Expansive Soil Research Articles

Effect of multicollinearity in assessing the compaction and strength parameters of lime-treated expansive soil using artificial intelligence techniques

Effect of multicollinearity in assessing the compaction and strength parameters of lime-treated expansive soil using artificial intelligence techniques

Enhancing Mechanical Properties of Expansive Soil Through BOF Slag Stabilization: A Sustainable Alternative to Conventional Methods

This study investigates the stabilization of expansive soil using basic oxygen furnace (BOF) slag, an eco-friendly steel by-product, as an alternative to conventional stabilizers like ordinary Portland cement. By evaluating varying concentrations of BOF slag and lime as an activator, the research aims to improve the soil’s mechanical properties, addressing issues like low bearing capacity and high shrink–swell potential. Bentonite clay was treated with different BOF slag ratios (10%, 20%, and 30%) and activated with lime (1%, 3%, and 5%). After mixing and compaction, samples were cured and tested for unconfined compressive strength (UCS), shear wave velocity (BE), and free swell. Microscopic analyses (SEM) provided insight into structural changes post-stabilization, revealing improved properties with increased BOF and lime concentrations. Notably, stabilization with 30% BOF slag and 5% lime achieves a compressive strength of 810 kPa, meeting the minimum subgrade soil stabilization requirement (700 kPa) set by the Federal Highway Administration. This research underscores the potential of BOF slag as a sustainable and practical material for bentonite clay stabilization, offering a promising solution for enhancing soil properties while contributing to environmental sustainability through industrial by-product repurposing.

Simultaneous Evaluation of Montmorillonite and Na/Ca Content for Assessing Unstabilized and Stabilized Natural Expansive Soils for Geoengineering Applications

Simultaneous Evaluation of Montmorillonite and Na/Ca Content for Assessing Unstabilized and Stabilized Natural Expansive Soils for Geoengineering Applications

Multi-directional deformation and hydraulic conductivity of expansive soils subjected to freeze-thaw cycles from three distinct initial saturation levels

Infrastructure construction in seasonally frozen regions, covering 23% of total land, faces challenges from freeze-thaw (F-T) induced damages. Expansive soils, as an important problematic soil undergo major hydromechanical properties changes influenced by F-T cycles. Sand-bentonite mixtures are extensively used for constructing earthen hydraulic barriers in cold regions. This study investigates the influence of F-T cycles on multi-directional strains and anisotropic hydraulic conductivity of different sand-bentonite mixtures prepared at optimum water content and experienced three distinct saturation levels. Results indicate that saturation level and bentonite content significantly influence volumetric strain under F-T cycles. The simultaneous effect of ice lens formation, expanding micro-voids, and suction generated by freezing processes cause different volumetric behaviors at varying saturation degrees. The dry specimen exhibits no strain under F-T cycles, while optimum and saturated specimens experienced final volumetric strains of 1.02% and 3.03%, respectively. Notably, during freezing, the specimen at optimum water content shrank, while the saturated specimen expanded. Increasing bentonite content from 40% to 70% developed freezing-induced shrinkage, from 1.73% to 4.72%, with higher thaw strain attributed to increased specimen plasticity. Also, dimensional variations revealed the cross-anisotropic nature of specimens, highlighting direct influence of water content on the shrinkage ratio. F-T cycles also increased hydraulic conductivity along both orthogonal directions by two orders of magnitude, while the anisotropy ratio decreased by about 3 after 9 F-T cycles, indicating altered pore structures. F-T cycles induce reduced swelling potential and compressibility over subsequent cycles. Microstructural observations also confirmed the F-T effects on the enhancement of porosity.

