Unconfined Compressive Strength Tests Research Articles

Investigating the Impact of Ground Granulated Blast Furnace Slag (GGBS) and Cement Kiln Dust (CKD) on fine grained Soil Subgrade in Al Hillah City

Abstract In many parts of the world, fine grained soils are regarded as one of the major concerns for civil engineering projects. To mitigate these problems, fine grained soils are typically replaced with stronger materials. However, due to the high cost of this approach, various researchers have tried alternative approaches, the most popular of which is soil stabilization. This method could be deemed suitable for pavements. The research focuses on stabilizing fine soil through the utilization of cement kiln dust (CKD) and ground granulated blast slag (GGBS). This research involves treating fine soil with 10% of the total binder consist from (GGBS+CKD), with the amount of GGBS to CKD determined by dry soil weight as follows: (10% GGBS + 0% CKD), (8% GGBS + 2% CKD), (6% GGBS + 4% CKD), (2% GGBS + 8% CKD), and (0% GGBS + 10% CKD). The compaction parameters, consistency limitations, and the findings of the Unconfined Compressive Strength (UCS) test were used to assess the enhancement levels. In addition, specimens were subjected to UCS testing after (7-28) days of curing. The findings demonstrated that the combination of GGBS activated by CKD notably enhanced the physical characteristics of fine soil. The Plasticity Index (PI) decreased from 7.4 for untreated soil to 4.8 for a mixture containing 10% binder, comprised of 2% GGBS and 8% CKD, and to 4.25 for a single-binder mixture with 10% CKD. Furthermore, the unconfined compressive strength test (UCS) results indicated that a 10% binder mixture of 8% GGBS and 2% CKD increased the UCS by 2.9 to 5.9 times compared to untreated soil after 7-28 days of curing.

Analysis of strength characteristics and microstructure of alkali-activated slag cement fluidized solidified soil

In order to solve such as difficulties in backfilling narrow foundation trenches in engineering, it was proposed to use alkali-activated slag cement (AASC) instead of traditional Portland cement to solidify silt and form AASC fluidized solidified soil. The effect of the content of AASC and the curing period on fluidized solidified soil has been studied by unconfined compression strength test, SEM and EDS. Moreover, the root cause for the improvement of the strength by the microstructure was explored. The results showed that: The fluidity increased first and then decreased with the increase of the content of AASC; 40% was the optimal content; in the same curing period, the unconfined compression strength increased with the increase of the content; 40% was the optimal content; the soil with different contents could reach the most of the 28d strength on Day 7; AASC generated a lot of low-Ca/Si C-S-H gel that consolidated soil particles into a denser structure. These results provide a theoretical basis for the application of AASC in fluidized solidified soil engineering.

Bio-Electrokinetic Improvement of Deltaic Soil

In addressing problematic soils, geotechnical engineers employ two key strategies: compatibility and improvement. This study focuses on soft and CL deltaic sediments, and seeks to enhance cementation by investigating microbially-induced calcium carbonate precipitation (MICP). Sporosarcina pasteurii bacteria, together with a cementation solution (urea and calcium-containing salt), were electrokinetically injected into deltaic clay soil from the Telar River in Iran. The initial samples, with a dry unit weight (γd) of 12.75 kN/m³, underwent injections in two modes: simultaneous injection of the bacterial and cementation solutions and individual injection in a sequential order. Unconfined compression strength tests and laboratory vane shear tests were conducted to assess changes in soil strength parameters, while a consolidation test was performed to investigate alterations in soil settlement parameters. A comparative analysis with an electroosmosis control sample revealed a remarkable increase in compressive strength and undrained shear strength for MICP bio-electrokinetic improvement. Moreover, the consolidation test demonstrated that the compression index (Cc) and recompression index (Cr) exhibited a more pronounced decline in the simultaneous injection than individual injection. This highlights the dual impact of the bio-electrokinetic method, namely the enhancement of shear strength and the mitigation of settlement in deltaic clay soil. The calcium carbonate content was measured for the samples, and the results indicated a higher degree of participation for the samples subjected to simultaneous injection. Microstructure analyses were conducted on samples, and calcite and vaterite were observed in bio-cemented samples.

