Three-dimensional site characterization for unsaturated soil nail wall analysis using integration of multivariate co-kriging and finite element method

To evaluate the effectiveness of a prestressed anchor cable combined with soil nailing technology in supporting deep foundation pits in loess regions, comprehensive field monitoring was conducted to measure horizontal and vertical displacements at the pit crest, as well as deep-seated horizontal deformations of the support system. A two-dimensional numerical model was developed using MIDAS GTS NX to facilitate comparative analysis. The results demonstrate that the integrated support system effectively controls deformation during excavation. The maximum displacement at the top of the support structure was recorded as 3.91mm, while the maximum horizontal displacement below a depth of 0.5m did not exceed 1.6mm-both values are substantially below the predefined alarm thresholds. The vertical profile of horizontal displacement exhibits a fluctuating pattern, with relatively smaller displacements observed at the elevations corresponding to soil nails and anchor cables, indicating localized reinforcement effects. Finite element analysis reveals that horizontal displacement within the excavation zone and surface settlement at the pit edge increase progressively with excavation depth, exhibiting an approximately linear trend. In the unsupported scenario, numerical instability occurred at an excavation depth of 3.6m, beyond which shear failure propagated through the soil mass. Although the simulated displacements prior to failure were higher than those measured in the field, this discrepancy is attributed to the minimal external loading under actual site conditions and the simplified representation of full-length grouting effects in the simulation model, which may underestimate the confinement provided by reinforced soil. In conclusion, the integration of prestressed anchor cables with soil nailing walls demonstrates high performance in deep foundation pit engineering in loess regions, offering effective deformation control and enhanced structural stability.

Soil nailing is widely used to improve slope stability, yet the mechanical response of soil-nailed slopes subjected to surcharge loading remains insufficiently understood, particularly at the mesoscopic level. In this study, the discrete element method (DEM) was employed to investigate the progressive failure process, macroscopic stability, and micromechanical behaviors of a soil-nailed slope subjected to point loading and distributed linear loading with varying magnitudes and loading widths. The numerical results show that surcharge loading significantly reduces slope stability and increases deformation. Under point loading, the safety factor decreases continuously with increasing load magnitude and the deformation remains highly localized. Under linear loading, the safety factor decreases sharply as the loading width increases from 0 to approximately 1.5–2.0 m, and then tends to stabilize, whereas displacement continues to increase monotonically. Micromechanical analyses indicate that surcharge loading promotes rapid accumulation of elastic strain energy, intensifies particle rotation, and increases stress heterogeneity within the slope. Load distribution also strongly affects the force transfer mechanism in the reinforcement system: narrow loads are mainly resisted by upper nails, while wide distributed loads mobilize deeper nails and shift the stabilizing effect to lower reinforcement layers. The results suggest that surcharge loads near the slope crest should be carefully controlled, and that sufficient setback distance is important for limiting stress transmission into the active failure zone. These findings provide insight into the failure mechanism of soil-nailed slopes under surcharge loading and offer practical guidance for reinforcement design.

Nondestructive integrity evaluation of soil nails using OFDR-based heated optical fibre

This study aimed to numerically investigate the propagation characteristics of elastic waves in GFRP soil nails. A two-dimensional axisymmetric finite element model was used to simulate the GFRP soil nail, and elastic waves were generated by an impulse load that represented hammer excitation. The results revealed that the elastic waves were reflected at both the defect location and nail end. The wave reflected from the defect exhibited a polarity opposite to that of the incident wave, whereas the end-reflected wave maintained the same polarity. This indicates that defect-reflected waves can be distinguished from end-reflected waves based on their polarities. In addition, the wave propagation velocity increased with the defect ratio, which was attributed to the differences in the effective stiffness and density governing wave propagation in the defective and grouted sections. These findings demonstrate that the elastic wave velocity and reflection characteristics can serve as effective indicators for assessing the integrity of GFRP soil nails.

Abstract Soil nailing has become a highly effective in-situ ground-reinforcement technique for stabilizing slopes and supporting deep excavations, valued for its cost efficiency, construction flexibility, and urban adaptability. This study assesses the behaviour and performance of soil-nailed systems through numerical verification and parametric analysis. The study developed a finite element model using PLAXIS 2D, with soil nails as embedded beam elements. The model was validated against two instrumented case studies, showing close agreement between simulated and measured wall displacements and nails internal forces. The study then conducted a parametric study to examine the impact of different geometric factors, such as nail length to-height ratio, nail inclination, and surcharge loading, on factor of safety and deformation characteristics under static and pseudo static conditions. The results indicate that increasing the nail length has the most significant effect in improving stability, the system performs best in denser soils, and using uniform nail lengths along the wall depth provides greater resistance under seismic loading.

