Free Swell Tests Research Articles

Geological Investigation of Clay Minerals (Swelling) Pt. Upb Antam Pongkor Bogor, West Java, Indoneisa

Rocks containing clay minerals can experience rock deformation when interacting with water, this can also caused by the argillic zone, in the underground tunnel at the Unfoloader 600 and Xc 600 loop 2 ciurug. The argillic process that causes actual material swelling that occurs in field causes rock mass around the mining development area to become weak. The location from tunnel cross cut of Unfoloader 600 and Xc 600 loop 2 contain active clay minerals which high percentage composition of swelling mineral material. The Unfoloader 600 location has a mineral swelling composition of 102.94% with 24 hours, justifying potential very high swelling. The minerals present based on XRD testing 70.8% illite, 25.4% kaolinite, 25.4% kaolinite and 3.8% montmorillonite. Location Xc 600 loop 2 has a mineral swelling composition of 131.25% with 24 hours, justifying potential for very high swelling. The minerals present based on XRD testing illite 49.7%, kaolinite 28.7%, quartz 20.3%, and montmorillonite 1.2%. The values obtained based on laboratory form free swelling tests and XRD that the location experienced of rock deformation, it’s swelling in the mining development area.

Parameters controlling the expansive behavior of bentonite-kaolin mixtures stabilized with alkali-activated waste

Expansive soils can cause large-scale damage to the infrastructure. Soil stabilization with Portland cement and lime has been widely utilized as a solution to this problem. However, these stabilizers are non-renewable and energy-intensive. Alkali-activated binders are alternatives with lower carbon dioxide emissions. This research evaluated an expansive soil stabilization with an alkali-activated binder produced from sugarcane bagasse ash (SCBA), hydrated eggshell lime (HEL) and sodium hydroxide (NaOH). Free-swelling tests alongside a statistical analysis evaluated the influence of dry unit weight (12.5 and 14.5 kN/m3), binder (4 and 10%) and moisture content (19.7 and 24.7%) and curing time (0 and 7 days) on the stabilized mixtures. A four factors factorial design with duplicates and central points was outlined. To better understand the NaOH and SCBA influence over the soil expansion additional tests were performed. In general, an increase on the studied factors reduced swelling, especially binder content. However, the alkali-activated cement presented no clear correlation between higher density and higher expansion. Swell reduced from 13.8% (12.5 kN/m3 and 19.7% moisture) and 8.8% (12.5 kN/m3 and 24.7% moisture) to 2.5% and 0%, respectively, after 7 days and 10% binder addition for the alkaline cement. For Portland cement, swell reduced from 13.8% (10.2 kN/m3 and 22.5% moisture) and 12.5% (10.2 kN/m3 and 27.5% moisture) to 1.8% and 1%, respectively, after 7 days and 4% binder addition. Samples containing NaOH expanded less than samples molded with only water. Finally, the alternative binder might be a viable option to replace Portland cement for expansion control.

Assessment of the Swelling Behavior of NaOH-Contaminated Red Earth in the Visakhapatnam Region of India Using X-ray Diffraction Analysis

Research on the impact of alkali contamination on the swelling behavior of red earth in the Visakhapatnam region has been notably limited. Therefore, this study aims to investigate the effects of alkali (NaOH) contamination on the swelling characteristics of the region’s red earth. The red earth of this region was found to be a well-graded sandy soil with 81% sand and 18% fines. X-ray diffraction studies showed that this region’s red earth mainly consists of quartz, kaolinite, and hematite. The soil is inherently non-swelling. However, the free swell tests showed considerable swell under contamination of NaOH solutions of various normalities (0.05, 0.1, 1, 2, and 4N). One-dimensional consolidation tests have shown that the swell increased with the concentration of the NaOH solution and with the duration of the interaction. Red earth exhibited 'an equilibrium swelling' of 5.6, 10, 15, 17, and 20% when contaminated with 0.05, 0.1, 1, 2, and 4N NaOH solutions, respectively. XRD studies revealed that the red earth sample contaminated with even 0.05N NaOH solution and cured for 56 days exhibited the formation of zeolites analcime and natrolite. Silicate minerals like paragonite and ussingite were also formed along with the zeolites. N-A-S-H compounds, hydrosodalites, and zeolites like super hydrated natrolite, zeolite SSZ16, and zeolite ZK-14 were formed at higher normalities of NaOH after a curing period of 56 days, which caused increased swell. The research demonstrated that the formation of zeolites resulting from the alkali contamination led to swelling in the red earth.

