Abstract: The concrete specimens with diameter of 300mm,height of 600mm, were preprocessed under 0 cycle,10 cycles,50 cycles,100 cycles,200 cycles of pore water pressure(upper limit of pore water pressure for 3MPa,the lower limit for 1MPa) .In order to study mechanical properties of concrete under different cycles of pore water pressures and different strain rates, we carried out conventional triaxial(σ₂=σ₃≥σ₁) compressive tests for these specimens under four strain rates(10^-5/s,10^-4/s,10^-3/s,10^-2/s)with confining pressure of 3 MPa. The results show that 1) with the increasing strain rate,the peak stress of concrete increases and the peak strain shows increasing trend. 2) Before 100 cycles of pore water pressure,the peak stress gradually increase, but after that the peak stress tends to decrease, so the peak stress of concrete changes by phase with the increasing cycles of pore water pressure. Variation of peak strain is irregular, whereas elastic modulus tends to decrease with the increasing cycles of pore water pressure.

Key words: concrete, cyclic pore water pressure, peak stress, strain rate, elastic modulus