Experimental Study Of Mechanical Properties Of T-Shaped Cross Fracture Specimens Under Cyclic Loading

The structure plane has an important influence on the mechanical properties of the whole rock mass.The rock mass is not only subjected to static load,but also under cyclic load during the course of Geo-technical engineering or the application of Geo-technical engineering.It has important theoretical and practical significance to study the mechanical characteristics of fractured rock mass under cyclic loading.Specimens containing single fracture and T-shaped cross fractured were made with gypsum material.Uniaxial static compression tests and uniaxial cyclic loading tests were carried out in,laboratory,and a high-definition camera recorded the whole process of deformation and failure of the specimens.The strength,deformation and failure modes of the fractured specimens with different geometrical characteristics under static load and cyclic load were studied.Based on the development law of residual strain under cyclic loading,the damage accumulation evolution law of fractured specimens with different geometric ch:aracteristics is studied,and the corresponding damage evolution equations are established.The m,ain conclusions are as follows:The introduction of secondary fracture produced a different effect on the uniaxial compressive strength of the specimen,which was different from the effect of single main fracture;The angle of the main fracture is different,the influence of the secondary fracture on the specirpen is also different;specimens consistent with variation of the primary and secondary crack angle have different uniaxial compressive strength.Different angle of the main fracture,the deformation of the sample at different stages is not the same;The influence of secondary crack on the deformation of the specimen is more obvious.All the T-shaped cross fracture specimen,the development rules of the total fatigue deformation and the total fatigue irreversible deformation are similar,which can be divided into three stages(I initial stage,II constant speed stage,III accelerated stage).Samples containing different primary and secondary crack angle,crack initiation,propagation,coalescence and failure modes are not the same both under static load and cyclic load.;Samples containing the same primary and secondary crack angle,crack initiation,extended,coalescence and failure mode under static load and cyclic load are not exactly the same.Damage evolution laws are different from the specimen that has different angle of the main fracture,and the influence of the secondary crack on the damage evolution law of the specimen is changed with the change of the angle of the primary and secondary cracks.Based on the understanding of the three phases fatigue damage evolution rules of T-shaped cross fractured specimens,the T-shaped cross fractured specimens fatigue damage evolution equation is proposed.