To address the adverse impact of high-temperature climates on soil subgrade and other earthen infrastructures, this study investigates the thermal effects on the mechanical properties of biopolymer treated soils. By conducting temperature-controlled direct shear tests and discrete element method (DEM) simulations, the study examines the influence of temperature on shear strength, deformation characteristics, and microstructural behavior of biopolymer treated soils. Two widely used biopolymers: xanthan gum (XG) and gellan gum (GG) are employed in this study. As the temperature rises from 5 degrees C to 65 degrees C, the shear strength of GG treated soil decreases by 50.1 %, whereas XG treated soil experiences a smaller reduction of 21.2 %. DEM simulations reveal that elevated temperatures result in broader shear bands and reduced inter-particle contact forces. Specifically, for untreated soil and XG treated soil, the shear band width increases by 25.9 % and 25.4 %, respectively, as the temperature increases from 5 degrees C to 65 degrees C. In contrast, for GG treated soil, the shear band width initially expands by 104.2 %, followed by a reduction of 66.8 %. Furthermore, as the temperature increases from 5 degrees C to 65 degrees C, the average contact force of untreated soil, XG and GG treated soil decreases by 15.0 kPa, 24.7 kPa, and 49.4 kPa, respectively. The GG treated soil shows a more significant loss in shear strength and more pronounced microscopic changes. These results suggest that both biopolymers effectively improve soil mechanical properties, while XG demonstrates superior thermal stability, making it more suitable for reinforcing subgrades and embankments in regions with substantial temperature fluctuations.

This study introduces a novel ternary geopolymer binder based on ground granulated blast furnace slag (GGBS), fly ash (FA), and desulfurization gypsum (DG) for stabilizing dredged sediment (DS). The primary motivation is to transform DS into a viable construction fill material by achieving the required strength standards for large-scale utilization. The research methodology integrates consolidated-undrained triaxial shear tests for mechanical evaluation and microstructural characterization for mechanism analysis. Results reveal that strength development is governed by synergistic gelation-crystallization. Key findings include: (1) Increasing DG content improves deviatoric stress-strain behavior through AFt crystallization, although 4% DG slightly compromises early strength. Confining pressure enhances peak strength by promoting densification. (2) Higher initial water content shifts failure to hardening, increasing ductility by 40-60% but reducing peak strength by 18-34% due to particle lubrication, partially compensated by confining pressure. (3) AFt formation substantially improves deformability, raising failure strain by 84-115% and secant modulus by up to 190% per 4% DG increment. (4) Microstructural analysis confirms that geopolymer and C-A-S-H gels establish the primary binding network, while AFt crystals refine pores. This binder system shows significant potential for treating high-water-content DS and provides a basis for optimizing strength-ductility performance.

With the growing emphasis on sustainable development in geotechnical engineering, biopolymers are emerging as eco-friendly soil improvement agents. However, the influence of temperature on the hydraulic performance of biopolymer-treated soils remains poorly understood. This study develops a novel model to describe the water retention and saturated hydraulic conductivity (ks) of biopolymer-treated soils under varying temperature conditions. The model integrates the temperature-dependent effects on biopolymer water absorption, swelling behavior, and hydrogel viscosity. Laboratory experiments were conducted to validate the model. As temperature increased from 20 to 60 °C, gravimetric water content of biopolymer decreased by 49%, leading to a reduced swelling effect. In parallel, biopolymer viscosity declined by 34%–50% between 5 and 65 °C. Elevated temperature diminished soil hydraulic performance. Saturated water content decreased by 4.9% at 1% biopolymer dosage, as temperature rose from 20 to 60 °C. Both air-entry value and residual water content also declined. Soil ks decreased by nearly four orders of magnitude with a 1% biopolymer dosage at 25 °C. However, this effect weakened at elevated temperatures, as ks increased by 4.3-fold when temperature rose from 5 to 65 °C. The proposed model accurately reproduced these results, offering a reliable tool for designing sustainable geotechnical systems under varying climatic conditions.

