Study On Characterization Method Of Rock Mass Strength Parameters In Mines Based On Microsesmic Monitoring Data

Deep mining engineering in underground excavation has become an important subject with the great demands of energy and resource for the rapid development of national economy. The dynamic disaster problem caused by rockmass excavation are the focuses in the fields of mining engineering and rock mechanics, and the existed disasters not only threaten the lives of mine workers, but also affect the normal production of mine. It is therefore highly significant for the designers to evaluate the rock mass conditions and properties using a proper engineering design and reasonable assessment system. Underground excavation engineering design and stability analysis as well as numerical simulation require inputs of proper parameters. Without them, the process of engineering design is not possible. Consequently, acquiring proper parameters has become an important issue in the field of rock mechanics. The rock mass strength parameters such as uniaxial compression strength by the proposed assessing methods are generally examined from the reduction of weighing of laboratory results. The results by those analysis methods could only take statistical factors into account, such as in-situ stress or pore water pressure. Unfortunately, the dynamics factors which dynamically influence rock mass stability are generally ignored. The parameters were obtained by these methods are often inaccurate, because mining is a dynamic process with a long period and three dimensional multipoint excavations under the surface. Over the last30years, microseismic monitoring technology, a high-tech and informationized dynamic monitoring technology, has been gradually applied in the prediction of dynamic disasters in mining engineering. The microseismic monitoring technology could monitor the whole failure process of rock mass using the location results of microseismic events, which could directly reflect the change of the fractures in rock mass, and thus it is of significant meaning for the assessment of rock mass strength parameters.In this dissertation, on the basis of summary and analysis of previous studies, geometric parameter information of discontinuities were acquired by digital measuring technique.And then, the static strength parameters of rockmass were estimated by Hoek-Brown strength criterion, and the study of representative elementary volume of rockmass strength was carried out based on network modeling of discontinuities and numerical simulation. Microseismic active law with the evolution of rock mass mechanics characteristics was researched. On this basis, the characterization method of rockmass strength parameters in mines based on microsesmic monitoring was proposed combined with numerical simulation technique. This study is theoretical and practical value. The main work in the paper can be summarized as follows:(1) Rockmass discontinuities were investigated by digital measuring technique, and real3D model of rockmass surface was built by software of Shapemetrix3D. Then geometric parameter information of discontinuities (dip, dip angle, strike and so on) were acquired. Finally, the quantitative analysis of rockmass discontinuities characteristics was realized.(2) Rockmass static strength parameters were estimated based on generalized Hoek-Brown strength criterion combine with the geometric parameter information of discontinuities. The monte-carlo method was used to realize three dimensional network simulations of rockmass discontinuities, then the change rules of uniaxial compressive strength and shear strength of rockmass of different sizes were studied by RFPA2D, and representative elementary volume of rockmass strength was obtained.(3) The microseismic monitoring system in Shirengou Iron Mine was introduced, and real-time monitoring and analysis of rockmass stability were realized. Through the deep analysis of geological data, construction documents and on-site observation, the monitoring system was obtained combine with the experimental analysis of sensor sensitivity and positioning accuracy of monitoring, which can satisfy the requirements of mine requirements. The waveform library of microseismic sign was built by waveform recognition.(4) The space-time distribution characteristics was analyzed in the key research area, and microfracture of rockmass was studied by using multi-parameters such as culmulative apparent volume, energy index, fractal dimension and b value, and so on. Combine with the field condition, the evolution law rockmass mechanics characteristic was researched by analysing microseismic activity law, and spatial diversity and time variability of rockmass strength were verified. It helps for analyzing rockmass strength based on microseismic monitoring data.(5) Through the processing and analysis of microseismic data, three parameters (microseismic events number, accumulated energy, average distance between the events) were obtained by processing and analysing microseismic monitoring datum accompany with rockmass failure of mine. Combined with numerical calculation result of stress field, correspondence of microseismic datum variables and stress variables were built by analyzing evolution law of microseismic monitoring datum and stress field datum with underground rockmass failure. Then dynamic calibration method of rock mass strength parameter was proposed based on microseismic monitoring datum by parameter inversion, and safety coefficient of underground rockmass stability was obtained.