Research on the Spatiotemporal Evolution Patterns and Predictive Models of Surface Displacement Induced by Buried Ground Fissure Activity

Differential surface settlement is a critical trigger for engineering disasters, with buried ground fissure activity serving as one of the core factors driving such subsidence. In this study, four groups of physical model tests were conducted. High-precision laser displacement meters were used to monitor real-time settlement at varying distances from the ground fissure. Based on this, the surface displacement evolution patterns of both loess layer structures and interbedded sand–soil structures under slow (0.01 m/h) and rapid (2 m/h) ground fissure activities were summarized. To evaluate the predictive performance of different models for time- and space-dependent nonlinear displacement evolution, five methods, namely polynomial regression, support vector regression (SVR), multilayer perceptron (MLP), random forest (RF), and gradient boosting decision tree (GBDT), were constructed and compared using the experimental displacement dataset. The physical model test results indicate that the interbedded sand–soil structure tends to suppress localized crack propagation while expanding the affected zone range, whereas the loess layer is prone to near-field deformation localization. The activity rate exerts a pronounced influence on fracture propagation within the loess layer, while its influence on the deformation of the interbedded sand–soil structure is relatively limited under the present test conditions. The model comparison results show that a cubic polynomial can effectively describe the displacement evolution pattern under slow and homogeneous conditions. MLP exhibited the most stable performance among the four machine learning algorithms, while SVR, GBDT, and RF provided complementary information for interpreting continuous displacement evolution and local nonlinear displacement variations. Overall, under the present physical model test conditions, the machine learning models provide a useful data-driven basis for quantitatively characterizing displacement evolution trends and interpreting the development of ground fissure-affected zones. Based on the experimental results—scaled up by a similarity ratio of 20:1 and incorporated with a safety factor of 1.1~1.3—the preliminary reference engineering avoidance distance in the ground fissure-affected zone is 20~24 m for the hanging wall and 14~16 m for the footwall, which are broadly consistent with the current codes and regulations. The findings provide controlled experimental evidence and a quantitative reference for ground fissure hazard assessment and engineering protection.