Lightweight Soil Research Articles

Dynamic Shear Strength Characteristics of EPS Lightweight Soil

Dynamic Shear Strength Characteristics of EPS Lightweight Soil

Study on the Application of Foamed Lightweight Soil in Road Widening Project: A Numerical Insight

Study on the Application of Foamed Lightweight Soil in Road Widening Project: A Numerical Insight

Dynamic failure process of expanded polystyrene particle lightweight soil under cyclic loading using discrete element method

Dynamic failure process of expanded polystyrene particle lightweight soil under cyclic loading using discrete element method

X-ray microstructural insight into the mechanical behaviour of ligth-weight cemented soils

Light-weight cemented soils (LWCS) – that is, materials prepared by mixing natural soil, water and cement with air foam, are characterised by a heterogeneous microstructure, consisting of large foam-induced voids distributed in a cemented porous matrix. The reduced volume weight coupled with a good mechanical strength makes LWCS suitable for many geotechnical applications. However, the role of the microstructure on their macroscopic mechanical behaviour is not completely clear. A novel experimental investigation on the mechanical response of LWCS under triaxial loading paths using in situ x-ray microtomography is presented here, focusing on the evolution of foam-induced porosity. The tomographies are acquired during the shear phase of multiple triaxial compression tests, performed at different confining stress levels. Image analysis is employed for obtaining porosity maps and incremental strain fields of the samples. At low confining stress, the sample deformation essentially consists in the progressive opening of sub-vertical dilatant fractures connecting the foam-induced voids. At higher confining stresses, localised compactions develop in the cemented matrix along the directions coherent with the deviatoric load path. The results presented above indicate that the deformation and failure mechanisms of LWCS strongly depend on the mean stress level.

Improving foamed mixture lightweight soil containing red mud properties by utilizing nano-SiO2

Red mud (RM) is an aluminum industrial solid waste with a global inventory exceeding 4 billion tons. To utilize RM efficiently, this study used RM as the primary material, with cement, steel slag powder, and desulfurization gypsum as supplements, to prepare foamed mixture lightweight soil containing RM (FMLSR) for subgrade filling. And the effect of nano-SiO2 on the fresh properties, unconfined compression strength, durability, and microscopic properties of FMLSR was investigated. The test results indicated nano-SiO2 significantly reduced the flowability of FMLSR. Therefore, to maintain suitable flowability, the nano-SiO2 content should not exceed 1.5%. When the content ranged from 1.0% to 1.5%, nano-SiO2 effectively enhanced the compression strength of FMLSR, reduced its volumetric water absorption, and improved its resistance to dry-wet cycles. Nano-SiO2 can also reduce the environmental risk of FMLSR by significantly lowering the pH of FMLSR leachate. Microanalysis revealed that nano-SiO2 enhanced the density of the skeletal structure of FMLSR by promoting the formation of ettringite, thereby improving its properties. The addition of nano-SiO2 increased the CO2 emissions of FMLSR, but as nano-SiO2 improves various aspects of FMLSR properties, this increase is acceptable. In conclusion, the suitable content of nano-SiO2 for FMLSR ranged from 1.0% to 1.5%.

Properties, Treatment and Resource Utilization of Bauxite Tailings: A Review

A substantial amount of bauxite tailings (BTs) at abandoned mine sites have been stored in waste reservoirs for long periods, leading to significant land occupation and environmental degradation. Although many studies of the resource utilization of BTs were conducted to address this challenge, there is still a lack of efforts to systematically review the state of the art in BTs. In the present paper, a systematic literature review was carried out to summarize and analyze the properties, treatment, and resource utilization of BTs. Physical characteristics and the mineral and chemical composition of BTs are introduced. The efficacy of physical, chemical, and microbial treatment methods for BTs in terms of dehydration are outlined, and their respective benefits and limitations are discussed. Moreover, the extraction process of valuable elements (e.g., Si, Al, Fe, Li, Na, Nd, etc.) from BTs is examined, and the diverse applications of BTs in adsorption materials, ceramic materials, cementitious materials, lightweight aggregates, foamed mixture lightweight soil, among others, are studied. Finally, an efficient and smart treatment strategy for BTs was proposed. The findings of the present review provide a scientific basis and reference for future research focusing on the treatment and resource utilization of BTs.

