Analysis and comparison of two types of ground fissures in Dali County in the Weihe Basin, China

Abstract

Dali County is located in the eastern Weihe Basin where frequent ground fissure disasters occur. Dali ground fissures are macroscopically part of the ground fissure group in the Weihe Basin and have caused serious damage to infrastructure and agricultural production in this area. In this paper, 25 ground fissures in Dali County are identified through investigation, and two typical ground fissures in Fengcun and Weizhuang are selected for research. Through field investigation, trench excavation, geophysical exploration, soil water content tests and collapsibility coefficient tests, the basic features, shallow structural characteristics, deep structural characteristics and genetic mechanisms of the two ground fissures are revealed. The strike of the Fengcun ground fissure is 45°, almost parallel to the Shuangquan-Linyi Fault; the length is 2 km, and the profile is ladder-like and extends deep with synsedimentary characteristics. The Weizhuang ground fissures are circular in plan view with a length of 315 m and trumpet-shaped in profile; they disappear in the paleosol layer. The mechanism of the Fengcun ground fissure is related to basin extension and fault activity. The ground fissures are the surface reflections of deep faults. The mechanism of the Weizhuang ground fissures is related to loess collapsibility and seepage. The Malan loess has differential settlement in collapsible and noncollapsible areas, and ground fissures are the boundary line for differential settlement of loess. Finally, based on the genetic mechanisms of ground fissures, Dali ground fissures can be divided into two types: tectonic and nontectonic.