Search

Muskeg soil is widespread in Canada. It covers around 15% of the Canadian landscape. Its problematic nature is attributed to its high compressibility and low shear strength when subjected to loads because of its high initial void ratio and water content. Therefore, in this study, microbially induced calcite precipitation (MICP), an emerging and potentially environmentally friendly technique for soil stabilization, is used for enhancing the compressibility and shear strength properties of muskeg soil. The urease active bioslurry approach is adopted in this study, which comprises the mechanical mixing of bioslurry with soil and the injection of cementation solutions in subsequent phases. Muskeg soil was collected from Bolivar Park, Surrey, British Columbia, Canada. Different bioslurry concentrations were tested for the compressibility properties to determine the optimum concentration. Afterward, the optimum concentration was used to check the effect of the bioslurry percentage by weight and the number of cementation solutions injected on the soil stiffness and strength. Microstructure analysis by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were conducted for untreated and treated samples to check the change in the soil microstructure due to stabilization. The results showed that the 0.4 mol/L bioslurry concentration demonstrated the best compressibility properties. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Organic soils are considered one of the most problematic soils due to their high compressibility and low shear strength at small strains. Characterizing organic soils based on their simple index properties is useful for the preliminary design stages of construction projects. There are three main index properties used for assessing organic soils properties, namely: the water content, the organic content, and the fiber content. Organic soils are distinguished by their relatively high water content. The organic content includes the carbonaceous and combustible components. Whereas the fiber content accounts for the presence of fibers in organic soils based on their botanical composition and the degree of decomposition. The data available in literature regarding organic soils parameters (index, compressibility and shear strength) were collected and analyzed in this study to obtain new correlations between the different organic soil parameters, and the simple index parameters (water content and organic content). The available correlations found in the literature depend on relating a certain parameter with either the organic content or water content. However, the organic content and the water content are related. Hence, the proposed correlations presented in this study aim to connect the particular soil parameter with both the water content and the organic content, using the same equation. Unfortunately, there is not much data in the literature about the soil texture or fiber content, and their relation with other parameters. Hence, all the proposed correlations in this study are not considering the fibre content or the soil fabric. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The findings from a comprehensive characterization of an organic soil deposit using multi-faceted geotechnical field and laboratory investigations are presented. The field-testing program comprised cone penetration testing (SCPT) with shear wave velocity (V s) measurements, full-flow ball penetration testing (BPT), and electric vane shear testing (eVST). The work was supplemented by a laboratory program comprising index testing, one-dimensional consolidation testing, and direct shear testing conducted on the tube and disturbed soil samples obtained from the site. Data originating from this wide range of testing tools deployed at a single site provided a unique opportunity to get insights into the strength and stiffness properties of organic soils and examine possible correlations between such properties and test measurements. The work confirmed the suitability of BPT for characterizing organic soils due to its ability to mobilize/test a larger representative volume of soils during penetration, thereby reflecting a practical average response for the tested soil mass. It was possible to develop simple correlations to directly estimate the small-strain stiffness (G max) and undrained shear strength (S u) of organic soils using data from BPT. With these capabilities, combined with the simplicity and the relatively easy field deploy ability, BPT emerges as a tool with high applicability for the geotechnical characterization of organic soils - an activity essential to support the design of buried energy pipelines that traverse over large distances in remote muskeg terrains in Canada. • The soil exhibited decreasing stiffness with increasing the effective stresses. • In the SCPT u , N kt factor of 8 gave best results for S u in the studied soil. • BPT is a potential test for better characterization of the organic soil. • In the BPT, N ball factor of 9 gave the best results for S u • G max could be approximated by 40 S u [ABSTRACT FROM AUTHOR]

An extensive torsional ring shear testing program has been conducted to measure the drained residual shear strength of soils at the wide range of effective normal stress (10 to 700 kPa) usually mobilized in reactivated and first-time landslides. Soils, mudstones and shales of different plasticity and gradation were tested in the program. The effects of the change in nonlinearity of shear strength envelope over the utilized normal stress ranges on slope stability analyses were investigated. Using this data, new empirical residual shear strength correlations were developed as a function of soil index parameters and wide range of effective normal stresses. In essence, the correlations are presented as revised versions of those previously developed for a limited number of normal stresses utilizing the same soil index parameters. Comparisons were made with a considerable amount of back-calculated shear strength data reported in the literature for reactivated landslides as well as results predicted from existing shear strength correlations to verify the increased suitability of the new correlations for use in slope stability analyses. A numerical expression was also introduced to express the residual shear strength correlations for direct incorporation in slope stability software. [ABSTRACT FROM AUTHOR]