Study on the effect of hydro‐chemical dissolution on shear properties of rock fractures using the improved discontinuous deformation analysis

Abstract

Hydro‐chemical erosion has critical effects on the short‐ and long‐term stability of fractured rock masses in subsurface engineering. Attempts have been made to study this water‐rock interaction process using numerical approaches. However, the majority of the existing approaches quantify the degradation based on the homogeneity hypothesis, which leads to unrealistic results in the case of rock mass with discontinuities. In this study, the hydro‐chemical degradation is represented through geometrical variation of a single crack and reflected in the modified bilinear constitutive model by introducing the hydro‐chemical damage factor. Then, discontinuous deformation analysis (DDA) method embedded in such improvements is chosen to implement the direct shearing process of the rock fracture after hydro‐chemical erosion. The results reveal that the peak shear strength decrease with the increase in the acidity solutions, and a logarithmic relation is found between the decreasing percentage of shear properties and soaking time, which are consistent with the laboratory results. Besides, based on the proposed method, the change in peak shear strength presents synchronism with the variation in the mineral ion and H+${H}^ + $ concentration, shown to be in good agreement with the basic understanding of the dissolution process. In addition, the failure patterns of the sheared samples under different normal stress are studied. This research provides an effective tool to quantify the hydro‐chemical damage from the microscale and will be a significant complement to the coupled numerical analysis of the water‐rock interaction process.

Study on Microscopic Characteristics and Rock Mechanical Properties of Tight Sandstone after Acidification–Supercritical CO2 Composite Action: Case Study from Xujiahe Formation, China

“…Compared with acid pressure, the combined action of thickener and acid pressure made the crack initiation and extension more obvious, leading to more micro-cracks around the main crack. Gao et al [15] used the discontinuous deformation analysis (DDA) method to study the effect of dissolution on the shear behavior of rock cracks. This research provides an effective tool for the micro-quantification of hydrochemical damage.…”