The category re-distinguish of surrounding rock at Tai-Ning tunnel

The new classification for the surrounding rock has been made by demonstrating and comparing, according to the indices of characteristics of engineering geology, rock mass structure and structure plane, hydrogeology, velocity of longitudinal wave, coefficient of deformation, Poisso nsratio, internal frictional angle and coefficient of softness. Then reasons for the deviation in classifying surr ounding rock has been analyzed and the reference effect on the similar engineering investigation has been ensured.