A method for observing overburden destruction of mine exploitation under weakly cemented aquifer

Abstract

The application discloses a kind of weakly cemented aquifer under mine exploitation overburden destruction observation method, including according to the geological conditions of mining face or planned mining face, select the area of weakly cemented sand and gravel rock under coal seam roof bedrock thickness larger as observation target area;According to the surface topographic features and construction conditions corresponding to the observation target area of working face, determine the preferred position of drill field;Based on weakly cemented sand and gravel rock occurrence characteristics, geological conditions and observation equipment, overburden destruction observation borehole structure design is carried out;Weakly cemented sand and gravel rock under coal seam mining overburden destruction observation borehole construction and observation data real-time recording and analysis.The method of the application simultaneously considers the influence of geological structure such as fault, collapse column, fold and surface river, finely arranges the observation borehole, and real-time monitors and intelligently analyzes the observation data, can accurately observe the overburden destruction height of weakly cemented sand and gravel rock under coal seam mining, and provides reliable basis for mine water prevention and control work.

Description

Technical Field

[0001] This invention relates to the field of mine water hazard prevention and control technology, and in particular to a method for observing overburden damage during mining in weakly cemented aquifers. Background Technology

[0002] Following coal seam mining, the roof deforms, moves, and fails. Based on the degree of failure, overburden failure can be divided into three zones from bottom to top: the caving zone, the fracture zone, and the bending subsidence zone. The failure height of the caving zone and the water-conducting fracture zone is a crucial aspect of roof water hazard prevention. Field testing can obtain accurate and reliable overburden failure height values, providing a reliable basis for safe coal mining under water bodies. Therefore, refined observation of the failure height of the caving zone and the water-conducting fracture zone under weakly cemented aquifers is of great significance for mine water hazard prevention.

[0003] Currently, there is no intelligent and precise on-site observation method for the overburden failure height in coal seams under weakly cemented aquifers. Existing technologies primarily rely on geophysical exploration and drilling to observe the overburden failure height, mainly through borehole detection, which is divided into underground borehole detection and surface borehole detection. Underground borehole detection involves observing the overburden failure height of the goaf roof in adjacent roadways of the working face; however, it is inconvenient due to underground space limitations, resulting in lower accuracy and reliability. Surface borehole observation typically involves placing boreholes on the surface corresponding to the goaf of the mining face, which is convenient to implement and offers high accuracy. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention propose a method for observing overburden damage during mining in weakly cemented aquifers.

[0006] This invention proposes a method for monitoring overburden failure during mining in weakly cemented aquifers, comprising the following steps:

[0007] (a) Determine the target area for monitoring the failure of the overlying rock under the thick sandstone and conglomerate layer: Based on the geological conditions of the longwall mining face or the planned mining face, select the area with a large thickness of bedrock under the weakly cemented sandstone and conglomerate as the target area for monitoring;

[0008] (b) Determine the location of the drilling site for overburden damage: Based on the surface topography and construction conditions corresponding to the target area of ​​the working face, determine the preferred location of the drilling site;

[0009] (c) Design of borehole structure for monitoring overburden failure in thick sandstone and conglomerate strata: Based on the occurrence characteristics, geological conditions and monitoring equipment of weakly cemented sandstone and conglomerate, the borehole structure for monitoring overburden failure is designed.

[0010] (d) Construction procedures and data recording and analysis of boreholes for monitoring overburden failure: Construction of boreholes for monitoring overburden failure in weakly cemented sandstone and conglomerate coal seams and real-time recording and analysis of monitoring data.

[0011] In some embodiments, in step (a), the geological conditions of the longwall face or the planned mining face refer to drawing contour maps of the thickness of the bedrock roof of the coal seam under the weakly cemented sandstone and conglomerate based on the geological data of the well field boreholes, and analyzing the variation characteristics of the thickness of the bedrock roof of the coal seam under the weakly cemented sandstone and conglomerate of the longwall face or the planned mining face.

[0012] In some embodiments, in step (a), the observation target area is the predicted overburden failure height H of the longwall face or planned mining face using empirical formulas or analogies. d And the thickness H of the bedrock roof of the coal seam beneath the weakly cemented sandstone and conglomerate. j For comparison, H is defined for weak rock strata. j ≥H d The +5M area is the target observation zone, and the medium-hard rock strata are delineated as H. j ≥H d The area at +10M is the target observation zone, and the hard rock strata are designated as H. j ≥H d The area within +15M is the target observation area.

