Main geological factors affecting coal mine production
Coal seam thickness change
The change of coal seam thickness is one of the main geological factors affecting coal mine production. The thickness change of coal seam, such as bifurcation, thinning and pinch-out, directly affects the normal production of coal mine.
First, the causes and characteristics of coal seam thickness change
The change of coal seam thickness is varied, but as far as its formation is concerned, it can be divided into two categories: primary change and epigenetic change.
(A) the primary change of coal seam thickness
The primary change of coal seam thickness refers to the change of coal seam shape and thickness caused by crustal activity, sedimentary environment change and other geological factors during mudstone accumulation and before the formation of sedimentary cover of coal seam roof strata. The main changes include the bifurcation, thinning and pinch-out of coal seam caused by unbalanced crustal settlement, the influence of peat swamp paleotopography on coal seam morphology and coal thickness, and the simultaneous erosion of rivers and seawater.
(2) epigenetic change of coal seam thickness
The epigenetic change of coal seam thickness refers to the change of coal seam shape and thickness due to the influence of various geological factors such as river erosion, structural change, magmatic intrusion, karst collapse and so on after the coal seam is covered by sediments or after the formation of coal measures.
Second, the influence of coal seam thickness change on coal mine production
The influence of coal seam thickness change on coal mine production is mainly manifested in the following aspects:
1. Affecting mining deployment
2. Affect coal mining technology
3. Affect the planned production
4. The excavation speed is improved.
5. The recovery rate will decrease.
Third, the research and treatment of coal seam thickness change
(A) observation and detection of changes in coal seam thickness
1. Coal seam observation
1) observation content of coal seam
2) observation method of coal seam
2. Coal seam detection
1) detection of coal seam thickness
(1) Exploration of coal thickness in coal roadway excavation.
(2) Exploration of coal thickness in coal mining face.
2) Detection of coal seam bifurcation and pinch out
According to the stability of coal seam bifurcation, it can be roughly divided into two types: one is that the layered distribution of coal seam after bifurcation is relatively stable; The other is that only one layer remains stable (that is, the main bifurcation layer) after coal seam bifurcation, and other layers will be pointed out soon in a short time.
3) detection of coal seam floor heave thinning
Thinning of coal seam floor heave refers to the phenomenon that coal seam is thinned due to coal seam floor heave and is pointed out. For this change, the commonly used detection methods are as follows:
(1) drilling controls the position of floor heave in the heading direction of roadway.
(2) The location and thinning range of the coal seam floor bulge are directly delineated by using the roadway to cross the bottom bulge.
(3) Using the observation data of coal seam while mining and exploring in layered working face, the elevation contour map of coal seam roof and floor is compiled, the topography of peat swamp basement is studied, and the position and scope of coal seam floor heave thinning are delineated.
4) Detection of thin strips caused by coal seam and river erosion
First of all, we should carefully observe and sketch the width, thickness, rock composition, bedding, gravel distribution, coal seam roof erosion, erosion surface characteristics, coal quality changes in erosion areas, etc. The erosion phenomena seen in each roadway are projected on the plan, compared and analyzed, the distribution range of ancient riverbed and the degree of damage to coal seam are determined, and the erosion zone range of ancient riverbed is circled.
(2) Quantitative evaluation of coal seam thickness stability
(3) Treatment of coal seam thickness change
1. Treatment methods in tunnel construction
(1) When the coal seam bifurcation is pointed out in the coal roadway driving, the driving scheme should be determined according to the specific situation. If the upper layer is known to be stable and exploitable, and the lower layer is often thinned and pointed out, the roadway should be driven close to the roof of coal seam. If the lower layer is stable and recoverable, and the upper layer is unstable, it should be excavated close to the coal seam floor. If all coal seams can be mined after bifurcation, the upper layer should be mined first, and then the lower layer should be mined.
(2) When the coal seam in the mining area becomes thinner, it is necessary to decide whether the roadway passes directly, or stop driving, or open another roadway from other places according to the thinning range. If the thin strip is not large, and it is known that there is coal recoverable in the working face, the driving roadway directly passes through the thin strip by picking the top or breaking the bottom.
(3) When the main transportation roadway encounters local coal seam thinning or pinch-out, the roadway can be constructed as planned, and the belt can be extinguished by thinning and pinch-out.
