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Heijingang Broadcast: Detailed Explanation of Ground Pressure Management (Part 1): Ground Pressure Manifestation, Generation and Definition of Ground Pressure, Ground Pressure Management Methods
Introduction
Ground pressure management is an indispensable part of mining engineering, directly related to mine safety production, mining efficiency, and resource recovery rate. Before delving into ground pressure management, we need a clear understanding of ground pressure manifestation, its generation, and definition, and master the four basic methods of ground pressure management. This article will elaborate on these aspects in detail.
Ground Pressure Manifestation and Definition
Ground Pressure Manifestation
Ground pressure manifestation refers to the phenomenon where, after excavation of the rock mass, the original rock stress equilibrium is disrupted, leading to redistribution of stress in the rock mass, causing deformation, movement, and destruction of the rocks around the roadway or mining area. The appearance of this phenomenon not only affects the normal progress of mining operations but also may pose a significant threat to mine safety.
This is directly observable. To help understand how ground pressure manifestation is generated, two key concepts are involved: original rock stress and secondary stress. What is original rock stress? That is, the inherent stress state within the earth's crust before any disruption. Consider this: before any disruption within the earth's crust, what forces act on any point within the original rock? How are they generated?
First, consider the self-weight stress of the original rock. Self-weight stress is generated by gravity, often referred to as weight. Another force is the horizontal unilateral force, which includes the earth's rotation and tectonic movements. Therefore, the causative force actually includes two aspects, forces in two directions: gravity and horizontal force.
However, after excavation of the rock mass, the original gravity and horizontal stress will change. This force may transfer to the surrounding rock or engineering structures, causing deformation and destruction of the surrounding rocks. This is a ground pressure phenomenon.
Definition of Ground Pressure
Ground pressure, also known as mining pressure, refers to the pressure generated by underground rocks and soil under natural and man-made factors. This pressure is the root cause of ground pressure manifestation. The magnitude and distribution of ground pressure are affected by various factors, including geological conditions, groundwater, and mining methods.
Generation of Ground Pressure
The generation of ground pressure is closely related to the stress state of the rock mass. Before excavation, the rock mass is in a state of original stress equilibrium, where the stress distribution is relatively uniform and in dynamic equilibrium. Once the rock mass is excavated, its original stress equilibrium is disrupted, and the stress in the rock mass will redistribute, forming a secondary stress field.
After excavation of the rock mass, the original gravity and horizontal stress will change. This force may transfer to the surrounding rock or engineering structures, causing deformation and destruction of the surrounding rocks. This is a ground pressure phenomenon. However, theoretically, this destruction is caused by force. Therefore, we call this force ground pressure, or mining pressure, the force that causes deformation, movement, and destruction of the original rock.
Four Methods of Ground Pressure Management
Method 1: Utilizing the supporting capacity of the ore rock and necessary supporting pillars
The ore rock itself has a certain supporting capacity, similar to the floor of a building, capable of preventing collapse within a certain area. During mining, this supporting capacity of the ore rock can be utilized, combined with necessary supporting pillars, to maintain the stability of the mining area. Specifically, through reasonable mine layout and pillar design, the pillars can support the pressure of the overlying strata, and the self-supporting capacity of the surrounding rock and pillars can maintain the stability of the mined-out area. The key to this method lies in the reasonable selection of mine room, pillar parameters, and mine room cross-sectional shape and layout direction, so that the stress distribution around the mine room is as reasonable as possible.
Method 2: Supporting the mining face through support
When the supporting capacity of the surrounding rock is insufficient to guarantee its own stability, or the remaining pillars are insufficient to support the stability of the roof of the mined-out area, support methods can be used to support the mining face. There are various support methods, including rigid support and flexible support. For roadways dominated by deformation pressure, flexible supports with large compressibility should be selected, such as anchor spraying support, compressible steel supports, etc. For roadways dominated by loose pressure, rigid supports with sufficient strength can be selected to support the weight of loose rocks, such as stone-concrete masonry, steel-wood supports, etc. The purpose of support is to prevent excessive deformation and destruction of the surrounding rock, thereby ensuring the safe progress of mining operations.
Method 3: Filling the mined-out area
Filling the mined-out area is an effective ground pressure management method. During mining, the rocks above and around the mined-out area lose their original support, leading to stress redistribution and surrounding rock deformation. By filling the mined-out area with materials, the deformation and displacement of the surrounding rock around the empty area can be reduced, thereby achieving the purpose of supporting the surrounding rock and maintaining the stability of the empty area. The selection of filling materials should depend on the specific situation, considering both their strength and stability, as well as their economic and environmental aspects. Filling the mined-out area can not only control ground pressure manifestation but also improve resource recovery rate and reduce surface subsidence.
Method 4: Caving method
The caving method is a method of actively releasing stress. During mining, due to the formation of the mined-out area and stress redistribution, stress concentration may occur in some areas. At this time, the stress can be released by caving, reducing the stress around the mining area and redistributing it to achieve a new stress equilibrium. The caving method can not only control ground pressure manifestation and improve mining conditions but also eliminate the potential safety threats of the mined-out area to production. However, the caving method requires careful operation to prevent triggering new geological disasters.
Conclusion
Ground pressure management is a crucial aspect of mining engineering. Through in-depth understanding and application of ground pressure manifestation, the generation and definition of ground pressure, and ground pressure management methods, ground pressure hazards can be effectively controlled, mining efficiency and resource recovery rate can be improved, and mine safety production can be ensured. In practice, appropriate ground pressure management methods should be selected according to the specific situation, and monitoring and early warning work should be strengthened to deal with potential ground pressure disasters. At the same time, with the continuous advancement of technology and innovation in mining technology, ground pressure management methods and means will also be continuously improved and enhanced.