[0013] In some embodiments, in step (b), the surface topography features and construction conditions are determined by marking the observation target area on the well field topographic and geological map and the well-to-surface comparison map, and by conducting on-site reconnaissance. The surface site corresponding to the observation target area avoids the influence of forest and grassland protection areas, rivers and drilling rigs and related observation equipment transportation roads, and the underground site avoids the influence of geological structures such as synclinal and anticline axes, faults and collapse columns.

[0014] In some embodiments, in step (b), the preferred location of the drilling site is determined to be an area with convenient transportation, outside of forest and grassland protection areas, and not less than 100m away from the river boundary on the surface of the target observation area, and an area 100m away from the geological structure boundary of the corresponding underground preferred syncline and anticline axis, fault and collapse column, etc. The drilling site is arranged within 10 to 30m of the roadway on both sides of the working face.

[0015] In some embodiments, in step (c), the determination of the loose layer thickness, sandstone thickness, and sandstone base burial depth based on the occurrence characteristics and geological conditions of the conglomerate is to draw contour maps of the loose layer thickness, sandstone thickness, and sandstone base burial depth according to the borehole geological data, thereby determining the loose layer thickness, sandstone thickness, and sandstone base burial depth corresponding to the drilling site location; the overburden failure observation borehole structure includes a borehole structure for the loose layer section, a borehole structure for the sandstone section, and a borehole structure for the observation section, with the borehole diameter and casing outer diameter designed progressively from the bottom of the observation section to the surface, and the casing opening exposed above the surface.

[0016] In some embodiments, in step (c), the loose layer drilling structure is designed with a first-stage casing in the loose layer, which is lowered into a stable rock layer 5 to 10 m below the loose layer. The length of the first-stage casing is designed in combination with the thickness of the loose layer, and the distance between the borehole wall and the outer wall of the casing is not less than 30 mm. The observation section drilling structure is determined according to the outer diameter of the observation equipment, and the diameter of the observation section is not less than 108 mm.

[0017] In some embodiments, in step (c), the drilling structure of the conglomerate section is designed based on the thickness of the conglomerate, with one additional casing stage for every 100m increase in conglomerate thickness. If the conglomerate thickness is less than 100m, it is calculated as 100m. The last casing stage in the conglomerate section penetrates 5-10m into the underlying stable rock layer. The outer wall of each casing stage in the conglomerate section should be larger than the maximum gravel particle size and not less than 50mm from the borehole wall. The length of each casing stage is H. m -H s +100k(H m For the depth of the sandstone and conglomerate base, H s H represents the thickness of the conglomerate layer, k represents the number of casing stages in the conglomerate section (k = 1, 2, 3...n-1), and the length of the nth casing stage is H. m + (5~10)m.

[0018] In some embodiments, in step (d), the drilling for monitoring the overburden failure is carried out 1 to 2 months after the formation of a goaf at the working face of the drilling location. The drilling is carried out step by step from the surface downwards. Mud drilling is used when drilling in the sandstone and conglomerate section. Before the first to n-1 stages of casing are lowered, cement grout is injected into the 5m thick sandstone and conglomerate section at the bottom of the borehole. After solidification for 24 hours, the casing is swept and lowered. n is the number of casing stages in the sandstone and conglomerate section. The observation section is drilled with clean water.

[0019] In some embodiments, in step (d), the real-time recording of the observation data adopts an intelligent data acquisition module to monitor and record the water level of the flushing fluid in the standard circulation pool of the drilling site and the water level in the borehole after each cycle of drilling footage, and generate a real-time dynamic change curve to monitor the flushing fluid leakage and water level changes. When the flushing fluid leakage increases to 5 times the average value of the observed section, an alarm is triggered. The flushing fluid leakage and borehole water level change curves are compared and analyzed to determine the characteristics of overburden damage.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] Weakly cemented aquifers are prone to borehole collapse during observation due to the influence of weakly cemented sandstone and conglomerate, and the formation has well-developed pores and fractures, making it unsuitable as the best observation stratum. The method for observing overburden damage in mining under weakly cemented aquifers in this invention takes into account the influence of geological structures such as faults, collapse columns, and folds, as well as surface rivers. It involves a fine arrangement of observation boreholes and real-time monitoring and intelligent analysis of observation data. This method can accurately observe the height of overburden damage in coal seams under weakly cemented sandstone and conglomerate, providing a reliable basis for mine water control. Attached Figure Description

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0023] Figure 1 Flowchart of overburden failure monitoring method for mining under weakly cemented aquifers;

[0024] Figure 2 This is a schematic diagram of the borehole layout for an embodiment.

