# Experimental Study on the Features of Infrasonic Waves of Sandstone under Shear Load
## 5 Conclusions  
To break the bottleneck in the monitoring and early warning of rocky landslides by infrasound, an experimental system collecting infrasonic signals generated during  
Figure 14: Direct shear experiment results of samples under different axial pressures. (**a**) Sample c1; (**b**) sample c2; (**c**) sample c3; (**d**) sample c4; and (**e**) sample c5. Figure 13: Relationship of the number and average excellent frequency of infrasound events with axial pressure. sandstone shear has been built. Characteristic parameters of infrasonic waves generated by sandstone under shearing load were collected by using time-frequency analysis and automatic infrasound event pickup technology. The results show that: (1) the shear deformation of sandstone samples is always associated with infrasound events. The normalized energy cumulative coefficient changes violently, mainly at the beginning of elastic deformation and peak destruction of the sample. When the sample enters the elastic deformation stage, the normalized energy cumulative coefficient of the infrasound rises sharply for the first time with a steady increase. When the normalized energy cumulative coefficient is between 0.6 and 0.75, and the normalized infrasound ratio is between 0.89 and 0.93, the sample is just before the peak destruction, and this feature can be taken as the mark of early warning of rock failure; (2) the shear destruction of the sandstone sample is closely related to its size. With increased sample size, the shear resistance strength of sample increases logarithmically, the total energy of infrasound events increases exponentially, and the average excellent frequency of infrasound events decreases linearly. When the rock sample is small, destruction mainly occurs through slip failure. With increased rock size, the fractures of loading damage increase in length, and the corresponding excellent frequency of infrasound becomes smaller and smaller; (3) sandstone samples are quite tight, and do not change much in saturation before and after soaking; therefore, the total energy and number of infrasound events do not change much, but the average excellent frequency of the infrasound events goes down linearly with increased saturation in general. The modeling of the overburden pressure on the rock by axial pressure shows that with increased axial pressure, the number of infrasound events increases linearly and the average excellent frequency of infrasound events increases exponentially, but the total energy of infrasonic signals does not increase correspondingly. According to the change law of infrasound characteristic parameters in the process of rock shear load, a method for judging rock stability by using infrasound parameters is established. According to this research idea, it is necessary to further carry out infrasound synchronous monitoring research of landslide physical model tests, which can provide a theoretical basis for the use of infrasound to carry out landslide warnings. C.Q., Writing--original draft; F.X., Y.L., Y.Z., H.H., J.C. and D.L. Data curation; P.S. Investigation; H.Z., Writing--review & editing; M.H., Funding acquisition. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The data used to support the findings of this study are available from the corresponding author upon request. This research was supported by the Key Laboratory of Mine Geological Hazard Mechanism and Prevention and Control (no. 2018-08), Xigaze City Science and Technology Plan Project (RKZ2020 KJ01), Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province (no. ZJRMG-2019-01), Chongqing Natural Science Foundation project (no. cstc2019)cyj-msxm0749, cstc2021 jcyj-msxmX0187), Ecological environment survey and ecological restoration technology demonstration project in the water-level-fluctuating of the Three Gorges Reservoir (no.