Strength and dilatancy of an unsaturated expansive soil at high suction levels

A series of suction-controlled triaxial tests was conducted on Nanyang expansive clay to investigate the effects of dry density and suction on dilatancy and strength. The suction of the soil samples was controlled using a vapour equilibrium technique, with four suction levels ranging from 3.29 MPa to 198.14 MPa, where water retention is dominated by adsorption. The experimental results show that the tested soil exhibits a brittle failure mode under high suction, significantly distinguishing the hydro-mechanical behaviour of the soil at high suction from that observed at low suction. This brittle failure mode significantly increases the contribution of suction to peak strength compared to residual strength, causes the soil to fail before reaching the critical state, a phenomenon not observed in soils under high suction, and results in dilatancy caused by damage to the soil particle aggregates rather than particle rearrangement. The dilatancy data obtained from the triaxial tests reveal that significant soil dilatancy occurs during shear after reaching peak strength, with the maximum dilatancy angle increasing with suction and decreasing with confining pressure. However, the initial dry density has a negligible impact on the soil's dilatancy under high suction levels. This observation further supports that, for unsaturated soils under high suction levels, dilatancy is attributed to damage to soil particle aggregates rather than the rearrangement of soil particles.

Influence of Dry-Wet Cycle Induced by Atmospheric Environment on the Stability of Expansive Soil Slope

Influence of Dry-Wet Cycle Induced by Atmospheric Environment on the Stability of Expansive Soil Slope

Study on the effect of cinder ash as an auxiliary additive mineral in hydrated lime treatment for expansive sub-grade soil in road construction

Expansive soils pose significant challenges to road construction globally due to their tendency to expand and contract with changes in moisture content, leading to pavement failure. In the construction industry, finding an economical and cost-effective alternative to conventional road construction materials is crucial. The use of a natural cinder ash and hydrated lime mixture as reinforcement has proven to be effective in addressing this issue. Cinder ash, a readily available waste material in countries like Ethiopia, is adaptable and water-resistant, making it an ideal choice for reinforcing expansive soil. This article investigates the strength performance of a cinder ash and hydrated lime mixture as a reinforcement material for expansive soil. The study involves mixing 0%, 20%, 25%, 30%, and 35% of cinder ash with soil stabilized with 2–5% hydrated lime. Expansive soil samples are prepared according to the ASSHTO & ASTM method and tested for compressive strength, California bearing ratio, bulk density, and water absorption. The findings reveal a 448.62%, and 374% increase in compressive strength and California Bearing Ratio respectively for the specimen containing 5% hydrated lime and 35% cinder ash, cured for 28 days. The water absorption is minimized at 15.23% for the 5% hydrated lime and 35% cinder ash mixture; while the maximum density of the soil is observed at 1.774 kg/m3 for the optimal combination of 5% hydrated lime and 35% cinder ash mix. The study suggests that using 5% hydrated lime and 35% cinder ash content for the stabilization of expansive soil significantly enhances the strength characteristics of compressed stabilized soil.

Prediction of swelling pressure of expansive soil using machine learning methods

Prediction of swelling pressure of expansive soil using machine learning methods

Behavior of Slab-on-Grade Resting on Expansive Soil

Abstract This paper discusses a case study of a residential building in Benghazi that features slab-on-grade foundations supported by expansive soils. Although such structures are uncommon in the area, they can suffer serious damage due to volumetric changes in the soil caused by wetting and drying. The building has a total plan area of 200 m², with tie beams located 1.2 m above the formation level, and expansive soil used as backfill. After being moistened and lightly compacted, 100 mm thick concrete slabs were poured between the tie beams, resulting in varying slab sizes. Following a month of heavy rainfall, significant cracking—longitudinal, diagonal, and warping—occurred in the slabs due to uneven deformation from the expansive soil. The paper includes photographs of these deformations and cracks, along with an analysis of the geotechnical properties of the expansive soil, including its swelling and shrinking characteristics. It also employs an approach to predict the pressure exerted on the slabs due to differential heave.