[0025] Figure 3 This is a schematic diagram of the drilling structure design for an example. Detailed Implementation

[0026] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0027] Existing methods for observing overburden failure are only suitable for relatively stable geological conditions. However, there is currently no reliable method for observing the height of overburden failure in weakly cemented aquifers. In weakly cemented aquifers, it is difficult to obtain complete core samples, as the rock disintegrates upon contact with water. Larger gravel particles easily cause borehole blockage. Traditional observation methods are prone to borehole collapse, stuck drill bits, and drill bit burial, resulting in significant economic losses due to the need to install other related observation equipment, and the inability to obtain final results. To address the problem of accurate and reliable observation of overburden failure height in coal seams mined in weakly cemented aquifers, this invention provides a method for observing overburden failure in mines mining under weakly cemented aquifers.

[0028] The following is a reference to the appendix. Figure 1-3 This invention describes a method for observing overburden failure during mining in weakly cemented aquifers, based on embodiments of the present invention.

[0029] like Figure 1 As shown, the method for monitoring overburden failure during mining under weakly cemented aquifers according to the present invention includes the following steps:

[0030] (a) Determine the target area for monitoring the failure of the overlying rock under the thick sandstone and conglomerate layer: Based on the geological conditions of the longwall mining face or the planned mining face, select the area with a large thickness of bedrock under the weakly cemented sandstone and conglomerate as the target area for monitoring;

[0031] (b) Determine the location of the drilling site for overburden damage: Based on the surface topography and construction conditions corresponding to the target area of ​​the working face, determine the preferred location of the drilling site;

[0032] (c) Design of borehole structure for monitoring overburden failure in thick sandstone and conglomerate strata: Based on the occurrence characteristics, geological conditions and monitoring equipment of weakly cemented sandstone and conglomerate, the borehole structure for monitoring overburden failure is designed.

[0033] (d) Construction procedures and data recording and analysis of boreholes for monitoring overburden failure: Construction of boreholes for monitoring overburden failure in weakly cemented sandstone and conglomerate coal seams and real-time recording and analysis of monitoring data.

[0034] In step (a), the geological conditions of the longwall face or planned mining face refer to drawing contour maps of the bedrock thickness of the coal seam roof under weakly cemented sandstone and conglomerate based on borehole geological data from the minefield, and analyzing the variation characteristics of the bedrock thickness of the coal seam roof under weakly cemented sandstone and conglomerate in the longwall face or planned mining face. The observation target area is the predicted overburden failure height H of the longwall face or planned mining face using empirical formulas or analogy methods. d And the thickness H of the bedrock roof of the coal seam beneath the weakly cemented sandstone and conglomerate. j For comparison, H is defined for weak rock strata. j ≥H d The +5M area is the target observation zone, and the medium-hard rock strata are delineated as H. j ≥H d The area at +10M is the target observation zone, and the hard rock strata are designated as H. j ≥H d The area within +15M is the target observation area, where M is the coal seam mining thickness.

[0035] In step (b), the surface topography and construction conditions are determined by marking the target observation area on the well site topographic and geological map and the well-surface-surface comparison map, and by conducting on-site reconnaissance. The surface site corresponding to the target observation area avoids the influence of forest and grassland protection zones, rivers, and transportation roads for drilling rigs and related observation equipment. The underground site avoids the influence of geological structures such as synclinal and anticline axes, faults, and collapse columns. The preferred drilling site location is determined by selecting an area with convenient transportation, outside of forest and grassland protection zones, and at least 100m away from the river boundary on the surface corresponding to the target observation area. The preferred underground location is an area 100m away from the boundaries of geological structures such as synclinal and anticline axes, faults, and collapse columns. The drilling site is then arranged within 10-30m of the roadways on both sides of the working face.

