No description available.

As testing stiff soils in the laboratory often leads to information which is not consistent with field performance, research was undertaken to determine in situ the soil properties. Among the devices which generated interest is the self-boring pressuremeter (SBPM). In this research, two stiff soils of the Commonwealth of Virginia were tested: A residual soil found in Blacksburg and a very stiff, non-fissured, and sensitive clay, of marine origin, known as the Miocene clay of the downtown Richmond area. Testing the residual soil of Blacksburg with the SBPM led to the following new operational approaches: (1) a systematic use of a steel-sheath known as "Chinese lantern" to protect the membrane of the probe, (2) the development of a loading frame providing adequate reaction when self-boring in stiff soils, (3) the development of a new calibration unit for the SBPM which allows to calibrate the probe under conditions more like those encountered in stiff soils and, (4) the development of a high capacity computerized data acquisition system. Testing the residual soil also allowed to establish a sound database for this soil. In the Miocene clay, the laboratory test results indicate that conventional sampling technique which consists in pushing Shelby tubes disturbs significantly the soil and leads to scattered test results. In contrast, tests performed on samples taken from high-quality block samples indicate consistent behavior patterns. SBPM test results in the Miocene clay indicate that the clay exhibits high lateral stresses. They also indicate the existence of an anisotropic state of lateral stress which can be explained from the regional topography. The soil parameters interpreted from the SBPM test results in the Miocene clay compare well with the soil parameters determined in the laboratory on the block samples. / Ph. D. / incomplete_metadata

No description available.

No / Municipalities and recycling and environmental authorities are concerned about the growing amount of carpet waste produced by household, commercial and industrial sectors. It is reported that 500,000 tonnes of carpet waste fibre are plunged into landfills annually in the UK. In the United States of America, around 10 million tonnes of textile waste was generated in 2003. In geotechnical engineering, expansive clay soils are categorised as problematic soils due to their swelling behaviour upon increase in the moisture content. The problematic nature of such soils is intensified with the increase in the plasticity index. This paper presents results of a comprehensive investigation into utilisation of carpet waste fibres in order to improve the swelling characteristics of compacted cohesive soils. Therefore, two different clay soils with markedly different plasticity indices (i.e. 17.0 and 31.5 %) were treated with two different types of carpet waste fibre. Waste fibres were added to prepare specimens with fibre content of 1, 3 and 5 % by dry weight of soil. Soil specimens with different dry unit weights and moisture contents were prepared so as to the swelling behaviour of fibre reinforced compacted clays is completely attained under various scenarios. The results indicated that the behaviour of the fibre reinforced soils seems highly dependent on the initial compaction state and secondary on the moisture content. It was found that the swelling pressure drops rapidly as the percentage of fibre increases in samples prepared at the maximum dry unit weight and optimum moisture content. Reducing the dry unit weight, while maintaining constant moisture content or increasing the moisture content at constant dry unit weight was found to reduce the swelling pressure.

This investigation has for its aim the confirmation of the correlation between soil moisture and the microflora of soils, and a lesser relation between the soil temperature and the microflora. The soils used in this study are typical clay soils of Denton County, Texas. The samples were taken from virgin pasture lands and analyses made monthly or semimonthly. The wide seasonal variation of temperature and rainfall afford a good opportunity for this study.

Offshore developments for hydrocarbon resources have now progressed to water depths approaching 2500 m. Due to the difficulties and high cost in recovering high quality samples from deepwater site, there is increasing reliance on in situ tests such as piezocone and full-flow (i.e. T-bar and ball) penetration tests for determining the geotechnical design parameters. This research was undertaken in collaboration with the Norwegian Geotechnical Institute (NGI), as part of a joint industry project, to improve the reliability of in situ tests in determining design parameters and to improve offshore site investigation practice in deepwater soft sediments. In this research, a worldwide high quality database was assembled and used to correlate intact and remoulded shear strengths (measured from laboratory and vane shear tests) with penetration resistances measured by piezocone, T-bar and ball penetrometers. The overall statistics showed similar and low levels of variability of resistance factors for intact shear strength (N-factors) for all three types of penetrometer. In the correlation between the remoulded penetration resistance and remoulded shear strength, the resistance factors for remoulded shear strength (Nrem-factors) were found higher than the N-factors. As a result, the resistance sensitivity is less than the strength sensitivity. The correlations between the derived N-factors and specific soil characteristics indicated that the piezocone N-factors are more influenced by rigidity index than those for the T-bar and ball penetrometers. The effect of strength anisotropy is only apparent in respect of N-factors for the T-bar and ball penetrometers correlated to shear strengths measured in triaxial compression. On the other hand, the Nrem-factors showed slight tendency to increase with increasing strength sensitivity but were insensitive to soil index properties. These findings suggest that the full-flow penetrometers may be used to estimate remoulded shear strength and are potentially prove more reliable than the piezocone in estimating average or vane shear strength for intact soil but the reverse is probably true for the estimation of triaxial compression strength.

