# Model Test Analysis of Subsurface Cavity and Ground Collapse Due to Broken Pipe Leakage
## 4 Conclusions  
Through a water circulation pipeline breakage testing apparatus, the problem of ground collapse disaster caused by pipeline breakage was studied in this paper. A 3D laser scanning technology was applied in experimental data processing to analyze and compare the patterns of cavity evolution development and the degree of ground collapse after pipeline breakage under different crack types and sizes in the pipeline. The following conclusions can be drawn:  
1. By studying three sets of experimental processes, the evolution of ground collapse under the action of pipe breakage was obtained and divided into three stages: the soil erosion stage, the stable stage of cavity development, and the ground collapse stage.
2. Among the different crack types, vertical damage had the worst damage and greatest impact on the degree of cavity development and ground collapse, with a short evolu  
Figure 9: Three-dimensional laser scanning cloud images.  
tionary process and sudden formation of ground collapse. Across the different crack sizes, there was an increase in both the underground cavity size and the degree of ground collapse with increasing crack size, leading to an increase in the seepage force of the water in the pipeline; however, this increase was significantly lessened below a certain critical size.
3. When studying the laws of cavity evolution and ground collapse development under the action of pipeline breakage, the two laws had a number of similarities, further revealing the significance of studying the evolution process of cavities for ground collapse prediction. Due to limited indoor conditions, the experiment conducted in this study had certain shortcomings: 1. The soil model box for the experiment was designed in the form of a semi-structure. Although silicone oil was applied to the walls of the model box, there are necessarily interaction forces between the soil in the model box and the inner walls of the model box, making it difficult to achieve the actual boundary conditions of the soil. 2. In order to better realize the development process of the underground cavity and to achieve the effect of ground collapse, the loading and unloading method was applied in the experiment; however, this method does not fully conform to the normal formation pattern of underground cavities. 3. The test box design was too small, and when the water pressure in the pipe was excessive, the water flowed to the ground from the boundary between the test box and the soil.  
F.T.: Conceptualization, Methodology, Writing--Review and Editing; W.T.: Writing--Original draft preparation; F.Y.: Investigation; X.Q.: Conceptualization, Supervision; Q.L.: Project administration; Z.H.: Data curation. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Natural Science Foundation of China (Grant Nos. 42277165 and 41920104007), the China Geological Survey Project Foundation (Grant No. DD20221734), and the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan) (Grant No. CUGCJ1821). Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request. The authors declare no conflict of interest.