Orientador: José Augusto de Lollo / Banca: Leandro Eugenio Silva da Cerri / Banca: Wilson Manzoli Júnior / Resumo: O colapso de solos é um fenômeno típico de solos altamente porosos quando saturados, induzindo recalques significativos em fundações de obras civis, comprometendo total ou parcialmente estas obras. Tal fenômeno é bastante comum nos solos arenosos que ocorrem em boa parcela do Estado de São Paulo e em particular na cidade de Ilha Solteira. A grande disseminação de processos de colapso de solos em todo o Estado faz com que seu estudo seja imprescindível para o entendimento das variáveis que os condicionam e dos fatores que os desencadeiam. A proposta deste trabalho foi caracterizar o processo de colapso de solos na área urbana de Ilha Solteira, em termos de sua ocorrência, condicionantes, mecanismos e conseqüências, com o objetivo de avaliar e representar cartograficamente o risco de ocorrência deste processo. Os estudos mostraram que na área estudada a associação do comportamento natural do solo com problemas em obras de infra-estrutura urbana (redes de água e esgoto) induz uma situação de alta suscetibilidade de ocorrência de colapso de solos, o que pode ser notado pela disseminação de ocorrências por toda a área. A avaliação do risco de colapso de solos permitiu classificá-lo em alto, médio e baixo grau. As informações obtidas na avaliação de risco fundamentam a elaboração de medidas para eliminar ou reduzir os riscos instalados e ainda para evitar a instalação de novas áreas de risco. O resultado final foi a elaboração de uma carta de cadastramento de risco de colapso de solos e, a partir desta, a elaboração de uma carta de zoneamento de risco, constituindo-se em importantes ferramentas para projetos e obras de ocupação, além de fornecerem subsídios para elaboração de planos de seguro de edificações. A metodologia utilizada para avaliação e representação de risco de colapso de solos poderá ser aplicada em estudos nos bairros mais... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: Soil collapse is a characteristic process in porous soils when saturated and produce large settlements in civil engineering foundations. This process is very common in typical fine sand soils present in State of São Paulo large areas, thus Ilha Solteira region. Due this process has affected large areas of São Paulo State the study of soils with collapsible behavior is very important to understand variables that cause or are responsible for the process. This work proposed to characterize the process of soil collapse (events, causes, mechanisms, consequences) in the Ilha Solteira urban area, purposing to evaluate and to present the risk of soil collapse on a chart. Studies showed that in the Ilha Solteira city the association of natural behavior of soil with problems in urban infrastructure works (water and sewage pipes) characterize a situation of high susceptibility of soil collapse, which can be observed by dissemination of occurrences by total area. The evaluation of soil collapse risk permitted to classify it in high, medium and small degree. Information gained in this risk evaluation is important for take the necessary steps for reduce, eliminate or avoid the problem of soil collapse. The final result was the representation of the soil collapse risk on cadastre and zoning charts, which constitute on important tool for adopting construction guidelines, besides to provide subsidies for elaboration of edifications insurance. Respecting locals specifications, the methodology utilized for evaluation and representation of risk of soil collapse can be applied in studies in other areas with similar problems. / Mestre

Made available in DSpace on 2014-06-11T19:29:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-06-27Bitstream added on 2014-06-13T18:58:48Z : No. of bitstreams: 1 oliveira_cmg_me_ilha.pdf: 7081146 bytes, checksum: ed75c1649780a952f48111b948b26147 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O colapso de solos é um fenômeno típico de solos altamente porosos quando saturados, induzindo recalques significativos em fundações de obras civis, comprometendo total ou parcialmente estas obras. Tal fenômeno é bastante comum nos solos arenosos que ocorrem em boa parcela do Estado de São Paulo e em particular na cidade de Ilha Solteira. A grande disseminação de processos de colapso de solos em todo o Estado faz com que seu estudo seja imprescindível para o entendimento das variáveis que os condicionam e dos fatores que os desencadeiam. A proposta deste trabalho foi caracterizar o processo de colapso de solos na área urbana de Ilha Solteira, em termos de sua ocorrência, condicionantes, mecanismos e conseqüências, com o objetivo de avaliar e representar cartograficamente o risco de ocorrência deste processo. Os estudos mostraram que na área estudada a associação do comportamento natural do solo com problemas em obras de infra-estrutura urbana (redes de água e esgoto) induz uma situação de alta suscetibilidade de ocorrência de colapso de solos, o que pode ser notado pela disseminação de ocorrências por toda a área. A avaliação do risco de colapso de solos permitiu classificá-lo em alto, médio e baixo grau. As informações obtidas na avaliação de risco fundamentam a elaboração de medidas para eliminar ou reduzir os riscos instalados e ainda para evitar a instalação de novas áreas de risco. O resultado final foi a elaboração de uma carta de cadastramento de risco de colapso