Distribution pattern and cause analysis of loess sinkholes along Pengyang section of Yinchuan-Kunming Expressway

The Yinchuan-Kunming Expressway section in Pengyang is marked by an exceptional development of loess sinkholes, which significantly compromise the stability of the roadbed and other structural elements. In particular, sinkholes near the roadbed and bridge abutments are susceptible to triggering landslides and collapse, thereby jeopardizing the integrity of the engineering project. A comprehensive analysis of the distribution patterns, causes, and expansion mechanisms of these sinkholes along the expressway was conducted. The findings indicate that sinkholes predominantly occur along the edges of plateaus, on both sides of gullies, at the heads of gullies, and behind landslide or collapse bodies, exhibiting forms such as vertical shafts, funnels, disc shapes, bead-like arrangements, and honeycomb patterns. The loess in Pengyang County, characterized by its loose structure, high porosity, well-developed vertical joints, strong collapsibility, and susceptibility to dissolution and erosion, constitutes the intrinsic factors facilitating sinkhole formation. Additionally, the region’s concentrated precipitation and terrain conditions are conducive to rainwater collection, infiltration, and erosion of slopes, and water plays a role in transportation and dissolution, representing the extrinsic factors. The synergistic effect of these intrinsic and extrinsic factors leads to the exceptional development of loess sinkholes in the Pengyang area.