Search Results (168)

Soil improvement is one of the fundamental practices in civil engineering, with a long-standing history. In today’s context, the rapidly increasing demand for construction driven by urbanization has further emphasized the necessity and significance of soil stabilization techniques. This study aims to determine the optimum parameters for improving sandy soils by incorporating sodium alginate (SA) as a biopolymer additive into the microbial calcium carbonate precipitation (MICP) process. Sand types S1, S2, and S3, each with distinct particle size distributions, were selected, and the specimens were prepared at medium relative density. Three distinct approaches, MICP, SA, and MICP + SA, were tested for comparison. Additionally, two different improvement methods, injection and mixing, were applied to investigate their effects on the geotechnical properties of the soils. In this context, hydraulic conductivity, unconfined compressive strength (UCS), and calcite content tests, as well as scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses, were performed to assess the changes in soil behavior. SA contributed positively to the overall efficiency of the MICP process. The study highlights SA-assisted MICP as an alternative that enhances the microstructural integrity of treated soils and responds to the environmental limitations of conventional methods through sustainable innovation. Full article

Expansive soils, characterized by the presence of surface and subsurface cracks, over-consolidation, and swell-shrink properties, present significant challenges to slope stability in geotechnical engineering. Despite extensive research, preventing geohazards associated with expansive soils remains unresolved. This study investigates shallow sliding failures in slopes of highly expansive soils induced by rainfall, using model tests to explore deformation and mechanical behavior under cyclic wetting and drying conditions, focusing on the interaction between soil properties and environmental factors. Model tests were conducted in a wedge-shaped box filled with Nanyang expansive clay from Henan, China, which is classified as high-plasticity clay (CH) according to the Unified Soil Classification System (USCS). The soil was compacted in four layers to maintain a 1:2 slope ratio (i.e., 1 vertical to 2 horizontal), which reflects typical expansive soil slope configurations observed in the field. Monitoring devices, including moisture sensors, pressure transducers, and displacement sensors, recorded changes in soil moisture, stress, and deformation. A static treatment phase allowed natural crack development to simulate real-world conditions. Key findings revealed that shear failure propagated along pre-existing cracks and weak structural discontinuities, supporting the progressive failure theory in shallow sliding. Cracks significantly influenced water infiltration, creating localized stress concentrations and deformation. Atmospheric conditions and wet-dry cycles were crucial, as increased moisture content reduced soil suction and weakened the slope’s strength. These results enhance understanding of expansive soil slope failure mechanisms and provide a theoretical foundation for developing improved stabilization techniques. Full article

Conventional cast-in-place counterfort retaining walls, while widely used to support the fill body in geotechnical engineering cases, suffer from extended construction cycles and environmental impacts that constrain their usage more widely. In this study, in order to overcome these limitations, the performance of two types of innovative prefabricated counterfort retaining wall system—a monolithic design and a modular design—was investigated through physical modeling. The results reveal that failure mechanisms are fundamentally governed by the distribution of stress at the connection interfaces. The monolithic system, with fewer connections, concentrates stress and is more vulnerable to cracking at the primary joints. In contrast, the modular system disperses loads across numerous connections, reducing localized stress. Critically, this analysis identified a construction-dependent failure mode: incomplete contact between the foundation and the base slab induces severe bending moments that can lead to catastrophic failure. Furthermore, this study shows that complex stress states due to backfill failure can induce detrimental tensile forces on the wall structure. To address this, a composite soil material–wall structure system incorporating geogrid reinforcement was developed. This system significantly enhances the backfill’s bearing capacity and mitigates adverse loading. Based on the comprehensive analysis of settlement and structural performance, the optimal configuration involves concentrating geogrid layers in the upper third of section of the backfill, with sparser distribution below. Full article

Biopolymers, owing to their environmentally friendly and sustainable characteristics, have become a promising alternative for soil stabilization in geotechnical engineering. The application of protein-based biopolymers as binders for soil stabilization is less prevalent in geotechnical engineering compared to polysaccharide-based biopolymers. This study explores the potential of gelatin, a protein-based biopolymer derived from animal collagen, for stabilizing silty sand and improving its geotechnical properties. Gelatin was mixed into the soil at concentrations ranging from 0.25% to 2% of the dry weight of soil, and its effects on various soil characteristics were evaluated. The tests conducted include liquid limit, plastic limit, compaction behavior, and unconfined compressive strength (UCS); the addition of 1% gelatin led to an approximate 1.69 times increase in the strength of the unamended soil. After 28 days of curing, the UCS improved by approximately 5.03 times compared to the untreated soil, and the treated soil exhibited increased resistance to deformation under load. Microstructural analysis using scanning electron microscopy (SEM) revealed that gelatin facilitated the formation of a cohesive matrix, enhancing particle bonding and reducing void spaces within the soil. Carbon footprint analysis (CFA) conducted on an isolated footing stabilized with gelatin showed that the carbon emissions were reduced by 99.8% and 99% compared to traditional stabilizers such as lime and cement. Additionally, the interaction between the biopolymer and the fine-grained soil is distinctly evident in the FTIR and XRD analysis through hydrogen bonding and the formation of cementitious compounds. Full article

