Dynamic mechanical properties of dry and saturated concretes and their mechanism
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摘要: 采用分离式Hopkinson杆装置，对混凝土进行干燥和饱和状态下的SHPB实验，并与准静态实验进行对比。结果表明：干燥和饱和混凝土均具有明显的应变率效应，中等应变率条件下的应力应变曲线上升段比准静态的曲线陡；饱和混凝土动态强度提高的幅度接近干燥混凝土的2倍，具有更强的应变率敏感性；存在一个应变率临界值，仅当应变率大于临界值时，饱和混凝土的动态强度才大于干燥混凝土的的动态强度；基于实验结果，给出了不同饱和度混凝土强度与应变率的关系。Abstract: We carried out SHPB tests on dry and saturated concretes using split Hopkinson and they were compared with quasi-static mechanical tests. The results show that the dry and saturated concretes produce an obvious strain rate effect: the ascending part of the stress-strain curve at moderate strain rate is steeper than that of the quasi-static curve; the increasing amplitude of dynamic strength of the saturated concrete, which has a stronger sensitivity to the strain rate, is nearly twice as that of the dry concrete; and there is a threshold of the strain rate, i.e., it is only when the strain rate exceeds this threshold that the dynamic strength of the saturated concrete becomes stronger than that of the dry concrete. Based on the experimental results, the equation showing the relationship between the concrete strength and the strain rate at different saturations is established and given.
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Key words:
- mechanics of explosion /
- threshold of strain rate /
- SHPB experiments /
- concrete /
- Stefan effect
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图 1 大口径分离式Hopkinson压杆示意图
Figure 1. Schematic diagram of large diameter split Hopkinson pressure bar
图 5 干燥和饱和混凝土的应力应变曲线
Figure 5. Comparison of stress-strain curves of dry and saturated concretes
图 6 干燥与饱和混凝土峰值应变与应变率关系曲线
Figure 6. Comparison of peak strain-strain rate curves of dry and saturated concretes
图 7 干燥与饱和混凝土强度与应变率关系曲线
Figure 7. Strength-strain rate curves of dry and saturated concrete
图 8 干燥与饱和混凝土动态强度与应变率拟合
Figure 8. Strength-strain rate fitting curves of dry and saturated concrete
图 10 不同应变率条件下饱和混凝土裂隙中水的作用力示意图
Figure 10. Schematic force of water in saturated concrete cracks at different strain rates
表 1 准静态条件下的实验结果
Table 1. Results under quasi-static conditions
状态 σ0/MPa ε0 /s-1 干燥 49.84 0.006 19 0.000 4 饱和 36.17 0.005 01 0.000 4 
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