Abstract:

There are intrinsic contacts between the mechanical strength of rock mass and rock，and also have significant differences. The site rock mechanical indexes are essential for the evaluation of the site rock mass mechanical properties. The site of Sanmen Nuclear Power plant is taken as the research object. Based on the rock mechanics test in laboratory combining with the site geological investigation, the effects of rock mass structure characteristics, stress distribution state and other factors are considered comprehensively. The geological intensity index (GSI) is induced to descript the structure characteristics and weathering degree of rock mass quantitatively, and Hoek-Brown criterion is used to estimate the mechanical parameters of rock mass. At the same time, the comparative analysis of mechanical parameters of rock mass is carried out according to the method of rock mechanics classification (RMR). The rock mass of medium weathered tuffaceous sand, slightly weathered tuffaceous sandstone and slightly weathered andesitic basalt, using Hoek-Brown method based on GSI, equivalent cohesion c values are 4.03, 6.20 and 6.10 MPa, internal friction angle φ values are 31.96°, 34.37°and 33.87°respectively; Using Hoek-Brown method based on RMR, c values are 4.42, 6.44 and 7.24 MPa, φ values are 28.92°, 32.43° and 34.51° respectively. The research results show that Hoek-Brown criterion is more rational to determine the rock mechanical strength index of nuclear power site. The important basis is provided for the foundation design of nuclear power plant from the obtained rock mass mechanical index.

Key words: mechanical parameters of rock mass, Hoek-Brown criterion, geological intensity index (GSI), rockmass block index(RBI), absolute weathering index(AWI), rock quality designation (RQD), rock mechamics classification（RMR）, nuclear power plants