Slope stability issues are a critical aspect of civil engineering, particularly in tropical regions like Malaysia, where extreme weather fluctuations and high rainfall frequently trigger slope failures. The combination of steep terrain and intense precipitation significantly increases the risk of landslides, threatening infrastructure, human settlements, and environmental sustainability. This research investigates the impact of heavy rainfall on slope instability at the Aminuddin Baki Institute, Genting Highlands, Pahang, Malaysia, an area characterized by complex topography and high precipitation. Using advanced geotechnical tools, SEEP/W for simulating rainfall infiltration and SLOPE/W for stability analysis, this study assesses slope performance under saturated conditions and evaluates three stabilization techniques: micro-helical anchors, soil nailing, and geotextiles. The analysis showed that rainfallinduced infiltration reduced the slope’s Factor of Safety (FOS) to 1.257, indicating a failure-prone condition. Upon implementing reinforcement methods, FOS values improved to 1.685 (micro-helical anchors), 1.647 (soil nailing), and 1.605 (geotextiles), corresponding to percentage improvements of 34.0%, 30.9%, and 27.7%, respectively, relative to the unreinforced condition. All methods exceeded the JKR minimum safety threshold of 1.5 for reinforced slopes. Among them, micro-helical anchors demonstrated the best performance due to their deeper engagement and anchoring mechanism. These findings highlight the importance of selecting effective and siteappropriate reinforcement strategies. The study contributes valuable insights into cost-effective and sustainable slope stabilization techniques suitable for landslide-prone, high-rainfall environments.

Abstract Building Information Modelling (BIM) is increasingly adopted in geotechnical engineering but remains hindered by the lack of standardised modelling methods and functional data structures. This paper presents a novel, generalisable BIM data model for tension-supporting elements (e.g., anchors, soil nails, rock bolts), which are used in almost every geotechnical project. Unlike previous efforts that focused primarily on construction-stage documentation, this study advances the state-of-the-art by integrating the full project lifecycle, including design, installation, inspection, and maintenance. The proposed data structure defines Level of Development (LOD) requirements for both geometry and metadata, aligned with project phases and maintenance needs. Three real-world cases from Norwegian infrastructure projects, covering tunnels, slopes, and foundations, form the basis for the proposed model, ensuring practical relevance and adaptability. The data structure is expandable so that maintenance-related information at different periods can be appended and back-traced. Even though realisation and testing in real projects are necessary, the proposed data structure is shown to be compatible with parametric design, the most widely used LOD frameworks, and common data exchange formats, e.g. “Industry Foundation Class” (IFC) for BIM. The current work is presented as a conceptual framework with full validation to be carried out in future infrastructure projects.

Slope stability is a major issue in Malaysia because of the nation's varied topography and unpredictable weather. Landslides or slope failures can happen without warning even after years of apparent stability. The ineffectiveness of conventional slope stabilization procedures may call for investigating advanced methods like soil nailing. This numerical study exclusively focused on the systematic analysis of slope stability reinforced with soil nailing. Geo-Studio 2018 (SLOPE/W) is used to determine the slope’s FOS with soil nails. Nail lengths of 6m, 9m, 12m, and 15m were evaluated, with a constant drillhole diameter of 150mm and a nail inclination of 10º. Slope angles of 30º, 60º, and 90º were considered, along with various soil types characterized by cohesion values of 0, 5, 10, and 15 kN/m² and friction angles of 5º, 15º, 35º, and 45º. The unit weight of the soil was consistently maintained at 17 kN/m³. Multiple regression analysis was employed to optimize the dataset, yielding an R-squared value of 0.80. The results demonstrated that the efficacy of soil nailing in enhancing slope stability was significantly influenced by nail length, slope angle, and soil properties. It was observed that longer nails and higher cohesion values contributed to improved stability, whereas steeper slopes and lower friction angles presented more significant challenges. These results highlighted the need to take into consideration a variety of elements in order to obtain optimal stability and offered crucial insights for developing and putting into practice soil nailing systems in a range of geotechnical settings. The study shows the impact of multiple regression analysis on geotechnical design optimization, especially in nail optimization. The study used this statistical technique to determine and measure the most important variables influencing soil nail performance. This method not only improved the accuracy of the design parameters but also provided a strong foundation for further study and real-world slope stabilization applications. A more sophisticated knowledge of the relationships between different design elements is made possible by the application of multiple regression analysis, which results in soil nailing solutions that are more dependable and efficient.

