The increasing vulnerability of retaining walls to rainfall-induced failures under changing climatic conditions necessitates rigorous evaluation of lateral earth pressures in variably saturated soils. Existing suction-dependent passive earth pressure formulations are limited to simplified hydraulic representations and predefined failure mechanisms, restricting applicability under field conditions with continuously varying boundary conditions and rarely achieved steady state. To address these limitations, a semi-analytical framework couples transient unsaturated flow with the slip-line method to evaluate temporal evolution of passive earth pressures in variably saturated backfills. Transient flow governed by Richards’ equation is solved numerically under constant-flux and rainfall-induced surface boundary conditions with a systematic boundary condition selection procedure. The influence of two soil–water characteristic curve (SWCC) models (Gardner, van Genuchten) and three corresponding hydraulic conductivity function (HCF) formulations (Gardner, van Genuchten–Mualem, van Genuchten–Burdine) on matric suction, suction stress, and the passive earth pressure coefficient is examined. Field-measured lateral swelling pressure data are used to assess the upper-bound nature of the predicted passive earth pressure, with the comparison indicating that the predicted values generally bound the measured response across the conditions considered, without implying equivalence between the two quantities. Quantitative results indicate that fixed log-spiral failure mechanisms overestimate the passive earth pressure coefficient by 12–21
Fractured limestone terrains present significant geotechnical challenges because complex interactions among fracture networks, groundwater circulation, and localized dissolution generate highly heterogeneous subsurface conditions. Although Electrical Resistivity Tomography (ERT) is widely applied for subsurface characterization in carbonate environments, differentiating localized karst-related features from conductive fractured zones remains challenging because similar resistivity responses may arise from different geological conditions. This study investigates the geoelectrical architecture of fractured limestone and proposes an interpretation framework that integrates resistivity magnitude, anomaly geometry, spatial continuity, structural context, and cross-profile correlation to improve the interpretation of conductive subsurface features. ERT surveys were conducted at five representative sites (A–E) in the Riyadh region, central Saudi Arabia, along proposed infrastructure corridors using a cross-star acquisition geometry comprising four intersecting Dipole–Dipole profiles arranged in two approximately orthogonal pairs at each site. The multidirectional survey configuration enabled anomaly verification through intersecting profiles, thereby improving confidence in subsurface interpretation. Resistivity values were interpreted together with anomaly geometry and spatial continuity to characterize variations in rock-mass conditions. The ERT results indicate a consistent geoelectrical framework comprising a unit of moderately to slightly fractured limestone (100–500 Ω m) and highly fractured limestone (10–100 Ω m), with pronounced spatial variations in structural features and conductive anomalies. Localized conductive anomalies (< 10 Ω m) interpreted as being consistent with possible sediment- or water-filled dissolution features were identified at Sites C and D. Site C exhibits multiple laterally associated conductive anomalies consistent with the most pronounced evidence of dissolution-related processes among the investigated sites, while Site D is dominated by a prominent structural discontinuity with a single localized conductive anomaly spatially associated with the inferred fault zone. Site B is characterized by structural discontinuities interpreted as minor faults or fracture zones, with no conductive anomalies below the dissolution threshold. In contrast, the laterally continuous conductive zone at Site E is attributed to clay-rich (argillaceous) fractured limestone rather than discrete dissolution features. The results suggest that integrating resistivity magnitude with anomaly geometry, spatial continuity, structural context, and cross-profile correlation improves the interpretation of conductive subsurface features and assists in differentiating localized conductive anomalies from laterally continuous fractured limestone. The integrated interpretation enhances subsurface characterization and provides valuable information for preliminary geotechnical site characterization and planning subsequent detailed ground investigations in karst-prone carbonate terrains.
Underground liquefied natural gas (LNG) storage caverns face low-temperature frost heave issues in their surrounding frozen rock masses. To investigate the frost heave mechanism of fractured rock masses under coupled low temperature−stress conditions, a specialized test system was designed and frost heave tests (freezing temperature −30 ℃) on sandstone specimens with single and double flaws under constant compression stress (6 MPa and 4 MPa) were conducted in this study. The results show that as the temperature drops, remains constant, and then recovers, the frost heave pressure within the flaw exhibits six phases. Overall, the peak pressure first rises and then falls as the flaw inclination angle increases, reaching a maximum in the range of 45°–60°. The magnitudes range from 5.35 to 9.07 MPa for single-flaw specimens and from 3.03 to 8.91 MPa for double-flaw specimens. The amplitude of the post‑peak decline and the subsequent rebound of frost heave pressure also depend on the flaw inclination angle. The maximum decline amplitude reaches 42.82
Rainfall-induced landslides threaten tropical railway infrastructure, where sparse monitoring limits the characterization of rainfall–instability relationships. This study investigated the long-term hydraulic response and stability of railway cut slopes in residual soils along a strategic railway in the Brazilian Amazon using alternative climate datasets. Satellite-derived precipitation (CHIRPS), satellite-informed soil moisture (SMAP), and gridded meteorological variables (BR-DWGD) were integrated with laboratory hydraulic relationships and field groundwater observations to define atmospheric forcing and initial hydraulic conditions. Daily sequential seepage–stability simulations spanning more than 40 yrs were performed for four representative slope inclinations. Increasing inclination reduced stability, and only the 40° slope exhibited simulated instability. Mean annual precipitation was highest during La Niña, intermediate during neutral conditions, and lowest during El Niño, whereas mean annual minimum factor of safety (FoS) followed the reverse ordering across all inclinations. Statistically significant differences supported an association between El Niño–Southern Oscillation variability and simulated stability. Mean monthly minimum FoS was lowest in April for steeper slopes, consistent with cumulative wet-season infiltration and broadly aligned with reported March–April slope-instability events along the railway. A criterion combining 7-, 15-, and 90-day rainfall accumulations provided a preliminary model-derived reference for investigating simulated instability. The underlying mechanisms involved matric suction dissipation and localized groundwater rise near the toe, without requiring full saturation of the overlying soil. Hydraulic contrasts can guide instrumentation placement. The framework supports slope screening for railway asset management and preliminary assessment of stabilization measures, providing a basis for subsequent site-specific investigation, calibration, and design refinement.
Geocell reinforcement improves shallow-foundation performance through soil confinement, load dispersion, and membrane resistance, but its effectiveness depends strongly on soil-geocell interaction. This study introduces a protrusion-reinforced geocell (PRG) system, in which rigid plastic cubic elements are attached to geocell walls with the intention of enhancing soil-reinforcement interaction. The proposed modification aims to improve load transfer and settlement control while retaining the basic configuration of conventional geocell reinforcement. Small-scale model tests were conducted on strip footings resting on sand slopes to compare unreinforced, conventional geocell-reinforced, and PRG-reinforced systems. The effects of footing setback ratio, a/B, and reinforcement back-length ratio, Lb/B, were examined using bearing pressure-settlement response, improvement factor, settlement reduction, and slope crest displacement. PRG generally outperformed conventional geocells for the tested geometries, producing higher improvement factors and greater settlement reductions, particularly at larger settlement ratios. The beneficial effects of increasing a/B and Lb/B became more pronounced beyond threshold settlement ratios, which may reflect progressive mobilization of reinforcement effects, although the underlying mechanisms were not directly measured. Reinforced models developed crest settlement rather than the heave observed in unreinforced slopes. Overall, PRG demonstrates potential as a practical modification of conventional geocell reinforcement for improving strip-footing performance on sand slopes, with broader relevance to geotechnical stabilization applications where improved soil-reinforcement interaction may contribute to performance.
