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Soft soils pose significant challenges to the constructions on or within them, which are commonly stabilized with lime or ordinary Portland cement. However, these two binders are energy-intensive with high-carbon footprint. The current study presents an investigation of using an alkali-activated binder (AAB), a low-carbon cementitious material, for soft soil stabilization. Experiments including unconfined compressive strength test, compressibility test and hydraulic conductivity test were carried out to investigate the mechanical and hydraulic properties of soils stabilized with AAB of different concentrations. Microstructural characterizations of soil samples before and after AAB stabilization were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The experimental results show that the AAB can greatly improve the strength of the stabilized soil and meanwhile significantly reduce its compressibility and permeability. The strength of the stabilized soil increases with curing period and higher AAB concentration; the compressibility potential of original soil is noticeably reduced from medium to a low level after AAB stabilization; the hydraulic conductivity of soft soil stabilized with 20% AAB is more than 700 times smaller than that of the untreated. The microstructural characterizations using XRD, SEM and EDX confirm the formation of calcium aluminosiliate hydrate (CASH) gel in the stabilized soil matrix. This gel binds the soil particles and fills the voids between them and, therefore, increases the strength and reduces the compressibility and permeability of stabilized soil.

The construction of superstructures on soft soils demands the desired bearing capacity. This can be achieved through various approaches, including improving soil properties using chemical methods, or by employing techniques such as increasing footing dimensions or using micro piles which are uneconomical and time-consuming. To overcome this, enhancement of bearing capacity of soft soils was done by simple and economical technique i.e., cutting the existing soft soil and filling the Cohesive-frictional soil with a defined ratio of top layer thickness to width of the footing. To conduct this analysis, Plaxis 3D software was employed to investigate soil behaviour and simulate various scenarios, to identify the optimum thickness of the fill layer required to enhance the desired bearing capacity of the strata while ensuring a prescribed settlement and load imposed by the superstructure following the Indian Standards for constructing a multi-storied building. The investigation determined that the optimum top layer thickness to footing width is 2. The findings of this study will contribute valuable insights into geotechnical engineering practices, offering a practical and economical solution for enhancing the bearing capacity of soft soils in construction projects.

Site amplification models were developed as part of the Next Generation Attenuation (NGA) project to evaluate potential seismic risks in areas of North America. However, these models have low validity in seismic risk prediction in deep soft soil deposits (DSSDs) due to the lack of sufficient seismic recordings collected from DSSDs and site-specific dynamic parameters of local soils. Soil profiles from Suzhou City, China were used to validate the NGA nonlinear site amplification model (referred to as WSA08) and establish a simpler one based on 1-D site response results with high-frequency dominated (HFD) input motions. Fully nonlinear (NL) method which can capture the nonlinear behavior of soft soils was used to establish the simple functional form of nonlinear amplification model. Compared with WSA08, an accommodation coefficient A was added to adjust the ordinate of the Amps, while the linear amplification component was removed due to the epistemic uncertainty of linear amplification in DSSDs. The practicality of the simple model was validated using another three HFD input motions at different periods.

Evaluating the stability of seawalls constructed on soft soils is critical but challenging. Traditional methods often depend on whether settlement velocity exceeds predefined thresholds, which can overlook subtle settlement fluctuations and may be less adaptable to varying construction and environmental conditions. To overcome these limitations, this paper presents a novel evaluation framework that combines a new settlement‐to‐loading index with a permutation entropy (PE) algorithm. By incorporating both settlement velocity and loading, the proposed index captures the behavior of seawalls under complex load conditions more comprehensively than fixed settlement velocity thresholds. The PE algorithm is then employed to analyze the time‐series data of the settlement‐to‐loading index, enabling the detection of small‐scale, transient fluctuations, which is a critical feature for soft soil scenarios characterized by significant and sporadic settlement spikes. A case study of a seawall in China demonstrates that this combined approach is more sensitive than conventional methods, effectively signaling early instabilities resulting from minor construction activities or rapid loading changes. Overall, the proposed method offers a physically meaningful, adaptable, and practical approach for evaluating seawall stability on soft soils, potentially reducing misjudgment in coastal infrastructure projects.

Spatial variability of engineering properties caused by the natural characteristic heterogeneity is a common feature in soil layers. Meanwhile, changes in soil properties during consolidation and large strains are commonly encountered during long-term consolidation analysis of soft soils; however, few studies have considered these factors. A 1-D consolidation model fully coupled with elastic viscoplastic constitutive model, called EVPC, is developed using piecewise-linear method for long-term settlement of soft clay. The EVPC incorporates the idea of ‘equivalent time’ to account for large strain, soil self-weight, compressibility and permeability with spatial variability and high nonlinearity, as well as creep during the consolidation process. A comparison with finite element simulations and oedometer tests with different thicknesses of soil layer under multi-stage constant loads verified the effectiveness and accuracy of the EVPC’s deterministic analysis. After that, the long-term settlement and excess pore pressure distribution of Berthierville clay layer from the field test are estimated using EVPC probabilistic analysis. All measurements from the field test are within the range of corresponded closely to the high probability density results of the probabilistic analysis, and the excess pore pressure is revealed to be more sensitive to the spatial variability of soil parameters than settlement.