Computational modeling offers a cost-effective approach to exploring complex geotechnical behavior. This study uses PLAXIS 2D finite element software to simulate nailed soil slopes under plane strain conditions, with models calibrated against laboratory-scale experiments involving a sand-filled Perspex box, steel nail reinforcements, and a rigid foundation. The soil mass, structural elements, and reinforcements are modeled using fifteen-node triangular elements, five-node plate elements, and two-node elastic spring elements, respectively. In this paper, parametric studies evaluate the influence of slope angles, mesh density, domain dimensions, constitutive models, and reinforcement configurations. Both prototype-scale and 3D-approximated models are included to assess scale effects and spatial behavior. The results highlight the significant impact of model size and material behavior, particularly when using the Hardening Soil model and its small-strain extension. Reinforcement optimization, including nail length reduction strategies, demonstrates the potential for maintaining slope stability while improving material efficiency. Validation against experimental data confirms that the numerical models accurately capture deformation patterns and internal stress development across different construction and loading phases. This study observed that the Hardening Soil (small-strain) material model significantly improved slope performance by reducing settlements and better capturing stress behavior, especially for steep slopes. Optimized redistribution of nail lengths across the slope depth enhanced stability while reducing reinforcement usage, demonstrating a cost-effective alternative to uniform configurations. The findings offer practical guidance for optimizing nailed slope stabilization in sandy soils, supporting safer and more economical geotechnical design for real-world applications.

Abstract Rainfall-induced slope failures are a critical geotechnical issue in tropical hillside developments, where intense and prolonged rainfall rapidly alters hydraulic and mechanical conditions in weathered soils. This study evaluates the hydraulic response and stability performance of reinforced and unreinforced slopes at The Residence, Istana Syarqiyyah, Kuala Terengganu, using coupled numerical modeling with GeoStudio SEEP/W and SLOPE/W in accordance with Eurocode 7 Design Approach 1, Combination 2 (DA1-C2). Transient seepage analysis showed that rainfall infiltration caused a substantial increase in pore-water pressure, with peak values in unreinforced slopes reaching 31.0 kPa, leading to progressive saturation and reduced effective stress. Incorporating drainage measures reduced peak pore-water pressures by approximately 63%, improving hydraulic stability. Slope stability analysis revealed an Overdesign Factor (ODF) of 0.508 for the unreinforced slope, below the safety threshold of 1.0, indicating high failure potential. The installation of an anchor-reinforced concrete (RC) retaining wall, integrated with soil nails, micro piles, tiebacks, and drainage elements, increased the ODF to 1.758 (above the JKR requirement of 1.5). These findings highlight the effectiveness of combined reinforcement and drainage systems in enhancing slope resilience under tropical rainfall, while emphasizing the need for field validation to confirm numerical predictions.

Slope stability analysis is an important task in geotechnical engineering but predicting the Factor of Safety (FS) and the optimal remediation strategy for unstable slopes is a complex and resource-consuming challenge. This study introduces a novel, two-stage artificial intelligence (AI) framework to be used as a complete decision support tool for engineers. First, comparative analysis of multiple machine learning (ML) models, which includes Linear Regression, Random Forest, XGBoost and LightGBM, was performed on a large synthetic data of 10,000 slope simulations. The LightGBM model for the prediction of the Factor of Safety showed good results in its prediction accuracy. Second, this optimized prediction model was incorporated in a "Smart Optimizer" tool. If a predicted slope is determined to be unstable (FS < 1.0), this tool automatically simulates the geotechnical effects of four common reinforcement techniques including: Retaining Walls, Soil Nailing, Geosynthetics, and Drainage. By comparing the predicted FS for all the different scenarios, the tool gives a clear indication of which stabilization method is the best. This framework goes beyond simply predicting stability to provide actionable and data-driven optimization to deliver a fast and reliable system for improving the safety and design efficiency of geotechnical projects.