de solos e, a partir desta, a elaboração de uma carta de zoneamento de risco, constituindo-se em importantes ferramentas para projetos e obras de ocupação, além de fornecerem subsídios para elaboração de planos de seguro de edificações. A metodologia utilizada para avaliação e representação de risco de colapso de solos poderá ser aplicada em estudos nos bairros mais... . / Soil collapse is a characteristic process in porous soils when saturated and produce large settlements in civil engineering foundations. This process is very common in typical fine sand soils present in State of São Paulo large areas, thus Ilha Solteira region. Due this process has affected large areas of São Paulo State the study of soils with collapsible behavior is very important to understand variables that cause or are responsible for the process. This work proposed to characterize the process of soil collapse (events, causes, mechanisms, consequences) in the Ilha Solteira urban area, purposing to evaluate and to present the risk of soil collapse on a chart. Studies showed that in the Ilha Solteira city the association of natural behavior of soil with problems in urban infrastructure works (water and sewage pipes) characterize a situation of high susceptibility of soil collapse, which can be observed by dissemination of occurrences by total area. The evaluation of soil collapse risk permitted to classify it in high, medium and small degree. Information gained in this risk evaluation is important for take the necessary steps for reduce, eliminate or avoid the problem of soil collapse. The final result was the representation of the soil collapse risk on cadastre and zoning charts, which constitute on important tool for adopting construction guidelines, besides to provide subsidies for elaboration of edifications insurance. Respecting locals specifications, the methodology utilized for evaluation and representation of risk of soil collapse can be applied in studies in other areas with similar problems.

Esta tese apresenta um estudo de caso de colapso dos solos que ocorreu durante e após o enchimento do reservatório da UHE Três Irmãos. A construção desta barragem e o subseqüente enchimento do reservatório elevaram significativamente o lençol freático, causando colapso do solo em algumas áreas. Muitos trabalhos de campo e de laboratório foram realizados para determinar o potencial de risco associado às edificações existentes no local. A elevação do lençol freático foi monitorada especialmente para o estudo de recalques de edificações. Esta pesquisa trata do estudo deste caso histórico, recuperando informações existentes e executando ensaios adicionais com sucção controlada para caracterizar o comportamento não saturado do solo. O conjunto de dados obtidos foi usado para modelar recalques reais de edificações monitoradas, considerando o Modelo Básico de Barcelona, BBM, (Alonso et al., 1990) como o modelo constitutivo mecânico do solo e o programa de elementos finitos Code_Bright. A tese apresenta a definição dos parâmetros constitutivos do solo, a calibração dos modelos, análises de sensibilidade do modelo adotado, mostrando que os resultados modelados se ajustaram satisfatoriamente aos valores de recalques medidos no campo. A partir dos resultados obtidos numericamente, constatou-se que as deformações por colapso aumentam com a redução da sucção sem saturar o solo e que os maiores colapsos são observados quando o solo é gradualmente submergido. Como a profundidade de influência da carga de fundação é muito baixa comparada à espessura da camada colapsível, muitas das deformações por colapso são resultados do peso-próprio do solo, durante o equilíbrio sob as condições hidrodinâmicas transiente e final. / This thesis presents a case history of soil collapse that took place during and after reservoir filling of Três Irmãos dam in Brazil. The construction of this dam and subsequent reservoir filling has raised the local groundwater table up to 20 m, causing soil collapse that affected many buildings. Many field and laboratory tests were conducted to determine potential risk and damage of existing buildings. The groundwater rise was monitored in some points of the region and the most susceptible buildings were also monitored specially for settlements. This work deals with the study of this case history of soil collapse, recovering existing information and performing additional suction controlled soil tests to characterize the non saturated soil behavior. This set of data was used to model the collapse settlement, considering the Barcelona Basic Model, BBM, (Alonso et al. 1990) as the soil constitutive model and the Code_Bright finite element program and, finally numerical results were compared with field ones. The thesis addresses soil parameters definition from laboratory and field tests, model calibration, sensibility analysis of the adopted model and it shows that the modeled results nicely fitted the measured values of collapse settlements. Amongst the many qualitative and quantitative findings, it is shown that collapse deformation arises from suction variation without saturating the soil and that the largest collapse rate is observed when the soil is gradually submerged. As the depth of influence of foundation load is very low compared to collapsible layer thickness, much of collapse deformation is the result of soil self weight, during equilibrium under the transient and final hydrodynamics condition.

