NEW METHOD OF FIELD MEASUREMENT AND CALCULATION FOR VOLUMETRIC FRACTURE RATE OF ROCK MASS

As an important parameter to characterize the fracture characteristics of rock mass,we characterize the fracture rate from the linear,surface and volumetric perspective. However,the available linear measurement method and statistical window method,which obtain the linear and surface fracture rate from 1-D or 2-D perspective,have the disadvantages of randomness of measurement results and limited application conditions. And the existing method of volumetric fracture rate also has some problems such as poor practical application and high cost. There is still a lack of easy-to-operate method to measure the rate of fissures in the field. Therefore,a new sphere method is proposed to measure volumetric fracture rate of rock mass in the field. Due to the unique tectonic and statistical regularity of the structure and diagenetic fissures,the sphere method observes each group of fracture occurrences from different directions. The development of the rock mass can be statistically inferred by measuring the developmental characteristics of each group of cracks on the limited exposed surface of rock mass. And its value can better reflect the development degree of the internal crack of the local rock mass. In addition,the spherical method can obtain the true value of the gap width and the gap spacing data along the normal direction of the fracture surface by using the patented instrument at the field. And the flatness of the exposed surface of the rock mass affect the measurement result hardly. Taking Dalongshan quarry in Anqing as the study area,field measurements of spheroid method show that the average volumetric fracture rate is 2.286% and the overall difference is concentrated in 1% ~4%. The method can realize rapid measurement on the basis of more convenient operation in the field. Combining the actual situation of the study area and the results of error analysis,the sphere method can reflect the degree of fracture development at each measurement point in the study area.