[0036] In step (c), based on the occurrence characteristics and geological conditions of sandstone and conglomerate, contour maps of loose layer thickness, sandstone and conglomerate thickness, and sandstone and conglomerate floor depth are drawn according to the borehole geological data to determine the loose layer thickness, sandstone and conglomerate thickness, and sandstone and conglomerate floor depth corresponding to the drilling site location; the borehole structure for overburden failure observation includes the borehole structure of the loose layer section, the borehole structure of the sandstone and conglomerate section, and the borehole structure of the observation section. The borehole diameter and casing outer diameter are designed step by step from the bottom of the observation section to the surface, and the casing opening is exposed to the surface.

[0037] In step (c), the drilling structure for the loose layer section involves designing a single-stage casing within the loose layer and lowering it into the stable rock layer 5-10m below the loose layer. Only one stage of casing is designed in the loose layer, and the length of the single-stage casing is designed based on the thickness of the loose layer. The distance between the borehole wall and the outer wall of the casing is not less than 30mm. The drilling structure for the conglomerate section is designed based on the thickness of the conglomerate. For every 100m increase in the thickness of the conglomerate, one stage of casing is added. If the thickness of the conglomerate is less than 100m, it is calculated as 100m. The last stage of casing in the conglomerate section extends 5-10m into the stable rock layer below. The distance between the outer wall of each stage of casing and the borehole wall in the conglomerate section should be greater than the maximum gravel particle size and not less than 50mm. The length of each stage of casing is H. m -H s +100k(H m For the depth of the sandstone and conglomerate base, H s H represents the thickness of the conglomerate layer, k represents the number of casing stages in the conglomerate section (k = 1, 2, 3...n-1), and the length of the nth casing stage is H. m + (5~10) m. The borehole structure of the observation section is determined according to the outer diameter of the observation equipment, and the borehole diameter of the observation section is not less than 108 mm.

[0038] In step (d), the drilling for monitoring overburden damage is carried out 1-2 months after the formation of a goaf at the drilling location. Construction proceeds from the surface downwards in stages. Mud drilling is used in the sandstone and conglomerate sections. Before lowering the first to n-1 stages of casing, cement grout is injected into the bottom 5m thick sandstone and conglomerate section of the borehole. After 24 hours of solidification, the casing is swept before lowering. The bottom of the nth stage casing is in stable rock strata and does not require grouting. Here, n represents the casing stage number in the sandstone and conglomerate section. Clear water drilling is used in the observation section. Real-time data recording utilizes an intelligent data acquisition module to monitor and record the flushing fluid level in the standard circulating pool at the drilling site and the water level in the borehole after each cycle of drilling. Real-time dynamic change curves are generated to monitor flushing fluid leakage and water level changes. An alarm is triggered when flushing fluid leakage increases to 5 times the average value of the observed section. By comparing and analyzing the flushing fluid leakage and borehole water level change curves, the characteristics of overburden damage are determined.

[0039] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0041] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for observing overburden failure during mining in weakly cemented aquifers, characterized in that, Includes the following steps: (a) Determine the target area for monitoring the failure of the overlying rock under the thick sandstone and conglomerate layer: Based on the geological conditions of the longwall mining face or the planned mining face, select the area with a large thickness of bedrock under the weakly cemented sandstone and conglomerate as the target area for monitoring; (b) Determine the location of the drilling site for overburden damage: Based on the surface topography and construction conditions corresponding to the target area of ​​the working face, determine the preferred location of the drilling site; (c) Design of borehole structure for monitoring overburden failure in thick sandstone and conglomerate strata: Based on the occurrence characteristics, geological conditions and monitoring equipment of weakly cemented sandstone and conglomerate, the borehole structure for monitoring overburden failure is designed. (d) Construction procedures and data recording and analysis of boreholes for monitoring overburden failure: Construction of boreholes for monitoring overburden failure in weakly cemented sandstone and conglomerate coal seams and real-time recording and analysis of monitoring data. In step (b), the surface topography features and construction conditions are determined by marking the observation target area on the well field topographic and geological map and the well-surface comparison map, and by conducting on-site reconnaissance. The surface site corresponding to the observation target area avoids the influence of forest and grassland protection areas, rivers, and transportation roads for drilling rigs and related observation equipment. The underground site avoids the influence of syncline and anticline axis, fault and collapse column geological structures. In step (b), the preferred location of the drilling site is determined in an area with convenient surface transportation, outside the forest and grassland protection area, and not less than 100m away from the river boundary, and the corresponding underground area is 100m away from the boundary of syncline and anticline axis, fault and collapse column geological structures. The drilling site is arranged within 10 to 30m of the roadways on both sides of the working face.