Esta tese apresenta um estudo de caso de colapso dos solos que ocorreu durante e após o enchimento do reservatório da UHE Três Irmãos. A construção desta barragem e o subseqüente enchimento do reservatório elevaram significativamente o lençol freático, causando colapso do solo em algumas áreas. Muitos trabalhos de campo e de laboratório foram realizados para determinar o potencial de risco associado às edificações existentes no local. A elevação do lençol freático foi monitorada especialmente para o estudo de recalques de edificações. Esta pesquisa trata do estudo deste caso histórico, recuperando informações existentes e executando ensaios adicionais com sucção controlada para caracterizar o comportamento não saturado do solo. O conjunto de dados obtidos foi usado para modelar recalques reais de edificações monitoradas, considerando o Modelo Básico de Barcelona, BBM, (Alonso et al., 1990) como o modelo constitutivo mecânico do solo e o programa de elementos finitos Code_Bright. A tese apresenta a definição dos parâmetros constitutivos do solo, a calibração dos modelos, análises de sensibilidade do modelo adotado, mostrando que os resultados modelados se ajustaram satisfatoriamente aos valores de recalques medidos no campo. A partir dos resultados obtidos numericamente, constatou-se que as deformações por colapso aumentam com a redução da sucção sem saturar o solo e que os maiores colapsos são observados quando o solo é gradualmente submergido. Como a profundidade de influência da carga de fundação é muito baixa comparada à espessura da camada colapsível, muitas das deformações por colapso são resultados do peso-próprio do solo, durante o equilíbrio sob as condições hidrodinâmicas transiente e final. / This thesis presents a case history of soil collapse that took place during and after reservoir filling of Três Irmãos dam in Brazil. The construction of this dam and subsequent reservoir filling has raised the local groundwater table up to 20 m, causing soil collapse that affected many buildings. Many field and laboratory tests were conducted to determine potential risk and damage of existing buildings. The groundwater rise was monitored in some points of the region and the most susceptible buildings were also monitored specially for settlements. This work deals with the study of this case history of soil collapse, recovering existing information and performing additional suction controlled soil tests to characterize the non saturated soil behavior. This set of data was used to model the collapse settlement, considering the Barcelona Basic Model, BBM, (Alonso et al. 1990) as the soil constitutive model and the Code_Bright finite element program and, finally numerical results were compared with field ones. The thesis addresses soil parameters definition from laboratory and field tests, model calibration, sensibility analysis of the adopted model and it shows that the modeled results nicely fitted the measured values of collapse settlements. Amongst the many qualitative and quantitative findings, it is shown that collapse deformation arises from suction variation without saturating the soil and that the largest collapse rate is observed when the soil is gradually submerged. As the depth of influence of foundation load is very low compared to collapsible layer thickness, much of collapse deformation is the result of soil self weight, during equilibrium under the transient and final hydrodynamics condition.

