Continuous Solid‐Fluidization Transition Mechanism of Loess Mudflow: Insights From Laboratory Experiments and Implications for Geophysical Processes

Abstract Solid‐fluidization transition‐induced flow‐like events pose significant threats to both ecological systems and human society. This geophysical phenomenon undergoes a continuous and catastrophic solid‐fluidization‐solid retransition, which often leads to severe disasters. A series of flume and rheological tests were conducted to explore the continuous solid‐fluidization‐solid retransition mechanism of sedimentary loess. The results showed that the flow distance after phase retransition increased by 39.5% compared with the first flowslip distance. With increasing rainfall intensity, the moisture content during phase transition tended to decrease while the time required for reactivation lengthened. Rheological analyses revealed that the reduction and recovery of storage modulus exhibited by thixotropy is a crucial mechanism in the phase retransition of soil, and they have significant time‐concentration dependence. A higher soil water content leads to a longer structural recovery time and stronger thixotropy, which agrees well with the results of flume tests. Our experimental data N Sav and N Bag showed a positive power‐law relationship and had similar fitting coefficients to the field case data, indicating that our experimental results have successfully captured the kinematic and rheological characteristics of real mudflow events. This study suggests that thixotropy can be used to interpret complex phase retransition processes in mudflow and can also help to explain the hypermobility and reactivation of many large geophysical processes, such as pyroclastic flows.