Effects of specimen size and loading rate on the mechanical property of Bentonil-WRK bentonite for engineered barrier system

This study aims to investigate the effects of specimen size and loading rate on the mechanical property of Bentonil-WRK bentonite buffer material for engineered barrier system. Highly instrumented unconfined compressive strength tests were performed on cylindrical specimens prepared using cold isostatic pressing (CIP) technique at varying testing conditions: (a) CIP pressures of 29.43 MPa, 39.24 MPa, and 58.86 MPa, (b) specimen sizes of 30 × 60mm, 40 × 80mm, and 50 × 100mm, and (c) loading rates of 0.5 %/min, 1.0 %/min, and 1.5 %/min. As CIP pressure increases, the unconfined compressive strength (qu), failure strain (εf), and elastic modulus (E) of Bentonil-WRK increase similar to Gyeongju compacted bentonite (KJ-II). Increase in diameter results in a decrease in qu and εf, and increase in E. Minimal effect of loading rate was observed on qu and εf. However, increasing loading rate tends to increase E. In addition, decrease in diameter increases the elastic threshold axial strain (εe,th). Increase in diameter and loading rate slightly increases Poisson's ratio. Prediction models are provided for assessing the effects of specimen diameter on qu and εf. Furthermore, correlation models of qu to ρd and E are proposed for Bentonil-WRK bentonite buffer material.

Mechanical properties and stability of zinc-contaminated red clay cured by MICP synergistically activated MgO

Microbially Induced Carbonate Precipitation (MICP) technology offers an innovative approach for the solidification and stabilization of heavy metal-contaminated soils; However, the mechanical strength and long-term stability of this remediation method have not been thoroughly investigated. This study introduces an innovative curing and stabilization technique using MICP-activated MgO to address the geotechnical challenges posed by zinc ion-contaminated soils. To investigate the effect of zinc ions on soil and the optimal efficacy of MICP-activated MgO in curing zinc contamination, experiments were conducted on zinc-contaminated soils with varying zinc ion concentrations (0.05%, 0.1%, 0.5%, 1.0%), dry densities (1.35, 1.4, 1.45, 1.5g/cm³), and activated MgO admixtures (1%, 2%, 5%, 10%). The effectiveness of MICP-activated MgO was evaluated through macroscopic analysis and stability tests, including unconfined compressive strength tests, direct shear tests, and the Toxicity Characteristic Leaching Procedure (TCLP). The results indicated that zinc ions disrupted soil particle cementation, enlarged inter-particle pores, and significantly reduced both unconfined compressive strength and shear strength. The optimal dosage of MICP-activated MgO for curing zinc-contaminated soil was determined to be 10%, resulting in an unconfined compressive strength of 1.196MPa and a Zn2+ leaching concentration of 0.1414mg/L. The combined actions of MICP-activated MgO facilitated the formation of alkaline magnesium carbonate, calcium carbonate, and magnesium hydroxide. These compounds filled the inter-particle pores of zinc-contaminated soil, encapsulating and co-precipitating zinc ions, thereby enhancing the soil's strength and stability. These findings establish a theoretical foundation for the engineering application of MICP-activated MgO in the remediation of zinc-contaminated soils.

Low-carbon metakaolin precursor for one-part and two-part geopolymer activation of demolition wastes

A critical part of civil engineering infrastructure works is to develop innovative construction materials for a low-carbon future development. This study delved into the feasibility of using metakaolin (MK) as a low-carbon precursor for one-part and two-part geopolymer stabilization of recycled demolition wastes. In this research, the effects of MK precursor were evaluated in combination with construction and demolition (C&D) waste aggregates such as crushed brick (CB), reclaimed asphalt (RAP) and recycled concrete (RCA) using one-part and two-part geopolymer activation. Various geotechnical tests were performed including compaction tests, repeated triaxial loading tests (RLT), unconfined compressive strength tests (UCS) and microstructural analysis. Results from this study indicated significant strength development of MK mixtures for both one-part and two-part geopolymer options. Furthermore, one-part geopolymer also showed better activation than two-part geopolymer under 7 days and 20℃ curing condition. Additionally, 30 % MK mixtures were optimal for road construction applications based on the obtained results. At 28 days or 40 ℃, MK mixtures performed best with RCA and CB as main aggregates, showing strength improvement of up to 250 % compared to 7 days and 20 ℃ curing condition. Resilient modulus (Mr) results indicated that the optimal mixtures experienced good resilient behavior with average Mr values ranging from 150 MPa to 200 MPa. Overall, MK precursor was found to be a suitable material for stabilizing demolition aggregates using geopolymer under various curing conditions.