Predictive models for treated clayey soils using waste powdered glass and expanded polystyrene beads using regression analysis and artificial neural network

Waste materials contribute to a wide range of environmental and economic problems. To minimize their effects, a safe strategy for reducing such negative impact is required. Recycling and reusing waste materials have proved to be effective measures in this respect. In this study, an eco-friendly treatment is investigated based on using waste powdered glass (WGP) and EPS beads (EPSb) as mechanical and chemical admixers in soils. For this purpose, Atterberg limit, standard proctor, free swell, and unconfined compression tests are performed on soil samples with different ratios of waste materials at their optimum moisture contents. The obtained test results indicate that adding WGP to cohesive soils increases the unconfined compressive strength (UCS) and reduces free swell (FS). In contrast, using EPSb reduces both FS and UCS of the treated soil samples. An optimum combination of both waste materials is determined for the improvement of the properties of high plasticity clay used in this study. Furthermore, multiple linear regression (MLR) and artificial neural network (ANN) methods are used to predict the FS and UCS of the clayey soils based on the data obtained here and the experimental test results reported in the literature. Once the FS and UCS values of untreated soil and additive percentages are defined as independent variables, both methods are shown to predict the FS and UCS values of the treated soil samples on a satisfactory level with the coefficient of correlation (R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}^{2}$$\\end{document}) values greater than 0.926. Additionally, when only the index properties (liquid limit, plastic limit, and plasticity index) of the soil samples with waste materials are used as dependent variables, the R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}^{2}$$\\end{document} values obtained by the ANN method are 0.968 and 0.974 for FS and UCS, respectively. The results of the untreated soil samples' FS and UCS tests are known, and the linear regression and ANN techniques yield similar results. Lastly, the ANN method is used to predict the FS and UCS of the treated samples in accordance to the limited predictors (e.g., only the Atterberg limits of the soil sample).

Compaction, strength, and volume change characteristics of excavated clayey soil stabilized with composite admixture of cement and autoclaved aerated concrete powder

Low-strength and highly compressible excavated clayey soils are common in geotechnical engineering, which cannot serve as a bearing stratum and typically end up being disposed of in landfills. Autoclaved aerated concrete powder (AACP) is a lightweight and porous waste material, with its stockpiles rapidly accumulating worldwide. To promote sustainable development in geotechnical engineering, a type of composite admixture consisting of cement and AACP was developed to modify clayey soils in this study. The physical and mechanical properties of untreated and the composite admixture-treated soil samples were investigated via Atterberg limits, compaction, bender element, constraint compression, free swell, and unconfined compressive strength (UCS) tests. The physicochemical and microstructural observations, including soil pH, scanning electron microscopy, and mercury intrusion porosimetry analyses, were conducted to interpret the macroscopic mechanical behaviors. Test results showed that the incorporation of AACP improved the workability of clayey soils, while cement further enhanced their mechanical properties. Hydration compounds primarily filled the voids with a diameter ranging from 0.1 to 1 µm. From the perspective of volume change behavior, 8% cement content was recommended. Shear wave velocity showed a strong correlation with the UCS, demonstrating that the bender element technique was an effective non-destructive tool for assessing the strength of compacted samples.

Free swelling behavior of MX80 bentonite under elevated temperatures up to 200 °C

This paper focuses on understanding trends in the swelling potential of MX80 bentonite under temperatures up to 200 °C using a high-pressure cell. The free swelling behavior of expansive clays under high temperature and high fluid pressure conditions that may be encountered in geological repositories for high-level radioactive waste is important as the swelling potential is closely linked with key transition points on the physical and chemical properties of these clays. Free swell tests performed at temperatures ranging from 22 to 200 °C under sufficient pressure to ensure that the pore water remains as a superheated liquid were performed to assess whether the swell index of bentonite follows similar non-monotonic trends with temperature as observed in the literature for the cation exchange capacity. The measured swell indices follow an increasing-decreasing trend with a transition close to 100 °C. The experimental results can be used to guide parameter selection in long-term simulations on the buffer behavior of the buffer material, which requires an understanding of temperature effects on the coupled thermal-hydraulic-mechanical properties governing these processes.