With the rapid urbanization and increasing development of underground spaces, foundation pit groups in complex geological environments encounter considerable challenges in deformation control. These challenges are especially prominent in cases of adjacent constructions, complex geology, and environmentally sensitive areas. Nevertheless, existing research is lacking in systematic analysis of construction sequencing and the interaction mechanisms between foundation pit groups. This results in gaps in comprehending stress redistribution and optimal excavation strategies for such configurations. To address these gaps, this study integrates physical model tests and PLAXIS 3D numerical simulations to explore the Nanjing Jiangbei New District Phase II pit groups. It concentrates on deformations in segmented and adjacent configurations under varying excavation sequences and spacing conditions. Key findings reveal that simultaneous excavation in segmented pit groups optimizes deformation control through symmetrical stress relief via bilateral unloading, reducing shared diaphragm wall displacement by 18–25% compared to sequential methods. Sequential excavations induce complex soil stress redistribution from asymmetric unloading, with deep-to-shallow sequencing minimizing exterior wall deformation (≤0.12%He). For adjacent foundation pit groups, simultaneous excavation achieves minimum displacement interference, while phased construction requires prioritizing large-section excavation first to mitigate cumulative deformations through optimized stress transfer. When the spacing-to-depth ratio (B/He) is below 1, horizontal displacements of retaining structures increase by 43% due to spacing effects. This study quantifies the effects of excavation sequences and spacing configurations on pit group deformation, establishing a theoretical framework for optimizing construction strategies and enhancing retaining structure stability. The findings are highly significant for underground engineering design and construction in complex urban geological settings, especially in high-density areas with spatial and geotechnical constraints. Full article

In light of rising environmental concerns, the rapid industrial recycling of building demolition waste material (BDWM) is now capable of supporting sustainable development in metropolitan regions. From this perspective, the current study investigated the geotechnical properties and applications of BDWMs as substitutes for natural materials (NMs) in road engineering infrastructures. For this purpose, the physical and geotechnical characteristics of both types of materials were initially examined, and then compared using laboratory-scale material comprehensive assessments such as sieve analysis (SA), the flakiness index (FI), the specific gravity test (Gs), the Los Angeles abrasion test (LAAT), Atterberg limits (AL), the water absorption test (WAT), the California bearing ratio (CBR), the direct shear test (DST), and the Proctor soil compaction test (PSCT). The BDWMs were collected from two locations in Iran. According to the results, the collected samples consisted of concrete, bricks, mortar, tile materials, and others. The CBR values for the waste material from the two sites were 69 and 73%, respectively. Furthermore, the optimum water content (OWC) and maximum dry unit weight (MDD) from the two sites were reported as 9.3 and 9.9% and 20.8 and 21 kN/m³, respectively, and the hydrogen potential (pH) as 9 and 10. The shear strength and CBR values indicated that the BDWM had a suitable strength compared to the NM. In terms of road infrastructure applications, the shear strengths were adequate for the analysis of common sub-base materials used in filling and road construction. Furthermore, the study’s findings revealed that BDWMs were suitable replacements for the NM used in road engineering operations and could make a significant contribution to sustainable development. Full article

With the ongoing acceleration in urban development, the volume of construction and demolition waste continues to rise, while the availability of natural aggregates is steadily declining. Utilizing recycled aggregates in concrete has become a vital approach to fostering sustainability within the construction sector. This research develops a life cycle-based environmental impact evaluation model for recycled aggregate concrete, applying the Life Cycle Assessment (LCA) framework. Through the eFootprint platform, a quantitative evaluation is carried out for C30-grade concrete containing varying levels of recycled aggregate replacement. Four replacement ratios of recycled coarse aggregate (30%, 50%, 70%, and 100%) were evaluated. The assessment includes six key environmental indicators: Global Warming Potential (GWP), Primary Energy Demand (PED), Abiotic Depletion Potential (ADP), Acidification Potential (AP), Eutrophication Potential (EP), and Respiratory Inorganics (RI). The findings reveal that higher substitution rates of recycled aggregate lead to noticeable reductions in RI, EP, and AP, indicating improved environmental performance. Conversely, slight increases are observed in GWP and PED, especially under long transport distances. Analysis of contributing factors and sensitivity indicates that cement manufacturing is the principal driver of these increases, contributing over 80% of the total GWP, PED, and ADP impacts, with aggregate transport as the next major contributor. This study offers methodological insights into the environmental evaluation of recycled aggregate concrete and supports the green design and development of low-carbon strategies in construction. Full article