Soft soils are usually treated to mitigate their engineering problems, such as excessive deformation, and stabilization is one of most popular treatments. Although there are many creep models to characterize the deformation behaviors of soil, there still exist demands for a balance between model accuracy and practical application. Therefore, this paper aims at developing a Mechanistic-Empirical creep model (MEC) for unsaturated soft and stabilized soils. The model considers the stress dependence and incorporates moisture sensitivity using matric suction and shear strength parameters. This formulation is intended to predict the soil creep deformation under arbitrary water content and arbitrary stress conditions. The results show that the MEC model is in good agreement with the experimental data with very high R-squared values. In addition, the model is compared with the other classical creep models for unsaturated soils. While the classical creep models require a different set of parameters when the water content is changed, the MEC model only needs one set of parameters for different stress levels and moisture conditions, which provides significant facilitation for implementation. Finally, a finite element simulation analysis of subgrade soil foundation is performed for different loading levels and moisture conditions. The MEC model is utilized to predict the creep behavior of subgrade soils. Under the same load and moisture level, the deformation of soft soil is largest, followed by lime soil and RHA–lime-stabilized soil, respectively.

More and more expressways built on soft soil foundations need to widen their embankments because they cannot fulfill the demand for the traffic volume. Geosynthetic-reinforced pile-supported embankment (GPE) is currently the most widely used method in practical projects. This paper proposes the pile-supported geosynthetic-reinforced soil wall (PGSW) technology to widen embankments, enjoying several evident advantages in construction. The existing embankments with and without piles in the foundation soil were widened by the PGSW and GPE technologies using a centrifugal model to compare these two technologies. In addition, the finite-difference numerical models were established to analyze the cut slope ratio of the existing embankment in the PGSW technology. The results indicate that the settlements of the existing embankment and the widened portion, as well as the differential settlement between the existing embankment and the widened portion, are smaller for the PGSW technology than the GPE technology. The widened portion has less influence on the bending moment of the pile near the centerline of the embankment and the toe of the widened portion in the PGSW than GPE technology. When the PGSW technology is adopted, the settlement on the embankment crest and the horizontal displacement of the lower part of the wall decrease with an increase in the cut slope ratio, and a cut slope ratio of 1.0:0.5 (vertical/horizontal) is advised.

The building industry requires methods that improve the quality of soil; if they want the foundation to be more durable and rigid, this is particularly true for residential construction. Modifying soft soils with metakaolin (MK) has proven to be an effective method for stabilizing soil. In this research, we studied the physiochemical properties of soft soil samples obtained from a construction site. The specimens were treated with different concentrations of metakaolin (0%, 5%, 10%, and 15% by weight of soil) and analyse to determine their strength and hydraulic conductivity. The observations showed that the hydraulic conductivity significantly decreased after the incorporation of metakaolin into the clay soil, compared to untreated soil. The hydraulic conductivity of the soil decreased by 70% for 15% metakaolin concentration. Forming of metakaolin hydrated calcium silicate gel (C-S-H) in the soil matrix results in increased pore-filling impact and reduced pore dimensions; both contribute to a reduction in hydraulic conductivity. The unconfined compressive strength (UCS) of the altered soil samples significantly improved after MK was incorporated into the mix. The UCS of the samples increased by 75% after adding the 15% MK substance. The increase in UCS can be attributed by the pozzolanic interaction that takes place between MK and soil. This interaction results in the production of new saturated products, which contribute to an increase in the material's strength. The strength and permeability of MK-treated soil show continuous changes as curing time extended; this observation is substantiated by the test outcomes, which demonstrate a decrease in permeability and an increase in strength as the curing period increases. In conclusion, MK has the ability to improve the resiliency of clay soil while simultaneously lowering its permeability. The results of the research indicate that addition of MK in clay soil improves its mechanical and hydrodynamic characteristics, making it a practical and effective approach. This finding has significant repercussions for the construction industry because it paves the way for an alternative that is both workable and inexpensive to the earth-stabilization methods that are currently in use.

The insertion ratio of the diaphragm wall is crucial for the deformation control of the deep excavation of a subway station in water-rich soft soils. Taking the deep excavation project of a subway station in water-rich soft soils as the background, a flow-stress coupling finite element analysis model is established to describe the combined effect of deep excavation and dewatering based on the Biot consolidation theory. The general characteristics of the coupling deformation of dewatering and excavation are studied, and the influence of the insertion ratio of the diaphragm wall on the ground deformation is analyzed. The results show that (1) both dewatering and deep excavation can cause lateral displacement of the diaphragm wall toward the pit, and the dewatering-induced settlement dominates the total settlement, as compared with that induced by excavation. (2) With the increase of the insertion ratio of the diaphragm wall, the maximum lateral displacement of the diaphragm wall under excavation gradually decreases until it converges to a constant, while the maximum lateral displacement under dewatering and excavation decreases first and then increases. (3) The relationship between the maximum ground settlement and the insertion ratio of the diaphragm wall shows a similar development trend to that between the lowest dewatering head and the insertion ratio of the diaphragm wall, which is approximately linear when the insertion ratio of the diaphragm wall is between 1.1 and 2.3. The control of hydraulic head outside the pit by the diaphragm wall is an effective way to reduce the ground settlement, which has a positive effect on reducing the construction risk and cost in water-rich soft soils.

Although stone-column embankments on soft ground have been widely studied, there is a limited number of studies in the literature in which overall stability is analysed when geosynthetic reinforcement is also incorporated at the embankment base. In the paper, a finite element-based stability analysis method is proposed and applied to analyse overall stability of geosynthetic-reinforced and stone column-supported embankments on soft soils. Fully mechanical-hydraulic coupled analyses are performed, a critical state model is used for soil constitutive behaviour and hardening non-linear elastoplastic models are incorporated to model the geosynthetics and soil-geosynthetic interfaces. Comparisons of the proposed method with other published methods are included in which the influence of the geosynthetic constitutive curve and of the area replacement factor of stone columns are analysed. Regarding the geosynthetic constitutive curve, its influence on other key variables—namely, excess pore pressure, geosynthetic tensile force, stress concentration ratio, settlement and horizontal displacement—is also analysed.