Study On Mechanism And Application Of Hard Rock Brittle Failure Process

With the high-speed development of Chinese economy, deep mining is becoming the main future development direction. With the increase of mining depth, the environment of rock mass is becoming worse and worse. The deterioration of mining condition brings about the phenomenon of roof collapse and rib spalling, even dynamic geological disaster such as rock burst. For example, rock burst happens in Hong Tou Shan copper mine and led to collapse of ramp for nearly100m and even out of production; the ground pressure of Fankou Lead-Zinc Mine increased dramatically and rock ejection occurs occasionally, meanwhile, the quantity of supporting greatly increased. These series of geological hazard problems cause huge losses of life and property for nation, mining enterprises and people, and seriously impede sustainable development of national economy and mining enterprises. Therefore, it is necessary to launch research work for Study on mechanism and application of hard rock brittle failure process.This thesis presents a thorough study of skarn collected from Shizhuyuan polymetallic mine in Hunan Province. Firstly, uniaxial compression test and uniaxial cyclic loading and unloading test were carried out, and both rock burst proneness and AE characteristics were studied carefully. By thoroughly analyzing the variation trend of AE events rate and energy release rate of skarn in true triaxial test, a new hard rock brittle failure prediction index based on AE (microseismic) monitoring precursory information was proposed. Aiming at the problems in the mining process in Shizhuyuan polymetallic mine in Hunan Province, synthesizing the methods of microseismic monitoring, numerical simulation and hard rock brittle failure prediction index, a collapse event was predicted accurately at the cross region of P4and C3. The main contents of the thesis are represented as following:1. Both uniaxial compressive test and unaxial cyclic test were carried out and the characteristics of skarn such as strength, failure mode, AE, energy release were studied. The energy release regularity and elastic-brittle behavior were specially focused. Rockburst tendency of skarn was determined. By analyzing the result of AE monitoring, the acoustic emission characteristics of skarn in uniaxial compressive test and unaxial cyclic test was aquired. Felicity effect exists in the cyclic process, and the mechanics of this phenomenon was quanitative analyzed by AE description and Felicity ratio.2. True triaxial tests such as biaxial test, true triaxial loading test and true triaxial unloading test were carried out with different stress paths. The characteristics of strength, AE regularity and failure mode were studied respectively. The existence of intermediate principle effect under true triaxial loading condition was proved. The rules of AE hits and energy were studied.3. Aiming at the noise problem in the AE monitoring process, by analyzing the characteristics of noises and effective sigals, a new noise identifying and filtering method based on neural networks was put forward.4. Aiming at the problems of hard rock brittle failure and geo-disasters, the AE events rate types were classified. By thoroughly analyzing the variation characteristics of AE events rate and energy release rate, a new rockburst prediction index based on AE (microseismic) monitoring precursory information was proposed.5. Aiming at the problems in the mining process in Shizhuyuan polymetallic mine in Hunan Province, synthesizing the methods of microseismic monitoring, numerical simulation and hard rock brittle failure prediction index, a collapse event was predicted accurately at the cross region of P4and C3, and the index has been proved practical.