Performance evaluation of Alccofine stabilised Marine clay as subgrade

Soil stabilization is a remedial measure that reduces permeability and compressibility, increases bearing capacity and shear strength of soil mass, which helps in reducing the settlement of structures. Marine clay is one of the major regional soil deposits in India, widely found in offshore and coastal areas. This is a type of low strength soft clay which majorly causes failure in pavements and foundation structures due to high settlements and low strength characteristics. The scope of this project is to improve the strength of marine clay by stabilizing it with alccofine. The work includes determination of index properties of marine clay by Hydrometer method, Atterberg’s test, Specific Gravity test, Free Swell test. The engineering properties of both virgin soil and soil stabilized with 3%, 6%, and 9% of alccofine are determined by various tests such as Standard Proctor test, California Bearing Ratio test. On the basis of CBR test, the optimum percentage of alccofine in marine clay is found out to be 6%.

Utilization of organoclay amended bentonite for hydraulic barrier applications under adverse electrolyte environment

Inorganic ions such as sodium and calcium are often found in industrial leachates, municipal solid waste leachates and deep geological repositories, which can significantly impact the geotechnical properties of hydraulic barrier materials. Researchers have suggested the utilization of organoclays as landfill liner amendments, especially when the liner is in contact with organic contaminants. This study focuses on the impact of inorganic salts (NaCl and CaCl2) on the geotechnical properties, such as consistency limits, swelling, and hydraulic conductivity of organoclay-amended bentonite (BOC) liners. Different concentrations of salt solutions (0, 0.1 N and 1 N) were selected for the execution of Atterberg limits, free swell tests, and oedometer tests. The surface charge characteristics of bentonite and organoclay were attained with the aid of zeta potential measurements. The variation in the surface topographies of soil samples at different electrolyte conditions was analyzed with the help of scanning electron microscope images. The addition of organoclays significantly reduced bentonite's swelling characteristics and liquid limit due to the unique hydrophobic and organophilic attributes of organoclay but increased the hydraulic conductivity. However, the influence of inorganic salts on the geotechnical parameters of organoclay-amended bentonites showed less variance than that of bentonite. Also, no soil samples exceeded the limiting hydraulic conductivity criteria required for landfill liners, i.e. 1 × 10−9 m/s. Hence, organoclay-amended bentonites could potentially be utilized for hydraulic barrier applications even in an electrolytic environment without compromising the hydraulic conductivity criteria.

Effect of calcined clay on the improvement of compaction, swell and microstructural characteristics of expansive soil

Expansive soil is problematic soil because its alternate swell shrink behaviour depends on the presence of water. Soil stabilization technique was widely adopted to alter the characteristics of the expansive soil which is suitable for construction. Among the various soil stabilization techniques, chemical stabilization was found to be more suitable method of sustainable stabilizing the soil due to its effective and timely reaction with the chemical compound. Calcined form of clay material is used as an admixture to study the effects on the improvement of soil properties. Calcined Clay (CC) is added into the virgin soil with different percentages of 2%,4%,6%,8% and 10% under varying 1,3,7,14,28 and 60 days of curing by conducting experiments such as standard proctor test, Free Swell test to analyse the compaction characteristics and swelling behaviour of the soil. In addition to that the X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) on virgin and treated soil were studied by varying 2% incremental of CC up to 10% at 28 days of curing. From the test results it shows the variation in the compaction characteristics by rising in Maximum Dry Density (MDD) and reduction in Optimum Moisture Content (OMC) that merges at 8% as an optimum to develop the soil behaviour and from the free swell test, it was found that the Free Swell Index (FSI) of the soil decrease from 210 to 80 at 10% calcined clay added soil and the Mineralogical studies also show the variation in the compounds. Thus, this naturally available calcined clay was used to improve the soil Compaction and swell characteristics that influences the reduction in deformation and increase in shear strength of soil which helped to minimize the environmental problem as well as one of the effective admixtures to improve the expansive soil characteristics.

