# Model Test Analysis of Groundwater Level Fluctuations on
## 5 Conclusions  
In this paper, based on the results of previous studies on overlying karst in Guilin, indoor model tests on karst cover deformation under groundwater level fluctuations were carried out, which mainly led to the following conclusions.  
1. Under the action of rainfall and other recharge, cavity supply, and drainage, the infiltration curve of the soil in the cover layer changes faster at the beginning and slows down gradually at the later stage as the time and intensity of rainfall and other recharge increase. The thicker the cover layer, the slower the overall deformation; when the rate of cavity supply and drainage is certain, the thicker the cover layer, the smaller the deformation produced by the fluctuation of the groundwater level; after the formation of the cavity, rainfall, and other recharge, cavity supply and drainage accelerate the deformation of the soil and the upward development of the cavity.
2. Under the condition of uniform initial water content and density, the cumulative amount and time of rainfall and other recharge required for the deformation to collapse process increases as the thickness of the cover soil increases, and the number of cycles of cavity drainage required also increases. This indicates that the fluctuation frequency of groundwater level can aggravate the expansion of karst collapse.
3. The karst cover is affected by a combination of self-gravity, subduction by surface water seepage, suction by water-air change and airburst during the deformation to collapse process. For the same thickness of cover soil, the relationship between the deformation due to different effects is: water level rise is greater than water level fall which is greater than rainfall and lateral recharge; for example, with a cover of 6 cm, water level rise (3.04 mm) > water level fall (1.63 mm) > rainfall and lateral recharge (1.44 mm).  
Figure 14: Surface collapse map.  
Figure 13: Cavity altarpiece.  
**Author Contributions:** Conceptualization, [PERSON], [PERSON] and X.G. ([PERSON]); methodology, [PERSON] ([PERSON]); validation, H.L., X.G. ([PERSON]) and M.X.; investigation, [PERSON] ([PERSON]); writing--original draft preparation, [PERSON] ([PERSON]); writing--review and editing, [PERSON]; supervision, [PERSON] and X.G. ([PERSON]); project administration, [PERSON] All authors have read and agreed to the published version of the manuscript.  
**Funding:** (1) National key research and development program subject \"R&D and experimental demonstration of key technologies for water resource regulation in Karst wetlands in the Lijiang River Basin\" (2019 YFC0507502). (2) The National Natural Science Foundation of China Project \"Research on the Collapse Mechanism of Karst Water-soil Coupling in Guilin under Extreme Climate Conditions\" (41967037). (3) Guangxi Science and Technology Program Project \"Wetland Water Resources Utilization and Water Ecology\" (RZ2100000161).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.