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Degradation modeling of concrete submitted to biogenic acid attackYuan, Haifeng, Yuan, Haifeng 03 December 2013 (has links) (PDF)
Bio-deterioration of concrete, which is very common in sewer system and waste water treatment plant, results in significant structure degradation. Normally, the process can be described by the two following parts: 1) Biochemistry reactions producing biogenic aggressive species in biofilms which are spread on the surface of concrete. As one of the most significant biogenic acid in sewer pipes, sulfuric acid (H2SO4) is produced by sulfur oxidizing bacteria (SOB). 2) Chemical reactions between biogenic aggressive species and cement hydration products which is responsible for concrete deterioration. A reactive transport model is proposed to simulate the bio-chemical and chemical deterioration processes of cementitious materials in contact with SOB and H2S or sulfuric acid solution. This model aims at solving simultaneously transport and biochemistry/chemistry in biofilms and cementitious materials by a global coupled approach. To provide an appropriate environment for SOB to grow, the surface neutralization of concrete (i.e., the absorption of H2S and aqueous H2S corrosion) is considered. To obtain the amount of biogenic H2SO4, the bio-oxidation of H2S by the activation of bacteria is simulated via a simplified model. To provide a suitable environment for SOB to grow, the abiotic pH reduction of concrete process is introduced. The production rate of H2SO4 is governed by the pH in the biofilms and the content of H2S in gas.It is assumed that all chemical processes are in thermodynamical equilibrium. The dissolution of portlandite (CH) and calcium silicate hydrates (C-S-H) and the precipitation of gypsum (C¯S H2) and calcium sulfide are described by mass action law and threshold of ion activity products. To take into account the continuous decrease of the Ca/Si ratio during the dissolution of C-S-H a generalization of the mass action law is applied. By simplifying the precipitation process of gypsum, a damage model is introduced to characterize the deterioration of concrete due to the swelling of gypsum. Thus, the porosity evolution and deterioration depth during deterioration process are taken into account. Only diffusion of aqueous species are considered. Different diffusion coefficients are employed for various ions and Nernst-Planck equation was implemented. The effect of the microstructure change during deterioration on transport properties is considered as well. For both biofilms and cementitious materials, the balance equations of total mass of each atom (Ca, Si, S, K, Cl) are used to couple transport equations and (bio-)chemical reactions. The model is implemented within a finite-volume code, Bil. Following the introduction of principle of the finite volume method, the coupling of the bio-chemistry process in biofilms and chemistry process in cementitious materials is illustrated. By this model, some experiments reported in literature, including chemical immersion tests (statical solution condition and flow solution condition) and microbiological simulation tests, are simulated. The numerical results and the experimental observations are compared and discussed. The influence of properties of cementitious materials (initial porosity, carbonated layer, etc.) and environmental factors (concentration of H2SO4, content of H2S, etc.) are investigated by this model as well. Furthermore, a long term predictionis conducted
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Manifestações e contradições da metrópole de São Paulo no antigo bairro de Santana: a paisagem, o valor da terra, a intervenção urbana e o fenômeno da deterioração urbana / Manifestações e contradições da metrópole de São Paulo no antigo bairro de Santana: a paisagem, o valor da terra, a intervenção urbana e o fenômeno da deteriorização urbanaGonçalves, André Vinicius Martinez 07 August 2006 (has links)
Esta dissertação parte da tese que o avanço da Metrópole de São Paulo em direção ao antigo bairro de Santana, em especial, a partir dos anos de 1950, gerou ao espaço geográfico local, uma considerável diversidade espacial, implicando hoje, um mosaico de ealidades, tanto no aspecto de ocupação e uso do solo, como em relação às práticas sócio-espaciais. Essas realidades instauradas em Santana, na perspectiva do presente estudo são refletidas, sobretudo, a partir de duas questões: as intervenções urbanas, uma parcialmente efetivada nos anos de 1970, denominada Plano Cura Piloto de Santana, e outra em curso, intitulada Operação Urbana Vila Maria - Campo de Marte; e o fenômeno da deterioração urbana em Santana, fenômeno este, entendido como uma das contradições geradas a partir da reprodução do espaço urbano sob égide do sistema capitalista. / This report based on the thesis that the growth of São Paulo city towards the old neighborhood Santana, mostly from the fifties on brought to the geographical locus a great deal of landscape diversity. Such diversity led the city to look like a huge mosaic composed of so many different realities both regarding land occupation and usage and social visual specially lifestyles. As for the research herein presented, the differences that are established from two issuer: the urban interventions; one partially effective in the seventies called Plano CURA Piloto Santana and another one named Operação Urbana Vila Maria - Campo de Marte, and the phenomenon is know as one of the conceived contradictions from the reproductions of the urban lifestyle the capitalism system.
