Dichotomy for stress-strain curves of sandstone is proposed to study staged features qualitatively with Lyapunov theory of chaotic dynamics. As former parts of all stress-strain curves of jointed sandstones are in chaotic state

the complicated system evolves only in nonlinear state. After ultimate limit

eighty-five percent of joint systems are in orderly state

which states that transfixed jointed sandstone has destroyed in macro state. Term of joints’ transfixion may be longer as the minimum initial stress increases. Then destructive state of sandstone after ultimate strength may be stepped decrease. If strain after ultimate strength is two-third of the complete strain

system state in the stage may dominate whole evolving state of joint system.