Abstract:

The rigid serve-controlled test machine and acoustic emission equipment are used to study the influence of space between 3D-cracks on the mechanical feature of mortar material; and the failure process of samples with pre-existing cracks is concluded. The analysis of complete stress-strain curves and AE data indicates that sample failure is due to the propagation and coalescence of cracks. Failure process of samples with pre-existing cracks could be divided into the following stages: microcrack initiation, initiation of pre-existing cracks, crack propagation and crack coalescence. The failure pattern is shear failure along single inclined plane. When the ratio of cracks space d and length of elliptic crack long axis 2c ranging from 0-1, as the ratio grows, the initiation stress and maximum stress of samples reduce. With the ratio d/2c growing from 1/3 to 2/3, the initiation stress and maximum stress fall suddenly, showing that this space scope is the sensitive range. When the ratio d/2c =1, the initiation stress and maximum stress of sample fall 22.48 % and 18.60 % respectively corresponding to the sample without pre-existing cracks. The ratio of initiation stress to maximum stress of all different samples ranges from 83.1 % to 78.9 %. As the ratio d/2c grows, the ratio of initiation stress to maximum stress declines, which indicates that as space d grows, the loading range between initiation stress and maximum stress increase.

Key words: mortar material sample, acoustic emission, space between cracks, initiation stress, maximum stress