Deep Penetration into Frictional Ductile and Brittle Materials.

摘要

The mooring of offshore platforms and tension piles may involve deep penetration into rocks. There is, however, a significant lack of the knowledge regarding deep penetration into a rock mass. The research, therefore, was intended to study the phenomena and mechanisms of deep penetration, first through experimentation and then, based on the experimental results, by developing models for frictional, ductile/brittle materials. In the experimental study, rapid and slow penetration tests and pullout tests were performed which involved a systematic variation of the testing conditions including brittleness of the material, confining conditions, joint conditions (orientation and spacing), nose shape of penetrator and penetration velocity. It was found that the brittle material was fractured due to penetration. A crushed zone near the penetrator, chipping at top surface and radial cracking were observed. By measuring the acceleration history in rapid penetration tests, the energy required to achieve a particular penetration depth was obtained. Through comparison with the results of slow penetration tests, it was also possible to assess the effect of penetration rate.