Karst ground collapse, a geological disaster in karst areas characterized by the sudden subsidence of surface rock and soil, poses significant risks to human life and property owing to its abrupt and frequent occurrence. Karst ground collapses can be classified into soil-cave-type and hourglass-type, based on the viscosity of the overlying layer. Among these, the hourglass-type presents a higher collapse risk owing to the lack of cohesive forces in the overlying layer. This study focused on hourglass-type karst ground collapse, utilizing physical model tests and the discrete element numerical simulations to develop and validate a collapse model. The physical model tests reproduced the collapse process and provided insights into its underlying mechanism. Numerical simulations were employed to evaluate the effects of karst channel conditions and drilling-induced vibrations on hourglass-type collapses. The results indicated that although the length of the karst channel had minimal impact on collapse speed and pattern, a wider karst channel resulted in a faster collapse and a larger final collapse pit. Moreover, vibration loads increased the collapse speed, shifted the collapse pit towards the vibration source, and expanded the scale of the collapse, thereby amplifying the overall damage extent.

The Jishishan M(s)6.2(M(w)6.0) Earthquake occurred on December 18th, 2023 in Gansu province was a small-scale thrust strong event (M >= 6) that caused significant casualties. After rapid inversion of rupture process, we performed joint inversions of seismic moment tensor and rupture process, and then compared and analyzed the fault parameters of this earthquake. On this basis, we discussed the disaster mechanisms related to the source process by determining the radiated seismic energy, and obtained the source characteristics within a broad frequency band. The results show that the earthquake fault is more likely to dip to the east. The major rupture area is located between Jishishan County and Dahejia Town, spatially consistent with the meizoseismal area indicated by the intensity distributions. The hanging wall effect, the Doppler effect of the rupture extending towards the northwest and shallower areas, and the amplification of high-frequency waves in shallow soil layers are likely the main source factors for the severe earthquake damage.