[Truncated abstract] This research has studied the penetration and extraction resistance profiles of different types of penetrometers in soft clay. The penetrometers of interest include the cone, T–bar, ball and plate. Effects of the surface roughness and aspect ratio of the T–bar penetrometer on its resistance have also been investigated. Undrained shear strength, Su, profiles derived from the penetration tests are compared with the shear strengths measured from field vane shear tests and laboratory (triaxial and simple shear) tests. Both in situ and centrifuge model penetration tests were undertaken for the research. In addition, ‘undisturbed’? tube samples were retrieved from both the field and the centrifuge strongbox samples (after completion of the centrifuge tests) for laboratory testing. The in situ testing was carried out in Western Australia, at the Burswood site near Perth, with tests including cone, T–bar, ball and plate penetrometer tests, and vane shear tests. Interestingly, the T–bar, ball and plate (‘full-flow’) penetrometers showed a narrow band of resistance profiles both during penetration and extraction, with a range of around 15 % between the highest and lowest profiles and standard deviation of 15 %. However, the cone penetrometer gave similar resistance at shallow depths but increasingly higher penetration resistance at depths greater than 7 m – a phenomenon that is also common in offshore results. During extraction, the cone penetrometer gave a higher resistance profile than the full–flow penetrometers for much of the depth of interest. The Su profile measured directly from the vane shear tests falls within the Su profiles derived from the penetration resistances of the full–flow penetrometers, using a single bearing factor, N = 10.5 (the value originally suggested in the literature for a T–bar penetration test). Again, the cone penetrometer demonstrated diverging results, requiring two separate values for the cone factor, Nkt (10.5 initially increasing to 13 for depths below 10 m) in order to give Su similar to the vane shear tests. This highlights the possible variability of the cone factor with depth. Cyclic penetration and extraction tests were performed at specific depths for each fullflow penetrometer. These tests comprised displacement cycles of ±0.5 m about the relevant depth, recording the penetration and extraction resistances over five full cycles. The results may be used to derive the remoulded strength and sensitivity of the soil. Laboratory tests such as triaxial and simple shear tests were performed on ‘undisturbed’ tube samples retrieved from the same site to evaluate the in situ shear strengths in the laboratory. However, the resulting Su data were rather scattered, much of which may be attributed to variable sample quality due to the presence of frequent shell fragments and occasional silt lenses within the test samples. In general, N factors for the full–low penetrometers, back–calculated using Su values measured from the simple shear tests, fell mainly in a range between 9.7 and 12.8 (between 10.4 and 12.2 for the standard size T–bar (250 mm x 40 mm))

MENVSC / Department of Ecology and Resource Management / See the attached abstract below

Expansive soils contain clay minerals that undergo a change in bulk volume in response to variances in environmental conditions. The ability to predict the occurrence and geotechnical behavior of swelling soils with a known degree of certitude would allow engineers to take measures to limit the damage resulting from these metastable soils. Research was conducted to investigate the regional distribution, mineralogy, and engineering properties of expansive soils in the Tucson Basin. Mineralogic studies employed X-ray diffraction procedures for the identification of clay mineralogy. The compilation of expansion-related soil parameters, from the geotechnical job-files of a local engineering consulting firm, allowed the development of an engineering database. The application of geostatistical analysis for the cartographical representation of mineralogic and geotechnical data permitted a regional characterization of expansive clay soils. Clay mineralogy was found to be directly related to the volumetric stability displayed by native soils, as well as the geology of the Tucson Basin.

