Low strength and moderate swelling tendency of kaolin clay pose significant challenges for geotechnical applications, necessitating effective stabilization techniques. This study investigated the stabilization of kaolin clay using lime and NaOH-activated Ladle Refining Furnace (LRF) slag. Mechanical properties of the stabilized clay were assessed through compaction, unconfined compressive strength (UCS), and free swell index (FSI) tests, while microstructural changes were examined using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). Mixtures containing varying proportions of lime (3
A series of dynamic loading tests were conducted to investigate the deformation characteristics of ballasted track subgrade under heavy haul train loading. The results indicate that cyclic loading not only induces compression in the ballast and subgrade soil, but also promotes the formation of an interlayer between them. This interlayer contributes to over 50
This study investigates the combined effects of silica nanoparticles (SiO₂) and fly ash (FA) on the geotechnical properties of a weak Iraqi CL soil. An extensive laboratory program comprising standard Proctor compaction, consolidation (CT), direct shear (DST), and soaked California Bearing Ratio (CBR) tests was conducted on untreated soil (Mix-1) and soils treated with FA and SiO₂. The soil was mixed with additive (by dry soil weight at "OMC") of 0.1
Geosynthetics are commonly used in pavement systems to mitigate reflective cracking; however, their potential contribution to improving the structural capacity of asphalt overlays has not been fully quantified. This study evaluates the structural benefits of geosynthetic paving interlayers using full-scale instrumented pavement models tested in an Accelerated Pavement Testing (APT) facility. Asphalt strain gauges were used to monitor tensile strains under repeated wheel loading. By quantifying stable response parameters such as tensile strain reduction, rutting rate reduction, and modulus Improvement Ratio (MIR), this work provides the experimental and analytical foundation required for the development of simplified design modification approaches. The geogrid-reinforced section exhibited reductions of approximately 38
Using soil-filled waste tires as retaining wall panels is an efficient approach for recycling waste tires. Wrapping waste tires with geogrids can further improve the integrity and stability of tire-reinforced retaining wall panels. However, the shear behavior of the interface between wrapped tires and reinforced soil remains poorly understood. In this study, the static and cyclic shear characteristics of the main interface in geogrid-wrapped tire-reinforced soil were investigated using a self-developed large-scale indoor direct shear apparatus. The peak shear stress, shear strength parameters, shear stiffness, and damping ratio of the interface were analyzed under different wrapping modes. The results show that the wrapping configuration has a significant influence on the interface shear behavior. Within the tested normal stress range of 20–60 kPa, the wrapped mode without folding generally exhibited higher shear strength than the wrapped mode with folding. Cyclic shear tests were conducted to examine the variations in interface shear stiffness and damping ratio. The advantages and disadvantages of different wrapping modes were compared. The results indicate that the wrapped mode with folding exhibited higher shear stiffness, a smaller hysteresis loop area, and a lower damping ratio than the wrapped mode without folding under certain loading conditions. In contrast, the wrapped mode without folding showed a relatively higher damping capacity, especially under higher normal stresses. These findings provide a useful reference for selecting appropriate geogrid wrapping configurations for waste-tire-reinforced retaining wall systems subjected to static and cyclic loading.
The air- and water-inflated double-layer rubber dam (AW-DRD) has higher water-retaining capacity than the conventional water-inflated single-layer rubber dam (W-SRD). A theoretical model was established to predict the tensile force and cross-sectional shape of the AW-DRDs. The Runge–Kutta–-Merson method was employed to solve the proposed differential equations. The theoretical model was verified by applying it to analyze the large-scale model tests in the literature. Fair agreements were obtained after comparing the cross-sectional profiles, critical water head, and tensile forces obtained from the proposed theory and model tests. It is found that the anchor force in the lower-layer rubber dam is higher than that of the upper-layer rubber dam, with a maximum difference of approximately 23.2
Expansive soil (ES) poses significant geotechnical challenges due to its high swelling–shrinkage potential, compromising the serviceability of overlying infrastructure. This study investigates the individual and combined effects of cationic superabsorbent polymer (SAP) and polypropylene (PP) fiber on the engineering behavior of ES. The experimental program evaluated changes in index and compaction characteristics, strength development, stress–strain and pore pressure response, compressibility, swelling behavior, freezing–thawing (F–T) durability, and microstructural features. The result indicates that SAP addition increased the Atterberg limits and caused an apparent shift toward coarser particle fractions, while reducing the maximum dry density (MDD). Similar reductions in MDD were observed for the PP fiber and SAP + PP fiber combination. The optimum combination of 1.5
Expanding road and railway networks in developing countries is essential for economic growth and reducing regional disparities. However, such projects often face significant geotechnical stability and risk management challenges. This study presents a three-phase optimization framework consisting of: (1) deterministic, probabilistic, and risk analyses; (2) Random Variable (RV)-based optimization; and (3) Random Field (RF)-based refinement. Soil variability is modeled using both RV and RF approaches. Two Artificial Neural Network (ANN) surrogate models are employed to improve computational efficiency by predicting failure probabilities and associated costs. Two application cases are presented to demonstrate the integrated framework for optimizing earth slopes in transportation infrastructure using Deterministic Design Optimization (DDO), Reliability-Based Design Optimization (RBDO), and Risk Optimization (RO). The application cases further demonstrate the model’s potential for early-stage roadway design under limited geotechnical data. Overall, the framework supports more reliable, cost-effective, and sustainable infrastructure development.