The unprecedented carbon dioxide (CO2) concentrations in the atmosphere, followed by a global surface temperature increase above pre-industrial levels during 2011–2020, of about 1.1°C (over land 1.59°C), have put an urgency on the UN goal of attaining net zero emissions by 2050. Until the transition to clean energy sources is attained, carbon dioxide capture, utilisation, and storage (CCUS) remain a near-term, high-priority mitigation measure to control carbon dioxide emissions from fossil-fuel-based processes. The present article contributes to the topic of CCUS by assessing, initially, the maturity for industrial-level application of current carbon dioxide capture technologies. Subsequently, the advantages and limitations of geoenvironmental applications of carbon dioxide in the neutralisation of industrial by-products are detailed, as well as the use of carbon dioxide as a working fluid for geothermal heat extraction from abandoned oil and gas wells. The challenges of subsurface formation characteristics for the storage of carbon dioxide, with emphasis on geomechanical behaviour, are discussed. Injection of carbon dioxide into hydrate sediments constitutes another carbon dioxide storage option that can also allow the use of methane as an energy source. Finally, the paper analyses the liability issues of carbon storage projects and the challenge of assessing long-term risks to provide insurance coverage to them.

Using vegetation on degraded soils often faces difficulties due to poor nutrients and limited water retention. Soil amendments such as compost and biochar are therefore required. However, their combined effects on soil and plant development are complex, as intense rainfall and high temperatures in tropical conditions may accelerate amendment degradation and alter soil properties over time. A two-year field experiment was conducted to monitor soil moisture dynamics, microstructure, vetiver grass (Chrysopogon zizanioides) growth, including shoot height, root depth, and root biomass. Four treatments were compared: unamended soil (S), soil + compost (C), soil + compost + raw biochar (C + RB), and soil + compost + pre-treated biochar (C + PB). S and C treatments exhibited relatively low water retention, associated with smaller proportions of sub-micropores and super-nanopores. C contained more large pores, promoting drainage but causing greater moisture fluctuations. In contrast, C + RB enhanced water retention by increasing fine-pore volumes, while C + PB achieved the highest and most stable soil water content. The improved moisture conditions in C + PB corresponded with deeper rooting and greater root biomass compared with other treatments. Pure compost promoted early plant growth but was less effective over multiple wet–dry seasons, as its organic matter decomposed rapidly under tropical conditions. Combining compost and biochar, particularly pre-treated biochar, offers a practical, field-ready approach to improve soil structure and moisture retention, thereby supporting sustained plant growth in degraded soils.

This study investigates the hydro-mechanical properties of biochar-amended cracked soils and their impact on slope stability under climate change. The laboratory tests analyzed the saturated water permeability (ks), soil water retention curve (SWRC) and shear strength of biochar-amended cracked soil during dry–wet cycles. Numerical simulations were conducted based on the laboratory test results to evaluate the stability of biochar-amended cracked soil slopes under infiltration conditions, using Monte Carlo simulations. The test results demonstrate that biochar amendment significantly reduces the crack ratio, with biochar pyrolyzed at 200 °C decreasing it by 40.8

Climate change can lead to soil moisture loss and shrinkage, forming crack networks that reduce soil strength and impermeability, hence posing serious risks to engineering safety. This study aims to investigate the influence of biochar on controlling soil cracking through laboratory tests, considering different soil dry densities, biochar pyrolysis temperatures contents, and dry-wet cycles. The selected biochar was derived from corn straw at two pyrolysis temperatures of 200 °C and 500 °C. Mechanisms of biochar in controlling soil cracking were revealed by using the methods of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), liquid-plastic limit tests, and image analysis. The results showed that biochar under pyrolysis temperature at 200 °C was more effective than that pyrolyzed at 500 °C in inhibiting soil cracking. The greatest reduction in soil cracking rate was 81.0

