<p>The focus of this study is on potential problems resulting from construction on expansive soils in Kibaha region, Tanzania. For the fact that most of the affected structures are founded on expansive soils, a clear understanding of the soil behaviour and their interaction with structures, specifically as they relate to shallow foundations, has been of more interest to the study in order to evaluate properly the source of the problem.</p><p>The geotechnical behaviour of expansive clay soils is investigated by looking into the geomorphologic, geological and climatic conditions and mineralogical composition of the soils in the study area. The geotechnical results are linked with the performance of the foundation as well as structures.</p><p>Two sites, representative of known problem-areas in Kibaha were selected for geotechnical tests. Geotechnical site investigation consisted of open trial pits, profile description and the collection of both disturbed and undisturbed samples.</p><p>The collected samples were submitted to soil laboratories at KTH and DIT for mineralogical composition tests, natural water content, density, Atterberg limits and swell tests (free swell and swelling pressure). The results of this investigation indicate that soil in Kibaha contains clay (31%), have high liquid limit (59%) and plastic limit (37%) which indicate high potential swell.</p><p>Since swell potential and swell pressure are key properties of expansive soils, the swell parameters were measured by free swell tests and one-dimensional oedometer swell tests respectively. The free swell ranged from 100% to 150% and the swell pressure was in the region of 45 kPa.</p><p>The properties of expansive soils were confirmed by the x-ray diffraction test which showed the presence of montmorillonite in the soil. It is from this fact that the source of the problem is in the expansive soils coupled with poor building materials.</p><p>Physical conditions of the surveyed properties in the area confirmed the hypothesis of building damages due to poor building materials triggered by expansive soils. In support of the obtained data, the actual behaviour of the foundations is supplemented with prototypes of strip foundations whose performances are to be monitored over a long period. Finally, suggested are the ways forward to solve the problem of foundation on expansive soil.</p>

No description available.

The focus of this study is on potential problems resulting from construction on expansive soils in Kibaha region, Tanzania. For the fact that most of the affected structures are founded on expansive soils, a clear understanding of the soil behaviour and their interaction with structures, specifically as they relate to shallow foundations, has been of more interest to the study in order to evaluate properly the source of the problem. The geotechnical behaviour of expansive clay soils is investigated by looking into the geomorphologic, geological and climatic conditions and mineralogical composition of the soils in the study area. The geotechnical results are linked with the performance of the foundation as well as structures. Two sites, representative of known problem-areas in Kibaha were selected for geotechnical tests. Geotechnical site investigation consisted of open trial pits, profile description and the collection of both disturbed and undisturbed samples. The collected samples were submitted to soil laboratories at KTH and DIT for mineralogical composition tests, natural water content, density, Atterberg limits and swell tests (free swell and swelling pressure). The results of this investigation indicate that soil in Kibaha contains clay (31%), have high liquid limit (59%) and plastic limit (37%) which indicate high potential swell. Since swell potential and swell pressure are key properties of expansive soils, the swell parameters were measured by free swell tests and one-dimensional oedometer swell tests respectively. The free swell ranged from 100% to 150% and the swell pressure was in the region of 45 kPa. The properties of expansive soils were confirmed by the x-ray diffraction test which showed the presence of montmorillonite in the soil. It is from this fact that the source of the problem is in the expansive soils coupled with poor building materials. Physical conditions of the surveyed properties in the area confirmed the hypothesis of building damages due to poor building materials triggered by expansive soils. In support of the obtained data, the actual behaviour of the foundations is supplemented with prototypes of strip foundations whose performances are to be monitored over a long period. Finally, suggested are the ways forward to solve the problem of foundation on expansive soil. / QC 20101118

Expansive soils are a worldwide problem that possesses various challenges for civil engineers. With increasing water content, they exhibit excessive volume changes, resulting in large horizontal and vertical stresses to the structures located or buried in these regions. The most common method to minimize this effect is to replace these types of clays around the proposed structure with nonexpansive soils. For the cases needing larger volume of replacement, either sidewalls or the foundations must be designed to cater for the anticipated pressures or a suitable improvement technique shall be applied in place. In this experimental study, it is intended to investigate the possible positive effects of trenches backfilled with granular material such as crushed stone or rock on the improvement of swell parameters of expansive soils. Thin-wall oedometer tests, conventional oedometer tests and larger size tests with moulds were performed on artificially compacted untreated and granular fill treated samples for this purpose. The trenches were modeled by opening a hole with a diameter that satisfies the predicted percent trench content at the center of the soil samples, which was then backfilled with granular material. Modified thin-wall oedometer tests were performed to measure the lateral swell pressures of both untreated and treated samples, whereas the conventional oedometer tests and tests on samples placed in moulds were performed to measure the vertical swell parameters of soils. It was observed that both the vertical swell percentages as well as the lateral swell pressures reduced considerably as the volume of granular material filled trench was increased. The treatment was observed to be more remarkable under the surcharge effect of a light weight structure or a fill placed on top.

