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Abstract To investigate time-dependence behaviors of compacted specimens，loading rate-dependency of the specimen in uniaxial compression was investigated in this study. A rock specimen was，at first，completely fractured and then compacted in a steel cylinder. After pushed out of the cylinder，the compacted rock specimen was loaded in the alternating loading rate test，in which a single rock specimen was loaded at two alternating loading rates with a predetermined strain interval ，to obtain two stress-strain curves corresponding to the two loading rates to investigate the loading-rate dependency accurately. It was found that strength recovery was remarkable for Tage tuff，Kimachi sandstone and Kawazu tuff，the uniaxial compressive strengths increase with the maximum axial load in the compaction test. But strength recovery was poor for Sanjome andesite under the testing conditions. In the alternating loading rate test，stress fluctuated with alternating loading rates through the whole test. For the four rocks，when the maximum axial load in the compaction test was large，loading-rate dependency of uniaxial compressive strength of the compacted specimens was found to be consistent with the intact ones. When the maximum axial load in the compaction test was small，the extreme values ， of parameter n of loading rate-dependency were calculated. Parameter n of the intact specimen lied in the maximum and minimum ，and did not differ too much. The results indicate that it is expectable for strength recovery to occur for rocks in the excavation disturbed zone after properly being supported for a long time. And time dependency of fractured rock around an underground opening was similar to that of the intact surrounding rock mass. It will be reliable to use the same parameters in the constitutive equation for rocks in the intact and excavation disturbed zones，to simplify numerical simulation of the time dependency behaviors of underground structures.
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Received: 25 June 2010
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2011, Vol. 30 
