The Effect of Layering on Cone Resistance: Calibration Chamber Tests

摘要

The analytical study of Vreugdenhil quantified the long-recognised effect of adjacent soil layers of different stiffness on cone resistance, q_c. The solution, obtained under the large assumption of linear elastic behaviour was well supported by the three sets of experimental results found in the literature. However, it was clear that further experiments were required before the elastic results could be adopted with confidence in practice. This paper reports a set of calibration chamber experiments carried out with a mini-cone (1 cm~2). Four tests, all on three-layer systems of sand, gave experimental response within 10 percent of the elastic solution when the thin included layer was denser than the surroundingthick layers and 20 percent when the thin layer was looser. These results suggest that after further verification on a wider range of soils and soil states, the simple elastic solution should be able to be employed usefully in practice. They also provide a reference for the verification of more complete analytical solutions. Furthermore, the good agreement between the elastic solution and the recorded penetration resistance implies that the far-field elastic response has an important influence on the resistance offered to the cone by the immediate zone of plastic deformation. Presumably, this is due to the influence of the confining stresses imparted by the elastic region to the plastic zone.