Proactive Measures for Preventing Highway Embankment Failures on Expansive Soil: Developing an Early Warning Protocol

Proactive Measures for Preventing Highway Embankment Failures on Expansive Soil: Developing an Early Warning Protocol

Investigation of cracking behavior of fine-grained clays exposed to different humidity environments and engineering implications based on X-ray computed tomography

Due to the humidity difference between fine-grained clay and atmosphere environment, the complex crack network is formed, which is the main channel for water storage and migration and hence poses a potential threat to engineering construction. Therefore, the appropriate characterization of cracking behavior of fine-grained clay is of great significance for exploring its microphysical properties. To this end, this work took expansive soils as research object and a series of desiccation tests and X-ray computed tomography tests were conducted to investigate the shrinkage cracking behavior. The results indicate that a higher desiccation rate records a smaller shrinkage strain, but it aggravates the cracking on a much larger scale. Especially at high desiccation rates, two-dimensional crack ratio shows a significant fluctuation. Small cracks tend to turn into large ones during desiccation, and the increasing desiccation rate primarily exerts a significant effect on the cracks with equivalent radius more than 1000 µm. The expansive soil is dominated by horizontal cracks, and a low desiccation rate mainly promotes the connection between horizontal cracks, whereas high desiccation rates enhance the connectivity of oblique cracks, which exerts an adverse effect on soil slopes. Besides, the rise in desiccation rate leads to a wealth of micro-scale pores and throats occurring in the soil. The fine-grained clays at higher desiccation rates present larger pore and throat volume, more connected pores, and higher average coordination number, thus enhancing the connectivity between pore and pore. Permeability simulation results also confirm the positive correlation between connected crack ratio and hydraulic conductivity of the soil. In terms of engineering significance, narrowing down the difference in humidity between fine-grained clays and atmosphere is the most effective measure to constrain the extension of cracks.

Constitutive Damage Model for Rubber Fiber-Reinforced Expansive Soil under Freeze-Thaw Cycles.

To elucidate the degradation mechanism of expansive soil-rubber fiber (ESR) under freeze-thaw cycles, freeze-thaw cycle tests and consolidated undrained tests were conducted on the saturated ESR. The study quantified the elastic modulus and damage variables of ESR under different numbers of freeze-thaw cycles and confining pressure, and proposed a damage constitutive model for ESR. The primary findings indicate that: (1) The effective stress paths of ESR exhibit similarity across different numbers of freeze-thaw cycles, the critical stress ratio slightly decreased by 8.8%, while the normalized elastic modulus experienced a significant reduction, dropping to 42.1%. (2) When considering the damage threshold, the shear process of ESR can be divided into three stages: weak damage, damage development, and failure. As strain increases, the microdefects of ESR gradually develop, penetrating macroscopic cracks and converging to form the main rupture surface. Eventually, the damage value reaches 1. (3) Due to the effect of freeze-thaw cycles, initial damage exists for ESR, which is positively correlated with the number of freeze-thaw cycles. The rubber fibers act as tensile elements, and the ESR damage evolution curves intersect one after another, showing obvious plastic characteristics in the late stage of shear. (4) Confining pressure plays a role in limiting the development of ESR microcracks. The damage deterioration of ESR decreases with an increase in confining pressure, leading to an increase in ESR strength. (5) Through a comparison of the test curve and the theoretical curve, this study validates the rationality of the damage constitutive model of ESR under established freeze-thaw cycles. Furthermore, it accurately describes the nonlinear impact of freeze-thaw cycles and confining pressure on the ESR total damage.

Influence of Red Mud on Swelling-shrinkage and Mechanical Performance of Compacted Expansive Soil

Influence of Red Mud on Swelling-shrinkage and Mechanical Performance of Compacted Expansive Soil

Mineralogical Analysis of Copper Slag Treated Expansive Soil Using X-Ray Diffraction

Mineralogical Analysis of Copper Slag Treated Expansive Soil Using X-Ray Diffraction

Dynamic Behavior of Rubber Fiber-Reinforced Expansive Soil under Repeated Freeze–Thaw Cycles

