A testing apparatus is introduced which can carry out both uniaxial compression tests and uniaxial tension tests on a same rock. This apparatus changes the situation of analyzing the test results from different rock samples under uniaxial compression and uniaxial tension respectively

which will lead to a wrong conclusion. And it also provides the possibility for studying the transitional characteristic of rock from being compressed to being sketched or from being sketched to being compressed. Furthermore

the deformation behavior of purple sandstone in Dayao Copper Mine is studied. The research indicates that the compressive elastic modulus of purple sandstone equals to the tensile elastic modulus

but the changes of Poisson's ratio in compression and that in tension are complicated. The tests also prove that rock compression and tension are not quite different courses. The deformation curve of unloading in compression joins continuously together with that of loading in tension.