Study on the Micro Mechanism of Failure Evolution of Desulfurization Gypsum–Fly Ash Fluidized Lightweight Soil Based on Discrete Element Method

Study on the Micro Mechanism of Failure Evolution of Desulfurization Gypsum–Fly Ash Fluidized Lightweight Soil Based on Discrete Element Method

Strength characteristics of lightweight soil with waste modified expanded polystyrene particles

With the increase in population and urbanization around the world, waste materials have a significant negative impact on the environment; therefore, it is essential to reduce the adverse effects of waste materials on nature through innovative and sustainable solutions. This study aims to reveal the threefold benefits of utilizing waste modified expanded polystyrene (WMEPS) as a soil improvement agent, including the reuse of a waste material by recycling it from nature, obtaining lightweight backfill material, and the enhancement of the compressive behavior of the soil. For this purpose, two different sizes of WMEPS were added to the soil to varying proportions by dry weight of the soil (i.e., 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, and 6%) and their unconfined compressive strength (UCS) behavior was experimentally investigated on both 1 and 28 day cured specimens. The results were evaluated in terms of stress-strain behavior, UCS value, UCS increase ratio, normalized energy absorption index, deformability index, and elastic modulus. In addition, the optimum WMEPS participation ratio was determined by linear weighted sum optimization method. As a result, by adding the optimum rate of 5% WMEPS to the soil, the dry density decreased by 15% and UCS increased by 45.22% for the specimen cured for 28 day.

Dynamic deformation characteristics of lightweight soil based on Davidenkov model

The dynamic deformation characteristics of lightweight soil were studied using consolidated-undrained dynamic triaxial tests to predict its non-linear stress and strain behaviour under a traffic load. The results showed that the influence of confining pressure on the attenuation of the dynamic shear modulus ratio became significant with increasing expanded polystyrene (EPS) particle content or cement content. The attenuation curve of the dynamic shear modulus ratio was evaluated using Davidenkov model parameters, A, B and γ 0. It was proved that the parameter A was mostly affected by EPS particle content and confining pressure, with its value ranging between 1.1 and 1.85. The parameter γ 0 was affected by cement content and confining pressure, and its value ranged between 0.0007 and 0.0016. The parameter B was found to range between 0.38 and 0.55, in general. The relationship curves between damping ratio and dynamic shear strain revealed two forms, S shaped and bell shaped. The verification tests showed that the Davidenkov model could predict accurately the dynamic deformation characteristics of lightweight soil both under a changing stress state and under constant gradient loading conditions. These results provide a theoretical basis for determining the deformation of a lightweight soil subgrade under a traffic load.

Study on Strength Characteristics and Hardening Mechanism of Alkali Residue–Based Lightweight Soil

Study on Strength Characteristics and Hardening Mechanism of Alkali Residue–Based Lightweight Soil

Features of Processes for Preparation and Performance of Foamed Lightweight Soil with Steel Slag Micronized Powder and Granulated Blast Furnace Slag