Orientador: David de Carvalho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-09T15:24:02Z (GMT). No. of bitstreams: 1 Gomes_RibamardeJesus_M.pdf: 3281674 bytes, checksum: 135d37dcb38ea7208dfdb87b862c01d7 (MD5) Previous issue date: 2006 / Resumo: Estuda-se o comportamento geotécnico de um perfil de solo tropical típico da região de Bragança Paulista - SP. Esse perfil é classificado pela pedologia como um Latossolo Vermelho Amarelo. Para atingir esse objetivo foram realizados ensaios de caracterização, ensaios triaxiais e ensaios edométricos no teor de umidade natural e saturado. Nos ensaios de caracterização constatou-se o comportamento laterítico do solo. Nos ensaios edométricos quando os corpos de prova foram inundados nas tensões normalmente adotadas em projetos de fundações de edificações de pequeno e médio porte, construções características da cidade, constatou -se indícios de expansibilidade e colapsibilidade, apontando para a necessidade de estudos mais aprofundados sobre esses fenômenos em outras localidades do município / Abstract: The survey has the objective to investigate the geotechnical behavior of a typical soil profile at Bragança Paulista city - São Paulo State - Brazil. This profile is classified by the pedology as Red Yellow Oxisoil. To achieve this aim were accomplished characterization geotechnical tests, triaxial tests and consolidation tests. In the characterization tests was proved the lateritic behavior of the soil. In the consolidation tests when the samples were saturated in the tensions normally stipulated in edifications foundations projects at small and medium conveyance the results had pointed colapsible and expansive soil existence at the referred city / Mestrado / Geotecnia / Mestre em Engenharia Civil

Made available in DSpace on 2014-07-29T15:18:18Z (GMT). No. of bitstreams: 1 0-CAPA 1.pdf: 300598 bytes, checksum: 0e9449ac9ab29b32b36cc8276ea57604 (MD5) Previous issue date: 2009-10-30 / The establishment of transportation infrastructure is critical to the development of the Urucu- AM region, a newly developed oil exploration area in the Amazonas state. The construction of such infrastructure is challenging due to the lack of suitable materials for the construction pavement base and subbase courses and adverse weather conditions, with alternating heavy rainfall and drought periods. Besides the shortage of suitable granular material, the presence of expansive soils is often verified. The presence of expansive soils associated with inadequate moisture content during compaction, results in the occurrence of cracks in the pavements, drastically reducing its performance and lifetime. A quantitative understanding of this type of problem requires the analysis of the interaction between the unsaturated soil surface and the atmosphere and the study the mechanical behavior (stress-strain) of unsaturated soil. Such understanding requires the determination of the variations in soil moisture and total volume. The quantification of tensile stresses also requires the establishment or evaluation of the constitutive relations of the unsaturated expansive soils involved. Experiments were conducted in the laboratory with the objective of characterizing the hydraulic and mechanical behavior of expansive soils from Urucu-AM. Chemical, physical and mineralogy characterization tests were carried out for the soil. Geotechnical characterization and Proctor compaction tests and compression were performed. To study the soil in the unsaturated condition, the main focus of this work, tests were performed using the filter paper technique and the axis translation technique under oedometric conditions. For the suction controlled oedometric tests, a cell developed specially for this purpose was employed. The oedometer allows for the independent control of vertical stress and matric suction and the monitoring of the variation of moisture and total volume study. State surfaces for void ratio, degree of saturation and gravimetric moisture content were determined. The results obtained show the expected mechanical behavior of the soil under wetting paths. / O estabelecimento de uma infra-estrutura de transporte é fundamental para o desenvolvimento da região denominada de província petrolífera de Urucu-AM. A construção desta infraestrutura esbarra em varias dificuldades entre elas a