Evaluation of Self-Boring Pressuremeter Tests in Boston Blue Clay

摘要

The research performed 'undrained' self-boring pressuremeter tests (SBPT) at two sites in a deep marine clay deposit of moderate sensitivity (Boston Blue clay) having a decreasing overconsolidation ratio with depth. The program involved 20 tests with the French PAFSOR and 14 tests with the English CAMKOMETER devices. The initial pressure recorded after self-boring was generally much less than the insitu total horizontal stress, perhaps mainly due to improper installation techniques. However, the Marsland-Randolph graphical iteration method yielded quite reasonable estimates, especially in the upper 'stiff' clay, and this technique should be further evaluated via SBPT programs in other clay deposits. Vaues of undrained shear strength obtained from elastic-plastic and various derived methods of analysis were very sensitive to the input data, often showed considerable scatter and generally exceeded the in situ shear strength appropriate for bearing capacity and stability analyses. In particular, derived peak strengths in the deep 'soft' clay were too high by a factor of two or more. However, most of the tests did give reasonable estimates of undrained shear modulus.