Mechanical behavior and constitutive model of cement-based grouted rock mass following high-temperature exposure
摘要
The mechanical properties of post-fire grouted surrounding rock play a critical role in ensuring tunnel safety and structural stability. However, there is limited research on the deterioration of mechanical properties in grouted surrounding rock exposed to high temperatures when treated with different grouting materials. This study systematically evaluates the mechanical behavior of grouted rock masses containing ordinary Portland cement (OPC), microfine cement (MC), and their composite (OPC–MC) after thermal exposure. Triaxial compression experiments are conducted on the grouted rock masses exposed to 25 °C, 200 °C, 400 °C and 600 °C. A thermal–mechanical–damage constitutive model is developed to characterize the mechanical response of post-fire grouted rock masses. The results show at 600 °C, the compressive strength of OPC-based grouted mass decreases by 52.22%, while that of MC- and OPC–MC-based grouted masses decreases by 31.11% and 43.48%, respectively. Below 400 °C, the compressive strength of OPC–MC-based grouted mass exhibits 73.9% and 16.4% higher than that of OPC- and MC-based grouted masses, respectively. Thermal damage mainly involved interfacial cracks at grout-rock boundaries, with MC-based grouted mass showing up to 10.9% mass loss. The proposed constitutive model demonstrates high predictive accuracy, with a coefficient of determination (R2 > 0.91). When OPC is replaced with MC at 50% by volume, the resulting grouted mass achieves mechanical properties comparable to, or even superior to, those of MC-based grouted mass, while maintaining excellent performance up to 400 °C.