Abstract: This paper presents the study results on the red clay in Chongzuo area. The results show that after the evaporation and the migration of water in the red clay soil samples, cracks appear on the surface of the soil and inside the soil mass. The cracks on the surface are in a circular and irregular shape, and the cracks on the crosssection are in a wide upper and a narrow lower shape. After encountering the water, the water seeps into the soil along the cracks, causing the soil on the crack surface to collapse and fill the cracks with the water, resulting in soil softening and reducing the bearing capacity, which affects the normal use of the building structures. By studying the changes in the bearing capacity of the red clay samples under the natural moisture content and the soaking for 10 hours using the lightweight dynamic penetration testing and the plate load tests, it was found that the estimated bearing capacity based on the number of dynamic penetration tests is basically consistent with the reduction in the bearing capacity determined by the plates load tests. If the foundation excavation encounters the water during the construction, a light dynamic penetration test can be used to determine its degree of softening and to guide the construction, which has good reference value for the practical engineering.

Key words: Surface Wave Method, Bearing Capacity, Fissures, Dynamic Cone Penetration Tests, Plate Load Tests, Water Actions