Utilization of Impression Creep Tests as Index Testing Technique in Rock Mechanics and Rock Engineering

Impression creep devices capable of applying a tip pressure up to 134 MPa for an indenter of 3 mm in diameter as an index creep testing technique was developed by the authors. In this study, a new monitoring system utilized in the impression creep devices is described and its utilization for evaluating creep responses of rock salt samples from Çankırı and Tuzköy in Nevşehir Provinces of Turkey and Oya tuff from Tochigi Prefecture in Japan are presented and discussed. The experimental results obtained from impression creep tests are compared with those from conventional creep tests and the suitability of impression creep tests as an index test is explored. The most critical issue in creep tests is the determination of stress level. This issue is investigated theoretically and experimentally. It is suggested the short-term impression test can be utilized for determination of the stress level in impression creep tests. The experimental results clearly demonstrated that both conventional and index tests could be quite comparable and similar type responses are observed and it is concluded that there is a high possibility for the utilization of the impression creep as an index creep test.