Characteristics and genesis mechanism of ground fissures in Taiyuan Basin, northern China

Since the 1980s, ground fissures in the Taiyuan Basin have experienced blowouts, resulting in a significant but hidden danger to cities in the Basin. This paper describes the plane and damage characteristics of the ground fissures based on the findings of field investigations and mapping. Most ground fissures in the Basin were determined as linear with pinch-out reappearances on the surface. They were characterized by both horizontal tension with maximum widths and vertical offsets of up to 40 and 15 cm, respectively. The ground fissure strikes in the Basin were observed to be consistent with those of nearby active faults and the long-axis direction of the groundwater depression funnel. The roads and houses that lie across the fissures were determined to be the most affected by ground-fissure disasters in the Basin. The primary damage modes for the roads were vertical offset and surface collapse, whereas buildings experienced foundation failure and tensile damage. Profiles obtained through geological drilling and trench exploration further revealed obvious tension and synsedimentary characteristics of the ground fissures correlated with existing faults. Correlation analysis shows that the formation of ground fissures in Taiyuan Basin is mainly related to faults and excessive groundwater extraction. Theoretical analysis revealed that the size and activity of ground fissures in the Basin were positively correlated with four factors-the dip of faults in an area, regional tensile stress, difference between the thicknesses of aquifers on either side of a fault, and groundwater exploitation. The significant increase in ground fissure activity since the 1980s mainly reflects uncontrolled groundwater discharge. Hence, prevention of excessive groundwater exploitation in the Basin would mitigate the destructive effects of the ground fissures.