Frequent road collapses caused by water leakages from pipelines pose a severe threat to urban safety and the wellbeing of city residents. Limited research has been conducted on the relationship between pipeline leakage and soil settlement, thus resulting in a lack of mathematical models that accurately describe the soil settlement process resulting from water erosion. In this study, we developed an equation for pipeline leakage, conducted physical model experiments on road collapses induced by drainage pipeline leakage, investigated the functional relationship between drainage pipeline leakage and soil settlement, and validated this relationship through physical experiments with pipelines of various sizes. The results indicated that drainage pipeline leakage triggered internal erosion and damaged the soil layers in four stages: soil particle detachment, seepage channel formation, void development, and road collapse. When the pipeline size was increased by a factor of 1.14, the total duration of road collapse induced by pipeline leakage increased by 20.78%, and the total leakage water volume increased by 33.5%. The Pearson correlation coefficient between the theoretical and actual settlement exceeded 0.9, thus demonstrating the reasonableness and effectiveness of the proposed settlement calculation method. The findings of this study serve as a basis for monitoring soil settlement and issuing early road collapse warnings.

This study investigated the deformation characteristics and mechanisms of the Baiyansizu landslide under the coupled effects of crack development, rainfall infiltration, and road loading. Numerical simulations were performed using GeoStudio software (Version 2018; Seequent, 2018) to analyze geological factors and external disturbances affecting landslide deformation and seepage dynamics. Four additional landslides (Tanjiawan, Bazimen, Tudiling, and Chengnan) were selected as comparative cases to investigate differences in deformation characteristics and mechanisms across these cases. The results demonstrate that rear-edge deformation of the Baiyansizu landslide was predominantly governed by rainfall patterns, with effective rainfall exhibiting a dual regulatory mechanism: long-term rainfall reduced shear strength through sustained infiltration-induced progressive creep, whereas short-term rainstorms generated step-like deformation via transient pore water pressure amplification. GeoStudio simulations further revealed multi-physics coupling mechanisms and nonlinear stability evolution controls. These findings highlight that rear-edge fissures substantially amplify rainfall infiltration efficiency, thereby establishing these features as the predominant deformation determinant. Road loading was observed to accelerate shallow landslide deformation, with stability coefficient threshold values triggering accelerated creep phases when thresholds were exceeded. Through comparative analysis of five typical landslide cases, it was demonstrated that interactions between geological factors and external disturbances resulted in distinct deformation characteristics and mechanisms. Variations in landslide thickness, crack evolution, road loading magnitudes, and rainfall infiltration characteristics were identified as critical factors influencing deformation patterns. This research provides significant empirical insights and theoretical frameworks for landslide monitoring and early warning system development.

Centrifuge tests were performed to study the dynamic properties of shallow soil with locally raised bedrock (i.e. variable soil depth). The test parameter was the slope of bedrock: 0 degrees (S0), 35 degrees (S35), and 45 degrees (S45). In each test, accelerations were measured along the soil depth, and the results of acceleration, displacement, Fourier transform, and response spectrum were compared. Based on the results, the transfer function (TF), the ratio of response spectrum (RRS), and the site period were estimated. The ground motion and site period of specimens with raised bedrock were smaller than those of the specimen without raised bedrock (i.e. with deeper soil). Further, parametric studies using 2-dimensional finite element (FE) analysis were performed to investigate the effect of design parameters on the response of shallow soil with variable soil depths. For design parameters, the length of raised bedrock and the length of foundation slab were considered. Parametric study results indicated that when the shallow soil region is wide, the results are similar to those of a 1-dimensional soil column. However, when the shallow soil region is narrow, the 2-dimensional response is smaller than the 1-dimensional soil column response. This was also observed in the actual site model.

Changes in the freeze-thaw cycles of shallow soil have important consequences for surface and subsurface hydrology, land-atmosphere energy and moisture interaction, carbon exchange, and ecosystem diversity and productivity. This work examines the shallow soil freeze-thaw cycle on the Tibetan Plateau (TP) using in-situ soil temperature observations in 0-20 cm soil layer during July 1982-June 2017. The domain and layer averaged beginning frozen day is November 18 and delays by 2.2 days per decade; the ending frozen day is March 9 and advances by 3.2 days per decade; the number of frozen days is 109 and shortens by 5.2 days per decade. Altitude and latitude combined could explain the spatial patterns of annual mean freeze-thaw status well. Stations located near 0 degrees C contour line experienced dramatic changes in freeze-thaw cycles as seen from subtropical mountain coniferous forest in the southern TP. Soil completely freezes from surface to 20-cm depth in 15 days while completely thaws in 10 days on average. Near-surface soil displays more pronounced changes than deeper soil. Surface air temperature strongly influences the shallow soil freeze-thaw status but snow exerts limited effects. Different thresholds in freeze-thaw status definition lead to differences in the shallow soil freeze-thaw status and multiple-consecutive-day approach appears to be more robust and reliable. Gridded soil temperature products could resolve the spatial pattern of the observed shallow soil freeze-thaw status to some extent but further improvement is needed.

A change in soil temperature (ST) is a significant indicator of climate change, so understanding the variations in ST is required for studying the changes of the Qinghai-Tibet Plateau (QTP) permafrost. We investigated the performance of three reanalysis ST products at three soil depths (0-10 cm, 10-40 cm, and 40-100 cm) on the permafrost regions of the QTP: the European Centre for Medium-Range Weather Forecasts interim reanalysis (ERA-Interim), the second version of the National Centers for Environmental Prediction Climate Forecast System (CFSv2), and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). Our results indicate that all three reanalysis ST products underestimate observations with negative mean bias error values at all three soil layers. The MERRA-2 product performed best in the first and second soil layers, and the ERA-Interim product performed best in the third soil layer. The spatiotemporal changes of annual and seasonal STs on the QTP from 1980 to 2017 were investigated using Sen's slope estimator and the Mann-Kendall test. There was an increasing trend of ST in the deeper soil layer, which was less than that of the shallow soil layers in the spring and summer as well as annually. In contrast, the first-layer ST warming rate was significantly lower than that of the deeper soil layers in the autumn and winter. The significantly (P < 0.01) increasing trend of the annual ST indicates that the QTP has experienced climate warming during the past 38 years, which is one of the factors promoting permafrost degradation of the QTP.