Anchored slopes have been widely adopted globally, yet their design faces two critical challenges: the unreliable characterization of geomaterial variability and the urgent need for low-carbon. To address the first challenge, we propose a novel sensitivity index of variability (SIV) formulated through Monte Carlo Simulation (MCS), which systematically quantifies robustness within reliability-based design. Meanwhile, in response to global low-carbon initiatives, carbon emission metrics are innovatively established as the optimization objective for robust geotechnical design (RGD), replacing conventional cost-centric approaches. Building on these methodological advancements, we develop a framework that simultaneously optimizes engineering robustness and environmental sustainability. The operational efficacy of this framework is demonstrated through a case study of a rock slope at the tailwater tunnel outlet of a hydropower station in southwest China. Comparative analysis with the initial design solution reveals that our framework achieves higher robustness while reducing carbon emissions, demonstrating the superior performance of this framework. This study offers a systematic approach to advance both safety and sustainability in geotechnical infrastructure. The proposed methodology is readily adaptable to other earth structures facing similar reliability–environmental trade-offs. Full article

Underground spaces offer significant potential for sustainable urban development, particularly in cold climate regions where surface thermal fluctuations are extreme. However, optimizing the wind–heat environmental performance of such spaces remains insufficiently explored, especially in relation to spatial morphology. This study addresses this gap by investigating how underground spatial configurations influence thermal comfort and ventilation efficiency. Six representative spatial prototypes—fully enclosed, single-side open, double-side open, central atrium, wind tower, and earth kiln—were constructed based on common underground design typologies. Computational fluid dynamics (CFD) simulations were conducted to evaluate airflow patterns and thermal responses under winter and summer conditions, incorporating relevant geotechnical properties into the boundary setup. The results indicate that deeper burial depths enhance thermal stability, while central atrium and wind tower prototypes offer the most balanced performance in both ventilation and heat regulation. These findings provide valuable design guidance for climate-responsive underground developments and contribute to the interdisciplinary integration of building physics, spatial design, and geotechnical engineering. Full article

The disposal of rice husk ash (RHA) in rice-producing regions poses critical environmental and public health challenges. However, RHA’s high amorphous silica content offers significant potential for soil stabilization, particularly in improving the mechanical properties of weak soils. This study investigates the shear strength of clay soil stabilized with rice husk ash (2%, 4%, 6%) and low cement dosages (2%, 4%, 6%) that incorporate layered subgrade systems (top, bottom, and dual-layer configurations). By optimizing rice husk ash incorporation with reduced cement content, this approach challenges conventional stabilization methods that rely heavily on cement. Sixteen soil-cement-RHA mixtures were evaluated through mechanical testing, supplemented by microstructural and elemental analyses using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Results demonstrated substantial improvements in shear strength across all subgrade layers. The dual-layer system with 2% RHA 6% cement (2%RHA6%C) achieved the highest cohesive strength (115 kN/m²) and maximum deviatoric stress (446 kN/m²). These findings highlight the viability of RHA as a sustainable, low-cement soil stabilizer, offering dual benefits: effective waste valorization and enhanced geotechnical performance. This study advances sustainable ground engineering practices by introducing a resource-efficient novel building material and provides a framework for layered stabilization systems in clay soils. Future investigations will focus on a broader range of soil types and extend the application of this approach to other sustainable ground engineering practices. Full article

The emphasis on sustainable and environmentally friendly practices in geotechnical engineering has generated interest in alternative soil stabilizing techniques. The present study examines the application of xanthan gum (XG) and guar gum (GG) to enhance the strength of a sand–bentonite composite and explore their potential for use as landfill liners or impervious barriers. The mixtures, consisting of 25% bentonite and 75% sand, were treated with XG and GG concentrations of different percentages (0.5%, 1%, 2%, and 3% by dry mass). The test results indicated that a 2% addition was optimal for both biopolymers. Using this optimum value of XG and GG significantly increased the unconfined compressive strength (UCS) by almost 3-fold compared to the strength of untreated samples. Meanwhile, XG demonstrated a slightly higher impact on strength attributed to its robust gel-forming and binding properties. Comparisons between the two biopolymers highlighted XG’s superior performance, with UCS improvements of up to 20% over GG-treated samples. These results underscore the potential of biopolymers as effective, sustainable alternatives to traditional stabilizers, providing both mechanical enhancements and environmental benefits. The present study contributes valuable insights into green soil stabilization techniques, supporting the development of more sustainable construction practices. Fourier Transform Infrared Spectroscopy (FTIR) was conducted to analyze the chemical interactions between sand–bentonite mixtures and biopolymers, which possibly provide insights into the bonding mechanisms responsible for the observed improvements in mechanical and volumetric behavior. Full article