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Qualidade de silagens de milho confeccionadas com diferentes filmes de vedação e desempenho produtivo de vacas em lactação / Quality of corn silage made from different sealing films and performance of dairy cowsBispo, Álvaro Wosniak 10 October 2013 (has links)
Foram realizados dois experimentos visando avaliar diferentes estratégias de vedação para silos do tipo trincheira. No experimento I, objetivou-se avaliar as características fermentativas, composição química e perdas de matéria seca e de matéria orgânica em silagens de milho vedadas com diferentes tipos de filmes plásticos e com ou sem a adição de camada de bagaço de cana. Os tratamentos utilizados foram: ETNC: filme dupla face de polietileno com 200 ?m de espessura; ETC: filme dupla face de polietileno com 200 ?m de espessura recoberto com camada de 10 cm de bagaço de cana e ET+ADNC: filme co-extrusado dupla face de poliamida e polietileno, com 120 ?m de espessura. O delineamento experimental foi de blocos casualizados. Os dados foram submetidos à análise de variância e suas médias foram comparadas pelo teste Tukey, a 5% de signigicância. A quantidade de silagem deteriorada foi menor para o tratamento ETC, enquanto que os demais tratamentos foram semelhantes entre si. Não foi observada diferença significativa entre os tratamentos para a composição bromatológica, entretanto, observou-se diferença para entre os diferentes pontos amostrados (TL: topo lateral, TC: topo central e C: centro) para as variáveis MS, FDA, amido, hemicelulose e DVIVMO, sendo que os piores resultados foram encontrados nas regiões periféricas (TL e TC) dos silo. Os tratamentos não influenciaram na contagem de microrganismo (BAL: bactérias ácido láticas, FF: fungos filamentosos e LEV: leveduras), porém, com relação ao local de coleta houve diferença para BAL e FF. Como esperado, a população de FF foi maior na periferia dos silos, enquanto que a de BAL foi maior no centro. A contagem de leveduras não sofreu influência do tratamento e local de amostragem. No experimento II, objetivou-se avaliar o desempenho animal em função da estratégia de vedação de silagens de milho. Foram utilizadas 15 vacas distribuídas aleatoriamente em cinco quadrados latinos 3x3, com períodos de 21 dias. Os animais foram mantidos em sistema de confinamento Tie-Stall com baias individuais e alimentadas duas vezes ao dia. Os tratamentos foram definidos de acordo com o método de vedação: ETNC, ETC e ET+ADNC. As dietas foram formuladas para serem isoproteicas, com 53% de silagem de milho (% MS). As porções deterioradas das silagens foram descartadas diariamente, as rações foram preparadas utilizando apenas silagem não deteriorada. O consumo de matéria seca, a produção e composição do leite foram determinados entre os dias 15 e 21 de cada período experimental. Os dados foram analisados utilizando o Proc Mixed, do software estatístico SAS. Os tratamentos ET+ADNC e ETC apresentaram maior eficiência energética enquanto que os tratamentos ET+ADNC e ETNC tiveram tendência de maior produção de leite corrigido para 3,5% de gordura e excreção de energia no leite; da mesma forma, a excreção de proteína no leite também foi aumentada. O tratamento ETC não promoveu melhoras no valor nutritivo das silagens, enquanto que os tratamentos ET+ADNC e ETNC apresentaram tendência em maximizar o desempenho das vacas. / Two experiments were conducted to evaluate different strategies to cover silos. The experiment I evaluate the chemical fermentation profile, chemical composition and losses of dry matter and organic matter in corn silage covered with different types of plastic film and with or without the added layer of sugarcane bagasse. The treatments were: ETNC: 200?m black-on-white polyethylene film; ETC: black-on-white polyethylene film plus sugarcane bagasse over the film and ET+ADNC: 125?m polyamide/polyethylene coextruded film. The experimental design was randomized blocks. The data were subjected to analysis of variance and their means were compared by Tukey test