Moisture-dependent resilient modulus of chemically treated subgrade soil

Traffic loads induce cyclic loading under influence of environmental factors, and is affected by the variation of moisture content and suction (s). These parameters are difficult to quantify, and the methods for determination are cumbersome. This paper presents extensive experimental studies used to obtain the resilient modulus-suction (MR-s) relationship of the treated subgrade soil. An optimum design of bentonite‑magnesium-alkalinization (BMA) was used an additive. The cyclic Triaxial frame with ELDYN system was employed to measure MR values and the suction was estimated using the filter paper test. A bimodal soil water characteristic curve (SWCC) was observed for treated soil with unheated BMA additive and pre-treatment at heated (BMAH) conditions due to the presence of cementitious products. The MR-s relationship was also developed for the stabilized soil using a normalized model. Results showed that the BMAH samples had a significant level of improvement of MR at higher suction levels as compared to BMA samples but this behaviour of BMAH didn’t sustain under fully saturated condition. The change in moisture contents under seasonal variation affects the subgrade performance. This study shows the soil additive can effectively improve the mechanical properties of the soil under various moisture contents. The MR for the treated soil can be estimated using the normalized model under the worst-case scenario of a subgrade when the soil is at a fully saturated condition

Calcium bentonite vs sodium bentonite : The potential of calcium bentonite for soil foundation

Bentonite is a favourable candidate as a sealing material in the deep geological repository to safe storage of highly radioactive nuclear waste in several countries. The high swelling characteristic made bentonite famously type of clay that extracted from smectite group with the main mineral is montmorillonite that has a double diffusion layer. The benefits of sodium bentonite like Wyoming bentonite has proven in the industry. Research on modifying the properties of calcium bentonite to high swelling clay like sodium bentonite for it be able to benefit the industry has been done. Most of the research attempted to improve the workability of calcium bentonite as an alternative material for replacing sodium bentonite in construction industry; however, very little is known about using raw calcium bentonite to improve weak soil subgrades. This paper highlighted the usage of calcium bentonite adapted in construction industry especially in soil stabilization activity and some experimental analysis has been made on the type of calcium bentonite found in British Columbia min

Stabilization of silty sand using bentonite magnesium-alkalinization: Mechanical, physicochemical and microstructural characterization

This paper investigates the mechanical, physicochemical, and microstructural characterization of treated silty sand using a novel additive. The additive from a mixture of bentonite, magnesium chloride, and alkaline solution was introduced for stabilization of soil. Atterberg limits, compaction, pH, and unconfined compressive strength (UCS) tests were used to assess the mechanical and physicochemical properties of the stabilized soil. Further investigation results on the optimum designed sample are discussed based on microstructural analysis using X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). Two curing types: unheated and heated at 60 °C for 24 h, were observed at 7, 14, 28 and 60 days in ambient temperature. Overall, it was found that the chemical additive improved the compressive strength of the soil and the heated curing tests showed significant strength improvement. The mechanical and physicochemical results revealed an optimum mix to improve silty sand strength using the addition of 40% bentonite with an alkaline activator (SS/SH) ratio of 0.5, an alkaline activator-to-MgCl2 (L/S) ratio of 0.7, and 3% MgCl2 by dry weight of the soil under heat curing condition at 60 °C for 24 h. The microstructure analysis confirmed the formation of the cementitious products, such as calcium aluminium silicate hydrate (C-(A)-S-H) and magnesium silicate hydrate (M-S-H) in the treated sample

Pulp and Paper Mill Fly Ash: A Review

The continual growth of pulp and paper industry has led to the generation of tremendous volumes of fly ash as byproducts of biomass combustion processes. Commonly, a major part of it is landfilled; however, updated environmental regulations have tended to restrict the landfilling of fly ash due to rising disposal costs and the scarcity of suitable land. The pulp and paper industries are therefore urgently seeking energy-efficient mechanisms and management for the beneficial use of fly ash in an ecological and economical manner. This paper offers a comprehensive review of existing knowledge on the major physicochemical and toxicological properties of pulp and paper mill fly ash to assess its suitability for various bound and unbound applications. The current state of various methods used for the valorization of pulp and paper mill fly ash into more sustainable geomaterials is briefly discussed. This paper also presents promising and innovative applications for pulp and paper mill fly ash, with particular reference to agriculture and forestry, the construction and geotechnical industries, and the immobilization of contaminants. It was identified from a literature review that modified pulp and paper mill fly ash can be environmentally and economically advantageous over commercial coal-based fly ash in various sustainable applications.Applied Science, Faculty ofEngineering, School of (Okanagan)ReviewedFacult