2. The method as described in claim 1, characterized in that, In step (a), the geological conditions of the longwall mining face or the planned mining face refer to drawing contour maps of the thickness of the bedrock roof of the coal seam under the weakly cemented sandstone and conglomerate based on the geological data of the well field boreholes, and analyzing the variation characteristics of the thickness of the bedrock roof of the coal seam under the weakly cemented sandstone and conglomerate of the longwall mining face or the planned mining face.

3. The method as described in claim 1, characterized in that, In step (a), the observation target area is the predicted overburden failure height H of the longwall or planned mining face using empirical formulas or analogy methods. d And the thickness H of the bedrock roof of the coal seam beneath the weakly cemented sandstone and conglomerate. j For comparison, H is defined for weak rock strata. j ≥H d The +5M area is the target observation zone, and the medium-hard rock strata are delineated as H. j ≥H d The area at +10M is the target observation zone, and the hard rock strata are designated as H. j ≥H d The area within +15M is the target observation area, where M is the coal seam mining thickness.

4. The method as described in claim 1, characterized in that, In step (c), the characteristics of weakly cemented conglomerate and geological conditions are based on the drawing of loose layer thickness contour maps, conglomerate thickness contour maps, and conglomerate floor burial depth contour maps according to borehole geological data to determine the loose layer thickness, conglomerate thickness, and conglomerate floor burial depth corresponding to the drilling site location; the overburden failure observation borehole structure includes the loose layer section borehole structure, the conglomerate section borehole structure, and the observation section borehole structure. The borehole diameter and casing outer diameter are designed step by step from the bottom of the observation section to the surface, and the casing opening is exposed on the surface.

5. The method as described in claim 4, characterized in that, In step (c), the loose layer drilling structure is designed with a first-stage casing in the loose layer, which is lowered into the stable rock layer 5-10m below the loose layer. The length of the first-stage casing is designed in combination with the thickness of the loose layer, and the distance between the borehole wall and the outer wall of the casing is not less than 30mm. The observation section drilling structure is determined according to the outer diameter of the observation equipment, and the diameter of the observation section is not less than 108mm.

6. The method as described in claim 4, characterized in that, In step (c), the drilling structure in the conglomerate section is designed based on the thickness of the conglomerate, with one additional casing stage for every 100m increase in conglomerate thickness. If the conglomerate thickness is less than 100m, it is calculated as 100m. The last casing stage in the conglomerate section penetrates 5-10m into the underlying stable rock layer. The outer wall of each casing stage in the conglomerate section should be larger than the maximum gravel particle size and not less than 50mm from the borehole wall. The length of each casing stage is H. m -H s +100k, where H m For the depth of the sandstone and conglomerate base, H s Let H be the thickness of the sandstone and conglomerate layer, k be the number of casing stages in the sandstone and conglomerate section, k = 1, 2, 3...n-1, n be the number of casing stages, n-1 be the (n-1)th stage casing, and the length of the nth stage casing is H. m + (5~10)m.

7. The method as described in claim 1, characterized in that, In step (d), the drilling for monitoring the overburden failure during mining is carried out 1 to 2 months after the formation of a goaf at the working face of the drilling location. The drilling proceeds from the surface downwards in stages. Mud drilling is used in the sandstone and conglomerate section. Before the first to n-1 stages of casing are lowered, cement grout is injected into the 5m thick sandstone and conglomerate section at the bottom of the borehole. After solidification for 24 hours, the casing is swept and lowered. n is the number of casing stages in the sandstone and conglomerate section. The observation section is drilled with clean water.

8. The method as described in claim 1, characterized in that, In step (d), the real-time recording of the observation data uses an intelligent data acquisition module to monitor and record the water level of the flushing fluid in the standard circulation pool of the drilling site and the water level in the borehole after each cycle of drilling footage. It also generates a real-time dynamic change curve to monitor the flushing fluid leakage and water level changes. An alarm is triggered when the flushing fluid leakage increases to 5 times the average value of the observed section. The flushing fluid leakage and borehole water level change curves are compared and analyzed to determine the characteristics of overburden damage.

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