at 5% significance. The amount of spoiled silage was lower for treatment ETC, while the other treatments were similar. There was no significant difference between treatments for the chemical composition, although differences were observed between different sampling sites (TL: side wall, TC: top center and C: bottom) for the variables DM, ADF, starch, hemicellulose and IVOMD, while the worst results were found in the peripheral regions (TL and TC) of the silo. Treatments did not affect the count of microorganisms (BAL: lactic acid bacteria, FF: filamentous fungi: LEV: yeasts), however the FF acount was greater in the TL and TC, while BAL was higher in the C. The yeast count was not influenced by treatment or sampling site. In the experiment II was evaluated performance of dairy cows fed corn silage covered with different sealing strategies. Fifteen lactating cows were randomly assigned to 5 replicated 3×3 Latin square design with 21-d periods. Animals were housed in sand-bedded tie-stall barn and individually fed ad libitum to achieve approximately 10% refusals twice daily. Treatments were defined according to the method of sealing: ETNC, ETC and ET+ADNC. Diets were formulated to be isonitrogenous with 53% corn silage (DM%) to meet the nutrient requirements of a dairy cow producing 35 kg×d-1 of milk. The deteriorated inedible silage was discarded every day and only edible silage was used to prepare the total mixed rations. Dry matter intake (DMI) and milk yield were recorded from d-15 to d-21 in each period, as well milk composition. Data were analyzed using the Mixed procedure of SAS. Treatments ET+ADNC and ETC showed higher energy efficiency while treatments ET+ADNC and ETNC tended to higher milk yield and energy excretion in milk, as well the excretion of protein in the milk was also increased. Contrary to expected, the ETC treatment did not improve the nutritive value of silages. In conclusion, treatments ET+ADNC and ETNC tended to maximize the performance of dairy cows.
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Estudo do impacto potencial das mudanças climáticas na biodeterioração de estruturas de madeiras no patrimônio cultural edificado do Vale Histórico Paulista / Study of the potential impact of climate change on wood structures decay in the built cultural heritage of Paulista Historic ValleyFelipe Sousa Neves Andrade 14 March 2016 (has links)
O presente trabalho busca contribuir com as pesquisas acerca das perspectivas de impacto das mudanças climáticas no patrimônio cultural do Vale Histórico de São Paulo, com enfoque na ação de fungos nas estruturas de madeira das edificações históricas. Diversos estudos têm sido realizados na Europa a respeito desse tema, mas no Brasil trabalhos desse tipo não são numerosos. A revisão da literatura a respeito das mudanças climáticas indica aumentos na temperatura do ar, alterações nos regimes de precipitação e em diversas outras variáveis climáticas em todo o planeta. Foram coletados dados meteorológicos da região estudada e dados de monitoramento do microclima do interior de algumas edificações. Também foram obtidos dados de simulação a respeito do clima nos próximos 100 anos na região. Podendo-se, assim, obter um cenário de possibilidades de mudanças no clima e no microclima das edificações. Investigou-se a presença de fungos degradadores de lignocelulose nas edificações em estudo e os impactos das variações de temperatura no desenvolvimento desse tipo de fungo. As conclusões do trabalho indicam que as mudanças no clima da região podem aumentar os riscos de deterioração dos prédios históricos da região estudada / This study aims to contribute to investigate the impact projections for of climate change on cultural heritage of the Historic Valley of São Paulo, focusing on the action of fungi in the wood structures of historic buildings. Several studies have been conducted in Europe on this subject, but in Brazil works of this nature are not numerous. A review of the literature on climate change indicates overall increases in air temperature, changes