2. Processing methods in mining work
When the coal mining face encounters thin strip or no coal zone, it can be directly advanced or bypassed. If the thin strip or non-mining area is small, the direct push method can be used; If the refinement range is large, the bypass mode can be considered; For a large area of non-mining area, explore the roadway, find out the scope of non-mining area, divide the working face into several blocks, first mine ① and ②, and then synthesize a working face ③ for mining.
In the second quarter of mine geological structure
Geological structure is one of the most important geological factors affecting coal mine construction and production. Geological structures include folds, joints and faults. Fault is the focus of mine geological structure research.
Mine geological structures can be divided into three types according to their scale and influence on production. Large-scale structures refer to large-scale folds and faults in mine field boundary, which have been basically identified in the exploration stage. Medium-sized structure refers to the secondary structure of influence level, mining area division and roadway layout distributed in the mine field. They have a great influence on coal mine production and are the focus of mine geological work. Small-scale structures refer to those folds and faults that are secondary in roadway or working face and easy to find out the whole picture.
First, the influence of fold structure on coal mine production and research
(A) the impact of fold structure on coal mine production
1. big fold
Large folds have been found in the exploration section, and their scale, direction and position affect the division of mine fields, the way of mine development and the deployment of development system, which is the main problem to be considered in mine design.
2. Medium fold
Medium-sized folds have little influence on the development and deployment of the whole mine, but they are closely related to the layout of the mining area, affecting the size of the mining area and the layout of the mining roadway.
3. Small folds
Small-scale fold refers to the fold with a length of several meters to several tens of meters exposed in the roadway during the preparation of the mining face. It affects the heading direction of coal seam roadway, thus affecting the length of working face, which brings certain difficulties to mechanized mining and roof management. Small folds often cause changes in the thickness of coal seams and complicate production conditions. When small folds are particularly developed, it may even make the coal seam impossible to mine.
(B) the study of fold structure in coal mine production
1. judgement of fold
Judging the existence of underground fold is mainly based on the regular change of coal and rock occurrence and the symmetrical reproducibility of rock sequence. For example, in Shimen roadway, the strata tend to be relative or inclined, or in coal seam roadway, the roadway bends due to the sharp change of coal seam strike, which indicates that there are folds (anticline or syncline).
In areas with simple structure and obvious rock marks, according to the rock sequence of the core and wings of the fold,
2. Observation of folds
(1) For the small pleats that can see the whole picture in the roadway, the position, direction and occurrence of the pleated crankshaft should be systematically observed. For medium-sized folds, when the whole picture cannot be observed in a roadway, it is necessary to accurately identify the coal seam, the sequence of rock strata and its top and bottom, the occurrence of rock strata, the change of coal seam thickness and its related secondary small structures, and then project the observation data to the plane and section, and make comprehensive analysis on the map to determine the extension direction of crankshaft.
(2) Observe and describe the occurrence, the width and amplitude of the fold, the extension and change of the fold and the extension trend to the deep.
3. Detection of folds
(3) Treatment of folds
By judging, observing and detecting the fold, the position, direction and occurrence change of the fold are basically found out. On this basis, the following measures can be taken to deal with wrinkles.
1. big fold
(1) Fold the crankshaft line as the minefield boundary. Some large synclines, which are difficult to mine due to the deep buried shaft, are mostly used as mine field boundary, and their two wings are mined by two or more mine fields respectively. Some large-scale wide and gentle anticlines are far away from the coal seams on the two wings, so it is difficult to form a unified production system underground, which can be bounded by crankshaft folds, and there are two mine fields on the two wings respectively.
(2) The treatment method of large folds in the development and deployment of mine field. Not all crankshafts with large pleats must be used as minefield boundaries, and large pleats can exist in some minefields. If there is a large anticline structure in the mine field, the total return air duct in the development system is often arranged near the axis of the anticline, and both wings of the coal seam can be used. In some mines with syncline structure, the transportation roadway is often arranged near the axis of syncline, and one transportation roadway is used to solve the transportation problem of the two wings of syncline.
2. Medium fold
(1) Take the folding crankshaft line as the center of the mining area to arrange the mining area to go up or down the mountain. For open and gentle folds, the syncline axis is the center of the mining area, and the coal mining faces are arranged to the two wings, and the strike length of the mining area can reach more than1000 mm.
