Experimental study of shear behaviour of high density polyethylene reinforced sand under triaxial compression

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dc.contributor.advisorKalumba, Denisen_ZA
dc.contributor.advisorChebet, Faridahen_ZA
dc.contributor.authorWanyama, Paulen_ZA
dc.date.accessioned2017-10-04T14:22:29Z
dc.date.available2017-10-04T14:22:29Z
dc.date.issued2017en_ZA
dc.description.abstractSoil reinforcement is an ancient technique which involves the addition of tensile elements like plastics in the soil to increase its engineering properties like shear strength, settlement, cohesion and bearing capacity. In consideration of this, a series of triaxial tests were undertaken to investigate the reinforcing effect of High-Density Polyethylene (HDPE) plastic material in Cape Flats sand, predominant in the Western Cape region of South Africa. Plastic strips of various lengths were randomly included to the soil at different concentrations to form a homogenous soil-plastic composite specimen prepared at varying compactive effort. Using a split mould, cylindrical specimens of 50 mm diameter and 100 mm height were prepared using the dry tamping technique. The test specimens were compacted to achieve target average dry densities of the composite sample. The plastic strip reinforcement parameters comprised of 7.5 mm to 30 mm lengths, and concentrations of 0.1 % to 0.3 % by weight of dry sand. Triaxial compression tests were performed using confining pressures of 50 kPa, 100 kPa, 200 kPa, 300 kPa and 400 kPa at a shear rate of 0.075 %/min, and to a maximum strain of 10 %. Laboratory results favourably suggest that there is an improvement in the soil shear strength properties due to these inclusions. The friction angle increased up to a peak value on varying plastic strip length and concentration, beyond which further addition of plastic material led to a reduction in the friction angle. The greatest friction angle was reported at plastic strip length and content of 15 mm and 0.2 % respectively. Additionally, the results indicate that a higher compactive effort leads to a greater increase in friction angle of the soil. The existence of a critical confining stress was observed from triaxial test results on soil-plastic composites. This threshold limit was influenced significantly by the plastic inclusions, and the range of confining stresses. Consequently, a bilinear failure envelope was reported in reinforced samples while unreinforced specimens realised a linear relationship. The Mohr-Coulomb failure line above the critical confining pressure almost paralleled the unreinforced linear relationship. An embankment model was developed using Slide Modeler software and the factor of safety of slope was analysed with unreinforced and reinforced backfill subjected to static and dynamic loading. It was observed that the safety factor increased due to polyethylene strip inclusions. Therefore, the proposed technique will find potential practical applicability in low-cost embankment or road construction.en_ZA
dc.identifier.apacitationWanyama, P. (2017). <i>Experimental study of shear behaviour of high density polyethylene reinforced sand under triaxial compression</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Geotechnical Engineering Research Group. Retrieved from http://hdl.handle.net/11427/25520en_ZA
dc.identifier.chicagocitationWanyama, Paul. <i>"Experimental study of shear behaviour of high density polyethylene reinforced sand under triaxial compression."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Geotechnical Engineering Research Group, 2017. http://hdl.handle.net/11427/25520en_ZA
dc.identifier.citationWanyama, P. 2017. Experimental study of shear behaviour of high density polyethylene reinforced sand under triaxial compression. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Wanyama, Paul AB - Soil reinforcement is an ancient technique which involves the addition of tensile elements like plastics in the soil to increase its engineering properties like shear strength, settlement, cohesion and bearing capacity. In consideration of this, a series of triaxial tests were undertaken to investigate the reinforcing effect of High-Density Polyethylene (HDPE) plastic material in Cape Flats sand, predominant in the Western Cape region of South Africa. Plastic strips of various lengths were randomly included to the soil at different concentrations to form a homogenous soil-plastic composite specimen prepared at varying compactive effort. Using a split mould, cylindrical specimens of 50 mm diameter and 100 mm height were prepared using the dry tamping technique. The test specimens were compacted to achieve target average dry densities of the composite sample. The plastic strip reinforcement parameters comprised of 7.5 mm to 30 mm lengths, and concentrations of 0.1 % to 0.3 % by weight of dry sand. Triaxial compression tests were performed using confining pressures of 50 kPa, 100 kPa, 200 kPa, 300 kPa and 400 kPa at a shear rate of 0.075 %/min, and to a maximum strain of 10 %. Laboratory results favourably suggest that there is an improvement in the soil shear strength properties due to these inclusions. The friction angle increased up to a peak value on varying plastic strip length and concentration, beyond which further addition of plastic material led to a reduction in the friction angle. The greatest friction angle was reported at plastic strip length and content of 15 mm and 0.2 % respectively. Additionally, the results indicate that a higher compactive effort leads to a greater increase in friction angle of the soil. The existence of a critical confining stress was observed from triaxial test results on soil-plastic composites. This threshold limit was influenced significantly by the plastic inclusions, and the range of confining stresses. Consequently, a bilinear failure envelope was reported in reinforced samples while unreinforced specimens realised a linear relationship. The Mohr-Coulomb failure line above the critical confining pressure almost paralleled the unreinforced linear relationship. An embankment model was developed using Slide Modeler software and the factor of safety of slope was analysed with unreinforced and reinforced backfill subjected to static and dynamic loading. It was observed that the safety factor increased due to polyethylene strip inclusions. Therefore, the proposed technique will find potential practical applicability in low-cost embankment or road construction. DA - 2017 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2017 T1 - Experimental study of shear behaviour of high density polyethylene reinforced sand under triaxial compression TI - Experimental study of shear behaviour of high density polyethylene reinforced sand under triaxial compression UR - http://hdl.handle.net/11427/25520 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/25520
dc.identifier.vancouvercitationWanyama P. Experimental study of shear behaviour of high density polyethylene reinforced sand under triaxial compression. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Geotechnical Engineering Research Group, 2017 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/25520en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentGeotechnical Engineering Research Groupen_ZA
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherCivil Engineeringen_ZA
dc.subject.otherGeotechnical Engineeringen_ZA
dc.titleExperimental study of shear behaviour of high density polyethylene reinforced sand under triaxial compressionen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMSc (Eng)en_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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