Large volumes of waste tires are generated due to the rapid growth of the transportation industry. An effective method of recycling waste tires is needed. Using rubber from tires to improve problematic soils has become a research topic. In this paper, the dynamic response of rubber fiber-reinforced expansive soil under freeze–thaw cycles is investigated. Dynamic triaxial tests were carried out on rubber fiber-reinforced expansive soil subjected to freeze–thaw cycles. The results showed that with the increase in the number of freeze–thaw cycles, the dynamic stress amplitude and dynamic elastic modulus of rubber fiber-reinforced expansive soils first decrease and then increase, and the damping ratio first increases and then decreases, all of which reach the turning point at the 6th freeze–thaw cycle. The dynamic stress amplitude and dynamic elastic modulus decreased by 59.4% and 52.2%, respectively, while the damping ratio increased by 99.8% at the 6th freeze–thaw cycle. The linear visco-elastic model was employed to describe the hysteretic curve of rubber fiber-reinforced expansive soil. The elastic modulus of the linear elastic element and the viscosity coefficient of the linear viscous element first decrease and then increase with the increase in the number of freeze–thaw cycles; all reach the minimum value at the 6th freeze–thaw cycle. The dynamic stress–dynamic strain curve calculation method is established based on the hyperbolic model and linear visco-elastic model, and the verification shows that the effect is better. The research findings provide guidance for the improvement of expansive soil in seasonally frozen regions.

Influence of Agro-Industrial Waste on Unconfined Compression Strength Parameters of Expansive Soil: An Experimental Investigation

Expansive soils pose a significant challenge in construction due to their potential to cause structural damage through its swelling and shrinking characteristics. Simultaneously, the disposal of numerous industrial and agricultural wastes poses challenges that contribute to environmental ecosystem damage. This experimental study explores the effect of agro-industrial waste on the mechanical properties of expansive soil. Specifically, the impact of incorporating agro-industrial waste materials, such as bagasse ash, plastic strips, and coir fiber, is investigated through assessments of unconfined compression strength. The unconfined compressive strength (UCS) test was conducted to examine various parameters of different combinations involving expansive soil, bagasse ash, coir fiber, and plastic strips. The results demonstrated notable improvements in Unconfined Compression Strength (UCS), particularly when incorporating a specific combination of 10% Bagasse Ash, 0.5% Plastic Strips, and 0.75% Coir Fiber) which resulted in a remarkable 49% increase in UCS. The findings show that including plastic strips enhances UCS by 2%, Coir Fiber improves it by 5%, and a combination of Bagasse Ash, plastic strips, and Coir Fiber leads to a 7% increase in UCS. The study on incorporating agro-industrial waste materials, such as bagasse ash, plastic strips, and coir fiber, reveals substantial improvements in the mechanical properties of expansive soil. This study contributes to the sustainable utilization of agro-industrial waste for soil improvement, offering a promising avenue for eco-friendly geotechnical solutions. Future work could explore the long-term performance and scalability of these materials in various soil conditions.

Study on the extension mechanism of fissures in expansive soil based on fracture mechanics test method

Expansive soil, characterized by widespread fissures, is a special type of soil prone to localized fissure propagation, leading to failure and instability, often resulting in landslides. Numerous studies have applied fracture mechanics theory to analyze soil failure along fissures, but no standardized testing method has been established. This paper reviews existing soil fracture toughness testing methods, designs an integrated system combining digital image correlation(DIC) technique and electrical resistance testing, and employs the Cracked Chevron-Notched Brazilian Disc (CCNBD) method to assess the fracture toughness of expansive soil. The deformation and internal damage accumulation processes of the specimens were monitored. The KΙc and KΙΙc of expansive soil were tested at moisture contents of 15 %, 20 %, and 25 % using specimens with three different crack length ratios (a/R). The role of water was explored by injecting water into the fissures. The results showed that KΙc of expansive soil ranged from 10 to 36 kPa·m0.5, with a linear negative correlation to moisture content and a proportional relationship to tensile strength, having a proportionality coefficient of 0.331. The KΙΙc ranged from 20 to 70 kPa·m0.5,and it is greater than KΙc under the same conditions. Based on the load, internal damage, strain, and fissure area during the tests, the failure process of expansive soil along fissures was divided into four stages: initial deformation stage(I), quasi-elastic deformation stage(II), fissure extension stage(III), and failure stage(IV). Water injection into the fissures reduced the soil's fracture toughness, with a more significant reduction as a/R increased and the failure showed progressive behavior. The CCNBD method, combined with DIC technique and electrical resistance testing, effectively measures the fracture toughness of soil, aiding in understanding the failure mechanism along fissures and providing a basis for preventing and controlling landslides and other hazards in expansive soils.