Steel slag micronized powder, granulated blast furnace slag, and cement were used as cementitious materials to prepare a foamed lightweight soil for roadbed filling to reduce the settlement and additional stress of the foundation and to solve the environmental problems caused by the storage of large amounts of steel slag. However, the instability of steel slag and the multi-angular nature of its surface limit the resource utilization of steel slag. Currently, concrete technology is unable to achieve a large amount of steel slag. Therefore, it is necessary to deeply explore the influence of steel slag content and the specific surface area of steel slag on the working performance, compressive strength, durability, and micro-mechanism of foam light soil. Through the modification of steel slag and the improvement of the production process, the preparation of foam light soil with a large amount of steel slag can be realized. In this study, the foamed lightweight soil with 1.0 Mpa was prepared by cementitious materials composed of 40% cement and 60% multi-mixture of steel slag micronized powder and granulated blast furnace slag. The study of SEM images and BET demonstrated that the larger specific surface area of steel slag powder was more conducive to improving the durability of the foamed lightweight soil. Meanwhile, XRD analyses confirmed that the reactions of f-CaO and f-MgO in steel slag were slowly released in the porous foamed lightweight soil system, which compensated for the shrinkage properties of porous materials. When the SSMP content was 0%, the shrinkage rate was 2.34 × 10−3, while when the SSMP content was 60%, the shrinkage rate was only 0.54 × 10−3. Furthermore, our study of the hydration process of samples indicated that the strong alkalinity of steel slag micronized powder hydration was helpful to stimulate the potential activity of the slag powder, which was beneficial to the improvement of the compressive strength of foamed lightweight soil. Thus, this study provides a valuable idea for reducing the settlement and additional stress of the original foundation and for solving the environmental problems caused by a large amount of steel slag storage.

Long-term mechanical properties of sludge-cured lightweight soil under the superimposed effects of drying-wetting and freezing-thawing

ABSTRACT Sludge-cured lightweight soils have unique advantages in roadbed treatment due to their properties such as low density and high strength. Its long-term mechanical law based on the superposition of drying-wetting and freezing-thawing (D-W-F-T) is studied through creep experiment. The test results show that: with the increase of the number of D-W-F-T, the deformation of the soil gradually increases, and the deformation tends to be stable when it reaches a certain number of times; the stress-strain isochronous curves are obviously nonlinear in general; The long-term strength increases with the increase of density and confining pressure, and decreases with the increase of the number of D-W-F-T; by comparing the isochronous stress-strain curve cluster method and the steady state creep rate vs. The comparative analysis suggests that the steady state creep rate versus stress level curve method be used to determine the long term strength.

Active Earth Pressure Characteristics of Light Weight Soil with EPS Particles Behind Rigid Retaining Wall

Active Earth Pressure Characteristics of Light Weight Soil with EPS Particles Behind Rigid Retaining Wall

Engineering Properties and Micropore Structure of Clay-Based Foamed Lightweight Soil

Engineering Properties and Micropore Structure of Clay-Based Foamed Lightweight Soil

Study on the Mechanical Characteristics of Large Shear Deformation of Lightweight Soil Solidified by Blowing and Filling with High Moisture Content

Study on the Mechanical Characteristics of Large Shear Deformation of Lightweight Soil Solidified by Blowing and Filling with High Moisture Content

Effect and Mechanism of Freeze–Thaw Cycles on Static and Dynamic Characteristics of Expandable Polystyrene Lightweight Soil

Effect and Mechanism of Freeze–Thaw Cycles on Static and Dynamic Characteristics of Expandable Polystyrene Lightweight Soil

Evaluation of Deformation and Settlement Properties of Cement-Stabilized Silt Mixed with EPS Beads of Various Sizes