Application of Bottom Ash with Hydrated Lime in Pavement SubgradeConstruction

Introduction: A structurally strong subgrade is always desirable in pavement construction so as to provide a resilient and durable foundation for the subsequent pavement layers for adequate performance under the given traffic load/volume and environmental conditions. Emphasizing the increased awareness for effective waste recycling and demand for a sustainable construction approach, re-utilizing industrial wastes in pavement subgrade construction can be a viable option. The potential re-utilization of bottom ash (BA), an incombustible by-product generated in huge quantities from coal combustion in thermal power plants, in replacing natural soil in the subgrade construction of pavements will not only limit the extent of disturbance to ecological balance through over-utilization of natural soil but also open an avenue for the reuse of bottom ash. Method: In this study, an effort was made to study the possible use of different percentage replacement of BA (0 to 60% with an increment of 15%) with natural soil with and without hydrated lime (5% by weight of soil-bottom ash mix) for applications in road subgrade. Laboratory investigations were conducted for basic soil characteristics, compaction properties, and strength evaluation through California bearing ratio (CBR) and unconfined compressive strength (UCS) tests. Result: The addition of 5% lime to the soil-bottom ash mixes decreased the plasticity index significantly. The highest MDD and the lowest OMC were found in soil with 45% bottom ash. The CBR results of control soil increased from 6.3% to 137.7% for soil-bottom ash mix containing 45% bottom ash and 5% hydrated lime, and the same combination showed a 104% increase in UCS. Conclusion: The observed results indicated that the coupled behavior of the bottom ash and hydrated lime treatment has effectively increased the soil's compaction and mechanical strength and its suitability for use in road subgrade construction.

Anisotropic behavior and mechanical characteristics of the Montney Formation

This study investigates the rock mechanics and anisotropic properties of the Montney Formation, Alberta, through two sets of experiments: unconfined compressive strength tests and triaxial compression tests, supplemented by ultrasonic wave velocity measurements. These tests enabled the calculation of dynamic and static stiffness properties and Thomsen anisotropy parameters (ε, δ, γ). Our findings reveal that the Montney Formation exhibits weak anisotropy, with ε values generally below 0.10, contrasting with other strongly anisotropic shale formations. Specimens exhibiting higher clay content and total organic carbon levels show more pronounced anisotropy. Static measurements exhibit a higher degree of anisotropy compared to dynamic measurements. The investigation also explored loading and unloading stiffness parameters, noting a higher E loading-to-unloading ratio for rock specimens with lower elastic properties. This provides important information on the rock's response to stress path effects during stimulation and exploitation. The study also discusses other rock mechanics parameters including Poisson's ratio, tensile strength, and brittleness. The research contributes to a more comprehensive understanding of the geomechanical and petrophysical behavior of the Montney Formation, aiding reservoir characterization and hydrocarbon exploration and production.

