Development Characteristics and Formation Mechanism of Landslides in Guojia Town, Qin’an County

This study takes the landslides in Guojia Town, Qin'an County as the research object. Through field geological surveys, drilling, it systematically investigates the development characteristics, formation mechanisms, and disaster modes of 25 landslides at the township scale. The results show that tongue-shaped medium-layer loess landslides are the predominant type (20 sites, 80 %), with the severity of deformation and damage decreasing from the front to the rear of the landslides. Loess landslides are primarily controlled by the maximum shear stress zone within the slope; under long-term weathering and rainfall infiltration, the shear zone progressively develops into a continuous sliding surface. These landslides tend to move rapidly during failure and generally stabilize after sliding. Loess-mudstone interface landslides are characterized by groundwater accumulation at the loess-mudstone contact, where the underlying mudstone top forms a weak structural zone. These landslides typically exhibit slow creep along the contact surface during rainy seasons or wet years. Loess-mudstone composite landslides are driven by the coupling of self-weight stress and long-term groundwater action; rainfall infiltrates along cracks to the mudstone contact, causing a sudden reduction in shear strength at the soil-rock interface, with sliding surfaces often initiating along joints within the bedrock. The disaster modes of landslides in the town are classified into two types: “slide-tension cracking type” and “creep-tension-shearing type,” with damaging effects on structures and farmland categorized as either “tensile failure” or “burial or toppling failure.” Finally, graded mitigation measures are proposed according to different landslide types and threat levels. The results provide a scientific basis for the early identification of potential landslide hazards and the formulation of disaster prevention strategies.