Landslides pose a significant threat to communities in hilly and mountainous regions of Nepal where steep terrain and heavy monsoon rainfall contributes to their occurrence. This study focused on the study of four landslide sites for case analysis. Comprehensive data collection included Slope length, Slope width, Slope Angle, Material Drainage, Aspect, Site Moisture, Type of Soil, Type of Erosion/Mass Movement, past history of Landslide. Based on this data and suggestion from the expert, various bioengineering and civil engineering techniques were proposed for soil stabilization and erosion control. Bioengineering measures such as grass seeding, shrub and tree plantation, brush layering, jute netting, along with civil engineering methods like riprap, gabion work, soil nailing, shotcrete, chutes, and drains are suggested. The study also included a cost comparison between bioengineering and civil engineering measures. The cost analysis revealed that the expenditure for bioengineering measures amounted to NRs. 3,202,854.52, while civil engineering works incurred NRs. 6,199,496.55. Typically, the cost ratio between vi bioengineering and civil engineering is expected to be 1:3. However, due to the inclusion of water management components like stream chutes and riprap in bioengineering, the observed ratio is closer to 1:1.94. In conclusion, this research highlights the significance of adopting bioengineering techniques as a sustainable, cost effective and community-centered approach to landslide risk reduction. The outcomes of this case study offers a holistic framework for mitigating landslide hazards in vulnerable areas like Adhikari Tole, ultimately contributing to the safety and well-being of its residents. The approach adopted in this study can serve as a model for similar landslide-prone regions in Nepal and other countries facing similar challenges.

Soil nails used to support excavations may be inserted into soils with bedding structures at different orientations. This paper examines for the first time the influence of such cases on probabilistic margins of safety for a typical soil nail arrangement by assigning rotated anisotropic random fields of soil strength parameters that are aligned with the bedding structure of the soil domain. The results using rotated anisotropic random fields on statistical outcomes for the computed global factor of safety are compared to results using homogeneous and isotropic random fields, and deterministic analyses. Analyses using rotated anisotropic random fields show that there is a detectable worst bedding direction that gives the highest probability of failure. However, the range of factor of safety for all random field cases is small and remains in the vicinity of the deterministic value. This is ascribed to the ability of the soil nails to anchor the entire reinforced soil domain together and prevent preferential failure paths to develop through the soil. The paper includes the calculation of the confidence in the point estimate of probability of failure for different conditions, and lessons learned in selecting domain size and level of discretization using the random finite difference method.

Abstract The analysis and design processes are carried out on Project of Slope Support of Taihu Mountain Villa. The extent of the settlement and factor of safety of soil is calculated (theoretically) and in practice using an engineering program for numerical analysis, the calculations are made by simulating the designed model and conducting the stages of the model. Five models are used the first one was a slope without treatment and the others were with treatment as soil nailing with different angles and loads and concrete cover casing. The Meyerhof model and Geo Studio software were used to estimate the factor of safety of the soil slope, as well as using the Plaxis program to calculate the settlement and analyze it. The Plaxis results of untreated model was far than the treated one. Additionally, the factor of safety with treated model is considered reasonably accepted for the slope satiability using the theoretical analysis especially for model treated with 15° soil nailing. The results of the numerical analysis showed that the stresses of the models give an indication for the severity of the slope stability.

ABSTRACT This paper introduces a novel pressure-grouted soil nail system incorporating a woven fabric membrane for confinement and an installation procedure for challenging soil conditions. Large model tests in sand, including installation and load tests, were conducted to evaluate its feasibility. The new system exhibited 100% to 280% higher pull-out capacity than gravity grouting due to increased grout zone diameter and enhanced confining stress. Experimental results for side shear, bearing resistance, grout zone diameter, and residual stresses were in agreement with analytical predictions. The proposed installation system can even be applied in soils deemed unsuitable for conventional pressure grouting.

Reinforced retaining walls are critical components of urban infrastructure, yet failures continue to occur due to complex geotechnical and environmental factors. This study investigates a collapse case, focusing on the influence of water infiltration from a damaged sewage pipe near a manhole. Photo documentation and portable dynamic cone penetration (DCP) testing were conducted to evaluate subgrade strength and identify localized weaknesses. Results revealed significant variability in ground rigidity, with particularly low resistance values near the manhole, indicating deterioration caused by seepage and soil softening. Stability analysis using MSEW software, under both static and seismic conditions, confirmed that affected wall sections did not meet safety requirements. Based on these findings, targeted remediation measures are proposed, including soil nailing, low-pressure grouting, and embankment reinforcement, complemented by continuous monitoring using displacement targets and inclinometers. This integrated approach offers both diagnostic insight and practical strategies to improve the design, maintenance, and resilience of MSE retaining walls, providing valuable guidance for engineers and decision-makers in preventing similar failures in densely built urban environments.

Behavior and Design Optimization of a Composite Soil Nail–Anchor Wall in Loose Sand Under Earthquake Loading

Prediction of Pull-Out Stress of Pressure-Grouted Soil Nails in Compact-Dense Sand Using CPT Results

Current understanding and uncertainties associated with climate change and the impact on slope stability: A systematic literature review