Dynamic mechanical behaviors of pre-fractured sandstone with noncoplanar and unparallel flaws

Field rock masses with irregular flaws are often vulnerable to dynamic damage caused by excavation, drilling and earthquake. Investigating the mechanical behaviors of flawed rocks with dynamic loads is essential for the design of rock engineering facilities. However, the fracturing mechanism and fragment characteristics of flawed rocks have not been fully revealed, especially for brittle rocks with unparallel and noncoplanar flaws. This study systematically investigates the static and dynamic mechanical behaviors of sandstone with noncoplanar and unparallel flaws. A loading-rate dependence of the strength, fractal characteristics and energy dissipation of the pre-fractured sandstone is demonstrated. The dynamic strength of unparallel-flawed sandstones behaves more sensitive to the strain rate than that of noncoplanar-flawed sandstones. The failure modes of the specimens under static compression are primarily controlled by tensile cracks, while shear cracks mainly effect the dynamic failure patterns. Under low dynamic strain rates, the specimens mainly break into columnar or lamellar structures with a significantly non-uniform size distribution, accompanied by a relatively small amount of energy dissipation. At high dynamic strain rates, the flawed rocks experience severe damage and break into many small fragments with relatively uniform sizes, associated with comparably high energy dissipation.

Automated summary

The static and dynamic mechanical behaviors of sandstone with noncoplanar and unparallel flaws were systematically investigated in this study. It was demonstrated that the strength, fractal characteristics, and energy dissipation of the pre-fractured sandstone showed a dependence on loading rate. The dynamic strength of unparallel-flawed sandstones was found to be more sensitive to strain rate compared to that of noncoplanar-flawed sandstones. The failure modes of the specimens were primarily controlled by tensile cracks under static compression, while shear cracks had a greater effect on the dynamic failure patterns. Under low dynamic strain rates, the specimens mainly broke into columnar or lamellar structures with a significantly non-uniform size distribution and relatively small amount of energy dissipation. At high dynamic strain rates, the flawed rocks experienced severe damage and broke into many small fragments with relatively uniform sizes, accompanied by comparably high energy dissipation.