Weibo Zhou

Bio: Weibo Zhou is an academic researcher from Wuhan University. The author has contributed to research in topics: Groundwater & Hydraulic fracturing. The author has an hindex of 4, co-authored 4 publications receiving 269 citations.

Distinct element modeling of strength variation in jointed rock masses under uniaxial compression

Abstract: Rock masses exhibit strong anisotropy due to the structure of fracture networks embedded within the mass. We use a particulate discrete element method to quantitatively investigate the effect of spacing and inclination angle of the joints on anisotropic strength under uniaxial compression. In all of the numerical models, the intact rock masses are represented by the bonded particle model, and the joint planes are simulated by the smooth-joint model. Observations are made of the evolving stress–strain curves relative to the distribution and orientation of micro fractures. Apparent from this is that: (1) for the same fracture spacing, the strength and deformation parameters of jointed rock masses change in a “U” shaped curve when plotted against an increase in the inclination angle of the joints. The maximum value occurs at the inclination angles of 0° and 90°, and the minimum value occurs at an inclination angle of 40° or 50°; (2) for the same joint spacing, the failure mode of the jointed rock mass with different joint inclinations can be classified into three categories: splitting tensile failure, shear sliding failure along the joint surface and mixed failure of the two modes above; (3) for the same joint inclination angle, the normalized compressive strength and normalized elastic modulus both increase with an increase of the normalized joint plane layer spacing.

Hydrodynamic Behaviors and Geochemical Evolution of Groundwater for Irrigation in Yaoba Oasis, China

Abstract: The Yaoba Oasis is an irrigated cropland entirely dependent on groundwater; previous investigations (1980–2015) revealed an over-abstraction of groundwater and deteriorating groundwater quality. For further exploring the hydrodynamic behaviors and geochemical processes of groundwater during the irrigation season, groundwater samples were collected and analyzed using different techniques including classical statistics, correlation analysis, Piper diagrams, and Gibbs diagrams. The results indicated that Na+, K+, SO42− and Cl− were the main ions in groundwater, which were significantly correlated with TDS. The water–rock interaction is manifested by the precipitation of calcite and dolomite and the dissolution of rock salt and gypsum as an increase in TDS related to evaporation. In addition, the increasing complexity of hydrochemical type is caused by the rapid variation of hydrodynamic regime, irrigation and evaporation, which are subjected to the constraints of salty water intrusion from the desert salty lake and infiltration of irrigation return flow. Existing wells should limit overexploitation to halt the decline in groundwater levels and cut down irrigation water to reduce the risk of groundwater contamination and restore ecological balance in desert oasis.

Investigating Hydraulic Fracturing Complexity in Naturally Fractured Rock Masses Using Fully Coupled Multiscale Numerical Modeling

Abstract: Naturally fractured rock mass is highly inhomogeneous and contains geological discontinuities at various length scales. Hydraulic fracture stimulation in such a medium could result in complex fracture systems instead of simple planar fractures. In this study, we carried out fully coupled multiscale numerical analysis to investigate some key coupled processes of fluid-driven fracture propagation in naturally fractured rock mass. The numerical analysis follows the concept of the synthetic rock mass (SRM) method initially developed in the discrete element method (DEM). We introduce a total of five case study examples, including fracture initiation and near wellbore tortuosity, hydraulic fracture interaction with natural fractures, multi-stage hydraulic fracturing with discrete fracture network (DFN), in-fill well fracturing and frac hits after depletion-induced stress change, and induced seismicity associated with fault reactivation. Through those case studies, we demonstrate that with an advanced numerical modeling tool, the complex fracturing associated with hydraulic fracturing in naturally fractured rock mass can be qualitatively analyzed and the extent of various uncertainties can be assessed.