In situ stress is an important parameter in rock mechanics, thus robust estimation of far-field stress to be used as boundary loadings for further rock engineering analysis based on the local in situ stress data seems indispensable. Here, as part of a preliminary investigation into this problem, we use the combined finite-discrete element method to examine how the mean of local stress tensors is related to the far-field stress. We have conducted a series of stress simulations on a model of a fractured rock mass subjected to various boundary loadings, and calculated the Euclidean mean of the stress data and compared them with the boundary loadings. The results shows that the Euclidean mean and boundary loadings are approximately equal, which gives us an indication that the Euclidean mean of the stress data can be a reasonable estimation of the far-field stress.
Unlike artificial materials like concrete and steel, natural materials such as rock masses are initially stressed in their natural state, mainly due to the weight of overlying strata and tectonic effects [1]. Thus, in situ stress is an important parameter in many aspects of rock mechanics, including rock engineering design, hydraulic fracturing analysis, rock mass permeability and earthquake potential evaluation [1–5]. In these stress-related applications, robust estimation of far-field stress based on the local in situ stress data seems indispensable. However, local values of the in situ stress field within a fractured rock mass may display considerable variability, and so determining the value of the far-field stress to be used as input or boundary loadings for further rock engineering analysis is difficult [1–3, 5].
Here, as part of a preliminary investigation into this problem, we use the combined finite-discrete element method (FEMDEM) to examine how the mean of local stress tensors is related to the far-field stress. We first explain the calculation of mean stress [6] and illustrate the rock mass model establishment for the FEMDEM simulation. Then, for the rock mass subjected to various boundary loadings, we calculate the means of stress data extracted from the model and compare these with the far-field stress. As a result we are able to give suggestions for the selection of appropriate far-field stress or boundary loadings for further rock engineering applications based on local in situ stress measurement data.
