Change of instantaneous strength of rock in uniaxial compressive creep test

In the former creep tests, the change of instantaneous strength of rock during creep is not measured. So it isn't known how the instantaneous strength changes in creep. By using the marble samples, the uni-axial creep tests are conducted to research the instantaneous strength change of marble during creep. First of all, with the standard cylinder marble samples, the initial uni-axial compressive strength is measured. Then, two types of axial stress are adopted for creep test. One is 0.88 times of the uniaxial compressive strength, and under the stress creep tests are conducted for 48, 96 and 240 hours respectively. The other is about 0.6 times of the uniaxial compressive strength, and under the stress, the creep only experiences the first stage of creep. After every creep test, the stress is not unloaded but increases to failure, so the different instantaneous uniaxial compressive strength of rock after experiencing different time period of creep is measured. The tests show that under the stress bigger than the long-term strength, the instantaneous uniaxial compressive strength increases apparently with the progress of creep, which can be bigger than the initial uniaxial compressive strength, and afterwards the strength gradually decreases. If the creep is under load less than the long-term strength, the instantaneous compressive strength after creep is also a little more than the initial compressive strength. At last, the micro-mechanism for strength change in creep is analyzed. The research is benefitial for understanding of the creep mechanism of marble and establishing the new creep model considering the strength changing property.