|
Abstract The loading rate dependency of stress-strain curve at very low stress level in the post-failure region is investigated with three testing methods. A testing method，in which a single rock sample is loaded at alternating loading rate with a predetermined strain interval ，is applied to Sanjome andesite，Inada granite and Tage tuff. With this method，two stress-strain curves corresponding to the two loading rates can be obtained. Experimental results indicated that loading rate dependency of stress-strain curve was clearly observed up to the very low stress level in the post-failure region，where failure progressed considerably. Next，unloading-reloading cycles are repeated in constant loading rate test with Sanjome andesite and Inada granite；and unloading curves at many points along stress-strain curve are obtained. Stress-strain curve at slow loading-rate obtained in alternating loading rate test is shifted along the unloading curves，and then it overlapped on stress-strain curve at a fast loading rate. A new testing method，in which alternating two loading-rates and unloading-reloading cycles are repeated with a single rock sample，is proposed and applied to Sanjome andesite，Inada granite and Tage tuff. It is found that the new testing method is easy to conduct and suitable for investigating loading rate dependency of peak strength and that of post-failure region of rocks. The percentage of change of stress in post-failure region is almost equal to that of the peak strength.
|
|
Received: 05 February 2010
|
|
|
|
