Development characteristics and mechanisms of damage-causing urban ground fissures in Datong City, China

Abstract

A set of widely developed ground fissures within the Datong Basin, northern China, have inflicted serious damage to farm fields, roads, houses, and building foundations in Datong City. Such emergence of large-scale ground fissures is rare in urban areas. The formation mechanisms of these features were therefore investigated in detail through surveying, mapping, trenching, drilling, and geophysical prospecting. The 11 fissures in Datong City are located on the hanging wall of the Kouquan fault (part of regional horst and graben terrain), and run approximately parallel, with a dominant strike of NE34°–70° and a maximum length of 5.5 km. These structures occur in clear zones with similar directions and lateral distributions on the surface. They possess evident synsedimentary fault characteristics, including y-shaped, trapezoidal, and traction structures in their profiles. The synergistic action of different tectonic factors and groundwater exploitation is responsible for fissure formation. Under the influences of regional tensile stress, upper mantle uplift, and fault block movement, activity along local faults created hidden fracture systems within the hanging wall. The over-exploitation of groundwater in the region subsequently accelerated fracture growth, and varying vertical compressibility of the strata on both sides of the local fault resulted in uneven subsidence on the surface, generating tensile zones and promoting the appearance of fissures at the edges of settlement funnels.