TRIAXIAL TESTING STUDY ON DAMAGE CHARACTERISTICS OF MUDSTONE

This paper presents the triaxial test results of mudstone from the foundation of the Nanjing third bridge on Yangtse River. It is found that the failure pressure,the plastic deformation and the residual strength of the mudstone after subversion increase as the confining pressure increases. Then,it studies and analyses the relation between the damage soften parameters and the confining pressure,when the strength of rocks microunit is of the Weibull distribution and the strength of rocks microunit conformed to the MohrCoulomb strength criterion. Connecting with the stressstrain full procedure curves,the initial damage characteristic is discussed. The results indicate that the relation of logarithm of pressure and confining pressure of initial damage is linear. By studying on the relation between damage variable and main stress,it is found the relation of damage variable and main stress submits to a hyperbola model. The hyperbola model can be transformed into a linear equation. So the model parameters can be gotten by regressive analysis based on the test results. The results indicate F0 increases as the confining pressure increases,but m declines,which reflects the brittleness tolerance of the mudstone declines as the confining pressure increases．