Experimental observation and geophysical modeling of the hydrological effects on Pleistocene glaciation deposits susceptible to landslide

This paper highlights the efficiency of a light package of geophysical techniques to study the structure of fluvioglacial deposits susceptible to land sliding. The geophysical investigation unaccompanied with the geotechnical study cannot correctly characterize the geological features in landslide studies. This study presents the results of combined surface waves and electrical resistivity examination of the Humarri terrace in Northern Pakistan, intended to characterize the hydrological effects on moraines deposits and their relationship with slope failures. A blended survey design was applied to investigate a different slope section 3D electrical resistivity tomography was used to monitor the evolution of a sinkhole after irrigation and rainy seasons on the terrace. According to geophysical investigations, electrical resistivities and volume wave velocities yielded a more reasonable subsurface structure. They traced the existing subsurface deformation up to the depth of 30 m and suggested that excessive saturation in this section can cause slope failure. The subsurface images from the blended survey identified several irregular water-saturated strata patches embedded between compact strata. These saturated or partially saturated moraines can convert to debris and be driven down a slope by gravity after exceeding the saturation limits. The hydrology monitoring data suggests that the water concentration from rainfall and irrigation activities keeps the shallow soil layers saturated throughout the year. The waterlogged sediments boost the deformation of interconnected sinkhole families, cracks, and localized subsidence. Subsequently, excessive irrigation water and rainfall are causing sinkholes, damaging the community infrastructure, and posing a failure threat to the Humarri terrace.