Soil-water characteristic curve (SWCC) represents one of the important properties describing the hydraulic characteristics of unsaturated soil, with extensive application value in geotechnical engineering, but the experimental process for obtaining SWCC is complex and time-consuming. This research proposes a prediction framework based on Bayesian-informed machine learning for SWCC applicable to different soil types, using easily measurable soil parameters. This model uses quantified particle size distribution, bulk density, and saturated water content as input features, and employs Bayesian-Markov Chain Monte Carlo methods to inversely derive Fredlund-Xing (FX) model parameters as output features. Deep Neural Network (DNN) and stacking models based on ensemble learning of five regressors were constructed to establish the prediction framework. Results show that both DNN and stacking models effectively capture complex nonlinear relationships between the three easily measured soil parameters and FX parameters, demonstrating good prediction accuracy. The stacked model shows better prediction results, with R2 exceeding 0.94 for all three parameters, outperforming the DNN model (R2 = 0.93). Through feature engineering and SHAP (Shapley Additive Explanations)-based feature sensitivity analysis, the relationships between input features and the three FX model parameters were physically interpreted, providing physical interpretability for the machine learning models. The prediction method offers a new approach for fast and accurate acquisition of SWCC, expanding the application of machine learning methods in the field of unsaturated soils.

Plant roots can significantly enhance the mechanical properties of soils, but accurately predicting the root reinforcement effects remains challenging. This study introduces a novel hypoplastic model for saturated soils reinforced with plant roots, by incorporating root effects into soil mechanical behavior. The model explicitly integrates root reinforcement into the soil constitutive equations by introducing easily obtained parameters, including root area ratio (RAR) and root tensile strength (Tr). To validate the model, two experimental datasets were used: one from this study, involving Cynodon dactylon root-reinforced soil in consolidated undrained triaxial tests, and the other from the literature, which includes data from Cryptomeria D. Don root-reinforced soils in consolidated drained and undrained triaxial tests. A comparison of the model calculations with experimental data showed that the model can accurately predict the stress-strain behavior and volume deformation characteristics of root-reinforced soils with varying root contents and confining pressures. Roots improve soil strength by resisting tensile stresses along shear planes. Furthermore, root reinforcement reduces volumetric compression by limiting soil contraction under stress. The sensitivity analysis indicates that both RAR and Tr significantly influence the mechanical behavior of root-reinforced soils, improving shear strength and reducing deformation, providing valuable insights for geotechnical engineering design. The proposed model offers a reliable theoretical tool for analyzing root-reinforced soils in ecological geotechnical engineering, supporting the advancement of sustainable root reinforcement applications.

Various materials have been proposed to improve chemical methods for stabilizing marine soft clay. However, there is still a lack of comprehensive understanding of the mechanical performance and micro-mechanisms of alkali-activated binders in marine soft clay treated with solid waste under chloride attack. This study aims to investigate the chloride erosion resistance of alkali-activated Ground Granulated Blast Furnace Slag (GGBS) marine clay stabilized with CaO (0–2

Recycled concrete aggregate (RCA), derived from construction and demolition waste, represents a promising secondary resource for sustainable waste valorization; however, its limited hydraulic performance, mechanical integrity, and ecological functionality restrict its large-scale reuse in environmental applications. In this study, biochar and gellan gum were employed to enhance RCA and develop a multifunctional cover material suitable for waste management purposes. Laboratory investigations were conducted to evaluate vegetation establishment, soil-water characteristic curves (SWCCs), saturated permeability, and shear behavior of the modified RCA. Compared with unmodified RCA, the incorporation of 5% biochar increased seed germination by approximately 183% and seedling height by about 46%, whereas excessive biochar content adversely affected vegetation growth. Combined modification resulted in an overall upward shift of the SWCC, with the saturated volumetric water content and air-entry value increasing by 59% and 300%, respectively. Meanwhile, the saturated permeability coefficient was reduced by approximately 85%, and vegetation growth further enhanced this reduction, suggesting improved resistance to water infiltration. Root reinforcement further increased shear strength and produced a more ductile shear response, as indicated by increased peak displacement, reduced post-peak stress loss, and sustained residual shear resistance. Overall, RCA amended with 5% biochar and 1% gellan gum exhibited the most balanced performance among the tested formulations in terms of vegetation establishment, hydraulic regulation, and mechanical stability. These findings suggest a promising pathway for upgrading construction and demolition waste-derived RCA into value-added cover materials, although long-term and field-scale validation remains necessary before practical implementation.

