Application Research Of The Hoek-Brown Strength Criterion To Rockmass Engineering

The determination of rock mechanics parameters reasonably is a basal work on the rock project,which is an important issue in the engineering practice and is related to the security and economy directly. The Hoek-Brown strength criterion used commonly in geotechnical engineering has been studied preliminary in this paper. The expression form,the different selecting methods for parameters in the criterion are introduced particularly,and its application conditions and other factors are discussed.According to this the equivalent conversion from Hoek-Brown criteria parameters to Mohr-Coulomb criteria parameters is calculated.The four Hoek-Brown criteria parameters have been sensitively analysised using the sensitivity analysis method. Finally,the Hoek-Brown criteria has been applied to the stability analysis for two projects examples,which result is compared to the result from Mohr-Coulomb criteria.The four Hoek-Brown criteria parameters have been studied using the sensitivity analysis theory based on the finite difference method and strength reduction method.The sensitivity analysis result indicates that the geological strength index(GSI ),the rock material constant mi ,the degree of disturbance to rock mass D and the rock uniaxial compressive strengthσcishow similar sensitivity to the three types of rock slope stability.It can be considered to linear relationship between the four influence parameters changed in rate and the slope safety factor.The order for parameters isGSI > D >σci> mi in accordance with the sensitivity.The influence to friction angleφforGSI is the identical for different mi .But with the increase of mi ,GSI moves right gradually corresponding to the extreme points ofφ,going to 90.The change rate ofφdecreases when mi changes from small to large for the same GSI .Finally,the author analysises the influence rule to Mohr-Coulomb criteria parameters for disturbance coefficient D .According to the result of the engineering analysis for the slope and underground tunnel examples,the slope safety factor is basically identical and only a small difference using the finite difference method and limit equilibrium method based on the same strength criterion. However,the result has some difference for different strength criterion, the slope safety factor based on Hoek-Brown criteria is less than that based on Mohr-Coulomb criteria.The potential slip surface position calculated by the limit equilibrium method and the finite difference method is basically the same based on the Hoek-Brown criteria,but which is slightly less than that based on Mohr-Coulomb criteria. The results on Hoek-Brown criteria show that the displacement and the plastic area are slightly larger that on Mohr-Coulomb criteriaThe Hoek-Brown criteria takes into account the excavation influence to rock mechanics parameters in the rock slope stability analysis,and reflects the dynamic process.So,the Hoek-Brown has obvious advantage in the jointed rock mass stability analysis.