Study On Dynamic Mechanical Properties Of Concrete Considering Pore Water Effect

Concrete materials are widely used in civil buildings and military protection engineering.During service,concrete structures may bear strong dynamic loads such as explosion and impact.In addition,there are significant differences in the long-term water saturation of concrete in different natural environments and humid environments.The static and dynamic characteristics of concrete materials with different moisture content are also significantly different.In this paper,through the static and dynamic material tests of concrete with different saturation under various strain rates,the static triaxial compressive properties,dynamic uniaxial tensile properties and dynamic uniaxial compressive properties of concrete considering pore water effect are studied.The main research results and conclusions are as follows:(1)The effect of pore water on static triaxial compressive strength is studied.And the axial static strength criterion of concrete with different saturation under different confining pressure is proposed.After applying confining pressure of 0.2f_c and 0.4f_c to cubic concrete specimens by true triaxial electro-hydraulic servo test system,the axial compression test was carried out.It is found that the strength of saturated concrete increases more obviously under the same confining pressure than dry concrete.(2)The effect of pore water on dynamic tensile behavior of concrete is studied.And the dynamic increasing factor equation of tensile strength of concrete with different moisture content is established.Instron testing machine was used for dynamic split ting tensile tests in the range of strain rates from 0.1to 40 1/s,and the results show that the viscous effect produced by pore water will strengthen the dynamic tensile strength of concrete and significantly improve the strain rate effect of concrete when the strain rate is lower than 3 1/s.However,when the strain rate is higher than 3 1/s,the strain rate effect of concrete with different saturation tends to be similar,and the strain rate effect of the material affected by the failure mode begins to play a leading role,and the viscosity of pore water is no longer obvious.(3)The effect of pore water on dynamic compression behavior of concrete is studied.And the dynamic increasing factor equation of compressive strength and elastic modulus of concrete with different moisture content are established.Dynamic compression tests were carried out by means of the split Hopkinson pressure bar with strain rates ranged from 45 to 170 1/s.The experimental results indicate that pore water will reduce the strain-rate effect of concrete dynamic compressive strength and elastic modulus.Pore water pressure has hydraulic splitting effect on concrete materials.The dynamic increasing factor of compressive strength and elastic modulus of fully dry concrete are greater than those of fully saturated concrete.