Geotechnical properties of polymer-amended TSRU oil sands tailings

Fine tailings from the tailings solvent recovery unit (TSRU) in the Athabasca oil sands are known to contain a relatively high pyrite content and a high residual hydrocarbon content which may alter their geotechnical properties. Little is known about TSRU tailings properties and therefore the potential for sub-aerial deposition. The goal of this study was to investigate the geotechnical properties of untreated, polymer-amended, and sand-mixed TSRU tailings to inform for the consideration of sub-aerial deposition and increase the general knowledge of these unique tailings. The polymer-amended tailings had more desirable properties for sub-aerial deposition, including a lower final void ratio, less energy required to desaturate, and higher compressibility, when compared to the untreated tailings. The sand mixed samples enhanced these properties, but may pose issues for transportation. The mineralogy indicated that the polymer-amended TSRU tailings have a high enough pyrite content for acid generation which may pose environmental issues for sub-aerial deposition. Overall, TSRU tailings exhibited different geotechnical properties when compared to the well-studied mature fine tailings, highlighting the need for further studies to inform the management of TSRU tailings.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The nature and origin of furrows in lake-bed sediments: Okanagan Lake, British Columbia, Canada

Recent sonar surveys of Okanagan Lake, in the central interior of British Columbia, revealed the presence of linear, contour-parallel furrows at depths of 50–130 m. Underwater video imagery shows these furrows to be approximately 0.5–1 m wide by 0.5–1 m deep with variable lengths extending 1–100 m. Their cross-sectional topology varies from semi-rectangular features with steep-walled sides that expose weak laminations in the sediments to shallow U-shaped troughs that appear to be infilled by lacustrine mud. The most likely origin of the furrows is extension deformation (i.e., tension fracturing) caused by periodic failure along the steeply inclined marginal slopes of this deep, glaciated lake basin. A positive feedback mechanism leading to arrested downslope movement, based on the recent findings reported in Carey et al. (2019), is suggested to apply. Less likely alternative explanations are considered and dismissed. The furrows highlight the nature of long-term geomorphic processes in lacustrine environments that contribute to sediment transport and deposition on the lake bed but are not directly linked to the action of surface waves and currents.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Micro-structural analysis of strength development in low- and high swelling clays stabilized with magnesium chloride solution - A green soil stabilizer

Although the effects of chemical additives on the geotechnical properties of soils have been investigated in recent years, the strength properties and micro-structural characteristics of clayey soils stabilized with magnesium chloride (MgCl2) solution, a green soil stabilizer, have not been clearly brought out. The objective of this study is therefore to investigate the time-dependent engineering properties, mineralogy, morphology and molecular characteristics of MgCl2 stabilized tropical fine-grained soils. Bentonite and kaolin, which represent high and low swelling clays, respectively were employed as the soils tested in this study. Compaction, unconfined compression strength (UCS) and standard direct shear tests were undertaken to assess the engineering properties of the stabilized clayey soils. The mechanisms that may have contributed to the stabilization process were discussed based on the micro-structural analysis using different spectroscopic and microscopic techniques such as X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometry (EDAX), Fourier transform infrared spectroscopy (FTIR) and Brunauer, Emmett and Teller (N2-BET) surface area analysis. From an engineering point of view, the MgCl2 improved the compressive strength of the bentonite and kaolin significantly. The 7-day UCS of MgCl2 stabilized bentonite and kaolin were approximately 2 times higher than that of unstabilized ones. The micro-structural study revealed that the stabilization process modified the porous network of the tested clayey soils. The pores of the soils had been filled by newly formed crystalline compounds known as magnesium silicate hydrate (M-S-H) and magnesium aluminate hydrate (M-A-H) for the bentonite and kaolin, respectively

Geotechnical Properties of Wood Ash-Based Composite Fine-Grained Soil

It is observed in Bangladesh that there is an extensive use of wood as a solid biomass for heat and electricity production, which led to increase in the amount of combustion residues known as ash. These ashes are discarded and dumped here and there, resulting in pollution of the environment. It could be managed by using wood ash as a stabilizer of soft clay. It is found that there is an enhancement of the engineering properties of existing soil in stabilized forms particularly unconfined compressive strength (UCS), shear strength parameters, workability, and compaction and compressibility characteristics. Therefore, laboratory tests associated with these properties were performed for some selected percentage of wood ash, for example, 0%, 5%, 7.5%, 10%, and 12.5%. Chemical investigation of wood ash depicts that it contains approximately 30% CaO, which directs it to behave like a pozzolanic material. Besides, the test result signifying that the soil could be made lighter with the increase of moisture content, strength, and reduction of compressibility due to the addition of ash content