escassez de materiais adequados para a construção de bases e sub-bases de pavimentos e as condições climáticas adversas, com alternância de períodos de alta pluviosidade e períodos de estiagem. Além da escassez de material granular adequado, observa-se com freqüência a presença de solos argilosos expansivos. A presença de tais solos, associada às condições freqüentemente inadequadas de umidade de compactação, resulta na ocorrência de trincas nos pavimentos, reduzindo drasticamente o seu desempenho e vida útil. Um entendimento quantitativo do problema requer a análise da interação entre o solo não saturado de superfície e a atmosfera e o estudo do comportamento mecânico (tensão-deformação) do solo não saturado. Tal entendimento passa pela determinação das variações de umidade do solo e sua variação volumétrica total. A quantificação das tensões de tração requer também o estabelecimento ou avaliação de relações constitutivas dos solos expansivos não saturados envolvidos. Foram conduzidos experimentos em laboratório com o objetivo de caracterizar o comportamento hidráulico e mecânico de solos expansivos de Urucu-AM. Inicialmente foram realizadas análises químicas, caracterização física e determinação da mineralogia, para caracterização das macro e microestruturas dos solos estudados. Foram executados também ensaios de caracterização geotécnica e compactação Proctor. Para o estudo do solo na condição não saturado, principal enfoque desta dissertação, foram realizados ensaios de papel filtro e de adensamento com controle de sucção. Para o ensaio de adensamento com controle de sucção foi utilizada uma prensa oedométrica especialmente desenvolvida para este fim. Como esta prensa foi possível aplicar de forma independente tensões verticais, sucção matricial e monitorar a variação de umidade e de volume do solo em estudo. As superfícies de estado de índice de vazios, grau de saturação de umidade do solo foram determinadas. Os resultados obtidos permitiram a determinação do comportamento do solo compactado durante trajetórias de molhagem.

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Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Expansive soils, one of the problematic soils, are encountered on all continents with exception of polar continents. Problems caused by their heaving and shrinking behaviour, particularly to light structures, have been reported from different countries to place large financial burden on developers. For this reason, many techniques have been developed and applied to prevent and/or remediate the damage caused by these soils. Soil stabilization with traditional chemical additives has been applied successfully since ancient times. In addition to traditional additives such as lime, cement, fly ash, etc., some non-traditional additives, such as polymer based products, salts, etc. have been used effectively for soil treatment. On the other hand, industries are increasingly challenged by waste management in an acceptable and environmentally friendly manner. In this regard, a number of researches have been done on using industrial waste for soil improvement purposes. The study and understanding of basic reactions involved in lime-soil stabilization persuaded many researchers to study the applicability of lime-rich products for soil treatment. Studies conducted by Khalid et al. (2012); Muchizuki et al. (2004) and Thacker (2012) showed that lime-rich products such as pulp fly and bottom ashes and CaO by-products, can be applied for soil stabilization. This research was thus performed to investigate the effect of lime-rich paper mill waste ash on expansive soil properties. Two commonly listed soil engineering properties namely volume change and strength were investigated. Soil strength was examined in terms of unconfined compressive strength (UCS), due to its correlations with a number of other soil properties, and the volume change in terms of free swell and swelling pressure. In addition to these two engineering properties, dry density and moisture content were also studied due to their involvement in structural design, as well as gradation, Atterberg limits and California Bearing Ratio (CBR). The choice of these properties was also influenced by the availability of a standard (ASTM D4609-08) specifically developed to assess the effectiveness of admixtures for soil