Experimental Investigation of Soil Disturbance Effect on Bearing Capacity of Organic Soil

The model test investigations on the soft soils are usually carried out on samples prepared in the laboratory and assuming site conditions. However, such soils that are prepared in the laboratory only partially reflect the site conditions. Considering this gap in the literature, this study mainly focuses on the bearing capacity and settlement behavior of the undisturbed organic soil obtained by a novel block sampling technique. The disturbed organic soil prepared in the laboratory was investigated with large-scale model experiments for two different footing types (square and rectangular). Vane Shear testing (VST), Dynamic Cone Penetration (DCP) tests, and finite-element analysis (FEA) were performed. The average bearing capacity values of disturbed and undisturbed soil were 60.98 kPa–68.71 kPa and 108.18 kPa–110.89 kPa for square and strip footings, respectively. Bearing capacity reductions of up to 40% were determined on laboratory-prepared soils. The cone reached the required depth (450 mm) with three blows for disturbed soil, while it was reached with four blows for undisturbed soil. Likewise, the undrained shear strength obtained by the VST was determined as 22.16 kPa and 16.60 kPa for undisturbed and disturbed soils, respectively. Shear strength losses of up to 25% for disturbed soils were observed. The bearing capacity values obtained from FEA were comparable to those obtained with the model tests. It was concluded that the degree of degradation of organic soils in the laboratory significantly affects the bearing capacity of the soil.