Effect of leachate and used motor oil on the geotechnical and mechanical characteristics of soils with different mineralogy under different moisture conditions

ABSTRACT In order to evaluate the geotechnical characteristics of four types of fine-grained clayey soil, including clay with low plasticity (CL), calcium bentonite (CB), sodium bentonite (SB), and a mixture of 50% CL and 50% SB (CL-SB) from the effect of water, leachate and used motor oil (UMO) was used. Unconfined compressive strength (UCS), indirect tensile strength (ITS), standard compaction, Atterberg limit, and free swelling tests are performed. This results showed that the PI of SB, CB, CL, and CL-SB soils with leachate is 43, 25, 10, and 33% higher than water, respectively. The PI of SB, CB, CL, and CL-SB soils with UMO is 72, 66, 12, and 43% lower than water due to the low dielectric constant. Adding leachate compared to water caused a decrease in maximum dry density (MDD) for CL, CL-SB, SB, and CB by 2.6%, 4%, 6%, and 4.5%, respectively. Also, adding leachate and UMO reduces UCS and ITS of all soils. Due to SB soil’s high cation exchange capacity, the changes in its mechanical and geotechnical characteristics were higher than in other soils. Finally, the increase in soil moisture during the sample construction decreased the soil strength due to the addition of leachate and UMO.

Experimental Studies and Sustainability Assessments of Quarry Dust for Chemical Treatment of Expansive Soils

Abstract Civil infrastructure constructed on expansive soils undergoes distress and loss of serviceability because of damage caused by moisture-induced volumetric changes. Traditional stabilization methods that employ calcium-based stabilizers are widely used mitigate the volume change-related distresses, but they increase the carbon footprint and emission of greenhouse gases during production and construction stages, compromising the treatment’s sustainability. This research study was designed to use silica-rich waste products, such as a quarry dust admixture with a calcium-based stabilizer, to enhance the performance of problematic soils and improve the sustainability of the system. An array of engineering tests, including unconfined compressive strength tests before and after moisture conditioning, one-dimensional free swell tests, and linear shrinkage tests, were performed on untreated and treated soils. Test results showed that the utilization of quarry dust as a co-additive significantly improved the strength and durability of the soil and reduced the shrink-swell potential to a greater extent than lime treatment alone. The sustainability assessment was then performed, which showed that the application of quarry dust can be considered a sustainable alternative that helps reduce the geoenvironmental problems related to handling and stockpiling waste products in landfills. Overall, silica-rich waste products have the potential to be appropriate and sustainable additives that work well with a traditional calcium-based stabilizer to modify expansive soil.

Hydraulic Conductivity, Microstructure, and Compositional Changes of Sand–Bentonite Backfill in Cutoff Walls Exposed to Organic Acids

Leachate, consisting of organic acids such as acetic acid (AA) and oxalic acid (OA), commonly is released into groundwater from municipal solid waste dumps and uncontrolled landfills. Slurry trench cutoff walls commonly are used to contain such contaminated groundwater, thereby protect the surrounding public and the environment. However, no studies have assessed comprehensively the effects of organic acid–laden groundwater exposure on the hydraulic conductivity and microscopic characteristics of sand–bentonite (SB) backfill in the cutoff walls. Several series of free swell, liquid limit, and flexible-wall hydraulic conductivity tests were conducted to quantify the effects of AA and OA exposure on the free swell index of bentonite and hydraulic conductivity and liquid limit of SB backfill. Results showed that the free swell index of bentonite and the liquid limit of SB backfill decreased with increasing concentrations of AA and OA. Exposure to AA yielded a lower free swell index of bentonite and liquid limit of SB backfill than those of OA with the same concentration. Increasing concentrations of AA and OA resulted in an increase in the hydraulic conductivity of SB backfills. Exposure to AA yielded higher hydraulic conductivity of SB backfill than OA with the same concentration. Mechanisms for increased hydraulic conductivity under organic acid exposure were ascertained based on the microstructure and compositional changes quantified by field-emission scanning electron microscopy (FESEM), mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), X-ray fluorescence (XRF), cation exchange capacity (CEC), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR) analyses.