Strength and deformation characteristics of waste mud–solidified soil

The treatment, disposal, and resource utilization of waste mud are challenges for engineering construction. This study investigates the road performance of waste mud–solidified soil and explains how solidifying materials influence the strength and deformation characteristics of waste mud. Unconfined compressive strength tests, consolidated undrained triaxial shear tests, resonant column tests, and consolidation compression tests were conducted to evaluate the solidification effect. The test results show that with an increase in cement content from 5 to 9%, the unconfined compressive strength of the waste mud–solidified soil increased by over 100%, the curing time was extended from 3 to 28 days, and the unconfined compressive strength increased by approximately 70%. However, an increase in initial water content from 40 to 60% reduced the unconfined compressive strength by 50%. With the increase of cement content from 5 to 9%, the cohesion and friction angles increased by approximately 78% and 24%, respectively. The initial shear modulus under dynamic shear increased by approximately 38% and the shear strain corresponding to a damping ratio decay to 70% of the initial shear modulus decreased by nearly 11%. The compression coefficient decreased by approximately 55%. Scanning electron microscopy and X-ray diffraction tests showed that a higher cement content led to the formation of more hydration reaction products, especially an increase in the content of AlPO4, which can effectively fill the pores between soil particles, enhance the bonding between soil particles, and form a skeleton with soil particles to improve compactness. Consequently, the strength of the waste mud–solidified soil increased significantly while its compressibility decreased. This study can provide data support for dynamic characteristics of waste mud solidified soil subgrade.

Application of industrial by-product waste as soil stabilising backfill material using a multi-layering method

Peat soil presents significant challenges for construction due to its inherent weak properties, including high water content, limited permeability, low shear Strength, low specific gravity, and acidity. Despite the potential of Mg-rich synthetic gypsum (MRSG) to improve soil properties, research on its use for stabilising severely poor peat soils is limited. This study addresses this gap by investigating the efficacy of MRSG in peat soil stabilisation using a novel multi-layering backfill approach. The methodology includes soil classification of peat soil. And, to understand the mechanical and chemical changes of stabilized peat soil, the unconfined compressive Strength (UCS) testing and microstructural analysis using SEM, EDX, and XRD before and after stabilisation are studied. Peat samples were treated with MRSG through backfilling method in 5, 7, and 9 layers and evaluated the strength increment after curing periods of 7, 28, and 60 days. Results demonstrate that MRSG significantly enhanced the compressive strength, increasing it to 210.33 kPa as early as 7 days for 9 layers of backfill incomparable with the untreated soil strength of 51.87 kPa. The new cementitious product in the soil known as ettringite was observed from SEM analysis and confirmed by the EDX and XRD analysis. By recycling industrial byproducts, this environmentally friendly method encourages sustainability and lessens dependency on raw resources, which is important for infrastructure construction and other projects in areas rich in peat.

Laboratory investigation on static and dynamic properties, durability, and microscopic structure of Nano-SiO2 and polypropylene fiber cemented soil under coupled seawater corrosion and cyclic loading

Cemented soils in coastal harbors are susceptible to adverse factors such as seawater corrosion and cyclic dynamic loading, which may consequently reduce their stability and durability. In recent years, Nano-SiO2(NS) has been widely used to enhance the mechanical properties of cemented soil. However, this enhancement may potentially lead to a reduction in ductility. Conversely, polypropylene fibers (PP) have attracted widespread attention for their potential to enhance the ductility of cemented soils, but their ability to improve the strength of cemented soils is limited. To address these issues, this study focused on utilizing five different nano-dosages combined with four different fiber dosages to enhance cemented soils. These enhanced soils were then subjected to curing periods of 7, 28, and 60 days in seawater environments. The study employed various tests including unconfined compressive strength tests (UCS), uniaxial cyclic loading tests, scanning electron microscopy tests (SEM), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) to investigate the potential impacts of these additives on durability, strength, corrosion resistance, and microstructure evolution. The results of the study indicate that seawater corrosion and cyclic loading contribute to a reduction in the stability of cemented soils. However, the addition of NS and PP effectively enhances the compressive strength and durability of these soils. The optimal combination ratio is achieved when the dosages of NS and PP are 3.6 % and 0.8 %, respectively. In this case, the growth rate of unconfined compressive strength of cemented soils surpasses the sum of each individual dosage, increasing by 137.7 %, 245.6 %, and 235.3 % after 7, 28, and 60 days of curing, respectively. Furthermore, the growth rate of PP on the compressive strength of cemented soils remains largely unaffected by seawater corrosion. The optimal composite dosage of cemented soils effectively mitigates the increase in porosity caused by seawater corrosion. C-S-H enhances the mechanical interlocking between hydration products and PP by encapsulating PP, reducing energy transfer losses in cemented soils, and increasing their dynamic modulus. The volcanic ash reaction and nucleation effect of NS further enhance this effect, and their combined use significantly improves the seawater corrosion resistance of cemented soils.

