The Tianjiaba landslide on the Hang Rui expressway was located in the south of Sinan County, Tongren City, Guizhou Province. From the night of 2 July to the morning of 3 July 2011, numerous house cracks, foundation subsidence, and surface cracks suddenly occurred in the Tudiwan and Tianjiaba villages on the north and south sides of the management area. Based on the field geological survey, drilling, pit exploration, surface displacement, fracture observation, and deep displacement monitoring data analysis the deformation characteristics and causes of the Tianjiaba landslide were comprehensively analyzed. In this study, the landslide was divided into three areas, in which fracture group 3 was the most severe. Among the ten inclinometer holes, the sliding surface displacement of No.8 inclinometer hole was the largest, i.e., 25 mm. The sliding surface slopes of fracture groups 1, 2, and 3 were small, i.e., 12.25°, 4.97° and 6.62° to 4.64°, respectively. The results showed that the displacement values of different positions of the landslide were different, and the ground displacement value was larger than the sliding surface displacement value. The maximum displacement of the ground was 242.68 mm, which is larger than the maximum displacement of the inclinometer hole. Because the displacement of the upper part was greater than that of the lower part, bulging cracks formed in the lower part of the landslide. When the displacement of the upper part was less than that of the lower part, tension cracks formed in the lower part of the landslide. According to the surface cracks and displacement values of inclinometer holes on the sliding surface, the landslide was in the initial sliding stage and filling the platform of the management area on the hillside was the main cause of the landslide.

This paper analyses the stability of the Duanjiagou landslide on the Bazhong to Guangan Expressway K134–K135 segment in China. The Duanjiagou landslide took place on 4 November 2015. In order to discover the cause of the landslide, we carried out field geological investigations. The indoor physical property experiments were performed by taking the undisturbed soil sample from the borehole cores. To study the strength of the soil, we carried out a saturation direct shear test and saturation residual shear test on sliding zone soil samples. According to the physical properties of soil and the saturated shear strength parameters of sliding zone soil, the stability was analyzed by the landslide force transmission method and numerical simulation method. The results showed that in the initial sliding stage, the safety factor obtained by using the average value of saturated shear strength parameters was in good agreement with the field observation situation. The landslide was at an unstable state. The softening of soil and roadbed excavation at the foot of the slope are the main reasons for landslides.

Xinjiang’s inland arid climate has led to widespread saline–alkali soils. Along with frequent strong earthquakes, they pose challenges to foundation and infrastructure construction. So, understanding the small-strain dynamic properties of saline–alkali soils is of scientifical and engineering significance. This study used resonant column and SEM tests to investigate the influence of microstructure on the small-strain shear modulus (G₀) of saline soil, considering variations in dry density and NaCl content. This study makes three distinctive contributions: (1) it provides quantitative evidence that NaCl (rather than Na₂SO₄) reduces G₀ in Taklamakan saline silty clay, with a critical inflection point at 10%—a finding opposite to the behavior of sulfate saline soils reported in previous studies; (2) it establishes a direct quantitative link between NaCl-induced macroporosity increase and G₀ reduction via the Young–Laplace equation, providing a mechanistic explanation at the pore scale; (3) it proposes a modified Hardin equation that explicitly incorporates NaCl content as a state variable, enabling practical prediction of G₀ for chloride saline soils in engineering design. Overall, these findings provide essential technical guidance for engineering design in regions affected by saline–alkali soils.