Seeing geological structure from mine safety

Mine geological work is an indispensable basic technical work in mining. It refers to the geological work directly for production in the production area or mining area of ​​the deposit in the mining process, according to the needs of the mine work. The geological work of the mine geological work Based on the project of mine mining activities, it is the technical basis and basis for mining production and management activities. The mining activities must be moved with the advancement of mining operations. There is no fixed working space and place, and the working environment conditions are greatly affected by engineering geology and hydrogeological conditions. Therefore, in order to ensure the smooth progress of mining activities, it is necessary to understand the impact of mine geological structure, hydrogeology and rock properties on mine safety.

Geological structure refers to the spatial form, state and relationship of geological bodies (rock layers, rock masses, ore bodies, etc.), which are the deformations and displacements of rock formations (or ore bodies) caused by geological processes (crustal movement, etc.). It mainly includes folds, faults, cracks and so on.

First, the occurrence of rock formation and its determination

    (1) Horizontal and inclined rock layers

Sediments are deposited in large areas with a nearly horizontal layered distribution. Generally, the rock layer with the inclination angle less than 5° is called the horizontal rock layer, and the rock layer with the inclination angle greater than 5° is called the inclined rock layer. If the rock formation is inclined in one direction and the inclination angle is nearly equal, it is called a monoclinic rock formation.

    (2) Thickness and exposed width of the rock formation

The thickness of the formation is divided into true thickness and the thickness of the straight lead. The vertical distance between the top and bottom of the rock formation is called the true thickness. The vertical distance between the top and bottom of the rock formation is called the vertical thickness. The exposed width of the rock formation refers to the width of the horizontal projection of the rock formation exposed to the surface.

    (3) Characteristics of the formation and characteristics of the rock formation

The occurrence of rock formation refers to the state in which the rock formation is produced in space. There are three elements in determining the occurrence of a rock formation: strike, inclination, and dip. The intersection of the rock level and the horizontal plane is called the strike line of the rock formation, that is, the connection of two points on the same rock level. The direction of the strike line is called the strike, indicating the direction in which the rock formation extends. The two ends of the line are each pointing to one side, for example, one head to the east and one head to the west. The direction of the rock formation is east-west.

On the rock level, the strike line of the vertical rock stratum is called the inclined line of the rock stratum. The projection of the inclined line on the horizontal plane is called the trend line, and the direction indicated by the trend line is the tendency of the rock stratum. The trend and tendency of the rock formation differ by 90°. The angle between the inclined line and the trend line is called the inclination of the rock formation.

    (4) Determination and representation of rock formation

Geological compass for determining rock formation. When measuring the tendency of the rock formation, the rear end (south end) of the compass is placed on the rock level, and the circular aquarium bubble is centered (even if the compass is horizontal), and the azimuth dial of the north reading needle is the tendency of the rock layer. When measuring the inclination of the rock formation, make the bottom of the compass stand upright, the long side of the compass close to the rock level, make it parallel to the rock layer, and then move the “semi-circular” iron piece behind the compass to center the column level bubble, reading the dip indicator in the middle. The number of ticks referred to by the line is the inclination of the rock formation.

In the geological map, the rock formation is usually represented by the symbol ┳30, the long line indicates the trend, the short line indicates the tendency, and the number indicates the inclination. In the transcript, the rock formation has two representation methods: azimuth method and quadrant angle method.

The azimuth method stipulates that the north is 0°, the east, the south, and the west are 90°, 180°, and 270°, respectively, and then the north is 360°. The angle between an orientation and the true north is the azimuth of the orientation. In field work, azimuth is commonly used to record the occurrence of rock formations, such as NE∠70°, indicating a tendency of 85° northeast and a 70° inclination angle. The quadrant angle method consists of four quadrants with four angles of 90°, which are defined as 0° in the north-south direction and 90° in the east and west directions. For example, the quadrant angle S75°E means south 75° east.

Second, folds and fault structures

    (1) Fold structure

The layered rock is deformed to form a undulating curved shape, but its continuity and integrity are not damaged. This structure is called a fold structure.

The fold is a bend in the fold and is the basic unit of the fold. The fold has two basic forms of anticline and syncline. The anticline is the tendency of the two-wing rock formation to be opposite. The morphological aspect is the upward bending of the rock layer. The core rock layer is older and the two-wing rock formation is relatively new. The slanting direction is the orientation of the two-wing rock formation, and the morphological aspect is the downward bending of the rock layer. The core rock layer is relatively new and the two-wing rock formation is relatively old.

    (2) Fracture structure

After the rock is stressed, it deforms to a certain extent, causing the continuous integrity of the rock to be destroyed, resulting in various faults and displacements of different sizes. This structure is called a fault structure. When a rock breaks, a fault structure that has no significant displacement along the section is called a joint (or a crack), and a fault with a significant displacement is called a fault.

1. Joints Joints are cracks in rocks, and the fracture surface becomes a joint surface. The joint faces can be flat, uneven, or even curved. The joints in the rock formation are mainly characterized by long and short, uneven, or parallel, or criss-crossing. Joints can be divided into two types: Zhang joints and shear joints according to the different mechanical properties.

2. Faults Faults are fracture structures in which rock fractures and structures occur with structural displacement and have significant displacement. The size of faults varies, with small faults extending only a few meters, relative displacements of only a few centimeters, and large faults extending from a few hundred to thousands of kilometers.