in precipitation regimes and several other climatic alterations across the planet. Meteorological data from the study area and microclimate monitoring data from the indoor microclimate of some buildings were collected. Climate simulation data concerned the next 100 years in the region were also obtained, thus resulting in a scenario of climate and indoor microclimate changes. Experimental analysis on the presence of lignocellulose-degrading fungi on cultural heritage materials were carried out. The findings of the study indicate that changes in the climate of the region can increase the risk of biodeterioration of historic buildings of the region studied
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Correlation of Chloride Diffusivity and Electrical Resistance for Cracked ConcreteUnknown Date (has links)
The durability of Reinforced Concrete (RC) structures in the Marine environment is
causing serious concern in the structural infrastructure. Reinforced concrete structures,
exposed to aggressive environments, are expected to last with little or no maintenance for
long periods of time. However, one of the most serious environmental exposures that
causes degradation is Chloride Diffusion, due to shrinkage, atmospheric corrosion, and
tide-induced wet and dry conditions at the air-water interfaces of coastal structures.
Therefore, chloride diffusivity, which correlates with the electrical resistivity, has a
significant impact on the durability of concrete. Concrete chloride diffusivity has been
experimented by multiple agencies and researchers on sound concrete, but there is a
considerable need for investigation of the durability of cracked concrete in the marine
environment. The two test methods carried out are presented: Standardized American Society for Testing
and Materials (ASTM) C1202 for Rapid Chloride Permeability (RCP) and ASTM D257
for Surface Resistivity (SR), and Nordtest (NT) Build 492 for Rapid Chloride Migration
(RCM) and Bulk Resistivity (BR) for both sound (uncracked) and cracked (micro and
macro) concrete. The limitations of the ASTM method, due to measurements before the
steady-state migration is reached, does not account for leakage in cracked concrete, and the
heating of the specimen due to higher current that increase the conductivity are indicated.
The Rapid Chloride Migration test provides for the non-steady state of diffusion. Again,
Bulk Resistivity, in contradistinction to Surface Resistivity is more accurate for cracked
concrete. The correlation betweeen RCM-BR are plotted. Chloride Permeability/Migration
is an important parameter that governs the Durability of Concrete.
The principal contribution is the highlighting of the inadequacy of the current widely used
standard ASTM C1202 for diffusivity testing, and the need for revision with further
investigation. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection
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Teste de envelhecimento acelerado em sementes de ervilha forrageiraDourado, Wilson de Souza [UNESP] 19 October 2012 (has links) (PDF)
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dourado_ws_me_botfca.pdf: 306085 bytes, checksum: 1b0f493f9f26322e6c5f3a7602ed38d5 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A ervilha forrageira difere da ervilha comum quanto a cor do tegumento, ao elevado teor de aminoácidos e foi selecionada visando a alimentação animal. O objetivo do trabalho foi verificar a eficiência de testes de vigor, com ênfase no envelhecimento acelerado para a avaliação da qualidade de sementes de ervilha forrageira visando seleção de lotes para a emergência de plântulas em campo e longevidade no armazenamento. Foram utilizados 10 lotes de ervilha forrageira avaliados quanto ao teor de água, massa de mil sementes, teste da primeira contagem, germinação, condutividade elétrica, emergência de plântulas em campo e teste de envelhecimento acelerado com as seguintes variações de metodologia: temperaturas de 41 e 42 °C; tempos de exposição das sementes de 48 e 72 horas e umidade