Earth fissures developed within collapsible loess area caused by groundwater uplift in Weihe watershed, northwestern China

Abstract

Abstract Earth fissures are geological hazards that frequently occur all over the world and greatly threaten the safety of people’s property and lives. This paper reports a case from a typical agricultural town in the Weihe watershed, northwest (NW) of China, Dali, which has been severely affected from earth fissures in recent years. A comprehensive survey was made on the geometric characteristics of the earth fissures developed in the study area through field investigations, trial trenches, boreholes, exploratory wells, and laboratory tests. The study indicates that fourteen nearly parallel fissures have developed in the area, with a fissure to fissure space of 140–350\u202fm, and a maximum length of any of the given fissures of 500\u202fm. The underlying faults, loess joints, and the Quaternary unconsolidated and collapsible sedimentary loess provide a favorable geological condition for the occurrence of the earth fissures. From 2003 to 2012, the groundwater level in the area rose about three meters due to agricultural irrigation and leakage of a water diversion canal. Collapsible deformation occurred in the loess, while seepage erosion expanded the original joints in the soil. The earth fissures occurred resulting from multiple geological environmental forces and human activities.