(2) Take the folding crankshaft as the boundary of the mining area. In closed folded crankshafts, secondary structures are often developed, so folded crankshafts are often used as mining boundaries.
(3) The working face directly pushes the pleated crankshaft. When the fold is wide and gentle, but the scale is not too large, a single wing mining area can be arranged, and the working face directly pushes over the folded crankshaft.
3. Small folds
(1) coal mining face to cut production. In the area where small folds are developed, common coal seams suddenly thicken or thin, or even are not recoverable, which makes the working face unable to pass, so it is necessary to re-open the cut for production.
(2) The transformation and straightening of transportation roadway in coal mining face. Coal mines require that transport lanes should not have large bends within 60m, and they cannot be used if there are too many bends. Due to the existence of small folds, coal seam roadway twists and turns. In order to meet the production requirements, it is necessary to transform and straighten the roadway.
Second, the influence of fault structure on coal mine production and research
(A) the impact of joints (cracks) on coal mine production and treatment
1. Affect the drilling blasting effect.
2. Affect the mining efficiency
3. Influence roof control method
4. Affect the layout of the working face
5. Impact on other aspects
(B) the impact of faults on coal mine production
Faults destroy the continuity and integrity of coal seams and have a great impact on coal mine production. Different fault scales have different effects on production. At present, the criteria for dividing the scale and grade of faults are not uniform. According to the working practice in coal mines, it is suggested to adopt the following classification standards: extra-large faults with a drop of more than 50m, large faults with a drop of 50-20-5m, medium faults with a drop of 20-5m and small faults with a drop of less than 5m.
The influence of faults on coal mine production is mainly manifested in the following seven aspects:
1. Affect the division of mine field.
2. Influence the development mode of mine field
3. Affect the layout of mining area and working face.
4. Affect safety in production
5. Increase coal losses.
6. Increase the amount of roadway excavation.
7. Affect the comprehensive economic benefits of coal mines.
(3) Fault research in coal mine production.
1. Fault judgment
Faults are not isolated, but are often accompanied by some geological phenomena different from normal conditions in coal strata near faults. These phenomena indicate that there may be faults ahead, so we should make better preparations. Before the failure, the possible symptoms mainly include the following phenomena:
(1) When the occurrence of coal seam and rock stratum changes greatly, there may be faults.
(2) When the thickness of coal seam changes and the roof and floor of coal seam are not parallel, there may be faults.
(3) When obvious small folds often appear in the driving roadway (such as Tangshan Coal Mine in Kailuan), or when the coal seam is often strongly folded, the sliding surface increases or becomes scaly broken coal (such as Longquan Coal Mine in Zibo), faults may exist.
(4) When cracks in coal seam and roof and floor increase obviously and have certain regularity, faults may exist.
(5) A series of small faults are often associated with large faults, which is an important sign to judge large faults.
(6) In high gas mine, the gas emission from roadway often changes obviously, and there may be faults. For example, when the Jiaoxi Mine of Jiaozuo Mining Bureau is driving the roadway, the hump phenomenon occurs in the tile period before and after the fault.
(7) In the mine with strong water filling, when the roadway is close to the fault, water dripping, water spraying and even water gushing often occur, and there may be a fault.
In practical work, according to the above symptoms, combined with the specific geological conditions of the mine and the fault data of the excavated section, a comprehensive analysis should be made to make the judgment more realistic.
2. Fault observation
(1) Determine the fault location.
(2) Observe the characteristics of fault plane.
(3) Observe related derivative structures of faults.
(4) Determine fault properties and fault mechanics properties.
(5) Measure the occurrence of fault plane.
(6) Determine the fault point.
3. Fault detection (looking for broken coal seams)
There are five main methods for judging fault properties and determining fault distance in coal mines:
(1) horizon correlation method.
(2) Adjoint derivative structure judgment method.
(3) Conventional analogy.
(4) Drawing analysis method.
(5) Production exploration method.
(4) Fault handling
1. Troubleshooting in the development design stage
(1) Determination of the boundary between mine field boundary and the mining area. When an oversize fault with a drop of more than 50m is encountered in the mine field, the oversize fault should be regarded as mine field boundary.
