Characteristics and mechanism of the loess liquefaction triggered by the M8.0 earthquake in 1695, Linfen City, China

In 1695, a magnitude 8 earthquake in the Linfen Basin triggered large-scale sliding of sandy soil layers in Butou Village, Linfen County, splitting the area into eastern and western villages. This study systematically investigates the characteristics and mechanisms of loess liquefaction during the Linfen earthquake through dynamic triaxial tests and microstructural analysis on six groups of saturated loess samples. The liquefaction potential of loess in the study area under different depths and seismic intensities was evaluated using a discriminant method for saturated loess liquefaction. The results indicate that pore pressure and strain increase simultaneously in the initial stage, followed by a rapid strain increase with lagging pore pressure response. After liquefaction, the microstructure undergoes reorganization: primary overhead pores are replaced by irregular connected channels, pore morphology tends to become more irregular, and structural indices such as apparent void ratio and fractal dimension generally increase. The stress path shifts significantly leftward with increasing dynamic stress, accompanied by accelerated decay of effective stress, indicating that high dynamic stress levels rapidly damage the soil skeleton and promote faster liquefaction. Under dynamic loading, structural instability of loess triggers a sharp rise in pore water pressure and loss of effective stress, ultimately leading to liquefaction failure through hydro-mechanical coupling.