Lime-treatment of clayey soil significantly increases its shear and tensile strengths.Consequently,the tensile strength of lime-treated soils deserves careful investigation because it may provide an appreciable benefi...Lime-treatment of clayey soil significantly increases its shear and tensile strengths.Consequently,the tensile strength of lime-treated soils deserves careful investigation because it may provide an appreciable benefit for the stability of earth structures.This study investigates the tensile and shear strengths of an untreated and lime-treated(3%of lime)plastic clay at different curing times(7 d,56 d and 300 d),through triaxial tension and compression tests.Triaxial tension tests are performed using“diabolo-shaped”soil samples with reduced central section,such that the central part of the specimen can be under axial tension while both end-sections remain in axial compression.Consolidated undrained(CU)conditions with measurement of pore water pressure allow analyzing the failure conditions through effective stress and total stress approaches.The results of triaxial tension tests reveal that the failure occurs under tensile mode at low confining pressure while extensional shear failure mode is observed under higher confining pressure.Consequently,a classical Mohr-Coulomb shear failure criterion must be combined with a cut-off tensile strength criterion that is not affected by the confining pressure.When comparing shear failure under compression and tension,a slight anisotropy is observed.展开更多
In many engineering applications,it is important to determine both effective rock properties and the rock behavior which are representative for the problem’s in situ conditions.For this purpose,rock samples are usual...In many engineering applications,it is important to determine both effective rock properties and the rock behavior which are representative for the problem’s in situ conditions.For this purpose,rock samples are usually extracted from the ground and brought to the laboratory to perform laboratory experiments such as consolidated undrained(CU)triaxial tests.For low permeable geomaterials such as clay shales,core extraction,handling,storage,and specimen preparation can lead to a reduction in the degree of saturation and the effective stress state in the specimen prior to testing remains uncertain.Related changes in structure and the effect of capillary pressure can alter the properties of the specimen and affect the reliability of the test results.A careful testing procedure including back-saturation,consolidation and adequate shearing of the specimen,however,can overcome these issues.Although substantial effort has been devoted during the past decades to the establishment of a testing procedure for low permeable geomaterials,no consistent protocol can be found.With a special focus on CU tests on Opalinus Clay,this study gives a review of the theoretical concepts necessary for planning and validating the results during the individual testing stages(saturation,consolidation,and shearing).The discussed tests protocol is further applied to a series of specimens of Opalinus Clay to illustrate its applicability and highlight the key aspects.展开更多
文摘Lime-treatment of clayey soil significantly increases its shear and tensile strengths.Consequently,the tensile strength of lime-treated soils deserves careful investigation because it may provide an appreciable benefit for the stability of earth structures.This study investigates the tensile and shear strengths of an untreated and lime-treated(3%of lime)plastic clay at different curing times(7 d,56 d and 300 d),through triaxial tension and compression tests.Triaxial tension tests are performed using“diabolo-shaped”soil samples with reduced central section,such that the central part of the specimen can be under axial tension while both end-sections remain in axial compression.Consolidated undrained(CU)conditions with measurement of pore water pressure allow analyzing the failure conditions through effective stress and total stress approaches.The results of triaxial tension tests reveal that the failure occurs under tensile mode at low confining pressure while extensional shear failure mode is observed under higher confining pressure.Consequently,a classical Mohr-Coulomb shear failure criterion must be combined with a cut-off tensile strength criterion that is not affected by the confining pressure.When comparing shear failure under compression and tension,a slight anisotropy is observed.
基金funded by the Swiss Federal Nuclear Safety Inspectorate ENSI (Grant no. H-100897)
文摘In many engineering applications,it is important to determine both effective rock properties and the rock behavior which are representative for the problem’s in situ conditions.For this purpose,rock samples are usually extracted from the ground and brought to the laboratory to perform laboratory experiments such as consolidated undrained(CU)triaxial tests.For low permeable geomaterials such as clay shales,core extraction,handling,storage,and specimen preparation can lead to a reduction in the degree of saturation and the effective stress state in the specimen prior to testing remains uncertain.Related changes in structure and the effect of capillary pressure can alter the properties of the specimen and affect the reliability of the test results.A careful testing procedure including back-saturation,consolidation and adequate shearing of the specimen,however,can overcome these issues.Although substantial effort has been devoted during the past decades to the establishment of a testing procedure for low permeable geomaterials,no consistent protocol can be found.With a special focus on CU tests on Opalinus Clay,this study gives a review of the theoretical concepts necessary for planning and validating the results during the individual testing stages(saturation,consolidation,and shearing).The discussed tests protocol is further applied to a series of specimens of Opalinus Clay to illustrate its applicability and highlight the key aspects.
