STUDY OF MECHANICAL PROPERTIES OF JINTAN SALT ROCK BASED ON DIRECT SHEAR TESTS

A series of direct shear tests are carried out by using testing machine RMT–150C to investigate the characteristics of salt rock in Jintan gas storage.The shear stress of dilatancy and failure characteristics are deeply analyzed by considering the salt rock as a kind of polycrystalline polymer.The results show that shear failure of salt rock is ductile failure,and the shear displacement corresponding to ultimate shear strength is generally 4–6 mm;the shear displacements of several specimens even reach 7–8 mm.The whole curves are relatively flater,the shear strength is not very clear,which is mainly due to the grain dislocation alternatively.Finally,the shear strength parameters c and is 3.16 MPa,44.7°,respectively.The residual strength and the normal stress is basically a positive correlation,and the residual strength is much higher,about 50%–80% of shear strength which indicates a strong bearing loading capacity for salt rock only by friction.Salt rock shear dilatancy occurs before the residual stress and after peak stress,and the initial stress of shear dilatancy is close to the stress for termination under much higher normal stress.Shear failure section of salt rock is not a plane but a fracture zone.It can be seen that part of the section has clear scrape which is similar to theplow effect.This will help to improve the shear capacity of salt rock.The results also have great reference for understanding the mechanism of Jintan salt rock and investigating the stability of underground gas storage.