Vacuum preloading is widely adopted in ocean engineering to treat dredged marine sludge. Integrating prefabricated horizontal drains (PHDs) facilitates simultaneous filling and dewatering, while incorporating lime mitigates clogging around the drains. This study investigates the effects of lime dosage on the hydro-mechanical behaviour of dredged sludge under vacuum preloading with PHDs through model tests. Results showed that adding 0.1% lime only increased vacuum pressure and shear strength within the 0 to −20 cm range below the PHD. Increasing lime dosage to 0.3% significantly enhanced vacuum pressure by 15% to 115% and shear strength by 65% to 222% due to enhanced aggregation and reduced clogging. Further increasing lime dosage to 0.5% resulted in marginal increases in vacuum pressure and shear strength, yet raised compressibility. All samples exhibited higher hydraulic conductivity (k) at −10 cm below the PHD than those at 10 cm above, regardless of the lime dosage. Only the addition of 0.3% lime increased k at −10 cm below the PHD whereas 0.5% lime decreased k due to pore filling by cementitious C-S-H products. This study underscores the importance of selecting an appropriate lime dosage to optimise the hydro-mechanical behaviour of dredged sludge treated with combined vacuum preloading and PHD.

Desiccation cracks significantly alter slope stability during extreme rainfall, yet the relative influence of crack depth versus crack intensity factor (CIF) across soil types remains poorly understood. In this study, four centrifuge tests were conducted on slopes subjected to various antecedent temperature loadings followed by extreme rainfall with a100-year return period. Coupled hydro-mechanical numerical simulations were then performed to investigate the underlying failure mechanisms of cracked slopes. Both measured and computed results demonstrate that, although high plasticity induces greater surface cracking, kaolin clay slopes are less prone to deep desiccation than silty clay slopes. This is primarily due to its lower permeability, which restricts upward water migration and evaporative water loss. Consequently, during intense rainfall, the silty clay slopes with lower CIF but deeper crack depth are more susceptible to sliding failure. This comparison highlights the dominant role of crack depth over surface crack intensity in triggering slope failure. Furthermore, distinct failure modes are observed in slopes subjected to extreme drought-rainfall, influenced by both crack depth and inclination. Deep vertical cracks trigger retrogressive failures reaching depths of up to 5 m, while shallow oblique cracks cause planar failure at depths of approximately 2–3 m. These findings imply that monitoring and regular maintenance of earthen infrastructures should prioritize characteristics of deep cracks, rather than surface crack intensity alone, as critical indicators for assessing and mitigating landslides risk.

Shallow slope instability is frequently triggered by desiccation cracking, yet conventional chemical stabilizers often encounter environmental and economic constraints. This study evaluates the synergistic potential of biochar produced at 200 °C and 500 °C, each added at 9% by dry soil mass, along with tall fescue, to mitigate cracking and improve hydraulic properties. Through laboratory experiments and micro-scale analyses, the underlying mechanisms of this integrated treatment were elucidated. The results show that biochar-vegetation integration significantly suppressed desiccation cracking. Specifically, the 500 °C biochar–vegetation treatment (V-T5) yielded the most effective crack inhibition, reducing the surface crack ratio by 51.4% compared to bare soil (BS) after three dry-wet cycles. Regarding hydraulic performance, V-T5 extended the constant-rate evaporation stage and increased the cumulative retained water by approximately 35% over the tested drying period. Furthermore, the integrated treatment effectively limited the increase in saturated hydraulic conductivity (ks) typically induced by dry-wet cycles. Mechanistic insights indicate that biochar improves water retention through its micropores, strengthens soil aggregation via polyvalent cation exchange, and optimizes nutrient availability for enhanced vegetation growth. These physicochemical effects, together with mechanical root reinforcement and rhizosphere-induced biogenic cementation, form a sequential mechanism from rhizosphere improvement and enhanced plant growth to structural reinforcement. These findings demonstrate the potential of combined biochar and vegetation as an environmentally sustainable approach for stabilizing shallow slopes under alternating wetting and drying conditions.