Collapse phenomenon is exhibited by two types of residual soils. The first category of collapsing residual soils is believed to be transported soils that have undergone post-depositional pedogenesis. The second category of collapsing residual soils is highly weathered and leached soils formed by in-situ weathering of parent rock. Residual red soils occur in Bangalore District of Karnataka State. Physical and chemical weathering of the gneissic parent rock formed the residual soils of Bangalore District. The red soils of Bangalore District are generally moderate to very highly porous (porosity range 35-50%). These soils are also unsaturated owing to presence of alternate wet and dry seasons and low ground water table. Moderately to highly porous, unsaturated red soils occur in Pernambuco State of Brazil. These residual soils formed by weathering of gneissic rock significantly collapse on wetting under external pressures. Kaolinite is predominant clay mineral in the red soils of Bangalore and Pernambuco Districts. Similarities exist in the mode of soil formation, clay mineralogy, porosity and degree of saturation (Sr) values of the red soils from Pernambuco State, Brazil, and Bangalore District. Given the collapsible nature of red soils from Pernambuco State, Brazil, the red soils from Bangalore District also deserve to be examined for their potential to collapse in the compacted and undisturbed conditions. The roles of initial dry density, compaction water content, clay content and flooding pressure (the external stress at which a laboratory specimen is inundated is termed as flooding pressure in this thesis) in determining the collapse behaviour of compacted soils are well recognized. However, the influences of above parameters on the collapse behaviour of compacted red soil specimens from Bangalore District are lacking. Such studies are essential as they help to identify the critical compaction parameters (dry density and water content), soil composition, and applied stress level that needs to be controlled by the fill designer in order to minimize wetting-induced collapse. The importance of matric suction in the collapse behaviour of unsaturated soils is well recognized. Yet, the influence of matric suction in the collapse behaviour of compacted soils has only been indirectly examined by varying the compaction water content/degree of saturation of the soil specimens. The climate of Bangalore District is characterized by alternate wet and dry seasons which affects the soil microstructure and the matric suction. Both these parameters have a significant influence on collapse behaviour of unsaturated soils. Cyclic wetting and drying is expected to have a significant bearing on the collapse behaviour of residual soils and is therefore examined. The red soil deposits of Bangalore District are important from foundation engineering view point as they are subjected to structural loading. Owing to the presence of alternate wet and dry seasons and low ground water table, red soil deposits of Bangalore District are more often than not unsaturated. These foundation soils would however be susceptible to increase in moisture content from causes such as infiltration of rainwater, leakage of pipes or watering of lawns and plants. Given the porous and unsaturated nature of undisturbed red soils from Bangalore district, their collapsible nature deserves to be examined for reliable estimation of foundation settlements. To achieve the above objectives, experiments are performed that study: 1.The influence of variations in compaction dry density, initial water content and matric suction, clay content and flooding pressure on the collapse behaviour of a representative red soil sample from Bangalore District. 2.The influence of repeated wetting and drying on the collapse behaviour of compacted red soil specimens. 3.The collapsible nature of undisturbed red soil samples from different locations in Bangalore District. The organization of this thesis is as follows: After the first introductory chapter, a detailed review of literature highlighting the need to study the collapse behaviour of unsaturated red soils of Bangalore District, Karnataka in the compacted and undisturbed states comprises Chapter 2. Chapter 3 presents a detailed experimental programme of the study. Details of representative and undisturbed red soil samples from Bangalore District, Karnataka State, India were used in the study are provided. Determination of collapse potential of compacted and undisturbed soil specimens using conventional oedometer is discussed. Determination of matric suction of compacted and undisturbed specimens by ASTM Filter paper method and pore size distributions by mercury intrusion porosimetry is detailed. Methods to perform cyclic wetting and drying of compacted red soil specimens in modified oedometer assemblies is detailed. These experiments are performed to examine the influence of cyclic wetting and drying on the collapse behaviour of compacted red soil specimens. Chapter 4 examines the collapse behaviour of a compacted red soil from Bangalore District. The influence of variations in compaction dry density, initial water content and matric suction, flooding pressure and clay content on the collapse behaviour of the representative red soil from Bangalore District are examined. Besides measuring the initial matric suction of the compacted red soil specimens, mercury