Abstract: Three-point bending tests were conducted on laminated composite rock specimens composed of fine sandstone. A CCD camera was used for observation and a digital speckle correlation method was adopted. The mechanical characteristics of the contact surface were analyzed during the whole process of deformation and damage of the laminated composite rock. The results are as follows. (1) With the application of load, the horizontal strain fields on the surfaces of the upper and lower specimens show alternating tensile and compressive strain zones with vertical distribution, and this phenomenon is especially obvious near the interlaminar contact surface. (2) The overall interlayer sliding displacement was fluctuating. The value of interlayer sliding displacement gradually increased with a maximal slip value of 0.174 mm as the load increased. (3) The value of horizontal stress on the contact surface fluctuated due to varying interlayer contact condition. The vertical stress curve between layers was “V” shaped distribution. (4) The interlayer friction coefficient changed continuously during the loading process, and it reduced from 3.5 to 0.2 in the early sliding stage, and remained at 0.15 in the stable sliding stage. (5) The deformation energy density curves of the upper and lower layers have the same trend, and the contact surface deformation energy density reached the maximum value of 4.2 J/m3 at the peak loading moment. The above research results can provide useful reference for remote rock interface DIC monitoring and rock sliding study taking values.

Key words: laminated composite rocks, three-point bending test, contact surface, mechanical characteristics