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Mechanical properties of concrete under confining pressure after cyclic loading
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摘要: 对不同围压(0, 2, 5, 10 MPa)下的水饱和混凝土试件，历经25次循环荷载作用后(荷载下限140 kN，上限260 kN，频率0.1 Hz)，进行了不同加载速率(地震荷载作用下的混凝土应变速率响应范围10-5/s~10-2/s)下的静动态常三轴抗压性能试验。分析了混凝土峰值应力、峰值应变以及损伤特性。结果表明：历经循环荷载后，随着加载速率的增加，混凝土峰值应力增大，峰值应变整体上逐渐增大，损伤变量D增长速度减缓；随着围压增加，混凝土峰值应力和峰值应变逐渐增大，损伤变量D增长速度降低，但损伤极限差值越来越大。基于上述试验结果，得到了历经荷载循环后混凝土动态峰值应力与围压、加载速率有关的经验计算式及历经荷载循环后混凝土动态峰值应变与围压、加载速率有关的经验式。Abstract: After 25 cycles of loads (the lower limit of load is 140 kN, the upper limit of load is 260 kN, the frequency is 0.1 Hz), the triaxial compression tests for different confining pressures (0, 2, 5, 10 MPa) of water saturated concrete under different loading rates (the response range of strain rate of concrete under seismic load is 10-5/s~10-2/s) are carried out, and the peak stress and peak strain of concrete and damage characteristics are analyzed in this study. The analysis results show that after cyclic loading: ① with the increase of the loading rates, the peak stress and the peak strain of concrete increase gradually, and the growth rate of damage variables slows down; ② with the increase of the confining pressures, the peak stress and the peak strain of concrete increase gradually. The growth rate of the damage variables is slowing down, but the D-value of damage limit is becoming larger. Based on the experimental results mentioned above, an empirical formula for the dynamic peak stress of concrete with the confining pressures and loading rates after cyclic loading is obtained from the experimental tests. And an empirical formula for the dynamic peak strain of concrete with the confining pressures and loading rates after cyclic loading has also been got based on the above test results.
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Key words:
- concrete /
- water environment /
- confining pressure /
- cyclic load
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图 1 围压2 MPa下加载速率10-5/s~10-2/s时试件的破坏
Figure 1. Failure of test specimen under 2 MPa confining pressures with loading rate from 10-5/s to 10-2/s
图 4 不同加载速率及不同围压下混凝土的峰值应力增幅对比
Figure 4. Comparison of peak stress increase of concrete under different loading rates and different confining pressures
图 5 峰值应力增加幅度与加载速率的关系
Figure 5. Relationships between amplitude of peak stresses and loading rates
图 9 峰值应变增加幅度与加载速率的关系
Figure 9. Relationships between amplitude of peak strains and loading rates
图 12 不同围压下损伤变量D随加载速率的变化
Figure 12. Changes in damage variables with loading rates under different confining pressures
图 13 不同加载速率下损伤变量D随围压的变化
Figure 13. Changes in damage variables with confining pressures under different loading rates
表 1 混凝土峰值应力统计
Table 1. Concrete peak stress statistics
围压/MPa 峰值应力/MPa 加载速率/10-5s-1 加载速率/10-4s-1 加载速率/10-3s-1 加载速率/10-2s-1 0 22.28/- 23.90/7.27% 26.87/20.60% 31.59/41.79% 2 28.08/- 31.30/11.47% 34.44/22.65% 41.18/46.65% 5 32.79/- 37.98/15.83% 46.24/41.02% 50.93/55.32% 10 34.46/- 41.33/19.94% 50.19/45.65% 59.96/74.00% 注：“/”前数值为峰值应力，“/”后数值为相对于第1列的增幅。 
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表 2 混凝土的峰值应变
Table 2. Peak strain of concrete
围压/MPa 峰值应变/10-3 加载速率/10-5s-1 加载速率/10-4s-1 加载速率/10-3s-1 加载速率/10-2s-1 0 3.330/- 3.841/15.32% 4.146/24.50% 5.155/54.80% 2 4.005/- 4.182/4.40% 5.289/32.05% 7.013/75.10% 5 4.724/- 4.370/-7.50% 6.774/43.39% 10.866/130.03% 10 4.579/- 5.263/14.94% 10.500/129.29% 12.274/168.03% 注：“/”前数值为峰值应变，“/”后数值为相对于第1列的增幅。
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