intrusion porosimetry was performed on selected compacted red soil specimens. Experimental results showed that compacted red soils from Bangalore District exhibited tendency to swell and collapse at the experimental range of densities and water contents. Red soil specimens compacted to relative compactions > 90 % at water contents below OMC swelled at flooding pressures lower than 200 kPa. Red soil specimens compacted to relative compactions < 90 % at water contents below OMC significantly collapsed at flooding pressures larger than 200 kPa. Hence maintenance of the design water content during construction of compacted red soil fills is essential to minimize wetting induced volume changes. Experiments showed that the relative abundance of coarse pores (60 to 6 μm, pore radius) were mainly affected on increasing the relative compaction of the specimens from 84 % (dry density = 1.49 Mg/m3) to 100 % (dry density = 1.77 Mg/m3). The relative abundance of the coarse and fine (0.01 to 0.002 μm) pores were both affected on increasing the compaction water content from 10.6 to 26.4 %. These variations in pore size distributions provided better insight into the variations of collapse potential with variations in compaction parameters. ASTM filter paper method showed that for the selected compaction conditions the initial matric suction of the compacted red soil specimens varied between 60 and 10,000 kPa. Further, variations in degree of saturation at a constant relative compaction or variations in relative compaction at a constant degree of soil saturation notably affected the matric suction of the compacted soil specimens. It was also inferred that a clay soil with a higher liquid limit is characterized by a higher matric suction at a given water content. Variations in clay content affected the collapse potentials of soil specimens compacted to dry densities of 1.49 and 1.66 Mg/m3. These specimens exhibited maximum collapse at about 26 % clay content. It is suggested that greater destabilization of inter-particle contacts caused by loss of matric suction on flooding was primarily responsible for the soil specimen containing the critical clay content of 26 % to exhibit maximum collapse potential. Increase in initial dry density, initial water content, clay content of the soil specimen and flooding pressure increased the time-duration of collapse of the compacted soil specimens. The time-duration of collapse was observed to range between 3 and 100 minutes for the tested specimens. Chapter 5 examines the influence of alternate wetting and drying on the collapse behaviour of compacted red soil specimens of Bangalore District. The compacted specimens were subjected to alternate wetting and drying cycles at surcharge pressures of 6.25 and 50 kPa in modified oedometer assemblies. Studies were also performed to examine whether the initial placement conditions have any bearing on the collapse behaviour of red soil specimens subjected to four cycles of wetting and drying. Mercury intrusion porosimetry was performed on a few desiccated red soil specimens. Experimental results showed that cyclic wetting and drying caused the desiccated specimens to exhibit similar or lower swell and collapse potentials than the compacted specimens. Such a behaviour resulted despite the desiccated specimens (specimens subjected to four cycles of wetting and drying are termed as desiccated specimens) possessing similar void ratios but much lower water contents than the compacted specimens. The restraining influence of the desiccation bonds and alteration of soil structure is considered responsible for the reduced swell and collapse tendencies of the desiccated specimens. The desiccation bonds imparted higher apparent preconsolidation pressures to the desiccated specimens. The initial compaction conditions also have a strong bearing on the collapse potentials of the desiccated specimens. Compacted red soil specimens subjected to cyclic wetting and drying under a higher surcharge pressure of 50 kPa exhibited larger swell potentials and lower collapse potentials than specimens desiccated at 6.25 kPa. Besides their lower void ratios, the presence of stronger desiccation bonds also contributed to their lower collapse potentials. The presence of stronger desiccation bonds in specimens desiccated under higher surcharge pressure was indicated by their higher apparent preconsolidation pressures. Chapter 6 examines the collapse behaviour of undisturbed red soil specimens from three locations in Bangalore District at a range of flooding pressures. Studies on the variations in initial water content and effect of remoulding on the collapse behaviour of the undisturbed specimens is supplemented by measuring the initial matric suction and performing mercury intrusion porosimetry experiments. Experimental results showed that based on their collapse potential at 200 kPa, the undisturbed red soils of Bangalore District classified as troublesome to moderately troublesome foundation soils. The bonded structure of the undisturbed red soil specimens imparted them higher apparent preconsolidation pressures and lower swell/collapse potentials than their remoulded counterparts. Variations in in-situ dry density, degree of saturation and relative distribution of pore sizes affected the matric suction and collapse potentials of the undisturbed specimens Chapter 7 summarizes the conclusions of this thesis.