Experimental Research On Rock Deformation Characteristics And Deformation Localization Evolution Based On 3D-DIC Technology

The mechanical properties of rocks are influenced by many factors,such as the composition and structure of rocks,moisture content and confining pressure,etc.Rock mechanics test is the most important method to study the mechanical properties of rock.Rock mechanics workers conduct uniaxial and triaxial compression tests under different conditions through laboratory tests to study the strength and deformation characteristics of rocks,and monitor the damage and failure process of rocks by means of various advanced equipment.Based on Jingkou sandstone,raw coal,Emochi andesite and Ogino tuff as research objects.through triaxial compression tests of rocks under different confining pressures and moisture conditions,the effects of confining pressures,moisture conditions and lithology on rock deformation characteristics and deformation localization evolution are analyzed.The main research work and conclusions are as follows:(1)Before the peak stress,the strain distribution on the surface of rock specimens under different test conditions is uniform,and the deformation increases at an approximate constant rate.The deformation concentration area appears near the peak stress,but the strain inside and outside the deformation concentration area were similar at the moment.After the peak stress,the strain in the deformation concentration area increases rapidly,forming the deformation localization zone,and finally in the deformation concentration area.Macroscopic fracture cracks occur at the location of deformation localization zone.(2)The strain of virtual strain gauge at different positions of rock specimens under different test conditions is basically consistent and approximately linear growth before the peak stress.The deformation of rock specimens is more uniform.After the peak stress,due to the different damage and failure conditions of specimens at different locations,there is greater separation.The difference of principal stress-radial strain curve at different locations is more obvious,which means the generation of uniform deformation.(3)By arranging virtual strain gauges inside and outside the deformation localization zone,the stress-strain curves inside and outside the zone are obtained,which are consistent before the peak stress.After the peak stress,the strain in the localization zone increases rapidly and continuously,resulting in large plastic deformation.The strain outside the localization zone has a certain degree of deformation rebound or basically remains unchanged,which means after the peak stress of specimen deformation is mainly concentrated in the deformation localization zone.(4)With the increase of confining pressure,the starting stress of Emochi andesite increases linearly and the starting stress decreases linearly;the deformation localization of Ogino tuff starts after the peak stress at the relative moisture content of 0,while the deformation localization starts before the peak stress at the moisture content;the deformation localization of Jingkou sandstone and Emochi andesite under the 9 MPa confining pressure starts after the peak stress,the deformation localization of raw coal and Ogino tuff starts before the peak stress.