Η επίδραση της ταχύτητας διάτμησης στην παραμένουσα αντοχή φλύσχη

Abstract

The aim of this thesis is the examination of the influence of the acceleration and the rate of displacement to the residual strength of soils which are connected to landslides in Greece, such as flysch. The thesis consists of two volumes. The first volume includes the eight chapters with the presentation of the laboratory investigation and the second volume includes the four appendixes. The first chapter is the introduction of this thesis where the aim and the flow structure are specified. The second chapter presents a literature review. The third chapter presents the ring shear apparatus of the Laboratory of Soil Mechanics, Foundation and Geotechnical Earthquake Engineering and its principles of operation. There are also described the sample presentation, the testing techniques and the calculation and presentation of results. The end of the chapter presents the procedure of direct shear box tests. The calibrations of ring shear apparatus, the motor drive units and the discussion of the testing errors in the accuracy of measurements are presented in Appendix A. The fourth chapter presents the tested soils and the laboratory program followed in ring shear and direct shear box tests. The samples used were from four different types of decomposed flysch from regions of Western Macedonia and Ipeirus. Twenty four ring shear tests were carried out for these samples. The fifth chapter presents the analysis of results from the ring shear and direct shear box tests for each flysch type. The extended presentation of ring shear tests is included in appendix B and from direct shear box tests is included in appendix C. The observations from the study of the microstructure in the shear zone are included in appendix D. This chapter presents the specification of shear mode in residual strength, the variation of residual strength with the normal stress and the envelopes of shear and critical strength in slow rate of displacement for each of the four flysch types. It also includes the results of the tests for the influence of the rate displacement in the residual strength for each flysch sample individual and for each flysch type. The sixth chapter presents the discussion of ring shear and direct ring shear test results according to the threshold strength, the fast peak strength, the fast residual strength, the slow peak strength after fast shearing and specimen consolidation. For each of the above strengths, there are specified the inflective parameters. There were specified four different types of variation of the fast residual strength with the increasing rate of displacement (types A, B, C, D), when there is ability of suction in shear zone. The seventh chapter presents the conclusions of the thesis for slow residual strength, threshold strength, fast peak strength, fast residual strength and slow peak strength after fast shearing and specimen consolidation. The practical implication is focused on the numerical simulation of the behaviour of pre-existed shear zones. This simulation is critical for the reliability of cinematic…