stabilization. Two main types of materials were used namely three clay materials and paper mill ash. According to the index properties, commonly used for expansive soil classification, three clays were classified into low, medium and high degrees of potential expansiveness. The ash results from the combustion of paper mill sludge, sawdust, bark, coal ash and bituminous coal in a multi-fuel boiler for the purpose of electricity and steam production. The tests mentioned above were conducted on both untreated and treated clays and the results were compared. Since the study was carried out on this material based on the fact that it contains lime, the procedure applied for lime-soil stabilization was considered. In general, it was observed that ash-soil treatment has a number of effects similar to lime-treatment and almost all studied properties were enhanced for all clays. It can thus be concluded that the paper mill ash from a multi-fuel boiler can be efficiently used for expansive soil treatment. For optimum use of this material for expansive soil treatment, more tests and further researches have been recommended. / AFRIKAANSE OPSOMMING: Uitsettende gronde, een van die probleemtipe-gronde, kom op alle kontinente voor, behalwe die twee poolkontinente. Probleme veroorsaak deur uitswellende en inkrimpende gedrag van hierdie gronde, veral finansiële onkostes van ligte strukture is al in baie lande aangemeld. Vir hierdie rede is baie tegnieke ontwikkel en toegepas om skade wat deur hierdie tipe gronde veroorsaak is, te voorkom en/of herstel. Hierdie tegnieke sluit grondstabilisasie met chemiese bymengsels in, veral tradisionele bymengsels, wat met groot sukses in die verre verlede toegepas en na moderne tye oorgedra is. Bykomend tot tradisionele bymengsels soos kalk, sement, vlieg-as ensovoorts is ʼn aantal nie-tradisionele bymiddels soos polimeergebaseerde produkte, soute en ander produkte ontwikkel vir grondstabilisasie. Aan die ander kant raak industrieë toenemend daarmee gemoeid om afvalstowwe op ʼn aanvaarbare en omgewingsvriendelike wyse te bestuur. Op hierdie gebied is ʼn aantal navorsingsprojekte al uitgevoer om industriële afval vir grondverbetering te gebruik en sodoende die las op nywerhede te verlig. Navorsing is onderneem om die basiese reaksies wat onstaan tydens stabilisasie van grond met tradisionele en moderne middels te bepaal en om die geskiktheid van kalkryke produkte vir grondstabilisasie te ondersoek. Baie navorsing is uitgevoer wat aangetoon het dat kalkhoudende produkte soos pulp vlieg- en oondresidu-as, asook CaO neweprodukte gebruik kan word vir stabilisasie. Gebaseer hierop is hierdie projek onderneem om die effek van papiermeulas, verkry deur die verbranding in ʼn veelvuldige brandstof-stoomketel, op die gedrag van uitsettende grond te ondersoek. Tydens hierdie studie is twee algemene ingenieurseienskappe van grond, naamlik sterkte en volumeverandering ondersoek. Grondsterkte is geëvalueer in terme van eenassige druksterkte (EDS) as gevolg van ? deur middel van die korrelasie met ʼn aantal ander grondeienskappe, en die volumeverandering in terme van vry-swel en sweldruk. Addisioneel tot hierdie twee grondeienskappe is droë digtheid en waterinhoud ook bestudeer aangesien beide in struktuurontwerp betrokke is. Verdere eienskappe wat ondersoek is, is gradering, Atterberggrense en Kaliforniese drakragverhouding (KDV). Die keuse van hierdie eienskappe is beïnvloed deur die beskikbaarheid van ʼn toetsstandaard (ASTM D4609-08) wat spesifiek ontwikkel is om die effektiwiteit van bymengsels vir grondstabilisasie te evalueer. Hierdie standaard is deurgaans as verwysing tydens die projek gebruik. Daar is waargeneem dat as-behandeling van grond ʼn aantal effekte het soortgelyk aan kalkbehandeling, met die uitsondering van die droë digtheid en optimum waterinhoud van een van die gronde wat getoets is. Byna al die eienskappe wat ondersoek is, soos EDS, KDV, ensovoorts, is verbeter behalwe in die geval van die eerste klei waarvan die plastisiteitsindeks verhoog het en die grond meer plasties geraak het. Daar kan dus afgelei word dat papiermeule-as vanaf ʼn stoomketel wat veelvuldige tipes brandstof gebruik geskik is vir die behandeling van uitsettende grond. Om die optimumgebruik van hierdie materiaal vir die stabilisasie van swellende klei te bepaal, is meer toetse en projekte nodig.

