ULTIMATE BEARING CAPACITY OF COLLAPSING KHON KAEN LOESS

Many researchers have found that Khon Kaen loess is collapsing soil with a severe degree. Khon Khaen loess, as classified as silty sand (SM) or clayey sand (SC), is a windblown deposit with a honeycomb structure. Therefore, the increasing degree of saturation is the cause of decreasing shear strength parameters and increasing settlements of Khon Kaen loess. This study evaluated the bearing capacity of undisturbed Khon Kaen loess between wet and dry conditions by the plate bearing test. Besides, the undrained shear strength parameters (cohesion, c, and friction angle, φ) between saturation and dry samples were also examined by the triaxial test under the unconsolidated undrained conditions. The undrained shear strength of undisturbed dry Khon Kaen loess was also investigated from the unconfined compression test. Due to the low degree of saturation, the initial matric suction was observed from soil-water characteristic curves (SWCCs) by the pressure plate test. The plate bearing result showed that the ultimate bearing capacity of Khon Kaen loess, for which the saturation degree is higher than 45%, is about 35 kPa. The ultimate bearing capacity of Khon Kaen loess at 8% of saturation degrees was beyond 1,100 kPa. There is also an excellent relationship between the undrained shear strengths from the triaxial UU-test (c and φ) in a residual regime and unconfined compressive strength with a matric suction. Besides, the prediction using Terzaghi’s theory and undrained shear strength from the unconfined compression test gives an appropriated ultimate bearing capacity rather than the general bearing capacity equation for soil compressibility.