A swelling-based biphasic analysis on the quasi-static biomechanical behaviors of healthy and degenerative intervertebral discs

Background and ObjectiveThe degeneration of intervertebral discs is significantly dependent of the changes in tissue composition ratio and tissue structure. Up to the present, the effects of degeneration on the quasi-static biomechanical responses of discs have not been well understood. The goal of this study is to quantitatively analyze the quasi-static responses of healthy and degenerative discs. MethodsFour biphasic swelling-based finite element models are developed and quantitatively validated. Four quasi-static test protocols, including the free-swelling, slow-ramp, creep and stress-relaxation, are implemented. The double Voigt and double Maxwell models are further used to extract the immediate (or residual), short-term and long-term responses of these tests. ResultsSimulation results show that both the swelling-induced pressure in the nucleus pulposus and the initial modulus decrease with degeneration. In the free-swelling test of discs possessing healthy cartilage endplates, simulation results show that over 80% of the total strain is contributed by the short-term response. The long-term response is dominant for discs with degenerated permeability in cartilage endplates. For the creep test, over 50% of the deformation is contributed by the long-term response. In the stress-relaxation test, the long-term stress contribution occupies approximately 31% of total response and is independent of degeneration. Both the residual and short-term responses vary monotonically with degeneration. In addition, both the glycosaminoglycan content and permeability affect the engineering equilibrium time constants of the rheologic models, in which the determining factor is the permeability. ConclusionsThe content of glycosaminoglycan in intervertebral soft tissues and the permeability of cartilage endplates are two critical factors that affect the fluid-dependent viscoelastic responses of intervertebral discs. The component proportions of the fluid-dependent viscoelastic responses depend also strongly on test protocols. In the slow-ramp test, the glycosaminoglycan content is responsible for the changes of the initial modulus. Since existing computational models simulate disc degenerations only by altering disc height, boundary conditions and material stiffness, the current work highlights the significance of biochemical composition and cartilage endplates permeability in the biomechanical behaviors of degenerated discs.

Enhancing the mechanical and hydromechanical behaviors of mudstone soils using sugarcane press mud

Geological hazards, such as landslides and soil erosion, are frequently found in regions where mudstone soils are prevalent. These soils can also present challenges for the construction of infrastructure, including roads, railways, and other facilities. While various methods exist for addressing the mechanical and hydromechanical properties of mudstone soils, the reuse of waste materials may be a cost-effective alternative. This study presents the effect of press mud, a by-product of sugar purification, as an alternative material for improving the performance of mudstone soils. Unconfined compressive strength tests were conducted to evaluate the mechanical properties of untreated and press mud-treated mudstone soils. In addition, free swell tests, one-dimensional consolidation tests, and three-dimensional volumetric shrinkage tests were performed to investigate the hydromechanical properties of the soils. These tests provided insights into the behavior of the mudstone soils under various conditions. In addition, microstructural analysis such as X-ray diffraction, X-ray fluorescence, Fourier-transform infrared spectroscopy, and scanning electron microscopy were performed to identify the soil improvement mechanisms. The results demonstrated that press mud can act as a binder and help enhance the peak and postpeak strengths of mudstone soils. The swelling and shrinkage characteristics improved when it was treated with press mud; however, the inclusion of press mud slightly increased the compressibility of mudstone soils. According to microstructural analysis, the formation of extra cementitious gels helped enhance the mudstone soils performance. These findings offer promising and environmentally friendly options for effectively treating mudstone soils and address the needs of engineers seeking sustainable solutions.