Properties of saline soil stabilized with fly ash and modified aeolian sand

Against the backdrop of saline soil solidification and the resource utilization of solid waste and aeolian sand in cold and arid regions, this study employs locally accessible fly ash and aeolian sand to solidify saline soil. By combining unconfined compressive strength tests, X-ray diffraction analysis, scanning electron microscopy, orthogonal experiments, and single-factor analysis, the strength characteristics, mineral composition, and interfacial structure changes of saline soil solidified with different freeze-thaw cycles and varying amounts of fly ash, aeolian sand, and alkali activators were investigated. The effects of each factor were analyzed to determine the optimal mixture ratio and to explore the solidification mechanism.The results indicate that the unconfined compressive strength of saline soil is most significantly enhanced when solidified with a combination of fly ash, aeolian sand, and alkali activators. The optimal mixture ratio was found to be 24 % fly ash, 7 % aeolian sand, and 4.5 mol/L alkali activator. With the incorporation of these solidifying materials, the failure mode of saline soil transitions from plastic to brittle, and the stress-strain curve exhibited a strain-softening behavior. The combined solidification method demonstrated the most pronounced effect in mitigating freeze-thaw damage, with the unconfined compressive strength of the solidified soil reaching 7.01 MPa after seven freeze-thaw cycles, compared to 0.03 MPa for the untreated soil, an increase by a factor of 234.This significant enhancement is attributed to the formation of substantial gel substances, which mitigate the strength loss caused by freeze-thaw cycles. The gel locking mechanism between particles in the solidified soil far exceeds the detrimental effects of freeze-thaw cycles, effectively inhibiting freeze-thaw deterioration. Additionally, the reaction pathways involving AFt and AFm phases reduce the content of SO42- and Cl- in the solidified soil, effectively suppressing salt expansion and significantly improving the soil's strength.

Engineering properties of pozzolanic cement-stabilized organic soil

In this study, the engineering properties of organic soil (OS) stabilized with pozzolanic cement (PC) were investigated. In tests, 10, 15 and 20% proportions of PC were added to organic soil. Consistency limit, Proctor, unconfined compressive strength (UCS), triaxial (TA), swelling and compressibility tests were performed on the OS stabilized with PC. The addition of PC to OS increased the maximum dry density (MDD) and optimum moisture content (OMC) values. The UCS values for the OS stabilized with PC increased up to day 56 and then there was a reduction in the UCS after day 56. The internal friction angle value increased by 26% and the cohesion intercept value increased by 86% for the OS stabilized with PC. With the increase in the cement content in the OS stabilized with PC, the UCS, internal friction angle and cohesion intercept values increased. Swelling of the OS stabilized with PC rapidly reduced up to day 10, and this reduction slowed after day 10. The compressibility of the OS stabilized with PC increased up until day 10, and this increase slowed after day 10. With an increase in the cement content in the OS stabilized with PC, swelling and compressibility values reduced. As a result of the study, it appears that pozzolanic cement is an effective stabilizer for organic soil.

Physico-mechanical properties of halite and gypsum–mudstone crushed rock backfills of the Mercia Mudstone Group

