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Geotechnical assessment of lateritic soils obtained from along the Ojota and Shagamu ends of the Lagos–Ibadan expressway was conducted to evaluate their suitability for use as sub-grade and sub-base materials. Laboratory tests, including moisture content, specific gravity, particle size distribution, fabric/plasticity, compaction, and California Bearing Ratio (CBR), were performed on eight (8) soil samples following British Standards (BS) 1377 methods for soil testing. The lateritic soils were classified as clayey sand, silty clay, and silty to clayey sand. They exhibited moderate plasticity and semi-pervious characteristics, suggesting suitability for use as sub-grade materials. Samples 3, 5, 7, and 8 were identified as more suitable for road construction materials, while Samples 1, 2, 4, and 6 showed susceptibility to seasonal volume changes due to high clay content. These samples would require minor soil stabilization to mitigate the effects of their active clay contents. Adequate drainage systems were recommended to prevent water accumulation, soil volume changes, loss of load-bearing capacity, and potential material failure beneath road pavements. The geotechnical properties of the lateritic soils from the tropical area of Ojota–Shagamu differed significantly from those of other lateritic soils found in southwestern Nigeria.

Clay minerals are an important indicator of soil plasticity, influencing clay activity. This study aimed to elucidate the effect of clay minerals, organic C and primary minerals on the Atterberg limit and clay activity. The study was conducted in the Kemuning sub-watershed, Jember, East Java. The study began by preparing a thematic map to determine sample points with stratified random sampling. They were taken as many as 35 disturbed soil sample points at 0-20 cm from the surface. Soil texture was determined using the pipette method, and organic C was determined by the spectrophotometer method. The liquid limit and plastic limit were used to determine the plasticity index. A microscopic analysis of sand mineralogy was carried out to compare activity values with a magnification of 20-40 times to assess the primary soil minerals. The results showed that clay and C-organic affect fluidity, plastic limit, and plasticity index. The presence of andesine, albite, olivine, and orthoclase in the sand fraction and the low clay activity indicated that kaolinite dominated the study area, with smaller amounts of illite and halloysite.

Purpose: The differences in particle composition and consistency limits result in the challenge in comparing the freezing points of different types of loess. The clay activity that well links the clay content and the plasticity index suggests a response to the above challenge. The purpose of this study is to evaluate the relationship between freezing point and clay activity of loess in different areas of Loess Plateau of China. Materials and methods: The test loess was sampled from eight typical areas of the Loess Plateau of China, which could be classified as the lean clay (CL). The clay activity of loess was obtained based on the plasticity index and the clay fraction (< 5 μm). The freezing point and soil freezing characteristic curve (SFCC) of loess were measured by the 5TM transducer from METER Group, while the soil water characteristic curves (SWCC) were determined by the filter-paper method. Results: When the clay activity is below 0.948, the freezing point increases with higher clay activity; otherwise it rises slightly, which is in contrast to the change of matric suction. A proportional function was approximated between freezing point and matric suction. The SFCC decays more sharply at greater initial water content, compared to that at higher clay activity. The free water content increases slightly with higher clay activity while the weakly bound water content declines, resulting in an insignificant change in the freezable water content. Based on the normalization of SFCC, an exponential model incorporating the effect of clay activity was established and verified. The clay activity of loess decays as the calcium chloride content increases, which shows a good linear relationship with freezing point. Conclusions: The freezing point of loess shows high relevance to the clay activity. The clay activity–based freezing point predictive model well considers the differences in clay content and consistency limits of loess in different regions. [ABSTRACT FROM AUTHOR]

Engineering geological investigation of some unstable and stable sections of the Ibadan-Iwo-Osogbo highway was undertaken to unravel the intrinsic reasons responsible for continuous pavement failure along this road. Eighty disturbed and forty undisturbed soil samples were collected at different depths from twenty test pits of six selected failed sections (FS) and two stable sections (SS). Road construction analysis was done on these soil samples using standard methods. Liquid limit (22 - 64% and 32 - 40%), plasticity index (13 - 41% and 12 - 18%) and percentage fines (47 - 59% and 32 - 41%) indicated fair to poor and fair to good subgrade materials of FS and SS respectively. Medium to high plasticity and high clay content of soils of FS are indicative that the soils possess medium to high swelling potential. The activity of clay in soils of FS was approximately 0.3 – 1.2 and classified as inactive to normal clay. High linear shrinkage (> 10%), low compacted density and predominance of fines in soils of FS caused the instability. Exposure to excessive moisture led to strength reduction of the soils. Triaxial compression showed cohesion (72.6 - 127.0 kN/m2) and internal friction (12.7° - 33.3°) indicating moderate to good shearing strength of the soils. A coefficient of compressibility of 0.1 – 0.5 kN/m2 indicated incompetency of the soils for road construction and the coefficient of consolidation was 0.01 – 0.30 m2 /year. The subsoil of the FS is impervious with a relatively low coefficient of permeability, indicative high saturation in the region. Thus, the pavement failure was caused by water absorbing clayey soil, poor geotechnical parameters of the soils and a poor drainage network.