To reduce the carbon footprint of Ordinary Portland Cement (OPC) and improve the strength and crack resistance of stabilized soils, a geopolymer binder (SDG-GP) composed of steel slag, desulfurization gypsum, and ground granulated blast furnace slag was developed in this study and combined with basalt fibers (BF) for dredged soil stabilization. A Box–Behnken response surface methodology was employed to evaluate the effects of SDG-GP content, BF content, fiber aspect ratio, and moisture content on the unconfined compressive strength (UCS) and crack ratio of stabilized soils, while the microstructural mechanisms were analyzed using TG–DTG, XRD, SEM–EDS, and MIP. The results showed that the optimized SDG-GP formulation (SS: DG: GGBS = 2:3:13) led to a marked increase in strength, with UCS rising from 2.12 MPa (15
Biochar has emerged as a promising sustainable soil amendment due to its potential to improve soil structure and enhance stormwater management. However, its effects on saturated hydraulic conductivity (Ksat) and unsaturated hydraulic conductivity (Kunsat) at high suction ranges (i.e., around 100 kPa) remain inconsistent due to variations in biochar properties. This study investigates the influence of nine commercially available wood-based biochars, applied at 3
Foam is extensively used to condition excavated sand for improving shield tunnelling efficiency and safety. Nevertheless, conventional foam often fails to achieve ideal conditioning effectiveness in water-rich environments. In this investigation, a novel viscosified foam specifically designed for water-rich sandy shield muck is developed via systematic compounding experiments. Furthermore, laboratory soil conditioning tests and field application are conducted to highlight the advantages of the viscosified foam. The obtained results show that the sodium dodecyl sulfate (SDS)/alkylamine oxide (OA-14) composite system exhibits remarkable thickening efficacy, which can enhance foam performance. The optimal compound mass ratio in the viscosified foaming agent is 2:1, and the recommended surfactant solution concentration is 3‰. The half-life of viscosified foam reaches 164.5 min, which is approximately 39 times that of conventional foam. Compared with conventional foam conditioning, the rheological state of the viscosified foam-conditioned sand is significantly improved, and its hydraulic conductivity exhibits two orders of magnitude reduction. Moreover, the average cutterhead torque decreases by 31.2
This study investigates the reinforcing effect of five-year-old, non-degradable municipal solid waste (MSW) fragments on the mechanical behavior of a low-plasticity silty soil using large-scale laboratory direct shear testing. The soil was randomly mixed with MSW at 0.0, 0.5, 1.0, and 2.0
Traditionally, road construction depends on natural, virgin aggregates, which are becoming scarcer, creating a need for alternative and sustainable replacements. Wastes and industrial byproducts show potential for incorporation in pavement structures, preventing landfill disposal and reducing reliability on natural resources, while ensuring adequate performance. Geosynthetics provide increased strength and durability, offering cost-effective and sustainable solutions for roads. This paper assesses benefits of combining an aggregate with exhausted sands and geogrids for unpaved forest roads. It includes: geotechnical characterisation of two exhausted sands, including their shear behaviour and load-bearing response; design of an unpaved forest road section for different foundation scenarios, considering different solutions for the base layer using unbound materials (aggregate, exhausted sands), without and with geogrid reinforcement; and a cost analysis of solutions designed for a particular case study. The physical and geotechnical characterisation of the exhausted sands demonstrates that their geotechnical application was viable, and that there were no statistical differences between the two exhausted sands. All the solutions were optimised by the inclusion of geogrids, which result in a significant reduction in the height of the base layer. Results also showed that, for the case study considered, using these materials over traditional aggregates is more cost-effective when the transport distances for exhausted sands supply do not surpass 200 km. Above this distance, if traditional aggregates are obtained at a shorter distance, profitability is reversed. In all solutions the use of geogrid further enhances cost savings in acquisition and transport.