Soil erosion poses a major threat to global soil resources. Traditional soil stabilization methods, however, tend to be expensive, ecologically damaging, and ineffective over the long term. Combining biocementation with vegetation offers a potentially sustainable alternative. Biocementation relies on microbially induced calcium carbonate precipitation (MICP) or enzyme-induced calcium carbonate precipitation (EICP). This review synthesizes recent studies on integrated biocementation–vegetation systems, emphasizing compatibility, key controlling factors, and mechanisms underlying their erosion-control performance. Regarding compatibility, this review explores how biocementation parameters and vegetation characteristics shape the success of this integrated approach. The analysis indicates that applying biocementation at lower intensities, paired with salt-tolerant plant species, can significantly improve harmony between the two methods. For anti-erosion performance, appropriate biocementation–vegetation parameters yield complementary advantages. Biocementation effectively bridges gaps in vegetation's early growth phases by stabilizing the soil matrix, supplying nitrogen and carbon sources, and enhancing water retention, which in turn supports robust plant establishment. Adding amendments like biopolymers or biochar further promises to enhance these synergies. Once established, mature vegetation delivers reliable erosion control even without ongoing biocementation. A practical three-phase implementation framework is outlined for future engineering projects. Overall, merging vegetation with biocementation for soil erosion control holds tremendous promise, offering not just theoretical compatibility and mutual reinforcement but also a viable, sustainable strategy that harmonizes ecological, economic, and engineering considerations.

The excavation of municipal solid waste landfill has generated numerous heavy metal (HM) contaminated humus soil. The humus soil can be used as the slope cover material to reduce rainwater infiltration after HM remediation and hydraulic properties improvement. This study is intended to explore the impacts of enzyme-induced carbonate precipitation (EICP) on both the immobilization of HMs and the enhancement of hydraulic properties in humus soil. The soil water retention curve (WRC), saturated permeability coefficient (ks) and exchangeable HM concentration were measured, respectively. The results show that EICP can reduce the exchangeable HM concentrations to meet standard requirements through promoting HM carbonate precipitation. The carbonate precipitations mainly form in soil macro-pores, leading to a decrease of more than one order of magnitude in ks and more obvious bimodal feature of WRC. The soil water retention ability can be improved through increasing the air-entry values for macro- and micropores, simultaneously reducing the desorption rate of macro-pores.

In a time of changing climate, the need to achieve a safe, low-carbon, green, environmentally friendly world has led to the emergence of a new interdisciplinary field, ecological-geotechnics (eco-geotechnics). Focusing on the interplay of soil/rock mechanics, ecology, botany, and atmospheric science among others, this newly emerged eco-geotechnics marks a paradigm shift towards sustainability and renewability. Eco-geotechnics investigates the interface between abiotic porous media and the complex biotic interactions within the rhizosphere. For example, it integrates atmosphere–plant–soil interactions through theory and engineering applications.This paper reviews the evolution of eco-geotechnics from unsaturated soil mechanics to a new interdisciplinary field by summarising theoretical advances and practical applications in the past few decades. Key theoretical developments include the modelling of energy and water balance, seepage–deformation coupling in vegetated soil, and root reinforcement considering diverse root morphologies. Examples of such applications include vegetated infrastructure, bio-cementation, sustainable landfill cover, cultivation of medicinal plants, and extraterrestrial agriculture. Finally, the review identifies critical research gaps and outlines directions for advancing eco-geotechnics in the context of climate change.

