Based on the observation data of VP-type broadband vertical pendulum inclinometers from 5 stations in Inner Mongolia, this study adopted a method combining the wave propagation theoretical model and the deep learning prediction framework to preliminarily reveal the multi-frequency quantitative influence mechanism of the overburden thickness of observation caves on the observation signals. The results show that the overburden thickness is significantly negatively correlated with background noise (especially in the north-south direction), but has a weak impact on low-frequency signals. It exerts a directional regulatory effect on the amplitude of M2 tidal waves: the amplitude of the north-south component increases linearly with the increase of thickness, while the east-west component shows a unique resonance amplification effect at the thickness of 20 m (the peak value is about 3.6 times higher than that at 10 m). When the thickness is greater than or equal to 20 m, it can effectively suppress the seasonal fluctuation of data, significantly reduce the variation amplitude, delay the peak value by 1-2 seasons, and simultaneously decrease the barometric admittance coefficient remarkably. Verified by the random forest model, it is found that the optimal thickness range of the cave overburden is 18-22 m (with 20 m as the optimal value). Lithology is a secondary influencing factor, while the overburden thickness and its interaction with the density of mountain lithologic media constitute the dominant control parameters. In this study, 20 m of overburden thickness was selected as the engineering threshold, which provides an important design basis for effectively suppressing background noise, ensuring the fidelity of tidal signals and resisting seasonal interference, and gradually promotes the construction of cave-based observation at stations from an empirical mode to a quantitative and engineering-oriented direction.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |