Study On Geological Strength Index In Hoek - Brown Criterion

The accurate determination about rock-mass mechanics parameters is an important and complex subject in rock engineering. Reduced rock mechanics parameters which are based on indoor rock tests, and compositely considered of fissures in the rock and size can meet the engineering requirements. This fact has been proved by large number of practices. In these methods,Hoek-Brown strength criterion method which has been widely used in engineering practice is a better method. In order to calculate parameters of the criterion, E.Hoek introduced disturbance factor D which considers disturbance of blast loading and unloading into the criterion, E.Hoek refer to the Rock Mass Rating improved Hoke-Brown strength criterion, but the Rock Mass Rating is limited. In order to overcome the limitations.E.Hoek introduced Geological Strength Index into the improved Hoke-Brown strength criterion, however,GSI affected by the subjective easily, large number of scholars works on the quantification on G5I.To study the effect of GSI to estimate the parameters of rock mass and evaluate the reliability of each methods,the paper taking Xiaohebian iron and Beiya gold slop project as the project background,using field investigation and tests in indoor and outdoor to study and discuss Geological Strength Index. Procedure is as follows:(1)The various methods to obtain geological strength index is described and classified. The paper improve the predecessors’ research and put forward a new method to quantitate the GSI based on the volume of rock mass joint and uniaxial compressive strength.(2)The paper research the influence of GSI effect on the parameters of rock mass.(3)According to rock test and field investigation, the paper using these methods to quantitate the GSI of rocks and analysis of the pros and cons of each method.(4)Combining with the determined GSI results, reduce the rock mechanics parameters by Hoek-Brown strength criterion. Compare the revised results with rock direct shear test results to verify the correctness of the determination of GSI. Apply the revised mechanical parameters to slope stability analysis in xiaohebian, and to further verify the correctness of the determination of disturbance factor.(5)The two sides for obtaining GSI are mass structure and surface structure.Using gray relational analysis method, the paper two representativeness indicators of rock mass structure and structure surface,and ues used the two indicators create a new geological strength index scale.