The elements of the fault include fault planes, fault lines, breaks and breaks, as shown in Figure 1. According to the relative motion of the two discs in space, the faults can be divided into four types: normal fault, reverse fault, translational fault and rotary fault. [next]

Third, the relationship between geological structure and mining work

The geological structure controls the spatial distribution and shape of the ore body, and therefore has a great impact on the safe production of the mine.

    (1) Relationship between folds and mining work

   1. The fold formed before mineralization plays a role in controlling the formation of the deposit, the distribution of the ore body, the spatial form, the occurrence, etc. Therefore, the shape of the fold determines the occurrence and occurrence conditions of the ore body, and directly affects The development of mineral deposits and the choice of mining methods.

2. The formation of ore-forming folds often complicates the shape of the ore body, complicating exploration and mining. The folds can raise the position of the same seam, or repeatedly expose the surface, easy to find and easy to mine. When the ore layer is subjected to the buckling effect, the ore distribution can be relatively concentrated. Generally, the thickness of the saddle or core of the ore layer is relatively large, which can reduce the total length of the roadway and facilitate mining.

3. The pressure in the anticline core is generally small, which is generally beneficial to the excavation project. However, the top rock fissure of the anticline core is developed, which is relatively broken, and may also cause an increase in water inrush. In the production process, it is easy to generate roofing and permeable. Waiting for an accident. In the oblique core, the top pressure is generally large, and it is also prone to accidents.

4, the fold can make the occurrence of the mineral layer changes, and sometimes can be carried by gravity, which is beneficial to intra-mineral transportation.

    (2) Relationship between joints and mining work

1. When hitting the rock in the joint development, do not open the eye along the joint surface, especially the Zhang joint surface to avoid the card brazing. When the blasthole is arranged along the joint, the energy of the explosive is lost due to the easy leak of the crack, which affects the blasting effect. Therefore, attention should be paid to the direction, development and extension of the joint during blasting.

2. In the open pit mining, if the joint development, especially by the impact of blasting and groundwater and surface water, often affect the stability of the slope, prone to landslides and collapse accidents, so pay attention to the choice of slope angle.

3. The direction of the joint surface sometimes affects the direction of tunneling. This is because, in the case of joint conditions, when the blasthole is arranged according to the normal situation, the blasting effect is affected by the joint, and the roadway is deviated from the centerline direction, so the blasthole arrangement should be appropriately changed to make it slightly skewed.

4. Joints affect the choice of mining methods. The joints, especially the sections where Zhang Jieli is very developed, should not be used in the open field method and the room-column method; in some wall-type cavings, the topping distance should be appropriately reduced.

5. When excavating, if the direction of the joint is parallel to the direction of the excavation, most of the pressure of the rock will be concentrated on the bracket, which will easily cause the roof to fall. If the working surface is parallel to the main joint surface, it is not only easy to fall off, but also easy to produce pieces. Therefore, when arranging the roadway and the working face, it is best to be perpendicular or at an acute angle to the main joint surface.

6. When mining operations are carried out in joint development areas, it is easy to cause roofing accidents, and support and roof management must be strengthened. The appropriate support method should be selected according to the density and direction of the joint. For the roadway developed by the roof joint, the working face bracket can not use the top column, but the shed should be used, and the bracket should be dense, and the top column can not be placed parallel to the main direction of the joint.

7. Jointing is a good passage for groundwater. If the large-scale Zhangjie is connected with the mining roadway, there is a danger of water inrush. When the amount of water in the mining process increases, the observation of the water inrush and the prevention and drainage work should be strengthened.

    (III) Relationship between faults and mining work

1. The ore-forming fault often cuts the ore body into several parts, which complicates the distribution, shape and occurrence of the ore body, increasing the exploration workload and construction difficulty.

2. The fault affects the layout of the mining development system. Faults often complicate development, increase the number and total length of roadways, and make tunneling difficult, and increase roadway support and maintenance. Therefore, in the design of the development system, it is necessary to clarify the situation of large faults, so that the development of the wells should avoid the fault-fracture zone as much as possible, especially avoiding the fracture zone parallel to the roadway and obliquely intersecting with the small intersection angle, not along the fault. Digging in.

3. The fault affects the design of the stope and the mining work. The fault complicates the shape of the ore body, or makes the mining easy to generate roofing, which complicates the work of the mining process and increases the loss and depletion of the ore. Therefore, in the design of the stope, it is necessary to fully understand the fault condition in the stope. If a fault with a large fault distance is encountered, it should be used as a boundary to divide the stope as much as possible to reduce the impact on the mining work. The newly discovered faults in the recovery process should be dealt with in time to avoid causing major hazards.

4. When encountering a large fault fracture zone in tunneling, it is necessary to strengthen the support or take special measures to pass the fault.

5. The fault is likely to cause water in the pit. The fault-fracture zone is a good channel for groundwater. Especially when the fault is connected by a rock or groundwater source with strong water permeability and multiple caves, the drip and dripping of the pit are increased, and the danger of water inrush is greater, and even water inrush accidents are caused. Therefore, when mining over a fault or near a fault, waterproof measures should be taken to prevent water seepage.

6. For open pit mines, the fault structure affects the stability of the slope. For underground mines, fault structure is an important cause of roofing accidents in underground mines. It should be fully considered when selecting mining methods. Some mining methods such as open field method and longwall mining method cannot be applied, and filling method and housing column must be adopted. law.

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