Copyright of Anadolu Tarım Bilimleri Dergisi is the property of Ondokuz Mayis Universitesi, Ziraat Fakultesi 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.)

Copyright of Rudarsko-Geolosko-Naftni Zbornik is the property of Faculty of Mining, Geology & Petroleum Engineering 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.)

We investigated some geotechnical properties of soils of Port Harcourt in 2009 under three land use types, namely mechanically cleared land, on-going building constructions and fallow land. A combination of target and random soil survey techniques guided field studies. Five soil samples were collected in each land use, giving a total of 15 soil samples which were air-dried and sieved. These soil samples were subjected to routine laboratory analysis and resulting data were analyzed statistically using means and correlation analysis. Soils were sandy, of slight to neutral acidity (pH = 5.9-7.6). Disturbed soils were older (silt-clay ratio= 0.13- water 0.50) when compared with fallow having a mean value of 2.1. Plasticity index values were low (< 35%) and differed due to the land use: 11.63% (building site), 12.29% (mechanically cleared land) and 14.57% (fallow). There was low colloidal activity: 0.36 (building site), 0.40 (fallow) and 0.41 (mechanically cleared land). Highest recorded maximum dry density was found in building site (2.03 Mg mG3), while 24.87% optimum moisture content was obtained in fallow soils. Plasticity index showed good relationships with moisture, clay and colloidal activity in the study sites.

O sistema de manejo afeta a matéria orgânica do solo, o que pode ter expressivo efeito na CTC de solos com argila de atividade baixa. Neste estudo, avaliou-se o efeito da utilização durante 21 anos do sistema plantio direto (SPD) sobre os estoques de carbono orgânico (CO), bem como a sua relação com o aumento da CTC de um Latossolo bruno (629 g kg-1 de argila), em Guarapuava, PR. O SPD promoveu acúmulo de CO na camada superficial do solo (0-6cm), o que refletiu-se num aumento de 2,63t ha-1 no estoque de CO, na camada de 0-20cm, em comparação ao preparo convencional. A baixa taxa de acúmulo de CO (0,12t ha-1 ano-1) foi relacionada à alta estabilidade física da matéria orgânica neste solo argiloso e oxídico. Apesar do pequeno acúmulo de CO no solo sob SPD, este teve reflexo positivo na CTC do solo, com um aumento médio, na camada de 0-8cm, de 15,2mmol c kg-1 na CTC efetiva, e de 20,7mmol c kg-1 na CTC a pH 7,0, em comparação ao solo em preparo convencional. Os resultados obtidos reforçam a importância do SPD quanto ao seu efeito nos estoques de matéria orgânica e, em consequência, na CTC de solos tropicais e subtropicais com predominância de argila de atividade baixa.Soil management affects the organic matter stocks, and thus the CEC especially in low activity clay soils. The main goal of this study was to evaluate the long-term (21 years) effect of the no-tillage on soil organic carbon (SOC) stocks and its relationship with CEC increase in a clayey Oxisol (Hapludox), in Guarapuava (PR), Southern Brazil. No-tillage soil had only 2.63t ha-1 more SOC than conventionally tilled soil at 0-20cm, and the highest net accumulation occurred in soil surface layers (0-6cm). The low accumulation rate of SOC in the no-tilled soil (0,12t ha-1 yr-1) was related to the high physical stability of soil organic matter in this clayey Oxisol. Despite the small effect on SOC contents, the no-tilllage had an expressive influence on the CEC of 0-8cm soil layer. The effective CEC increased 15.2mmol c kg-1 and the potential (pH 7.0) CEC increased 20.7mmol c kg-1 in this soil layer, in comparison to conventional tillage system. The results support the positive effect of no-tillage on soil organic matter stocks and on CEC of tropical and subtropical soils with predominantly low activity clay minerals.

SUMMARY A constitutive model, accounting for multiphase and multiscale coupling, is proposed for the water retention domain and the stress-strain response of compacted clayey soils. The model is based on a conceptual interpretation of the microfabric evolution of compacted soils along generalised hydromechanical paths, detected by means of mercury intrusion porosimeter tests. Multiphase coupling is provided by the mutual interaction between the mechanical and the hydraulic states. Multiscale coupling is introduced by a measure of the size of the aggregates, which influences both the retention and the stress-strain response, in the phenomenological constitutive equations. Model capabilities are verified by comparison with relevant experimental data from laboratory tests on compacted Boom clay and other selected experimental data on different compacted clayey soils. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Chemical Engineering is the property of Wiley-Blackwell 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.)