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

A new testing technique is developed as an index creep device for evaluating time-dependent responses of rocks. Rock samples from Çankırı, Tuzköy in Nevşehir and Kağızman in Kars Provinces of Türkiye and Oya tuff from Tochigi Prefecture in Japan with well-studied time-dependent properties are selected for index creep tests. The impression creep devices developed are capable of applying tip pressure up to 433 MPa for an indenter of 3 mm in diameter for index creep testing technique. 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 creep test is explored. The most critical issue in creep tests is the determination of stress level. This issue is investigated through experimental, theoretical and numerical methods. It is proposed that 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 creep and index creep tests are quite comparable and similar type responses are observed and it is concluded that the impression creep technique can be utilized as an index creep test.