The thermo-mechanical (TM) behaviour of the energy pile (EP) group becomes more complicated in the presence of seepage, and the mechanism by which seepage impacts the EP group remains unclear.In the current work, a 2 x 2 scale model test bench of EP group was set up to investigate the TM behaviour of EP group with seepage. The test results indicate that the heat exchange performance of EP group with seepage can be significantly enhanced, but also leads to obvious differences in the temperature distribution of pile and surrounding soil along the seepage direction, and thus causes evident differences in the mechanical properties between the front pile and the back pile in pile group. Compared with the parallel connection form, the thermal performance of EP group with the series connection form is slightly attenuated. However, the mechanical properties of various piles in the EP group differ significantly. Under the action of seepage, the mechanical balance properties of various piles in the forward series form are optimal, followed by the parallel form, and the reverse series form is the least optimal. A 3-D CFD model was established to further obtain the influence of seepage and arrangement forms on EP group. The findings indicate that seepage can not only mitigate thermal interference between distinct piles but also expedite the process of heat transfer from pile-soil to reach a state of stability. Concurrently, the thermal migration effect induced by seepage will be superimposed along the seepage direction, resulting in the elevation of thermal interference of each pile along the seepage direction, and the superposition of thermal migration effect increases with the time. Under the same seepage condition, the cross arrangement can enhance the thermal performance of EP group, optimize the temperature distribution of pile and soil, and thus the imbalance of mechanical properties among pile groups can be reduced. In addition, the concepts of thermal interference coefficient and heat exchange rate per unit soil volume are introduced to facilitate a more precise evaluation of the thermal interference degree of each pile in the pile group and the heat exchange performance under different pile arrangement forms.The standard deviation and mean value in the statistical method are used to evaluate the equilibrium of mechanical properties of pile group, which is more intuitive to compare the differences in mechanical properties of pile groups under different working conditions.

An indirectly coupled model, integrating the Richards' equation, the diffusion wave approximation equation, and the Green-Ampt infiltration model, has been developed to efficiently analyze surface flow and groundwater seepage under heavy rainfall conditions. Model effectiveness was validated through rigorous soil column and slope model experiments. Using this model, the sensitivity of slope stability to rainfall intensity and soil permeability heterogeneity was investigated utilizing local factor of safety (LFS) analysis. Increased rainfall intensity was found to notably impact slope stability, while the influence of permeability anisotropy on stability varies with slope steepness. This method was subsequently applied to analyze the slope stability of a soil heritage site impacted by extreme precipitation during Typhoon Lekima. Preliminary comparisons revealed that the steady-state average infiltration rate, when surface runoff was considered, was higher than the rate computed without it. Additionally, potential hazard zones were identified near areas with maximal water accumulation and runoff velocity when surface runoff was considered. Building on these findings, LFS changes were evaluated at various locations during and after 20 h of rainfall. The study indicated decreased stability in the shallow layer during rainfall, with slight improvement in the deeper layer. Post-rainfall, the shallow layer stability recovered, whereas the deeper layer stability declined due to increased depth of rainwater infiltration. The results suggest that the indirectly coupled model, combined with LFS analysis, is a robust method for effectively evaluating shallow layer stability of slopes in extreme rainfall conditions.

Water loss in paddy fields occurs through various pathways, and previous studies have primarily focused on water seepage in the field, often overlooking the potential for the field-bund area. In this study, 3 typical paddy fields in the plain river network area of southeastern China were selected to clarify the differences in the soil structure and hydraulic characteristics at different positions within the field-bund area: the field, inner bund, middle bund and outer bund. The interactions between basic soil properties and hydraulic characteristics were also evaluated. The results revealed that the outer bund presented the lowest soil porosity (6.92 %), followed by the field (7.52 %), middle bund (7.77 %), and inner bund (8.09 %). The soil pores in the field presented the smallest mean diameter and fractal dimension and the highest degree of anisotropy. The deep layer of the bund contained more macropores, and the soil pores exhibited greater spatial distribution heterogeneity. The bottom layer in the field and bund presented the lowest average Ks value of only 0.05 mm min(-1), indicating the presence of a plow pan and a notable tendency for lateral seepage. Differences in the soil structure and hydraulic parameters between the field and bund created a driving force for lateral seepage and rendered the field-bund area a hotspot for water loss. For the analysis of the underlying water loss mechanism, the structural equation model represented 65 % of the total variance in the hydraulic parameters. The micropore characteristics had the greatest positive direct effect on the hydraulic parameters, with a standardized path coefficient of 0.39 (p < 0.001). The soil physical properties were not directly related to the hydraulic parameters but exerted an indirect effect through aggregate stability and micropore and macropore characteristics, with a total indirect standardized path coefficient of -0.41.

