The aim of this research work is to deepen the understanding of joint shear behavior under different boundary conditions. For this purpose, joint closure tests under quasi-static and dynamic conditions, direct shear and cyclic shear tests under CNL and DNL boundary conditions of plane joints are performed using GS-1000 big shear box device. The dissertation also presents the procedure to simulate the shear box device and simulating the behavior of plane joints at the micro-scale using FLAC3D. Special attention has been given to understand the influencing factors of the normal stress level, direct shear rate, horizontal cyclic shear frequency, normal impact frequency, horizontal cyclic shear displacement amplitude and vertical impact force amplitude.
Lab test and numerical simulation results show that the quasi-static joint stiffness increases with increasing normal force. Dynamic joint stiffness decreases with increasing superimposed normal force amplitudes. Normal impact frequencies have little influence on the joint stiffness. Rotations and stress changes at the plane joint during shearing are proven. Rotations and development of stress gradients can be decreased significantly by increasing the size of the bottom specimen and applying a shear velocity at the upper shear box and normal loading piston. Furthermore, peak shear force increases with increasing normal force. Friction angle of cyclic shear tests is smaller than that of direct shear tests. Moreover, significant time shifts between normal and shear force (shear force delay), normal force and friction coefficient (friction coefficient delay) during direct shear tests under DNL boundary conditions are observed and the reference quantity ‘shear-velocity-normal-impact-frequency’ (SV-NIF) to describe the behavior under DNL boundary conditions is defined. Peak shear force and minimum friction coefficient increase with increasing SV-NIF. Relative time shift between normal force and shear force decreases with increase of SV-NIF. The mechanical behavior of the GS-1000 big shear box device is simulated and the loss of normal force caused by the tilting of the loading plate is quantified.
Finally, the novel direct and cyclic shear strength criterions under DNL conditions are put forward. The shear strength criterions are in close agreement with the measured values, which indicates that the novel shear strength criterions are able to predict the shear strength under DNL conditions.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa.de:bsz:105-qucosa-227649 |
| Date | 17 August 2017 |
| Creators | Dang, Wengang |
| Contributors | Technische Universität Bergakademie Freiberg, Geowissenschaften, Geotechnik und Bergbau, Prof. Heinz Konietzky, Prof. Heinz Konietzky, Prof. Andreas Henk, Prof. Zilong Zhou |
| Publisher | Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola" |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis |
| Format | application/pdf |
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