da atmosfera de envelhecimento, mediante a utilização de água destilada (100% UR), solução saturada de cloreto de potássio (87% UR) e solução saturada de cloreto de sódio (76% UR). Os resultados encontrados foram comparados à emergência de plântulas em campo e armazenamento pelos tempos de 90, 180, 270, 360, 450, e 540 dias. Os testes de envelhecimento acelerado com água à 41° C por 48 horas, cloreto de potássio a 41 °C por 72 horas e 42 °C por 48 horas: são promissores para avaliar o vigor de lotes de sementes de ervilha forrageira fornecendo informações semelhantes à emergência de plântulas em campo. Nenhum das variáveis do teste de envelhecimento avaliadas mostrou eficiência na seleção de lotes quanto ao desempenho no armazenamento / The pea pea differs common as the color of the coat, the high content of amino acids and was selected in order to feed. The aim of the study was to assess the efficiency of vigor tests, with emphasis on accelerated aging to assess the quality of pea seeds aimed selection of lots for field seedling emergence and longevity in storage. We used 10 batches of pea evaluated for water content, weight of thousand seeds, test the first count, germination, electric conductivity, seedling emergence in field and accelerated aging test with the following variations in methodology: temperatures of 41 and 42 °C; seeds exposure times of 48 and 72 hours and humidity aging, using distilled water (100% UR), saturated potassium chloride (87% UR) and saturated chloride sodium (76% UR). The results were compared to seedling emergence in field and storage for times of 90, 180, 270, 360, 450, and 540 days. The accelerated aging tests with water at 41 °C for 48 hours, potassium chloride at 41 °C for 72 hours and 42 °C for 48 hours: are promising to evaluate the effect of seed lots of pea similar information to seedling emergence in the field. None of the variables evaluated aging test showed efficiency in selecting lots for performance in storage
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Manifestações e contradições da metrópole de São Paulo no antigo bairro de Santana: a paisagem, o valor da terra, a intervenção urbana e o fenômeno da deterioração urbana / Manifestações e contradições da metrópole de São Paulo no antigo bairro de Santana: a paisagem, o valor da terra, a intervenção urbana e o fenômeno da deteriorização urbanaAndré Vinicius Martinez Gonçalves 07 August 2006 (has links)
Esta dissertação parte da tese que o avanço da Metrópole de São Paulo em direção ao antigo bairro de Santana, em especial, a partir dos anos de 1950, gerou ao espaço geográfico local, uma considerável diversidade espacial, implicando hoje, um mosaico de ealidades, tanto no aspecto de ocupação e uso do solo, como em relação às práticas sócio-espaciais. Essas realidades instauradas em Santana, na perspectiva do presente estudo são refletidas, sobretudo, a partir de duas questões: as intervenções urbanas, uma parcialmente efetivada nos anos de 1970, denominada Plano Cura Piloto de Santana, e outra em curso, intitulada Operação Urbana Vila Maria - Campo de Marte; e o fenômeno da deterioração urbana em Santana, fenômeno este, entendido como uma das contradições geradas a partir da reprodução do espaço urbano sob égide do sistema capitalista. / This report based on the thesis that the growth of São Paulo city towards the old neighborhood Santana, mostly from the fifties on brought to the geographical locus a great deal of landscape diversity. Such diversity led the city to look like a huge mosaic composed of so many different realities both regarding land occupation and usage and social visual specially lifestyles. As for the research herein presented, the differences that are established from two issuer: the urban interventions; one partially effective in the seventies called Plano CURA Piloto Santana and another one named Operação Urbana Vila Maria - Campo de Marte, and the phenomenon is know as one of the conceived contradictions from the reproductions of the urban lifestyle the capitalism system.
