To surrender the invisible killer, coal mines have invited this 'safety symbol'

The "Intelligent Integrated Monitoring and Early Warning System for Rockburst" developed by China University of Mining and Technology has become the "alarm bell" for special disasters in coal mines after the transformation and application of many coal mines in China. It has successfully solved the problems and difficulties of one coal mine after another, and has gone abroad to play a role in many countries. At the beginning of May, in a coal mine in a city of Shandong Province, people and cars came and went as usual on the ground, but in the depth of more than 1000 meters underground, there was a crisis everywhere. A powerful energy could be gushing out at any time. The staff were watching the monitoring screen closely to see its trend.

Just five days ago, China University of Mining and Technology issued an alarm for the "Intelligent Integrated Monitoring and Early Warning System for Rockburst Pressure" installed in the mine. The inversion results of seismic wave CT show that the velocity of seismic wave around a driving face is obviously abnormal and is in a strong shock dangerous state. After receiving the alarm, the staff will immediately stop excavation, evacuate underground personnel and take pressure relief measures. On May 5, there was a sudden loud noise in the underground, even the surface shaking. A large-energy and strong mine quake broke out in the underground. Fortunately, timely disposal did not cause casualties.

R&D mine "CT", alleviating unfamiliar pressure

On October 20, 2018, Shandong Longyan Coal Industry Co., Ltd. had a major accident, the underground roadway was crushed by a powerful force, and the outburst of coal and rock mass blocked the passage... The accident resulted in 21 deaths and 1 injury. The investigation and analysis found that the accident was caused by a relatively unfamiliar term "rock burst" (also known as rock burst) rather than traditional mine accidents such as gas explosion, pit fire, mining water permeability, etc. In recent years, with the increase of mining depth and intensity of coal resources, the dynamic phenomena of rock strata such as rock burst have become more and more serious, and rock burst has become one of the major disasters in the field of deep resources mining. Dou Linming, a professor at China University of Mining and Technology, told reporters: "The deeper the coal mine is mined, the greater the mine pressure. Generally, there is a danger when the mining depth exceeds 400 meters. The danger coefficient of 1,000 meters is relatively high. At present, the deepest coal mine in China has reached 1,500 meters underground." Fortunately, in the face of this "unfamiliar pressure", there are already ways to "alleviate" it. After the scientific research achievements of China University of Mining and Technology have been transformed and applied in many coal mines, the above accidents can be avoided.

On May 11, 2008, Huating Coal Industry Group Co., Ltd. (hereinafter referred to as Huating Coal Industry) in Gansu Province, as usual, hundreds of miners are orderly mining underground. Suddenly, the chief engineer Zhou Peng received the alarm information from the monitoring system. The monitoring data showed that the ground pressure of 250102 working face had increased abnormally. Despite the normal situation, Zhou Peng eventually issued an early warning slip for safety, and the miners immediately evacuated from the mine.

On May 12, a violent rock burst occurred in 25102 working face, which caused serious damage to the roadway, and a train about 100 meters long with dozens of tons of equipment was overturned. Fortunately, the miners have been evacuated safely. Before that, some people in Huating Coal Industry would still be suspicious about this monitoring and early warning system. Since then, the whole mine has regarded this technology as a treasure, and no fatal accidents have occurred because of rock burst.

Like earthquakes, rock burst, as a dynamic disaster, has no obvious macro-precursor when it occurs. It has the characteristics of sudden, instantaneous vibration and great destructiveness. It is difficult to determine the time, location and intensity of the occurrence in advance.

"The original rock burst can not be monitored, and the accuracy of monitoring can reach 90% through our research. At present, we can predict the danger, location, approximate time and intensity of rock burst." Dou Linming said.

Professor Dou Linming is the chief expert of the Center for Rockburst Research of China University of Mining and Technology. He has taken the lead in putting forward the theory of dynamic and static superimposed impulse, the impulse energy principle of coal and rock mass impact failure, the strong and weak structural effect of roadway surrounding rock and the principle of strength weakening and alleviation of rock burst in China. In the long-term scientific research practice, Dou Linming's team has developed electromagnetic radiation technology, regional microseismic monitoring technology and system, dual-source integrated CT stress detection technology and system, which can quantify the invisible underground rock energy and its changes on the computer.

"The principle of CT early warning technology for impact risk is similar to that of CT examination in hospitals. The stress distribution in coal and rock mass can be inverted by artificially actively exciting seismic source or by shaking caused by rock burst (passive seismic source). Based on stress anomaly, stress gradient and wave velocity stress relationship, the early warning criterion for impact risk can be established to realize the inversion and impulse of regional stress field. Fight danger warning." Dou Linming said.

In 2013 and 2014, the State Administration of Safety Administration and China Coal Industry Association organized experts to appraise the achievements of "Research on Spatio-temporal Monitoring and Early Warning Technology of Mine Shock Rock Pressure Microseism" and "Principle and Technology of Mine Shock Rock Pressure Vibration Wave CT Prediction" developed by China University of Mining and Technology.

And this international leading achievement is also favored by many coal mines, and it soon spreads all over the country and is translated into practical application in mine operation. Since 2008, China's coal industry has entered a period of rapid development. On the one hand, the output of coal mines has risen rapidly, on the other hand, the mine is digging deeper and deeper towards the underground.