# Model Test Analysis of Groundwater Level Fluctuations on
## 1 Introduction  
Karst collapse is a karst-driven geological action and phenomenon in which the rock and soil above a karst cavity are damaged by deformation caused by natural or man-made factors, and a collapse pit (hole) is formed on the ground [1]. Karst collapse is a widespread geohazard problem worldwide, with more than 1/3 of China's land area covered by soluble rock [2]. The widespread distribution and sudden hazard of karst collapse have attracted the great attention of the international community. In the past two decades, the problem of karst collapse has become more and more serious, especially in the present day when roads are opened on every mountain and bridges are built over every river; some underground projects can hardly avoid crossing the karst development area, leading to the accelerated generation of karst collapse [3; 4; 5]. This geological disaster problem has seriously hindered local economic construction and social development and has posed a certain threat to the safety of people's lives and properties [6]. Therefore, scholars at home and abroad have paid great attention to karst collapse, and have carried out a lot of scientific research work and achieved fruitful scientific results. At present, the research results on karst collapse at home and abroad can be summarized as follows: collapse causes and collapse mechanisms, influencing factors, stability analysis and prediction, physical model tests and numerical research, monitoring, and prevention [7; 8; 9; 10; 11]. Karst collapse in China is mainly influenced by a variety of factors such as topography, stratigraphic lithology, geological formations, changes in groundwater dynamics, and human engineering-economic activities [12; 13]. Field tests are limited in many ways, making it difficult to map the characteristics of the overlying karst soil cavities and the corresponding collapse conditions, and even more difficult to determine a series of standard test conditions that are fully compatible with them. Among the many triggering factors affecting karst ground collapse, groundwater is the most important one. The changes in groundwater level, magnitude, and frequency, and its hydrodynamic characteristics are the most active and dominant dynamic factors in the formation of karst collapse [14; 15; 16; 17; 18]. The vast majority of karst collapses occur under dramatic changes in groundwater dynamic conditions, and the causes are categorized by domestic scholars as subduction, disintegration, vacuum absorption, and airburst [19]. In the karst collapse of groundwater changes in the collapse mechanism, some scholars have studied many cases of karst ground collapse closely related to the changes in the water table, analysis of the impact of groundwater on karst ground collapse, verification of the \"subduction theory, vacuum absorption theory, airburst theory\" of the three existing mechanisms [20; 21], and it is also pointed out that the types of collapse and the collapse mechanism are different under different geological conditions. The number of karst collapse hazards caused by fluctuating water levels is also increasing, exacerbating the threat and damage to life and property [22]. Therefore, for the collapse induced by the change in groundwater level, the study of the development law of cover deformation due to groundwater fluctuation is particularly important for karst collapse, and it is of great value for the prediction and prevention of karst collapse. However, as karst collapse is characterized by suddenness, concealment, complexity and uncertainty [23; 24; 25; 26], a comprehensive and systematic theory of collapse has not yet been established. Other scholars have carried out research work on the causes and influencing factors of karst collapse by taking the final state of karst collapse as the research object [27].