Experimental study and mechanism analysis of permeability sensitivity of mechanically damaged concrete to confining pressure

This study experimentally examined variations in the permeability of mechanically damaged concrete under the application and relaxation of confining pressure and investigated the mechanism of the variation from the perspective of pore structure. The results showed that mechanical damage significantly altered the pore structure of concrete specimens, and as a result of micro-cracking the porosity increases above 0.1 micro metre in size. During the loading phase, the permeability gradually decreased with increasing confining pressure, the plot of which could be divided into three segments-sensitive, transition, and insensitive segments. In the unloading phase, the permeability was gradually recovered with the relaxation of the confining pressure. Permeability values during the relaxation were lower than those during pressure application. This is related to the partial opening of microcracking and pore, while the deformed microcracking and pore cannot be fully recovered. The confining pressure changes the pore structure dominated by mesopores into micropores.