The applications of in-situ geological mapping and 2D-resistivity image exploration in the case of the colluvium slope are discussed. Based on a study of high-quality borehole cores newly drilled, the records of excavation profiles, and with reference to the previous geological reports, we delineated in detail the up-date geological information about the subsurface soil and rock strata, the geological structures, and some hydrogeological characteristics of the foundation site and its vicinity campus area for the new library building. This detailed geological information are important both for the engineering purposes of the building construction and for future campus slope stability evaluations. Two new significant findings are important and worthy of note. Firstly, a new oblique-slip fault (A fault) striking northwest parallel to the south side of the University Avenue is mapped, which extends coincidently with the trace of slope gradient changes and has obvious effects on groundwater behaviors. Secondly, there exist many bedding slips in the rock strata, especially ubiquitously developed in the thin interbeds of sandstone and shale underlying the thick sandstone beds. These well-developed bedding slips indicate that the rock masses have slid off each other in the past, representing the weakest planes in rock masses, and will slide off if the slope fails further in the future. Therefore, these pre-existed bedding slips will play a key role in slope stability.
Huafan University is situated on a dipslop of Miocene formation composed of interbeds of sandstone and shale. The elevation of the sloping surface varies from 500 to 550 meters. For purposes of slope stability evaluation and hazard mitigation, a series of studies, including surface geological mapping, subsurface investigation of borehole cores, and geophysical 2D-resistivity profiling have been carried out. Results of these extensive studies reveal that the main campus area is truncated by two intersected faults of different properties, and many bedding slips developed in underground bed rocks.