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Estudo do impacto potencial das mudanças climáticas na biodeterioração de estruturas de madeiras no patrimônio cultural edificado do Vale Histórico Paulista / Study of the potential impact of climate change on wood structures decay in the built cultural heritage of Paulista Historic ValleyAndrade, Felipe Sousa Neves 14 March 2016 (has links)
O presente trabalho busca contribuir com as pesquisas acerca das perspectivas de impacto das mudanças climáticas no patrimônio cultural do Vale Histórico de São Paulo, com enfoque na ação de fungos nas estruturas de madeira das edificações históricas. Diversos estudos têm sido realizados na Europa a respeito desse tema, mas no Brasil trabalhos desse tipo não são numerosos. A revisão da literatura a respeito das mudanças climáticas indica aumentos na temperatura do ar, alterações nos regimes de precipitação e em diversas outras variáveis climáticas em todo o planeta. Foram coletados dados meteorológicos da região estudada e dados de monitoramento do microclima do interior de algumas edificações. Também foram obtidos dados de simulação a respeito do clima nos próximos 100 anos na região. Podendo-se, assim, obter um cenário de possibilidades de mudanças no clima e no microclima das edificações. Investigou-se a presença de fungos degradadores de lignocelulose nas edificações em estudo e os impactos das variações de temperatura no desenvolvimento desse tipo de fungo. As conclusões do trabalho indicam que as mudanças no clima da região podem aumentar os riscos de deterioração dos prédios históricos da região estudada / This study aims to contribute to investigate the impact projections for of climate change on cultural heritage of the Historic Valley of São Paulo, focusing on the action of fungi in the wood structures of historic buildings. Several studies have been conducted in Europe on this subject, but in Brazil works of this nature are not numerous. A review of the literature on climate change indicates overall increases in air temperature, changes in precipitation regimes and several other climatic alterations across the planet. Meteorological data from the study area and microclimate monitoring data from the indoor microclimate of some buildings were collected. Climate simulation data concerned the next 100 years in the region were also obtained, thus resulting in a scenario of climate and indoor microclimate changes. Experimental analysis on the presence of lignocellulose-degrading fungi on cultural heritage materials were carried out. The findings of the study indicate that changes in the climate of the region can increase the risk of biodeterioration of historic buildings of the region studied
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Effects of Surface Treatments on National Bridge Inventory Condition Ratings for Concrete Bridge Decks in UtahDe Leon, John Taani 01 April 2018 (has links)
Although the application of surface treatments on bridge decks is expected to positively impact bridge deck condition, the effectiveness of specific surface treatments on extending bridge deck life has not yet been quantified on Utah bridge decks. Therefore, the objectives of this research were to develop and analyze deterioration curves for bare concrete bridge decks and decks with specific treatments commonly used in Utah. The scope of this study was determined by the types and extent of electronically available data, including selected static inventory information; maintenance, rehabilitation, and reconstruction histories; and National Bridge Inventory (NBI) condition ratings for the bridge decks. Bridge deck selection criteria and analysis procedures were developed to enable evaluation of the effects of surface treatments on bridge decks in Utah. Characteristics of a typical bridge were defined, and a list of typical bridges was produced to minimize potentially confounding effects of atypical bridge characteristics in comparisons of deterioration curves for monolithic concrete decks, decks with a bituminous overlay, decks with an epoxy overlay, and decks with a latex-modified concrete overlay. Climatic differences were taken into account by grouping bridges not only by overlay type, but also by Utah Department of Transportation region, which was used in this research as a general surrogate for latitude. Individual bridge deck deterioration curves were then combined to generate average deterioration curves aligned by deck construction time and average deterioration curves aligned by deck treatment time. To at least partially account for the potentially different effects of different treatment times, the bridge groups involving overlays were divided into two treatment time categories, early and late, for analysis. The average deterioration curves aligned by deck construction time suggest that certain treatments applied at certain times can achieve average NBI ratings greater than those for monolithic concrete during selected years of bridge deck life. The average deterioration curves aligned by deck treatment time suggest that certain treatments applied at certain times can achieve improvements in NBI ratings that correspond to apparent increases in bridge deck service life. Primarily because the NBI rating system is based mainly on visual inspection, the full benefits of early applications of surface treatments are not apparent in the results of this research. Supplemental perspectives may be gained about the performance of specific surface treatments by evaluating bridge deck deterioration in terms of delamination, half-cell potential, and chloride concentration, for example, which are direct measures of the deterioration process typically experienced by concrete bridge decks in Utah.