Geotechnical and environmental radioactivity investigations at Al Sādis Min Uktōber city, Cairo municipality (Egypt), for the high-speed railway construction

The present study aims to evaluate the possibility of constructing a new high-speed railway (HSR) at Al Sādis Min Uktōber city, Cairo (Egypt): geotechnical and environmental radiological hazards are estimated from several collected soil and water samples. A variety of laboratory geotechnical tests such as grain size, free swelling test, liquid and plastic limits, chemical analysis and uniaxial compression strength are applied to sixty-one drill holes. A geotechnical examination of the coarse-grained soil at the foundation level classified it as poorly graded soil. The results of the investigation of fine-grained soil at the foundation level shown that the liquid limit ranges from 22% to 55%, the plastic limit ranges from 12% to 28%, the plasticity index varies from 11% to 33%, free swelling varies from 51% to 71%. Mechanically, the uniaxial compressive strength values on rock samples range from 6.96 MPa to 142.39 MPa. The radioactive study is performed to detect the 226Ra, 232Th, and 40 K activity concentrations of the soil samples: their mean values are 34 ± 10 Bq·kg−1, 14 ± 5 Bq·kg−1 and 552 ± 20 Bq·kg−1, respectively. The values of radiological hazard indexes are not exceeded the permissible limits: e.g. the mean value of absorbed dose rate is 47 ± 6 nGy h−1; the annual gonadal dose equivalent is 0.3 ± 0.04 mSv·y−1; the lifetime cancer risk is 02 ± 0.2·10−3. Thus, the soil in the studied railway area is safe to use in building materials and infrastructure applications: the radiological hazards and the geotechnical studies confirmed the studied area is suitable to construct a new community having a HSR. According to the SWOT-PEST and environmental impact analyses, the construction of the HSR meets the criteria of the Kyoto Protocol, the EU Climate and Energy policy, and other international treaties.

The Investigation of the Addition of Sodium Lignosulfonate to Lime Column Used For Improving the Expansive Soils

The lime column (LC) technique has been commonly used for the improvement of expansive soils. The achievement of this technique depends on the lime diffusion into the expansive soils, but lime diffusion into the expansive soil is generally a slow process due to the low permeability of these soils. In this study, sodium lignosulfonate, which is used as a superplasticizer in the concrete industry, was added to lime columns to accelerate the diffusion of lime particles. First, treated expansive clay specimens with thirty-seven 4.5 mm diameter columns were prepared in an oedometer ring. These columns were filled with two different mixtures: water-lime and water-lime-sodium lignosulphonate to investigate the effect of the addition of sodium lignosulphonate. Free swell tests were done on these treated expansive clay specimens that were subjected to different curing periods, it was observed that the treated specimens with sodium lignosulphonate lime columns (NaLS-LC) are more effective than the treated specimens with lime columns (LC). A treated expansive clay specimen (in a 30cmx30cm mold) with seven pieces of 45 mm diameter sodium lignosulphonate lime columns were prepared to observe the alteration of engineering properties of untreated expansive clay specimen (US) located between the columns. Free swell and unconfined compressive strength tests were done on the undisturbed expansive clay specimens taken from the mold between the columns. SEM-EDX analyses were made to investigate whether the ettringite mineral, which leads to swelling of the expansive soil during lime stabilization, forms or not. While the ettringite mineral formed during the curing period in the lime column stabilization method, the addition of sodium lignosulphonate to lime columns blocked the formation of the ettringite mineral. It can be stated that sodium lignosulphonate lime columns (NaLS-LC) show better performance than lime columns (LC), in the treatment of expansive clays.

Improvement of swelling soil by using lime sludge and sodium chloride

Construction on swelling soil is a major challenge to geotechnical engineers all around the world. This type of soil has a quite complex behavior as they undergo the category of problematic soils. The seasonal variations in the climate cause swelling and shrinkage, affecting soil’s water retention. The prediction of future climate change will worsen this problem, increasing the importance of the matter. The attention has been directed to experimental modeling and field investigations. In previous references, this problem was targeted by adding additives which are relatively expensive and non-environment friendly. In this study, waste and recycled materials are used in the lab to enhance the undesirable expansive soil characteristics to keep the environment clean and sustainable and reduce pollution. The additives are selected not only for its availability and cheapness but also to reduce the damage of environment due to disposal of waste. Therefore, the aim of study is to observe the behavior of expansive soils when mixing with various percentages of sodium chloride (NaCl) and lime sludge (LS). The percentages used in this work to determine the swelling properties of expansive soil were 1%, 2%, and 3% NaCl by weight with 3%, 6%, 9%, 10%, 12%, 15%, and 20% of LS by weight. The experimental tests held in the laboratory were liquid limit (LL), plastic limit (PL), free swell (FS), plasticity index (PI), swelling pressure, swelling and infiltration test, and physical models. The results show that by increasing the percentage of NaCl and LS, a significant improvement is obvious to the swelling properties of soils. Added to that, a decrease in PI of the swelling soil is clearly observed which reflects a decrease in swelling pressure and free swell of the swelling soil.

