on open-pit coal mine slopes according to claim 3, characterized in that, The grouting borehole targeting design includes: Vertical or inclined grouting holes are drilled on the side steps to the water guide channel as grouting holes. The grouting holes are arranged in no less than two rows. The row spacing between adjacent rows of grouting holes is no greater than the set row spacing. The plane projection spacing of the grouting holes is no greater than the set projection spacing. The grouting holes in each row are arranged in a cross pattern.

5. A method for water retention treatment of burnt rock on open-pit coal mine slopes according to claim 4, characterized in that, Under the condition that the igneous rock is located below the water inrush point: When the water guiding channel is a transverse channel, the grouting borehole is a vertical grouting borehole. The distance between the opening position of the vertical grouting borehole and the top of the slope is not greater than a first set distance. The casing length of the vertical grouting borehole is calculated and determined based on hydrostatic pressure, using the following formula: ,in, The length of the casing for vertical grouting boreholes. Not greater than The largest integer, It is the hydrostatic pressure; When the water guiding channel is a vertical channel or a combined longitudinal and transverse channel, the grouting borehole is an inclined grouting borehole. The distance between the opening position of the inclined grouting borehole and the slope crest line is not less than a second predetermined distance. The casing length of the inclined grouting borehole is calculated based on the borehole inclination angle and hydrostatic pressure. The calculation formula is as follows: The vertical distance between the slope bottom line and the inclined grouting borehole is calculated by combining the borehole inclination angle, the vertical distance between the steps, the slope angle, and the distance between the opening position of the inclined grouting borehole and the slope crest line. The calculation formula is as follows: The vertical distance between the slope baseline and the inclined grouting borehole is determined to be not less than a set safety distance, wherein the set safety distance is 20m; in the above formula, The length of the casing for the inclined grouting borehole. For hydrostatic pressure, The drilling angle is... The vertical distance between the bottom line of the slope and the inclined grouting borehole. The distance between the opening position of the inclined grouting borehole and the top line of the slope. The vertical distance between the steps, The slope angle.

6. The method for water retention treatment of burnt rock on open-pit coal mine slopes according to claim 4, characterized in that, Under the condition that the igneous rock is located at the lateral igneous rock location: When the distance between the lateral calcined rock boundary and the slope crest line is greater than a first predetermined distance, the grouting borehole adopts the vertical grouting borehole. The distance between the opening position of the vertical grouting borehole and the slope crest line is not greater than the first predetermined distance. The casing length of the vertical grouting borehole is calculated and determined based on hydrostatic pressure, and the calculation formula is as follows: ,in, The length of the casing for vertical grouting boreholes. Not greater than The largest integer, It is the hydrostatic pressure; When the distance between the lateral igneous rock boundary and the slope crest line is less than the first predetermined distance, or when the lateral igneous rock is located below the sidewall, the grouting borehole adopts the inclined grouting borehole. The distance between the opening position of the inclined grouting borehole and the slope crest line is not less than the second predetermined distance. The casing length of the inclined grouting borehole is calculated by combining the borehole inclination angle and hydrostatic pressure. The calculation formula is as follows: The vertical distance between the slope bottom line and the inclined grouting borehole is calculated by combining the borehole inclination angle, the vertical distance between the steps, the slope angle, and the distance between the opening position of the inclined grouting borehole and the slope crest line. The calculation formula is as follows: The vertical distance between the slope baseline and the inclined grouting borehole is determined to be not less than a set safety distance, wherein the set safety distance is 20m; in the above formula, The length of the casing for the inclined grouting borehole. For hydrostatic pressure, The drilling angle is... The vertical distance between the bottom line of the slope and the inclined grouting borehole. The distance between the opening position of the inclined grouting borehole and the top line of the slope. The vertical distance between the steps, The slope angle.

7. A method for water retention treatment of burnt rock on open-pit coal mine slopes according to claim 4, characterized in that, The grouting borehole targeting design also includes: If residual water inflow exists after the completion of the inclined grouting borehole for the treatment of the step above the water inflow point, additional inclined grouting boreholes are designed on the step below the water inflow point. The supplementary grouting inclined hole and the inclined grouting borehole of the upper step intersect in space to form a cross water-blocking curtain, and the vertical distance between the bottom line of the slope and the supplementary grouting inclined hole is not less than the set safety distance.

8. A method for water retention treatment of burnt rock on open-pit coal mine slopes according to claim 1, characterized in that, The process of injecting grouting material into the grouting borehole using a downward segmented grouting technique includes: Grouting can be carried out alternately in layers or sections from top to bottom; Before grouting, a water pressure test is conducted. Grouting is carried out under the condition that the water pressure volume is greater than or equal to the set water pressure volume, and the grouting material is prepared according to the water pressure test results. The grouting material is mainly cement grout. When encountering water inrush points and grout leakage from step cracks, water glass, quick-setting agent and sawdust are added to the cement grout.

9. A method for water retention treatment of burnt rock on open-pit coal mine slopes according to claim 8, characterized in that, The grouting termination criteria, which employ dual control of orifice pressure and flow rate, include: The smaller of the tensile strength of the grouting rock layer and the water pressure of the sintered rock body is selected as the grouting end pressure. The injection rate per meter is not greater than the set injection rate and the grouting duration reaches the set time as the grouting end flow rate indicator; If the grouting end pressure and grouting end flow rate are not reached in the previous stage, the construction of the next stage shall be stopped.

10. A method for water retention treatment of burnt rock on open-pit coal mine slopes according to claim 1, characterized in that, The construction inspection hole and the extraction of the rock core from the inspection hole include: The inspection holes are divided into two types: vertical inspection holes and oblique inspection holes. The vertical inspection holes are arranged above the main water guiding channel sealing section, and the oblique inspection holes are arranged between the grouting boreholes. The degree of complete filling of the core fractures is determined by taking core samples from the same stratum of the exploratory borehole and the grouting borehole and using computer tomography to test the reduction in porosity. High-density electrical resistivity tomography was used to detect no water-rich abnormal areas in the upper part of the grouting section.

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