Study On Mechanical Properties Of Red Sandstone Under Uniaxial Impact And One - Dimensional Dynamic And Static Combined Loading

In order to study the dynamic characteristics of rock, red sandstone is chosen as the object of research,use the improved SHPB test device to conduct the indoor dynamic test (single axis impact and the one-dimensional static and dynamic combination test), analyse of the dynamic characteristics of the red sandstone from the aspects of the stress-strain curve, secant modulus, dynamic compressive strength, dynamic growth factor, energy-transferring law, failure mode, fractal feature and so on, come to the following conclusions:(1) The stress-strain curve of single axis impact and the one-dimensional static and dynamic combination test can be divided into three stages:elastic stage, yield stage, plastic stage. With different strain rates, the three stages have their own characteristics.In the uniaxial impact test, with the increase of the strain rate, the changes of the secant modulus of rock specimen generally appear the increasing trend. In the one-dimensional dynamic and static combination tests, under different axial compression, the secant modulus of the specimens do not change regularly with the strain rate, however, with the increasing axial pressure, the secant modulus take on the trend that increase first and then decrease;(2) In the uniaxial impact and one-dimensional static and dynamic combination test, the dynamic compressive strength of specimens show the obvious strain rate effect, increase with the increasing strain rate, but in one-dimensional static and dynamic combination test, when the strain rate is constant, with the increase of the axial pressure, the dynamic compressive strength will show the trend that increase first and then decrease;(3) In the uniaxial impact and one-dimensional static and dynamic combination test, absorption energy of red sandstone with the unit volume will increase with the strain rate and the incident energy, however, in one-dimension static and dynamic combination test, when the strain rate is constant, absorption energy with the unit volume can take on the trend that increase first then decrease with the increase of axial compression decreases;(4) In the uniaxial impact test, the failure modes of rock is tensile failure. In the one-dimensional dynamic and static combination test, the failure modes of rock is shear failure. Because of the different strain rates, there will be some differences. With the increase of strain rate, the degree of fragmentation of rock will be greater;(5) In the uniaxial impact and one-dimensional dynamic and static combination test, the rock fragmentation shows excellent fractal characteristics,the fractal dimension D of the rock values increases with the incident energy, that is, with the increase of the incident energy, the rock fragmentation is smaller.