Experimental Study On The Behavior Of Large Aggregate Concrete Under Triaxial Compressive Dynamic Stress States

Concrete is the most widely used material in civil engineering, large aggregate concrete is one kind of concrete which is mainly used to build hydraulic structures such as dams, sluices, embankments and so on. During the course of its usage, concrete in hydraulic structures is usually under different stress states namely:biaxial tension-compression, biaxial compression-compression, triaxial tension-compression-compression, triaxial compression-compression-compression stress states, both the stress state of concrete and the loading rate should be fully considered in the nonlinear analysis of hydraulic structures. The loading rate is less than10-5/s usually, but it will be between10-4/s to10-2/s when earthquake occurs. So studying on the multi-axis mechanical properties of large aggregate concrete and wet-screened concrete can provide experimental basis for the nonlinear analysis of hydraulic structures.So far, experimental studies on mechanical properties of large aggregate concrete and wet-screened concrete have been proceeded by a lot of scholars, they are mainly about the uniaxial mechanical properties under static and dynamic loading, multi-axis mechanical properties under biaxial tension-compression, biaxial compression-compression and triaxial tension-compression-compression stress states, however, no studies have been carried out on the mechanical properties of large aggregate concrete under triaxial dynamic compression-compression-compression stress states. Dynamic triaxial compressive tests on large aggregate concrete and the corresponding wet-screened concrete were carried out in this article based on the National Natural Science Foundation of China (51079019) and the State Key Program of National Natural Science Foundation of China(90815026), the specific researching contents and conclusions are summarized as follows:(1) Dynamic uniaxial compressive tests were carried out, the effect of strain rate on uniaxial compressive strength of large aggregate concrete and the wet-screened concrete was investigated, the relationship between uniaxial dynamic compressive strength and strain rate is proposed.(2) Dynamic triaxial compressive tests on cubic specimens of large aggregate concrete were carried out, but failed to get the ultimate triaxial dynamic compressive strength due to the limited loading ability of the test system. Dynamic uniaxial compressive tests were carried out on the large aggregate concrete damaged by previously loading it twice with triaxial compressive loads applied at different loading rates, the effects of loading history and loading rate on the uniaxial dynamic compressive strength of large aggregate concrete are analyzed.(3) Dynamic triaxial compressive tests on cubic specimens of wet-screened concrete were carried out, the experimental results show that the triaxial compressive strength of wet-screened concrete increases differently at different stress ratios and increases with an increase in the strain rates. The relationship between triaxial dynamic compressive strength and strain rate and an octahedron stress space failure criterion for wet-screened concrete are proposed.