The expansion of China’s highways and railways, as well as the growing demand for them, has focused attention on the impact of traffic loads on foundation settling, uneven deformation, and ground cracking. These effects have garnered considerable research attention, with particular emphasis placed on integrating innovative materials into the soil matrix. This investigation involved loading experiments utilizing a combination of lightweight soil, expanded polystyrene (EPS), and cement. Consolidation tests assessed the extent of deformation and settlement, incorporating varying proportions of EPS and cement. The test results show that when subjected to confined conditions, the stress–strain relationship curve assumes a hyperbolic shape closely linked to the e-p curve. This shape effectively captures the unique structural characteristics exhibited by lightweight soils. As the size of the EPS particles and the applied stress increase, a corresponding rise in the strain of the specimens is observed. Simultaneously, as the strain magnitude increases, the elastic modulus experiences a decline. Additionally, it is noted that this trend further increases as the doping of the cement with EPS particles increases. When the EPS volume ratio and cement mix ratio remain constant across different specimens, there is a decrease in structural strength as the size of the EPS increases. In lightweight soil, settlement can occur rapidly, with approximately 95% of total consolidation deformation happening within a few minutes, which suggests that the settlement is instantaneous and primarily consolidation settlement. The structural strength of lightweight soil shows a negative correlation with the size of EPS, implying that larger EPS size may lead to a reduction in strength. Therefore, it is recommended to consistently use EPS beads with a diameter of 3–4 mm during construction.

Research on the mechanical properties of EPS lightweight soil mixed with slag.

Expanded polystyrene (EPS) bead lightweight soil composites are a new type of artificial geotechnical material with low density and high strength characteristics that can be widely used in engineering projects. To promote the wide application of EPS bead lightweight soil in engineering, when slag is used to replace part of the cement as a binding agent, it can better improve the effect of soil and reduce engineering costs. The mechanical properties of EPS lightweight soil mixed with slag were analyzed by conducting an unconfined compressive strength (UCS) test and triaxial test on lightweight soil with different EPS bead contents and slag contents. The particle sizes of the EPS beads are 1~3 mm, the EPS contents are 1%, 2%, 3%, and 4%, and the slag-cement composite binding agents are 10%, 15%, 20% and 25%. The results show that the UCS decreases significantly with increasing EPS bead content at different EPS bead contents and slag contents; the UCS of the specimen with 30% slag content is the largest; and the UCS of lightweight soil without slag is comparable to that of lightweight soil with a slag content of approximately 60%. The peak stress in triaxial increases with increasing confining pressure, and the modulus of deformation decreases linearly with increasing EPS bead content. the slag-cement composite binding agent has a significantly better reinforcing effect than single mixed cement. The stress‒strain curves of EPS lightweight soil mixed with slag exhibits hardening and softening characteristics. EPS bead content and slag content determine the stress‒strain characteristics of the EPS lightweight soil mixed with slag. The macromechanical properties based on the microscopic mechanism of the EPS lightweight soil mixed with slag shows that different slag contents affect the failure pattern of EPS lightweight soil mixed with slag. The research results can provide a reference for engineering design and application.

Engineering properties and optimal design of foam lightweight soil composite fly ash: An eco-friendly subgrade material

Foam lightweight soil is used frequently in engineering construction for soft soil areas due to its superior lightness and economy, but its greater cement usage will result in cost increase, resource waste, and environmental pollution. This study modified foam lightweight soil with industrial solid waste (fly ash) in place of some cement to propose an eco-friendly and useful lightweight subgrade filling material. A series of macro-micro tests were conducted to investigate the engineering properties and micro-mechanisms of foam lightweight soil composite fly ash (FLS). The results showed that the axial stress-strain and shear stress-displacement curves of FLS showed softening types. The fluidity, compressive strength, toughness and shear strength of FLS first increased and then decreased with the increasing fly ash content. The mechanical strength of 20% FLS was the optimal value for meeting the application requirements of subgrade engineering. Due to the volcanic ash and micro-aggregation effects, fly ash consumed the calcium hydroxide to produce more calcium silicate hydrate for filling the pores of sample and improving its internal structure. According to the results of numerical simulation, the settlement deformation and lateral deformation of subgrade could be better controlled by using 20%FLS as filling material compared with ordinary soil. Consequently, it is feasible to apply FLS in subgrade engineering.

Deformation Characteristics of Fiber-Reinforced Cured Lightweight Soils under Dry and Wet Cycles and Intermittent Loading

Deformation Characteristics of Fiber-Reinforced Cured Lightweight Soils under Dry and Wet Cycles and Intermittent Loading