Potential Squeeze of Open Drilled Shafts in Soft Clay

This paper describes the results of a study investigating the influence of soil shear strength, overburden stress, and shaft diameter on the squeeze susceptibility of an open shaft in soft clay. Both field instrumentation and finite element analysis were conducted. The inclinometer data from monitoring two shafts of different diameters showed that up to a particular depth in the same soil layer, noticeable lateral deformation was recorded; however, the magnitude was significantly greater in the larger diameter shaft than in the smaller diameter shaft. The finite element analysis showed similar results as observed in the field. Based on the data collected from field observations, in-situ tests, laboratory tests, and the finite element analysis, this study shows that there exists a relationship between the above mentioned variables and the potential for clay squeeze. A formula containing the shear strength, depth of excavation, and diameter of shaft was developed to provide an assessment of squeeze susceptibility. The results of this study can provide guidelines on the potential for shaft squeeze and indicate whether temporary steel casing or slurry will be required during caisson construction.