EFFECTS OF LOADING STRAIN RATE ON MECHANICAL PERFORMANCES OF SALT ROCK

Through the triaxial compression test of salt rock under different confining pressures and loading strain rates,influences of loading strain rate on salt rock compressive strength,axial strain,radial strain,Young s modulus and failure mode are analyzed.In the test scale of loading strain rate,it is found that the influencing characters of salt rock can be divided into three different stages,i.e.elastic stage in which loading strain rate has no effect on salt rock properties,preliminary plastic stage caused by compressive strength difference,and strain hardening stage caused by the stability of strength difference.The final result is that compressive strength increases with the increasing loading strain rate.Test samples under high loading rate have notable internal damage.Cracks appear in these samples are long and obvious which are different from the cracks under low loading rate.The uniaxial compression experiment is undertaken on the rock samples which have been loaded by triaxial compression test.It is found that the Young s modulus becomes smaller as the loading rate increases,so high strain rate leads to inattentive internal structure and causes more serious structural damage of salt rock.Comparing test results under different confining pressures and combining with uniaxial compression test results,it is found that confining pressure is the precondition of whether the loading rate has influence on properties of salt rock.The higher the confining pressure is,more obvious the influence of loading strain rate on mechanical performances of salt rock is.From the results of experiment,analysis of different strain loading rates of every stage in construction and operation of salt rock cavern in actual project,several beneficial suggestions are proposed.