This manuscript presents a rheological investigation of cement–bentonite slurry mixtures for jet grouting applications, using ground granulated blast furnace slag (GGBFS) as a partial replacement for ordinary Portland cement (OPC). While the strength of GGBFS-stabilised soils has been widely studied, its rheological properties for jet grouting applications remains largely unexplored. In this study, slurry samples of GGBFS–OPC–bentonite mixtures are tested using an MCR 702e Modular Compact Rheometer. The results are assessed for their fit to several non-Newtonian rheological models. Among them, the Herschel–Bulkley model best describes the flow behaviour of samples with different GGBFS contents of 60
Expansive clay or Black Cotton Soil (BCS) poses notable challenges in pavement and foundation construction due to its behaviour of high swelling, plasticity, and low strength. This study aims to evaluate the geotechnical and microstructural performance of BCS stabilized with Red Mud (RM) under 10 M sodium silicate activation and to determine the optimum blend suitable for subgrade applications. BCS was blended with 10–30
Geogrid-encased stone columns (GESCs) are an effective ground improvement technique for mitigating earthquake-induced liquefaction in saturated sands. This study investigates the dynamic response and liquefaction resistance of GESCs through 1:10 scale shaking table model tests under a three-phase loading protocol comprising static, seismic, and post-seismic stages. Four real earthquake records—EI-Centro (EI), Wenchuan (WC), Traft (TR), and an artificial record (RG)—were applied to model foundations constructed in untreated sand and sand improved with ordinary stone columns (OSCs) and GESCs. Settlement, excess pore water pressure (EPWP), column-soil stress ratio, and acceleration response were continuously monitored. Results indicate that seismic loading contributes most significantly to settlement and EPWP generation. Both OSC and GESC foundations exhibit greater sensitivity to the EI and RG motions. The lateral earth pressure in OSCs undergoes more pronounced variation across the loading stages, whereas GESCs maintain more stable confinement. Despite seismic densification and geogrid confinement, the column-soil stress ratio decreases in the post-seismic stage due to structural degradation. Acceleration spectra for OSC and GESC display multiple peaks, in contrast to the single dominant peak in untreated sand. Under EI and RG inputs, GESCs exhibit higher peak acceleration amplification factors (np) than OSCs, while the opposite trend is observed under WC and TR motions.
Large volumes of dredged sediments (DS) excavated from water reservoirs pose significant environmental and disposal challenges. This study investigates the feasibility of stabilizing DS with cement and recycled concrete powder (RCP) for use as a subbase material. A total of 25 mixtures were prepared with cement contents ranging from 3 to 10 q_u ), California Bearing Ratio (CBR), resilient modulus ( M_R ), and wave velocities obtained from free–free resonance (FFR) tests at different curing times. Durability was assessed through wetting–drying (W–D) cycles, while microstructural characteristics were examined using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results indicate that cement significantly enhances the strength and stiffness of DS. Untreated DS exhibited a q_u of approximately 386 kPa, whereas cement-stabilized mixtures with 3–10 q_u and key engineering parameters were developed to support pavement design. The optimal mixture satisfies the Thai Department of Highways (DOH) subbase requirements and Austroads M_R criteria, offering a balanced solution in terms of performance, cost, and environmental impact. These findings demonstrate the technical, economic, and environmental feasibility of using cement–RCP stabilized DS as a sustainable subbase material.
A pragmatic method for considering creep deformation during the process of primary consolidation is proposed. The main point of the method is using a modified yield stress in the calculation of consolidation settlement with conventional method. The modified yield stress is evaluated by a well-documented strain rate–yield stress relationship, which is based on isotache concept, and a newly proposed method for evaluating the plastic strain rate ( ε̇_EOP ) at the end of primary (EOP) consolidation based on Terzaghi’s consolidation theory. The results of finite element analysis as well as the results of applying the method to some reported test data and analyzed cases in the literature indicate the method is an effective and practical one.
Unused waste vehicle tires can be easily disintegrated into microplastics in landfills. The barrier performance of the liner material in a landfill plays a crucial role in terms of environmental protection. Furthermore, there is an eager need to make research on the engineering properties of soils that are contaminated with microplastics. In order to determine the compaction properties and plasticity characteristics of a sand-bentonite mixture that represented a barrier contaminated with tire wear microplastics, standard Proctor compaction, liquid and plastic limit tests were conducted on 0.05, 0.1, 0.2, 0.5, 1 and 2
To address the negative skin friction in pile foundations caused by soil settlement under large-area surcharge loading, this study investigated two foundation treatment methods used in coastal reclamation areas: shallow vacuum preloading (≤ 5 m) and subsequent deep (secondary) vacuum preloading (15–20 m). Field tests on the negative skin friction of a single pile were conducted using two groups of PHC pipe piles in the New Campus Project of Zhejiang Oriental Vocational and Technical College. By monitoring pile and surrounding soil settlement, pore water pressure, pile shaft axial force, and shaft skin friction, the evolution of negative skin friction and the dynamic characteristics of the neutral point were analyzed. The test results show that deep vacuum preloading can significantly reduce pile settlement, surrounding soil settlement, the peak pile shaft axial force, the peak negative skin friction along the pile shaft, and the neutral point depth ratio. Over time, pile settlement, soil settlement, pile shaft axial force, and negative skin friction all increased, whereas the neutral point moved upward and gradually stabilized. Compared with shallow vacuum preloading, deep vacuum preloading reduced the average negative skin friction coefficient along the pile shaft by 30.00
