Indirect Estimation of Rock Uniaxial Compressive Strength from Simple Index Tests: Review and Improved Least Squares Regression Tree Predictive Model

Uniaxial compressive strength is an important mechanical parameter for rock mass engineering. Hence, how to determine the UCS simply and accurately have drew numerous attention. In this paper, the references related to UCS estimation using indirect tests were reviewed, and three stages of the development of indirect UCS estimation were classified. Meanwhile, the merits and drawbacks of different kinds of indirect tests for evaluating UCS were analyzed, and a indirect parameter (Schmidt hammer rebound value (L-type)) was determined to estimate the UCS values. For establishing more precise predictive model, more than 700 groups of data set were collected from 20 references. Subsequently, the improved least squares tree algorithm was utilized to establish the predictive model. The fitting coefficients indicated that the predictive model can be applied to engineering practice.