With the rapid development of lightweight and environmentally friendly building materials, foamed concrete has been widely adopted as a novel material for lightweight filling and foundation applications. However, its bearing capacity under localized loading conditions requires further investigation. This study focuses on silt-based foamed concrete with a 30% silt content. A series of unconfined compression tests and triaxial shear tests were conducted to determine its key mechanical properties. Large-scale indoor model tests were then carried out to evaluate the effects of the wet density (600 kg/m³, 700 kg/m³, and 800 kg/m³) and the loading position on vertical bearing performance. The results show that silt-based foamed concrete exhibits a basin-shaped deformation pattern under vertical loading, similar to traditional foundations. Based on experimental data and shear strength parameters, a formula for the ultimate bearing capacity of silt-based foamed concrete was developed by extending Terzaghi’s bearing capacity theory. This provides a theoretical basis for its application in geotechnical engineering. Full article

The carbon emissions from the cement industry account for approximately 8% of global carbon emissions, which exerts significant pressure on the environment. In this paper, the microbial-induced calcium carbonate precipitation (MICP) technology was introduced into the carbonization modification research of recycled hardened cement powder (RHCP), and the carbon sequestration performance of RHCP under different pressures was studied. The physicochemical properties of the carbonated products were characterized by microscopic testing methods, and the carbon sequestration mechanism under different pressures was obtained. Subsequently, carbonated RHCP (C-RHCP) was tested as a partial cement substitute for solidified sludge to evaluate its mechanical and durability properties. The results show that when the pressures were 0.3 and 0.5 MPa, the carbon sequestration capacity of RHCP was relatively good, reaching 59.14 and 59.82 g/kg, respectively. Since the carbon sequestration amounts under the two pressures were similar, and considering the energy consumption, in this study, a reaction pressure of 0.3 MPa was selected to prepare C-RHCP. Compared with pure cement, the 28-day unconfined compressive strength (UCS) of the sludge cured with 30% C-RHCP increased by 12.08%. The water stability coefficient of the solidified sludge in the C-RHCP group was greater than 1 after soaking for 7, 14, and 21 days, while the water stability coefficient of the cement group decreased to 0.92 at 14 days. After 20 freeze–thaw cycles, the mass losses of the cement group, the RHCP group, and the C-RHCP group were 31.43%, 38.99%, and 33.09%, respectively. This research not only provides an environmentally friendly strategy for the resource utilization of RHCP but also pioneers a new synergistic model that combines microbial mineralization with the modification of industrial solid waste. It demonstrated significant scientific value and engineering application prospects in reducing carbon emissions in the cement industry and promoted sustainable geotechnical engineering practices based on the “waste–waste” principle. Full article

This paper presents a systematic review of the progress of the research on limestone-calcined clay cement (LC3), focusing on its low-carbon characteristics, sustainable applications, and performance. LC3 can be used to address the high carbon emission problem in the cement industry, as its use significantly reduces carbon dioxide emissions (by 30%–40%) due to clinker being partially replaced with calcined clay and limestone in its fabrication. Studies have shown that the hydration reaction of LC3 generates calcium-aluminum-silicate hydrate (C-A-S-H), carbon-aluminate, and calcium alumina, which optimize its microstructure and endow it with comparable mechanical properties (28 day compressive strength close to or exceeding that of OPC) and better durability (outstanding resistance to sulfate erosion and carbonation) compared to ordinary Portland cement (OPC). LC3 has been used in 3D printing, ocean engineering, geotechnical reinforcement, and other applications, all of which have verified its engineering feasibility. Despite the significant environmental and economic advantages of LC3, its high-temperature performance, freeze–thaw resistance, and long-term durability still need to be further investigated. This paper provides theoretical support and practical references for the development and promotion of low-carbon cement materials. Full article

This review presents a comprehensive synthesis of existing studies on the correlations between soil electrical resistivity and fundamental geotechnical properties, with the aim of improving the applicability of resistivity testing in geotechnical engineering. Based on both laboratory and field research, the analysis highlights moisture content as the most influential factor inversely affecting resistivity, followed by plasticity index, clay content, and dry unit weight. Statistical approaches—including regression analysis and Spearman’s rank correlation—and artificial neural networks (ANNs) were evaluated for their effectiveness in modeling these nonlinear relationships. ANNs demonstrated superior predictive performance, particularly in heterogeneous and fine-grained soils. The review also examines the influence of temperature and salinity, emphasizing the need for multivariable models for robust interpretation. While resistivity testing shows great potential for non-destructive soil classification and compaction assessment, limitations related to soil type specificity, environmental variability, and model generalizability are noted. This work provides an important foundation for the development of data-driven, non-invasive techniques for subsurface characterization and outlines directions for future research, including field validation and hybrid modeling. Full article