Soil-water retention capacity of expansive soil improved through enzyme induced carbonate precipitation-eggshell powder

Enzyme Induced Carbonate Precipitation (EICP) has been extensively investigated as a promising approach to improve engineering properties of soil, while Eggshell Powder (ESP) is an agricultural waste that effectively fills soil pores. The ESP provides abundant nucleation at sites for the EICP process, further promoting the effective precipitation of calcium carbonate. The research presented in this paper investigated the Soil Water Characteristic Curves (SWCC), permeability coefficient, and microstructure of expansive soil before and after EICP and EICP+ESP modification. A series of laboratory experiments were conducted, including soil water characteristic tests, permeability tests and Scanning Electron Microscopy (SEM). The results proved that the addition of EICP and EICP+ESP into natural expansive soil resulted in a gradual decline in air entry value, residual water content, and permeability coefficient, indicating an increase in water retention capacity and a decrease in permeability. Furthermore, with the intrusion of EICP and EICP+ESP, the contact between particles becomes smoother, and the soil pores become more equally distributed. Ultimately, there was an enhancement in water retention capacity of the natural expansive soil. This study emphasizes the synergistic potential of combining EICP and EICP+ESP as stabilizing additives to enhance the water retention capacity of expansive soil. Moreover, the reuse of ESP provides a sustainable solution for the resource utilization of agricultural waste and the improvement of expansive soil using bio-inspired methods.

On-site monitoring of expansive soil slope protected by soilbags based on the universal Beidou monitoring system

To explore an effective method for deformation monitoring and behavior prediction of expansive soil slope, field tests are conducted for a flexible slope protection scheme with soilbags that has been implemented in an expansive highway soil slope. A new monitoring system, i.e., the universal Beidou deformation monitoring system, is developed to overcome the limitations of traditional Global Navigation Satellite System (GNSS) software and hardware, simplify the hardware structure and realize the power sharing mode; furthermore, this system can create and upload a large amount of monitored data to a cloud platform to enable real-time calculation. Compared with traditional GNSS, the volume of equipment required is reduced by approximately 75%, and the cost is reduced by approximately 80%. Secondly, a multilevel safety early-warning evaluation system is constructed by integrating the monitoring results of the universal Beidou deformation monitoring system, bag damage states, rainfall conditions, and slope fissure development; additionally, a deformation early-warning mechanism of flexible support of soilbags was established. Finally, the deformation and collapse of flexible supports of soilbags can be successfully predicted in the field. This research on flexible support of soilbags provides new ideas and methods of deformation monitoring, safety evaluation, and early warning for expansive soil slopes.

Sustainable soil stabilization using industrial waste ash: Enhancing expansive clay properties

This study investigates the use of various industrial waste materials—silica fume (SF), cement kiln dust (CKD), calcium carbide residue (CCR), rice husk ash (RHA), and ground granulated blast furnace slag (GGBS)—as eco-friendly stabilizers for expansive clay soil (ECS). Laboratory tests were conducted to assess the impact of different proportions (3 %, 6 %, and 9 %) of these additives on the soil's physical, mechanical, and microstructural properties. Results indicated that the inclusion of industrial waste significantly improved the soil's behavior, with notable reductions in liquid limit (up to 37.66 %), plasticity index (up to 74.76 %), and swell potential. Additionally, unconfined compressive strength (UCS) and shear strength increased substantially, with UCS values rising from 114.64 kPa to 1582.91 kPa at 30 days of curing for 9 % GGBS. Microstructural analyses confirmed the formation of cementitious compounds, which enhanced soil particle bonding and durability. These findings suggest that industrial waste materials can serve as effective and sustainable alternatives to traditional soil stabilizers, offering both performance improvements and environmental benefits.