A dual-porosity model for analysis of temperature effects on hydro-mechanical behaviour of GMZ bentonite under unconfined conditions

A model for coupling thermal, hydraulic, and mechanical properties of GMZ bentonite is presented. The model considers a binary classification of the pores into macropores and micropores and describes the effect of the changes in the two classes under free swelling conditions on the bentonite water retention behaviour. The macropores are assumed to be water conduits, while the water occupying the micropores is assumed to be immobile. The effects of temperature on the mobile and immobile water are considered separately. Variation of mobile water is determined by the water retention curve considering temperature effects, and immobile water is calculated from the deformation of micropores due to different relative humidities (RHs) and temperatures. The model is used to simulate free swelling tests of GMZ bentonite carried out from low RH to high RH under different temperature conditions. A comparison with available experimental data shows that the model offers a good predictive capability and can be used for further understanding the temperature effects on the hydraulic-mechanical behaviour of bentonite. The work underpins engineering assessments of the GMZ bentonite behaviour required for the construction of the deep geological repository at Beishan under coupled thermo-hydro-mechanical effects.

Additives optimisation for expansive soil subgrade improvement based on rough set theory

The swell-shrink characteristics of the expansive soils, due to the properties of their clay minerals, make them unsuitable for engineering constructions in their natural forms. One of the most frequently used methods for the modification of these soils is stabilisation using additives. In this study, a new approach based on rough set theory (RST) is presented for soil additives optimisation. The RST is a mathematical data mining approach for the analysis of imperfect knowledge or unclear description of objects. The additives used in this research are sawdust ash (SDA), stone dust (SD) and ordinary Portland cement (OPC). The unconfined compressive strength test, the California bearing ratio test and the differential free swell test were used for evaluating the properties of the stabilised soil. The results of this study indicate that the RST can effectively be used for additives optimisation in the stabilisation of expansive soils.

INVESTIGATION OF CLAY STABILIZER POTENTIAL FOR HIGH CLAY CONTENT FORMATION

Clay swelling has been studied for decades due to its damaging problem in the reservoir. It has caused permeability impairment due to blockage at the pore throat and reduction of the available pore spaces in the reservoir. The past few decades have seen rapid development of clay stabilizers to treat clay minerals near-wellbore region areas. However, there a limited study investigating the potential of clay stabilizers to prevent clay swelling throughout the reservoir. The present study aimed to investigate the potential of potassium chloride (KCl) and Poly-diallyldimethylammonium chloride (PolyDADMAC) as cationic clay stabilizers to mitigate the clay swelling phenomenon throughout the reservoir. This study conducted a series of free swelling tests on bentonite with varying brine salinity and clay stabilizer concentration. In addition, the rheological properties of KCl and PolyDADMAC were measured at 24°C and 98°C and at a 7.34 s–1 shear rate to determine its flow potential throughout the reservoir. The results showed that 0.3 wt.% to 1.5 wt.% of KCl and PolyDADMAC were able to control the expansion of bentonite immersed in an aqueous solution, with PolyDADMAC has shown excellent performance, whereas the bentonite expansion in PolyDADMAC solution is significantly lower than KCl. This result is driven by the fact that PolyDADMAC has greater amounts of cationic charges to neutralize abundant negative charges on clay mineral surfaces. Furthermore, the viscosity of 0.3 wt.% to 1.5 wt.% of KCl and PolyDADMAC at 24°C and 98°C recorded is low, which is 0.25 cP to 1.45 cP and 0.83 cP to 2.32 cP respectively. This low value proves its potential to be penetrated throughout the reservoir, not limited to near the wellbore region only.
 Keywords: Cationic clay stabilizer, salinity, bentonite swelling, viscosity