This paper presents a three-dimensional finite element analysis to investigate the response of frame buildings with varying foundation configurations to urban tunnel construction induced ground movements. Four foundation configurations are considered, including raft, strap footing, strip footing and isolated footing foundations. Tunnelling-related and structural parameters are also varied during the analysis. Sandy ground is typically modelled using a hypoplastic constitutive model calibrated using element tests, and the reliability of the model is validated through comparisons with existing centrifuge data from literature. Soil displacements and foundation movements at the soil-foundation interface are presented, and structural distortion and associated modification factors are calculated and linked to relative soil-building stiffness. The results demonstrate that tunnelling-induced soil-structure interaction is predominantly governed by foundation configuration. Continuous foundations (raft, strap) along tunnel cross section effectively restrain horizontal soil and structural displacements but tend to mobilize larger shear strains within frames, while discontinuous foundations (strip, isolated) lead to localized settlements, non-uniform load redistribution, and occasionally higher damage concentrations at lower stories. Building self-weight amplifies both settlements and strains, footing width enhances lateral restraint, and eccentricity mainly affects short frames. Modification factor analyses further confirm that structural deformation scales consistently with relative soil-structure stiffness and aligns well with existing empirical envelopes. Overall, foundation type and continuity are identified as the decisive factors controlling tunnelling-induced building responses, with weight, width, and eccentricity serving as secondary influences. The findings of the research may provide useful guidance for the risk assessment in urban tunnelling projects.

Understanding the effect of vegetation on anisotropic saturated hydraulic conductivity is essential in the design and performance assessment of bioengineered geostructures. Therefore, this study examines how the age and root biomass of Vetiver grass influence the anisotropic saturated hydraulic conductivity of rhizosphere. Because conventional permeameters cannot reliably measure horizontal and vertical saturated hydraulic conductivity in intact vegetated soils, a recently developed cubic triaxial permeameter was utilized. A total of 76 saturated hydraulic conductivity tests were conducted on specimens cultivated and grown under controlled conditions for 2, 5, and 8 months. The results revealed that increasing plant age and root biomass reduced horizontal saturated hydraulic conductivity by up to 11-fold and vertical saturated hydraulic conductivity by up to two-fold compared with the bare soil, due to root-induced clogging of preferential flow paths. Specifically, the development of dense secondary roots clogs lateral pore spaces, while vertically grown primary roots induce partial preferential flow paths. Although the bare soil exhibits a clear anisotropic behavior (k(h)/k(v )> 3 for void ratio of 0.70), vegetated soils with higher root biomass exhibit almost an isotropic behavior. These findings provide valuable insight for designing and optimizing vegetation-based water management, green landfill covers, and slope stabilization systems.

Biopolymer amendments can modify soil structure and water dynamics, thereby influencing plant establishment and soil functional performance. This study examined the combined effects of three biopolymers (xanthan gum, guar gum, and chitosan) and three grasses-bermudagrass (Cynodon dactylon), tall fescue (Festuca arundinacea), and ryegrass (Lolium perenne)-on vegetation establishment and soil hydro-mechanical behavior. Cultivation tests showed that tall fescue exhibited the greatest adaptability among tested species, while xanthan had the least inhibitory effect on early growth, increasing final germination rate and shoot height by 10.0% and 10.3%, respectively, relative to unamended soil. Biopolymer addition markedly enhanced soil water retention, raising saturated water content from 25.7% to 30.8%, while xanthan-tall fescue (X-T) treatment further increased it to 32.2%. At a matric suction of 100 kPa, the saturation degree of X-T reached 74.1%, more than three times that of unamended soil, indicating a substantially improved moisture environment for plant development. Xanthan gum greatly reduced saturated hydraulic conductivity (from 7.4 x 10(-7) m/s to 3.4 x10(-9) m/s), whereas X-T treatment maintained a relatively high conductivity (1.4 x 10(-8) m/s) due to root-induced preferential flow pathways. These biopolymer- and root-driven changes in soil structure and water transport translated into higher shear resistance under both saturated and unsaturated conditions, with the strongest improvements observed at elevated matric suction. The biopolymer bonding regulates pore-scale water retention while roots modify flow pathways and contribute mechanical anchorage. This coupling between biopolymers and vegetation provides a promising strategy for improving soil functional quality and plant establishment on disturbed or engineered slopes.