Study On The Long-term Dynamic Stability Of The Rock Mass In The Face Of Tunnel In The Cold Region Induced By Heavy Load Train

There are abundant mineral resources in the cold region of Northwest China.After long-term seasonal freezing and thawing,the railway slope rock mass will suffer from the dynamic load of heavy-duty train,which will often lead to the problems of slope damage and local instability.It is of great significance to study the stability and longterm service life of frozen thawed slope under the action of heavy-duty train in cold region.In this paper,based on the actual engineering situation of the tunnel face slope of Dongfeng tunnel in Shanxi section of Shuo-Huang railway,the sandstone samples in the perennial freeze-thaw zone of the slope are collected,and the research work such as freeze-thaw cycle test,static physical mechanical test,SHPB dynamic mechanical test,numerical test,theoretical analysis and numerical simulation calculation of the long-term local stability of the slope are carried out,and the static and dynamic forces of the freeze-thaw sandstone are analyzed The main contents are as follows: 1(1)Based on the physical and mechanical nature of the freeze-thaw damage of rock mass,the damage process of rock mass under the action of freeze-thaw and dynamic load is analyzed,and the degradation rule of rock mass macro mechanical parameters under the action of freeze-thaw cycle is determined by combining the relevant research results.(2)The mechanical properties of slope rock under the freeze-thaw cycle are tested and analyzed.The variation laws of acoustic wave velocity,microstructure and macro mechanical parameters of surrounding rock are tested and analyzed.The degradation model of macro mechanical parameters of slope rock is established,and the static mechanical parameters of sandstone after long-term freeze-thaw cycle are derived.(3)Based on the SHPB test device,the mechanical properties of sandstone under uniaxial impact compression are studied,and the stress-strain curve,failure form and energy dissipation law of slope rock mass are obtained.The SHPB numerical test of rock sample is carried out by using the dynamic finite element calculation method,which reveals the dynamic mechanical parameters change law of sandstone sample under the long-term freeze-thaw condition,and establishes the The degradation model of dynamic compressive strength considering the strain rate and freeze-thaw cycles is proposed.(4)Based on the established dynamic strength degradation model of freeze-thaw rock mass,the HJC constitutive model is improved,and through the secondary development of LS-DYNA dynamic finite element calculation program,the long-term dynamic stability evolution law of Dongfeng tunnel face slope is obtained.