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Pavement Deterioration and PE Pipe Behaviour Resulting from Open-Cut and HDD Pipeline Installation TechniquesAdedapo, Adedamola Adedeji 14 September 2007 (has links)
The damaging impact of continuous utility cuts on flexible pavement performance has been shown to be a major problem for urban roads and pavement mangers due to high reconstruction and maintenance costs. Horizontal Directional Drilling (HDD) is a trenchless construction method that does not require continuous trenching. HDD pipe installation techniques can reduce reinstatement costs, shorten construction periods, and lower social costs due to reduced user traffic delays. In this thesis, a detailed field study and numerical investigations was completed to quantify pavement deterioration and polyethylene (PE) pipe performance when pipelines are installed under flexible pavements using both traditional open-cut and HDD construction methods.
Two 200mm SDR-17 DIPS HDPE pipes were installed 1.5m below a flexible pavement using open-cut and HDD construction technique. A state-of-the-art instrumentation and data acquisition systems were developed to measure HDD drill rig, PE pipes and pavement responses during pipe installations and for a period of about three years afterwards. Field data from (GPR) surveys, falling weight deflectometer (FWD) tests, surface distress surveys, and ground surface elevation survey were used to evaluate pavement deterioration due to the pipeline installations. The mechanisms of ground deformations during HDD and open-cut pipe installation were numerically investigated with FLAC3D, a commercial finite difference program. A hybrid constitutive model consisting of the traditional Duncan-Chang hyperbolic model and Mohr-Coulomb perfectly plastic model was developed and implemented in FLAC3D to simulate the non-linear stress-strain and stress dependent behavior of granular materials.
Field test results show that the HDD installed pipe have significantly lower construction induced strains and ring deflections when compared to the open cut-and-cover installation and the mechanism of pipe deformation differs for the two construction techniques. The two pipes performed satisfactory over the long-term monitoring period as deflections and strain levels were below acceptable limits and there was no apparent deterioration of the pipe.
Pipe deflections resulting from environmental effects (freeze and thaw) were found to be more significant than those due to material creep. Furthermore, the modified Iowa’s and Plastic Pipe Institute’s (PPI) ring deflection equations were found to over estimate pipe deflection for the open-cut and HDD installed pipes by about 114 and 50 percent, respectively.
Results from field tests found that the HDD installation did not results in any observable change in the condition of the pavement structure performance, while the structure and integrity of pavement section in the vicinity of the open-cut was adversely impacted by utility cut excavation. It was determined numerically that when an unsupported excavation is created within a typical flexible pavement structure, distress zones that extend laterally from the face of the excavation to a distance of approximately 80% of the depth of excavation is developed. The results of the analyses suggests that better restoration techniques are required to eliminate the adverse effect caused by the stress relief within the pavement structure during a utility cut. Furthermore, the area of potential pavement deterioration should be extended beyond the edge of the utility cut to encompass the ‘distress zones’ when determining fees to cover pavement damage and restoration costs.
Results obtained from numerical simulations advanced the understanding of the mechanism, magnitude, and extent of deformation within the pavement structure during HDD pipe installation in frictional and cohesive subgrade soils. Relationship between HDD annular bore pressures and displacements have been incorporated into design Charts and Tables for use in estimating maximum allowable bore pressures for HDD installation beneath flexible pavements. Critical bore pressures that would limit ground deformations and prevent excessive pavement deformations are presented. Critical bore pressures were compared to estimated allowable bore pressures obtained from the widely used Delft Geotechnics equation. The Delft Geotechnics equation was found to over estimate allowable bore pressure for HDD installation beneath flexible pavement.
HDD pipeline installations under flexible pavement were found to have significantly lower restoration costs, social costs and maintenance cost than open-cut pipeline installations.
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