Os resíduos de mineração, quando dispostos diretamente sobre o solo podem vir a causar contaminação do meio, em decorrência da presença de metais potencialmente tóxicos. Desta forma, a disposição adequada de tais resíduos torna-se necessária, tanto para futuras áreas de disposição como para as que foram degradadas pela disposição inadequada. Neste contexto, esta pesquisa teve por objetivo avaliar a viabilidade geotécnica e geoquímica de solos argilosos transportados, para serem empregados como barreiras selantes (liners) na disposição de resíduos de mineração. Isso visou solucionar o problema ambiental da região do Vale do Ribeira, onde tais resíduos (enriquecidos por metais potencialmente tóxicos) foram dispostos diretamente sobre o solo, contaminando esse compartimento. Desta forma foram caracterizados três solos (SA, SB e SC) coletados na região do Médio Vale do Ribeira (município de Eldorado Paulista). Nestes solos foram realizadas caracterização geotécnica (ensaios granulométricos, limites de consistência, condutividade hidráulica e ensaios de compactação) e caracterizações geológicas-geoquímicas (análises mineralógicas, análises químicas, parâmetros físico-químicos e teor de matéria orgânica). Além das caracterizações foram realizados ensaios de adsorção (batch test), sendo que a solução contaminante foi cloreto de chumbo nas concentrações de 50, 100 e 150 mg kg-1. De maneira geral, notou-se que o solo menos adequado para ser empregado como barreira selante é o SB. O solo SA apresentou características geológicas-geoquímicas mais adequadas para retenção dos metais, principalmente Pb (maior CTC, maior SE, argilominerais não expansivos, presença de ilita, maior teor de matéria orgânica e maior delta pH). Já o solo SC é mais adequado quanto aos parâmetros geotécnicos (maior fração argila, menor fração areia, maior LL, maior IP, maior umidade ótima, e maior índice de vazios). Todos os solos exibiram baixa condutividade hidráulica (10-8 a 10-9 m/s), o que é considerado adequado para uso em barreira selante. Quanto a adsorção de Pb, nota-se que os três solos atuam na retenção do mesmo, sendo que os solos SA e SC apresentaram maior capacidade de adsorção que o solo SB. Desta forma, com todos os resultados conclui-se que os solos SA e SC são viáveis para serem usados na construção de barreiras selantes na região do Vale do Ribeira, por apresentarem características de retenção apropriadas para o metal analisado. / When the mining wastes are disposed on the soil, they may cause environment contamination due to the existence of potentially toxic components. Therefore, the correct disposal of these wastes is necessary, for new areas of disposal as much for areas degraded by the incorrect disposal. In this context, this research aimed to evaluate the geotechnical and geochemical viability for transported clay soils to be applied as liners to dispose mining wastes. This way, the environmental problem of the Vale do Ribeira may be solved, where such wastes (containing potentially toxic metals) were disposed on the soil and contaminated it. Thus, three soils samples (SA, SB and SC) were collected in Eldorado Paulista so they could be characterized. In these soils were conducted geotechnical tests (gradation, Atterberg limits, hydraulic conductivity and Proctor compaction) and geological and geochemical analysis (mineralogical, chemical, physic-chemical and soil organic matter content). Besides, were conducted batch tests using a contaminating solution of PbCl2 with the concentrations of 50, 100 and 150 mg.kg-1. In general terms, the least proper soil to be used as liner is the SB. The SA soil presented the most proper geological and geochemical characteristics for metal adsorption, mainly Pb (higher CEC and surface area, its clay-minerals are not expansive, existence of ilite, higher content of soil organic matter and higher &#916pH). The SC soil is the most proper to be used as liner regarding its geotechnical properties (more clay fraction and less sand fraction, higher liquid limit and plasticity index, water content optimum and void index). All soils presented low hydraulic conductivity (10-8 to 10-9 m/s), that is considered proper to be used in liners. Concerning the Pb adsorption, the three retain it, but the SA and SC soils presented better adsorption capability then the SB soil. Therefore, considering all the results, it may be concluded that the SA and SC soils are preferable to be applied in liners in Ribeira Valley, because they present the most proper characteristics for adsorption of the analyzed metal.