3-D Rock Mass Strength Criteria—A Review of the Current Status

The presence of complex discontinuity patterns, the inherent statistical nature of their geometrical parameters, the uncertainties involved in the estimation of the discontinuity geometrical and geo-mechanical properties and complex three dimensional (3-D) in-situ stress make the accurate prediction of rock mass strength a difficult task. It has been a great challenge for the rock mechanics and rock engineering professions to develop a rock mass strength criterion in three dimensions that incorporates the effect of the minor and intermediate principal stresses and captures the scale dependent and anisotropic properties resulting from the discontinuity geometry parameters, such as the number of discontinuity sets, 3-D discontinuity intensity, and the distributions of the discontinuity orientation and size. Rock mechanics and rock engineering researchers have dealt with this topic for more than 55 years. The paper provides a critical review of the current state of the art regarding 3-D jointed rock mass strength criteria. The shortcomings of several rock mass strength criteria are discussed. The historic development of rock mass strength criteria that incorporate the effect of the minor and intermediate principal stresses and capture the scale dependent and anisotropic properties is presented. The most advanced 3-D rock mass strength criteria currently available in the literature are presented, including suggested future improvements.

A New Approach for Identification of Potential Rockfall Source Areas Controlled by Rock Mass Strength at a Regional Scale

The identification of rockfall source areas is a fundamental work for rockfall disaster prevention and mitigation. Based on the Culmann model, a pair of important indicators to estimate the state of slope stability is the relief and slope angles. Considering the limit of field survey and the increasing requirements for identification over a large area, a new approach using the relief–slope angle relationship to identify rockfall source areas controlled by rock mass strength at a regional scale is proposed in this paper. Using data from helicopter-based remote sensing imagery, a digital elevation model of 10 m resolution, and field work, historical rockfalls in the Wolong study area of Tibet where frequent rockfalls occur are identified. A clear inverse relationship between the relief and slope angles of historical rockfalls enables us to calculate the rock mass strength of the landscape scale by the Culmann model and the relief–slope angle relationship curve. Other parameters used in our proposed approach are calculated by ArcGIS and statistic tools. By applying our approach, the potential rockfall source areas in the study are identified and further zoned into three susceptibility classes that could be used as a reference for a regional rockfall susceptibility study. Using the space partition of historical rockfall inventory, our prediction result is validated. Most of the rockfall source areas (i.e., 71.92%) identified in the validation area are occupied by historical rockfalls, which proves the good prediction of our approach. The dominant uncertainty in this paper is derived from the process of calculating rock mass strength, defining the specific area for searching potential rockfall source areas, and the resolution of the digital elevation model.