[Objective] Ground collapse induced by underground pipeline ruptures in red clay areas has become increasingly frequent, posing serious threats to daily life safety and economic property. [Methods]To address this issue, this paper aims to systematically reveal the deformation and failure patterns of ground collapse resulting from pipeline leaks under varying flow rate conditions. The research methodology centered on a series of meticulously designed semi-structured physical model tests, which simulated the realistic scenario of pipeline leakage beneath a red clay overburden. During these tests, an integrated monitoring system was deployed to capture the entire failure process comprehensively. This system included high-speed cameras to document the macroscopic deformation and failure progression of the soil mass, along with an array of sensors comprising soil pressure sensors, pore water pressure sensors, and a laser displacement meter. The collective data from these instruments enabled precise tracking of the wetting front migration, the dynamic variations in internal soil stress and pore water pressure, and the evolution law of ground surface displacement. [Results]The experimental results yielded several key findings. Primarily, the study demonstrated that under identical pipeline rupture conditions, a decrease in pipeline flow rate significantly influences the collapse dynamics. Specifically, the erosive capacity of the leaking water on the surrounding soil matrix gradually weakens as the flow rate diminishes. This reduction in hydraulic energy directly leads to an alteration in the fundamental migration mechanism of the wetting front and is accompanied by a marked decrease in the soil erosion rate. Concurrently, the development trajectory of subsurface soil cavities undergoes a notable shift; with lower flow rates, the dominant direction of cavity evolution changes from primarily horizontal to predominantly vertical. Furthermore, this shift is associated with a corresponding reduction in the ultimate size of the cavities and a decrease in the critical overburden thickness necessary for a collapse event to manifest at the surface. Despite these variations in the developmental stages, the ultimate mode of ground collapse induced by the pipeline leakage was observed to be consistent across the tested flow rates. The final failure is invariably attributable to the leaking water flow accumulating and generating sufficient pressure to rupture and breach the overlying soil stratum. [Conclusion]In conclusion, this research successfully elucidates the distinctive failure mode triggered by underground pipeline rupture and leakage specific to red clay geological conditions. The insights gained from this study, particularly concerning the influence of flow rate on the collapse process, provide a solid theoretical foundation and support for several critical engineering applications. These applications include, but are not limited to, the implementation of full-life-cycle safety monitoring strategies for urban underground pipelines, the construction of scientifically grounded early-warning systems for assessing ground collapse risks, and the informed design of effective engineering prevention and mitigation schemes. This work ultimately contributes to enhancing urban safety and infrastructure resilience.
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