LAUSR

The strain rate-dependent mechanical behavior of shale is characterized using triaxial compression tests under a constant confining pressure of 50 MPa and axial strain rates $$\dot{\varepsilon }_{1}$$ε˙1 ranging from 5 × 10−6 s−1 to 1 × 10−3 s−1. This study is conducted on the Longmaxi shale from Dayou in China, which is predominantly composed of brittle minerals including quartz (55%), albite (15%) and cristobalite (3%). The experimental results show that higher axial loading strain rates $$\dot{\varepsilon }_{1}$$ε˙1 lead to higher elastic modulus and higher peak shear strength, both following exponential relationships with $$\dot{\varepsilon }_{1}$$ε˙1. When $$\dot{\varepsilon }_{1} \le 1 \times 10^{ - 5} {\text{s}}^{ - 1}$$ε˙1≤1×10-5s-1, failure results in a single linear fracture, whereas a more complex multiple crisscrossing fracture network is formed when $$\dot{\varepsilon }_{1} \ge 1 \times 10^{ - 4} {\text{s}}^{ - 1}$$ε˙1≥1×10-4s-1. Failure in shale specimens can be described by a damage parameter $$D$$D, which is strongly affected by the axial strain $$\varepsilon_{{1{\text{s}}}}$$ε1s. In addition, the strain rate $$\dot{\varepsilon }_{1}$$ε˙1 had different effects on $$D$$D, which also depends on axial strain $$\varepsilon_{{1{\text{s}}}}$$ε1s. Energy accumulation and dissipation are also closely related to $$\dot{\varepsilon }_{1}$$ε˙1 with the total absorbed energy $$U_{\text{A}}$$UA, the recoverable elastic strain energy $$U_{\text{A}}^{\text{e}}$$UAe and the dissipated energy $$U_{\text{A}}^{\text{d}}$$UAd at the peak stress increasing with $$\dot{\varepsilon }_{1}$$ε˙1. As for the total energy accumulation $$U_{\text{A}}$$UA, the recoverable elastic energy $$U_{\text{A}}^{\text{e}}$$UAe decreases while the dissipated energy $$U_{\text{A}}^{\text{d}}$$UAd increases with increasing strain rate.