Abstract
This study is based on the tunnel-face slope engineering of Dongfeng tunnel in Shanxi section of China’s Shuozhou-Huanghua Railway. The sandstone specimens in the perennial freeze-thaw zone of the slope were collected to carry out freeze-thaw cycle static physical mechanics test and split Hopkinson pressure bar (SHPB) dynamic mechanical test. Thus, the damage process of sandstone under freeze-thaw cycle and impact load is studied. Also, the dynamic compressive strength and dynamic elastic modulus of sandstone are analysed under different loading strain rates and freeze-thaw cycle based on LS-DYNA, a dynamic finite element program. The results showed that the dynamic compressive strength of sandstone subjected to multiple freeze-thaw cycles under 0.04 MPa air pressure has a greater damage ratio than that under 0.055 MPa and 0.07 MPa air pressure, which was more likely to cause damage to slope sandstone than in actual engineering; the dynamic compressive strength and elastic modulus of sandstone decrease greatly within a certain range of freeze-thaw cycles and loading strain rate, leading to significant deterioration. When the freeze-thaw cycle exceeded 200 times and the strain rate was greater than 200 s−1, the physical and mechanical properties of sandstone gradually tended to be stable.
Highlights
During the construction of mining, roads, and tunnels, in cold regions, the construction zone is often subjected to blasting vibration, heavy truck transportation vibration, earthquake vibration, and other dynamic loads. e frost heaving effect of the pore water inside the rock with the temperature change promotes the development of pores, and when the pores are subjected to dynamic loading, there is a serious impact on the stability of the rock engineering
By comparing the damage values of sandstone specimens under different impact air pressure, it can be found that the dynamic compressive strength of sandstone under 0.04 modulus (GPa) Uniaxial compressive strength (MPa) air pressure suffered from the highest damage rate after being affected by freeze-thaw cycle, and such strength suffered from the lowest damage rate under 0.07 MPa air pressure
Compared with the split Hopkinson pressure bar (SHPB) impact test in the laboratory, the strain rate was smaller in the heavy-haul train, so it could be inferred that the dynamic mechanical properties of sandstone under the action of the heavy load train were more affected by the freeze-thaw cycle, which should be paid enough attention to
Summary
The dynamic compressive strength and dynamic elastic modulus of sandstone are analysed under different loading strain rates and freeze-thaw cycle based on LS-DYNA, a dynamic finite element program. E results showed that the dynamic compressive strength of sandstone subjected to multiple freeze-thaw cycles under 0.04 MPa air pressure has a greater damage ratio than that under 0.055 MPa and 0.07 MPa air pressure, which was more likely to cause damage to slope sandstone than in actual engineering; the dynamic compressive strength and elastic modulus of sandstone decrease greatly within a certain range of freeze-thaw cycles and loading strain rate, leading to significant deterioration. When the freeze-thaw cycle exceeded 200 times and the strain rate was greater than 200 s−1, the physical and mechanical properties of sandstone gradually tended to be stable
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