Development stage and characteristics of large-scale ground pressure in stope

November 15, 2019

According to China's 30 years in Liaoning, Hunan, Jiangxi, Yunnan, some large-scale metal mining occurred in ground pressure, it can happen, summed up the whole process of the development of regular understanding, divided into three stages:

The first is the stage of occurrence and slow development. This stage of development is very slow, with a few months in the short and ten years in the elderly. Gongchangling such as iron ore is 2 to 3 months, tin ore mine from 5 to 12 months, while Jiangxi tungsten ore generally experience one to ten years. The main features of the ground pressure are: the rock sounds in the surrounding rock, the roof of the stope partially falling, the pillars being crushed, and the deformation and destruction of the mine roadway.

The second is accelerated development, severe rock movement and collapse. The roadway and surrounding rock are obviously deformed, the rock sound is fierce, the roadway, the pillar or the wall is crushed and collapsed. When the large-scale ground pressure is active, the rock layer moves, the roadway of the stope collapses, and the surface sinks and cracks to form a step. The large-scale rock movement time is completed within a few hours to a few days and the elderly are completed within three months.

The third is the attenuation stabilization phase. After large-scale ground pressure activities, the deformation and damage of the stope and roadway tend to be moderated, while the surface cracking and subsidence generally last for a while, but its speed gradually slows down, and the surrounding rock stress tends to a new equilibrium state, which is quite stable. stage.

With the progress of the mining work, the mining range continues to expand, the temporary equilibrium state of the rock mass is destroyed, and the ground pressure activity occurs again, repeating the above development process. For example, three large-scale ground pressure activities occurred in the Tongyu District of Gongchangling Iron Mine in eight years, with a period of 2 to 6 years.

The tungsten deposits in Jiangxi are divided into the initial stage, the slow development stage, the accelerated development stage and the four stages of severe rock movement and collapse (see table).

Characteristics of the development stage of large-scale ground pressure activities of tungsten ore

development stage	Surface features	Main features of the well
The initial phase	No change or change is not obvious	1. The movement phenomenon is found only at the measurement points of a few weak-faced developments or at the intersections of weak and dense spaces, and the mobile area cannot be fixed. 2. Extrusion of fault mud or fault opening
Slow development stage	Small cracks or small subsidence pits	1. Unstable rock mass moves slowly along the weak surface 2. The goaf is slowly closed 3. Core parts of the pillars are peeled, slag, and partially collapsed. 4, can delineate the rock migration boundary 5, generally experience one year to ten years
Accelerated development stage	Many continuous cracks and small subsidence pits appear, which can be moved and collapsed.	1. Rock mass acceleration 2. The roadway and the wall are obviously deformed or closed, partially collapsed. 3. Hear the sound of rock mass rupture, the ground audio frequency is significantly increased, and the sound speed is significantly reduced. 4, the development is relatively rapid, generally going through several months, up to one year
Drastic rock movement, collapse Local collapse stage	The subsidence pits are connected into pieces, and a crack group mainly composed of several backbone cracks is formed in the moving area, and a fracture step is generated.	1. Rock movements grow sharply 2. The roadway, the pillar, the wall, and the pillar are broken, crushed, collapsed or sunk along the weak surface. 3. The weak surface of the unstable rock layer moves over a large area and collapses into the empty area. 4, half of the occurrence of various physical effects, such as rock sounds, impact waves, etc. 5, the development is relatively rapid, usually a few hours to a few days, the elderly for three months

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