I. Classification of mining site pressure activities
According to the ground pressure, the characteristics, the scale of the activity and the degree of damage can be divided into two types: localized ground pressure and large area ground pressure. The former has a small spread (1 to several stopes), which has little impact on production and safety, and is slow to develop (months to decades); while the latter has a wide range (several stages), which is destructive and develops rapidly ( Hours to several days), which seriously affects production and threats to safety, and even the whole mine is shut down, causing significant resource losses. Taking Jiangxi tungsten mine as an example, the ground pressure is classified in Table 1.
Table 1 Classification of pressure activity in tungsten mining
Characteristics | Large-scale ground pressure activities | Localized pressure activity |
Activity range | It has a wide range of influences and a wide range of activities, affecting several stages. The length is ≥300m, the width is 100~200m, the height is >150~200m, and the spread area is more than tens of thousands to hundreds of thousands square meters. | The sweeping surface is small, the range of motion is narrow, one to several, up to a dozen stope, or movement and collapse between one, two, and several veins |
destruction level | Destructive, seriously threaten the safety of operations, loss of ore resources, damage to the production process system, endangering more than three stages, affecting production for a long time, and some years | Cracks and damages in surface buildings and regional damage in underground areas have not caused serious threats, but have an impact on production and safety. |
Development | If the empty area is untreated, the fourth stage develops very quickly, often within hours to days. | In the first, second or even ten years after the recovery of the nugget, the ground pressure activity occurs. In the whole process, the development is slow, but in part, the fourth stage develops rapidly and the situation is very strong. |
Example | 1. The 6-stage large rock movement and rock fall of the Pangushan Mine on September 24, 1967; 2. The large rock movement and rock fall of the three stages on May 28, 1970 in the Xiadou Mine of the Lower Ridge Mine; 3. Xiaolong Mine's three major stages of rock movement on April 11, 1972, rock collapse; 4, Mountain Ridge iron ore sand mining in 1979 from 5 to more than 57 months old stage rock movement and localized collapse; 5, Shirenyu Mine, April 23, 1979, 7 stages of large rock migration, rock fall | 1. Dajishan Mine: 1969, 625 stage, 1 to 6 veins, 6 to 8 horizontal pillars, patios, deep holes, damaged by rock movement 2. Pangushan Mine: Collapse of the wall between the 11th, 12th and 13th veins in the period 831-899 in June 1966 3. Yanmeishan Mine: Deformation and sinking of the top five mining top pillars in October 694, October 1975 4, Xiaolong Mine, August 18, 1971, the 290-hole collapsed wall collapsed 5. Tieshan Ridge Mine: In September 1969, the 3161 stope collapsed partially, causing impact waves. 6. Lower ridge mine 樟 矿 mining area: 240 stage 4~1 large loading charge chamber, blasthole affected by ground pressure and deformation, cracking, moving 7. Shirenyu Mine: Earthquake activity in the Central District on April 21, 1979 |
Due to the small scale and slow development of localized ground pressure, if effective control measures are taken in time, large-scale ground pressure can be avoided. Conversely, when the local pressure is out of control, the ground pressure increases rapidly, and as a result, a large area of ​​ground pressure may be caused.
    Second, factors affecting the pressure of mining sites
(1) Gob area
The volume of the goaf is a factor that is unfavorable to the stability of the rock mass with the size of the mining and the recovery time. It is related to the geometry and spatial distribution of the ore body. Generally speaking, the larger the volume of the goaf, the worse the stability of the rock mass, especially the larger the volume of the continuous empty space, the more sufficient the conditions for inducing the ground pressure activity. . Former tin ore mine south ground pressure occurs, there is 815,000 meters underground mined-out area 3, Pangushan tungsten ore is 1.789 million m 3, Gongchangling iron ore is 92 million m3. Judging from the reasons for the occurrence of ground pressure activities in some old mines in China, the goaf is the root cause of ground pressure activities.
(2) Time effect
The large amount of observations obtained in mines with ground pressure indicate that time is an important variable under other conditions. Because of the large-scale activities of the rock mass, there must be a development process. From the relationship between rock movement and time measured by tungsten deposits such as Tieshan Ridge, Xiaolong, Dajishan and Tumei, Jiangxi Province (Fig. 1, Fig. 2), it is seen that the ground pressure activity has a slow movement, accelerating the movement and collapse. process. Local ground pressure activities, some local collapse, and some no collapse, which is determined by other conditions (such as lithology, rock mass structure, etc.).
Fig.1 Relationship between displacement of rock mass and time in 518 stage 110 Dongda alley of Jiangiayu mining area
(Local type of ground pressure type, 30m roadway collapse around 6141 measuring point)
1-6141 measuring point; 2-6145 measurement; 3-6146 measuring point; 4-6153 determination
Fig. 2 Relationship between displacement and time of unstable rock mass in Xiaolong Mine (type of large-scale ground pressure activity)
1-14 #测点;2-15 #测点;3-16 #测点;4-K 5点点
(3) Structure weak side
Observations have shown that for large-scale ground pressure activities, large continuous structural weak surfaces (such as faults, fracture zones, etc.), on the one hand, control the occurrence of large-scale damage, that is, the cutting surface or sliding surface that becomes the moving boundary of the rock mass; Aspects promote the acceleration of its occurrence and development. It is observed from the surface of the Gongchangling iron ore mine that the surface crack caused by the underground ground pressure activity generally occurs along the fault and thus forms a sinking step. Antimony tin ore mine, Pangushan tungsten ore, phosphorus ore Jingxiang larger rock moves, geologic formations subject to the control plane of weakness.
(4) Mining depth
The gravity of the overburden is directly proportional to the ground pressure. Generally, the greater the depth of mining, the greater the ground pressure. If there is a structural influence, the horizontal stress is often greater than the vertical stress.
(5) Groundwater
On the one hand, groundwater acts as a melting, softening and muddy on the rock mass structure surface, which reduces the strength of the weak surface; on the other hand, under the action of the fissure water pressure, the frictional resistance acting on the crack surface is reduced, thereby reducing the rock mass. Shear strength. The large-scale ground pressure activities of Jiangxi Tungsten Mine and Gongchangling Iron Mine generally occur during the Spring Festival thawing or rainy season.
(6) Mining technology
When the geological conditions of the deposit are certain, the mining sequence of the ore block, the structural parameters of the ore block, and the mining process will have an important impact on the pressure of the mining site.
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