Permanent disposal of radioactive waste in deep geological repositories (DGRs) relies on engineered barriers, such as crushed rock backfills, to ensure that wastes are isolated and contained. The performance of crushed rock backfill, during construction, operation and closure, relies on optimizing its mechanical properties. This paper explores how density and composition influence the strength of (i) crushed halite and (ii) crushed gypsum–mudstone mixtures of the Triassic Mercia Mudstone Group, which is a potential DGR host rock in the UK. Unconfined compressive strength (UCS) testing of compacted halite demonstrated that strength correlated with compaction density, with UCS increasing from 220 kPa at a density of 1.72 g cm −3 up to 6600 kPa at the maximum achieved density of 1.83 g cm −3 . Direct shear testing revealed an angle of internal friction for crushed halite samples of 39°–40° at a density of 1.5 g cm −3 . Direct shear testing of gypsum–mudstone composites from 100% gypsum to 100% mudstone revealed that higher gypsum percentages provide greater frictional shearing resistance, whilst higher mudstone percentages promote more cohesive strength. Data are also presented on bulk materials characterization by X-ray fluorescence (XRF), scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS) and optical microscopy. This research provides insights into how the strength properties of compacted crushed halite and gypsiferous mudstone backfills can be engineered through control of density and composition.

Bacterial activity and cementation pattern in biostimulated MICP-treated sand-bentonite mixtures

The application of microbially induced carbonate precipitation (MICP) in clayey soils has attracted much attention, and many studies used clay as an additive to enhance microbial mineralization efficiency in sandy soils. Within the sand-clay-bacteria-calcite system, the property and content of clay play crucial roles in affecting bacterial growth and calcite formation. More important, bentonite is particularly sensitive to changes in the geochemical environment. In this study, the sand-bentonite mixtures were treated by biostimulated MICP, aiming to provide insights into the behavior of this system. The bacterial activity and cementation pattern at different bentonite contents were evaluated through a series of tests such as enrichment tests, unconfined compressive strength (UCS) tests, cementation content measurements, mercury intrusion porosimetry (MIP) tests, scanning electron microscopy (SEM) observations, and energy dispersive X-ray spectroscopy (EDS) analyses. The findings showed that the bentonite presence promoted the enrichment of indigenous ureolytic bacteria, with lower bentonite levels enhancing ureolytic activity. Macroscopic and microscopic characterization indicated that the bentonite-coating sand structure was more conducive to the formation of large-sized calcite crystals capable of cementing soil particles compared to sand-supported and bentonite-supported structures. Additionally, excessive calcium ions (Ca2+) concentrations in the cementitious solution would lead to predominant calcite deposition on soil particle surfaces, contributing minimally to strength improvement.

Experimental study on the effect of waste plastic powder and marble powder on the swelling behavior and strength parameters of a clay soil

This research aims to provide insights into how the combination of waste plastic powder and marble powder affects the geotechnical properties of clay soil. The findings from this study can have practical implications for construction, foundation design, and environmental sustainability, as the reuse of waste materials can potentially improve soil properties and reduce environmental impacts. In this context, we executed a series of experiments involving samples that were fortified with varying proportions of plastic powder (0%, 1.5%, 2%, 2.5%, and 3%) and stabilized using marble powder at concentrations of 3%, 4.5%, 6%, and 7.5 %. The findings indicate a gradual decrease in liquid limits, swell potentials, and swelling pressure as the proportions of waste plastic powder and marble powder increase. The stress-strain curves obtained from the unconfined compressive strength (UCS) tests revealed that the incorporation of waste plastic powder into marble-stabilized soil led to an increase in UCS. These results emphasize the positive impact of waste plastic powder in enhancing the mechanical properties of the specimens. This research aims to provide insights into how the combination of waste plastic powder and marble powder affects the geotechnical properties of clay soil.

Experimental study on the road performance of molybdenum tailings sand stabilized with cement and fly ash

The large accumulation of molybdenum tailings (MoT) has resulted in a series of hazards, including environmental pollution, damage to water resources, and increased risk of geological disasters. This study employs ordinary Portland cement (OPC) and fly ash (FA) stabilization of MoT sand and seeks the optimal mix ratio through experimentation. The strength properties of MoT sand stabilized with different proportions of OPC and FA are studied and analyzed through unconfined compressive strength tests, splitting tensile strength tests, and splitting rebound modulus tests. Additionally, the microstructure of MoT sand stabilized with OPC and FA is analyzed using scanning electron microscopy (SEM). The results indicate that with an increase in OPC content, the compressive strength, splitting tensile strength, and splitting rebound modulus all increase. With an increase in FA content, the compressive strength gradually increases, while the splitting tensile strength and splitting rebound modulus show a trend of initially increasing and then decreasing. The results show that the optimal mix proportion for OPC and FA-stabilized MoT sand is 7 % OPC content and 15 % FA content. This mixture is suitable for a heavy traffic base of expressways and class I highways, as well as for an extra heavy traffic base of class II and below highways. The research results can provide reference for using OPC and FA stabilized MoT sand as roadbed material.