Saturation development and distribution at the soil-bedrock interface are important for predicting shallow landslide occurrence. Previous studies have indicated that saturation is generated in bedrock depressions and valleys and that bedrock groundwater seepage generates locally saturated areas. However, the effects of soil permeability, which is known to be heterogeneously distributed, on saturation development and distribution are poorly understood. In this study, we performed unprecedented high-resolution (approximately 50 cm grid) soil pore water pressure and soil temperature monitoring using 141 tensiometer-thermocouple sets in a plot measuring approximately 5 x 4 m to investigate the effects of topography and bedrock groundwater seepage on saturation development and distribution. We then measured permeability distribution of two soil profiles, including at the soil-bedrock interface, using the Guelph Permeameter method (GP method) for comparison with saturated zone distribution and saturation duration. The results indicated that a perennial saturated area was formed by bedrock groundwater seepage and was distributed downstream from a certain bedrock surface altitude in the lower region of the study plot. After a peak of rainfall, the perennial saturated area expanded upslope owing to the increased seepage. In areas without the influence of bedrock groundwater, saturation was observed to retreat rapidly at high permeability points and persist over long periods at low permeability points; however, the saturation duration was inconsistent with the bedrock surface topography. Therefore, it is suggested that the bedrock altitude controls the saturation distribution generated by bedrock groundwater, whereas the distribution of saturation that is associated with direct rainwater infiltration may be controlled by the permeability distribution during recession periods. Although the plot size was small, the unprecedented high-resolution observations suggest that the permeability distribution, rather than the bedrock topography, may control the saturated zone distribution following rainfall.

For deep-filled building site, it is not acceptable to neglect water seepage and land settlement caused by the coupling effect of wetting and loading. However, previous soil column tests employed in investigating the water seepage always failed to consider the vertical stress. In this article, a stress-controlled soil column test was conducted to investigate the effect of vertical stress on water seepage and deformation of the compacted soil. The soil column was equipped with a vertical loading device and a water-recharge device to control the boundary conditions and water sensors, tensiometers, dial indicators and a data collector to monitor the displacement and water movement. The soil column test was utilised to perform seepage tests on compacted loess with vertical stresses of 0 and 400 kPa. The time-history data of wetting front depth, volumetric water content (VWC), suction and vertical displacement have been monitored directly. The VWC and suction profiles, soil-water characteristic curves and hydraulic conductivity curves were then obtained with the monitored data. The test results demonstrated that the vertical stress affected the water seepage and consolidation of the compacted soil, but this effect gradually decreased as the depth of the soil column increased. Moreover, the reliability of the proposed test method was verified by the comparison of some available test results. The findings of this study contribute to a better understanding of water seepage and consolidation characteristics of the compacted soil subjected to vertical stress. A stress-controlled soil column test equipment is developed for investigating soil water migration and deformation characteristics.The time-history curves about wetting front depth, volumetric water content (VWC), suction and vertical deformation are measured directly using a developed stress-controlled soil column test equipment.The VWC and suction profiles, soil-water characteristic curves and hydraulic conductivity curves are obtained.The validity of the test method and developed soil column is verified by the comparison of partial test results.

Sudden leaks often occur when constructing shield tunnels within saturated sandy cobble strata. Therefore, it is important to examine the reasons for water seepage and understand the mechanisms behind such problems. This paper presents a study that combines laser scanning technology with the Python programming language to create software for monitoring tunnel deformation. The software was employed in a practical subway tunnel scenario, successfully acquiring deformation data pertaining to the tunnel's structural segment through the analysis of point cloud data from the tunnel lining. Furthermore, the seepage-stress coupling theory was employed to establish a three-dimensional model of shield tunnel excavation, interlinking groundwater and stratigraphic factors with the sequence of shield tunnel excavation. The origins and mechanisms of water damage resulting from seepage and leakage are explicated through an examination of the seepage field, displacement field, and deformation of the tunnel structure pre- and post-excavation. Additionally, on-site monitoring data is considered. The mechanism of tunnel leakage is outlined as follows: Tunnel excavation completion induces alterations in the seepage field, leading to an accelerated inflow of groundwater into the soil beneath the tube sheet during shield excavation. The tube sheet of the shield tunnel, composed of sand and gravel layers, experiences vertical elliptical deformation that exacerbates shifts in the displacement field due to tunnel deformation's inception and progression. Excessive tube sheet deformation triggers fracture cracks, ultimately engendering the creation of seepage channels. These channels, in turn, foster seepage and water damage. The results of this paper provide a reference for preventing and remedying water infiltration and leakage in shield tunnels constructed of sandy cobble strata.

Suspended waterproof curtains combined with pumping wells are the primary method for controlling groundwater levels in foundation pits within soft soil areas. However, there is still a lack of a systematic approach to predict the groundwater drawdown within the foundation pit caused by the influence of these suspended curtains. In order to investigate the variation of groundwater level within the excavation during dewatering processes, the finite difference method is employed to analyze the seepage characteristics of foundation pits with suspended waterproof curtains. Basing on the concept of equivalent well, this study examines the coupled effects of aquifer anisotropy (ki), aquifer thickness (Mi), well screen length (li), and the depth of waterproof curtain embedment on the seepage field distortion. A characteristic curve is established for standard conditions, which exposes the blocking effect of the curtain on the amount of groundwater drawdown in the pit. Additionally, correction coefficients are proposed for non-standard conditions, which, in turn, results in a prediction formula with a wider range of applicability. Comparative analysis between the calculated predictions and the field observation data from an actual foundation pit project in Zhuhai City validates the feasibility of the quantitative prediction method proposed in this research, which also provides a 21% safety margin.