The focus of this study is on potential damages to buildings resulting from expansive soils in Tanzania, particularly clay soils in Kibaha. For the fact that most of the affected structures are founded on expansive soils, a clear understanding of the behaviour of soils and their interaction with structures has been of interest to the study in order to evaluate properly the source of the problem.The geotechnical behaviour of expansive clay soils is investigated by looking into the geomorphologic, geological and climatic conditions and mineralogical composition of the soils in the study area.Two sites, representative of known problem-areas in Kibaha were selected for geotechnical tests. Geotechnical site investigation consisted of open trial pits, profile description and the collection of both disturbed and undisturbed samples. To extend and amplify the findings, supplementary samples were collected from the environs of the two sites.The collected samples were submitted to soil laboratories at KTH, ARU, SEAMIC and DIT for mineralogical composition tests, natural water content, density, Atterberg limits and swell tests. The results of this investigation indicate that soils in Kibaha contains clay (31%), have high liquid limit (59%) and plastic limit (37%) which indicate high potential swell.Since swell pressure, free swell and swell percent are key properties of expansive soils, the swell properties were measured by free swell tests and one-dimensional oedometer swell tests. The free swell ranged from 100% to 150% and the swell pressure was in the region of 45 kPa. The coefficient of linear extensibility (COLE) was determined for characterizing expansive clays. For all tested samples, COLE ranged from 0.09 to 0.14 indicating that soils fall in the region of high to very high expansion potential rating. The properties of expansive soils were confirmed by the x-ray diffraction test which showed the presence of smectite in the soil. Furthermore, total suction measurement technique using filter paper method indicated that the soils have high suction values, signifying that they have a tendency to swell upon wetting depending on plasticity of particular soil.The depth of the active zone was measured as a function of moisture variations in the profiles during two extreme weather conditions. The active zone depth was found to be between 1.0 and 2.0 m deep. Procedures to assess models to predict swell in the case study were outlined together with their validity.Vertical and horizontal spatial variability in selected soil properties was defined using geostatistical techniques through the fitting of variogram. The indicator semivariograms of both clay contents and free swell gave a range of 20 m horizontally and 1.0 m vertically, with the horizontal variograms exhibiting greater ranges than the dipping variograms.Physical conditions of the surveyed properties in the area confirmed that building damages are associated with poor building materials triggered by expansive soils. In support of the obtained data, the actual behaviour of the foundations was supplemented with prototypes of strip foundations whose performances were monitored over a period of four months. Finally, suggested are the ways forward to solve the problem of foundation on expansive soil / QC 20100824

The coupled and uncoupled consolidation theories for saturated-unsaturated soils have been discussed. A new method for constructing the constitutive surfaces for saturated-unsaturated soils has been proposed. The consolidation processes for saturated-unsaturated soils have been explained by thermodynamic analogue. One dimensional consolidation theory for saturated-unsaturated soils is presented and a new method is proposed to calculate the immediate settlement, total settlement and the time history of the consolidation settlement manually in the same way as what we have done for saturated soils with a higher accuracy. It makes the consolidation theory of unsaturated soils as applicable as that of saturated soils. This method can also be used to perform uncoupled two or three dimensional consolidation calculation for both expansive soils and collapsible soils. From the analysis, the equivalent effective stress and excessive pore water pressure can be easily calculated. At the same time, the physical meanings for the parameters in the constitutive laws for saturated-unsaturated are illustrated. A new set of the differential equations for the coupled two or three dimensional consolidation of saturated-unsaturated soils are proposed, together with the corresponding method to solve the differential equations. It is also proved numerically and analytically that during the consolidation process the Mandel-Cryer effect exists for unsaturated expansive soils and there is a ??reverse?? Mandel-Cryer effect for unsaturated collapsible soils. A new method is proposed to estimate the volume change of expansive soils. A complete system is proposed for the numerical simulation of residential buildings on expansive soils. The strength of this method lies in its use of simple and readily available historic weather data such as daily temperature, solar radiation, relative humidity, wind speed and rainfall as input. Accurate three dimensional predictions are obtained by integrating a number of different analytical and numerical techniques: different simulation methods for different boundary conditions such as tree, grass, and bare soils, coupled hydro-mechanical stress analysis to describe deformation of saturated-unsaturated soils, jointed elements simulation of soil-structure interaction, analysis of structure stress moment by general shell elements, and to assess structural damage by the smeared cracking model. The real-time and dynamic simulation results are consistent with filed measurements.