Optimization of silty soil solidification agent ratio and mechanism of strength change based on design-expert

ABSTRACT In order to achieve the resource utilization of silty soil, based on the solidification mechanism of existing inorganic solidification agents, coal gangue and fly ash were selected as substrates, and quicklime and sodium silicate were used as activators to study a new type of muddy soil solidification agent. This project adopts mixture experimental design and unconfined compressive strength testing methods, and uses design expert software to analyze each component to obtain independent variable relationship strength prediction formulas. By using scanning electron microscope, Particles (Pores) and Cracks Analysis System, the changes in micro pore structure characteristics of Reinforced soil were obtained. The research results indicate that the relationship between the influence of various variable factors on strength gain is as follows: sodium silicate>calcium oxide>fly ash>coal gangue. As the age increases, the porosity shows a trend of first increasing and then decreasing. It has been revealed that the strength growth of Reinforced soil with curing agents is mainly due to the compaction and filling effects of hydrated calcium silicate, hydrated calcium aluminate, and a small amount of ettringite. This study is expected to provide reference for the solidification of high moisture content muddy soil.

Unconfined Compressive Strength Testing on Expansive Clay Soils Stabilized with Cement and Lime

Soil stabilization offers an alternative solution to overcome the problem of expansive clay soil characteristics. Unconfined compressive strength tests were conducted on original and expansive clay soils containing cement and lime to investigate the effectiveness percentage of two pozzolan materials. The amount of material stabilization with percentages 2, 4, 7, 10 % cement, and 5% lime for each sample was adopted. The dimensions of the cylindrical sample were 3’’ in height and 3/2’’ in diameter. The relative density was 80% for all samples and sheared at a strain rate of 1 %. The properties of the original expansive clay soil are (w) 40.11%, (γd ) 1.3 gr/cm³, (Gs) 2.59, (LL) 60.05%, (PL) 38.16%, (IP) 21.88% and (qu) 0.61 kg/cm2. The test results indicate that the clay exhibits high plasticity. Based on the results, the effective combination percentage of two pozzolan materials to enhance the characteristics of expansive clay soil is 2% to 7 % cement and 5% lime. However, adding 10% cement and 5% lime causes the UCS value to decrease. The finding of this investigation shows the combination of two pozzolan materials, especially cement and lime, can effectively enhance the UCS values. This enhancement is observed at specific percentages of cement and lime addition. These results underscore the importance of carefully selecting proportions to achieve desired soil stabilization outcomes.

Experimental study on root-reinforced soils (R2S) and soil root (S-R) interaction in nature

ABSTRACT Biotechnical stabilization, involving vegetation such as trees and shrubs, is commonly employed to reinforce/stabilize soil masses. This research aimed to examine the interaction between soil and roots, focusing on two grass species readily found locally in Kashmir valley: a standard turf grass and a flood channel grass known for its extensive root system. Variables included root length, vegetation type, and root percentage, while strength assessments such as Unconfined Compressive Strength (UCS) tests and Direct Shear Tests (DST) were conducted. Three soils, including two naturally occurring and one artificially prepared in the laboratory, were examined for studies on S-R interaction. UCS values increased considerably for different soil types with the maximum enhancement seen in artificial soil wherein the UCS increased from 65 kPa to almost 400 kPa. Cohesion (c) also showed enhancement from 21 kPa in the control sample to 29 kPa for 1.0% root content and 25 mm root length. Micro-structural analysis was performed and the micrographs clearly showed signs of root surface roughness, adherence of soil particles and interlocking between the grains and root fibers. By stabilizing soil masses, roots can play an important role in slope stability, soil conservation, and other geotechnical applications.