Search

The advancement of a slender object into soil (to depths of 10s of metres) is of fundamental interest to Geotechnical Engineers. Considerable advances have recently been made in beginning to understand some detailed aspects of the fundamental behaviour for penetration in sand using physical models. In this project, a 180° axisymmetric model is developed, which allows viewing of soil movement as a circular penetrometer advances into the soil. The model was tested in a geotechnical centrifuge with digital photographic techniques used to track soil movement. A series of 10 centrifuge tests is reported. The soil displacement during pile installation was measured. The soil strain paths during installation were also calculated from the measured soil displacements. The stress along the pile shaft was also measured by strain gauges during the pile installation. The displacements show reasonable correspondence with circular (cylindrical) cavity expansion. The amount of displacement generally increases with penetration. After about 8 to 10 diameters of penetration, the amount of movement does not vary significantly with depth. After the probe passes there is little systematic movement. The magnitude of displacements drops quickly as the radial position increases. The influence of re-driving, soil density, gravity levels and probe tip shape was examined. Results reveal that displacements are much less in the re-driving test. The centrifuge acceleration has some influence on the displacement and strains. It is found that there is no significant deviation in displacement and strains for different soil density and probe tip shape.