Multiscale hierarchical analysis of rock mass and prediction of its mechanical and hydraulic properties

TLDR

Engineering geological and hydro‑geological characteristics of foundation rock and surrounding rock mass are key determinants of underground engineering stability. The study introduces multiscale hierarchical digital rock‑mass models to represent rock‑mass structures across scales and their scale dependence. The authors define four scales—regional, engineering, laboratory, and microscale—and employ image analysis, geostatistics, Monte Carlo simulation, and a custom computer code to build and numerically analyze models that link down‑scale structures to up‑scale mechanical and hydraulic behavior. The proposed models enable rational and precise evaluation of rock‑mass mechanical and hydraulic properties, offering a unified, simple solution across scales.

Abstract

Engineering geological and hydro-geological characteristics of foundation rock and surrounding rock mass are the main factors that affect the stability of underground engineering. This paper presents the concept of multiscale hierarchical digital rock mass models to describe the rock mass, including its structures in different scales and corresponding scale dependence. Four scales including regional scale, engineering scale, laboratory scale and microscale are determined, and the corresponding scale-dependent geological structures and their characterization methods are provided. Image analysis and processing method, geostatistics and Monte Carlo simulation technique are used to establish the multiscale hierarchical digital rock mass models, in which the main micro- and macro-structures of rock mass in different geological units and scales are reflected and connected. A computer code is developed for numerically analyzing the strength, fracture behavior and hydraulic conductivity of rock mass using the multiscale hierarchical digital models. Using the models and methods provided in this paper, the geological information of rock mass in different geological units and scales can be considered sufficiently, and the influence of downscale characteristics (such as meso-scale) on the upscale characteristics (such as engineering scale) can be calculated by considering the discrete geological structures in the downscale model as equivalent continuous media in the upscale model. Thus the mechanical and hydraulic properties of rock mass may be evaluated rationally and precisely. The multiscale hierarchical digital rock mass models and the corresponding methods proposed in this paper provide a unified and simple solution for determining the mechanical and hydraulic properties of rock mass in different scales.