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Abstract The current application of geophysical logging technique to the investigation of rock mass engineering in coal mine，especially the geophysical strata rating(GSR)，is introduced. GSR is mainly based on sonic logging data(density and gamma logs are used simultaneously)；and the formulation relies on a geomechanical understanding of the factors(bedding or fracture) that influence sonic velocity，and does not attempt to estimate rock strength，rather to provide a method for estimating the quality of rock mass quantificationally and comprehensively. Engineering practice indicates that geophysical logging technique with its innate ability has been playing a helpful role in quantitatively identifying the rock mass quality and changes in rock mass，such as delineating the range of soft rock，recognition of key strata，and exploration of potential regions of water inrush. It also comes to the conclusion by comparison that GSR is more reliable than uniaxial compressive strength which is used only in quantitative description of sedimentary rock. Seismic prospecting is also employed to bridge the gap among boreholes and is helpful to understand what is going on there. A new academic thought of geophysically quantitatively describing rock mass quality，namely，it is possible to statically quantitatively describe the rock mass with geophysical logging technique before mining，and dynamically quantitatively describe the rock strata movements associated with mining during retreating with microseismic monitoring or electromagnetic radiation.
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Received: 13 November 2008
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