(2) Selection of wellbore position. Generally, the shaft should be arranged in the footwall of a large fault with a large dip angle, 30 ~ 50m away from the fault.
(3) Layout of transportation alleys. Transportation alleys should be arranged in hard rock strata, and the direction should be changed as little as possible. However, at the fault dislocation, the coal strata on the upper and lower walls of the fault are displaced greatly, and even meet the aquifer on the other wall, so the diversion of the roadway must be considered.
(4) Division of mining areas. In the area damaged by fault cutting, the position, drop, size, shape and existing production system of cutting blocks should be comprehensively considered, and mining blocks should be divided, so as to leave larger faults in the coal pillars between blocks as much as possible.
(5) Determination of mining field development mode. The influence of various geological factors should be considered when choosing the mining field development mode, in which faults play an important role.
2. Fault treatment in roadway excavation stage
(1) The roadway crosses the fault. Roadway crossing fault can be divided into two ways: driving through the top (or floor) of coal seam and driving along fault plane.
(2) The inclined lane passes through the fault. When inclined roadways such as uphill and downhill encounter faults, they can take various forms to pass through the faults according to production needs.
When the fault drop is small, according to whether the fault disk is ascending or descending, the top lifting, bottom digging or the combination of top lifting and bottom digging are adopted to pass through the fault respectively.
3. Fault treatment in mining stage
(1) adopts the method of forced passage.
(2) adopt the method of reopening the incision. When the fault drop is greater than the coal thickness, the method of re-opening the cut can be adopted for inclined faults or inclined faults, that is, re-opening the cut in the other plate of the fault in advance, stopping mining when the working face advances to the fault, and moving the working face to a new cut to continue mining.
(3) Using the method of dividing the working face. When the fault drop is greater than the coal thickness, for the strike fault, the middle roadway can be dug on both sides of the fault, and the original working face can be divided into two working faces for mining respectively. For oblique faults with large drop at one end and small drop at the other end, combined mining and separate mining can be adopted to jointly mine the upper and lower coal seams of the fault.
In the third quarter magma intrusion into coal seam
I observation and research on magma intrusion in coal seam
(a) General characteristics of magmatic intrusions
1. The emergence of magmatic intrusions
Magmatic intrusions found in production mines mainly include the following two types:
(1) rock wall.
(2) bedrock.
2. Lithology of magma intrusion
(2) Observation of magmatic intrusions
All exposed positions of magmatic intrusions should be carefully observed and sketched. The content of observation has the following four aspects:
1. Color, mineral composition, structure, structural characteristics and name of magmatic intrusion.
2. Occurrence and extension of magmatic intrusions.
3. Relationship between magmatic intrusions and fault structures.
4. The damage of coal seam, including the contact relationship between magma intrusion and coal seam, the width of natural coke, the metamorphic degree of coal seam, etc.
(3) Detection of magma intrusion
(4) Comprehensive research on data of magmatic intrusions.
Second, the influence of magma intrusion on coal mine production
(a) Influence of magma intrusion on coal quality
(B) the impact of magma intrusion on coal mine production
Thirdly, the treatment of magma intrusion into coal seam.
The fourth quarter karst collapse column
Karst collapse column refers to the karst cave formed by groundwater dissolution of carbonate rocks and other soluble strata under coal seam, which collapses under the gravity of overlying strata to form a cylindrical or conical column. Referred to as collapse column, commonly known as "waste pit" or "carbon-free column"
Collapse columns are widely distributed in Carboniferous-Permian coal-accumulating areas in North China, especially in Shanxi and Hebei.
A, the cause of the collapse column
(A) the geological conditions of karst development
(2) cave collapse mechanism
Second, the characteristics of collapse column
(A) the morphological characteristics of the collapse column
(2) the characteristics of surface exposure of collapse column
(3) Underground characteristics of collapse column
(4) Distribution characteristics of collapse columns
Three, the observation and research of collapse column
Four, the influence of collapse column on coal mine production and treatment
Section 5 Other Geological Factors Affecting Coal Mine Production
A, mine gas
Second, the roof and floor of coal seam
Third, the hazards of mine geothermal
Fourth, mine pressure.
Five, coal seam spontaneous combustion and coal dust