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Impact of Hydraulic Hysteresis on Hydro-mechanical Behaviour of Infilled Fractured Rocks in Unsaturated Condition

Mousavi, Masoud | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48227 (09)
  4. University: Sharif University of Technology
  5. Department: Geotechnical
  6. Advisor(s): Khosravi, Ali
  7. Abstract:
  8. Recent studies have shown that comprehensive characterization of the behavior of infilled rock fractures under saturated and unsaturated conditions requires knowledge of morphological details of fracture surface, as well as state of stress of infill materials and their initial innate conditions (e.g., void ratio, water content, degree of saturation and dry density). This study presents the details and typical results from a new testing approach to study the hydro-mechanical behavior of the infilled rock fractures under different stress states and saturation conditions. The new testing approach incorporates the axis translation technique for suction control, a flow pump for the measurement of infill’s degree of saturation, and the Digital Image Processing (DIP) technique for volume change measurements. Results of this study indicated different hydro-mechanical behavior of the fractures depending on the level of suction and confining pressure applied to the system, infill material thicknesses and drying and wetting paths. The results suggested that variations in hydraulic properties of infilled fractured rock do not always correspond to changes in properties of the infill materials, but can be a result of a complex interaction of several factors, including morphological details of the fracture surface and the thickness and properties of the infill materials. The specimens subjected to higher values of suction or confining pressure presented higher strength during shear. The effect of matric suction was lower in fractures with lower infill thicknesses. This study also describes a semi-empirical equation to interpret the effects of wall-roughed nature of the fractures and presence of partially saturated fine materials within the fractures on the behavior of infilled rock fractures during shear. The proposed equation incorporates the soil-water retention curve parameters and hardening due to changes in either volume or degree of saturation into existing models originally developed for fractures with saturated infills. Application of the proposed equation is then demonstrated through comparison between predictions and experimental data developed using the experimental testing program. The model was found to provide adequate prediction of the shear strength data upon drying and subsequent wetting, highlighting its ability in capturing the dependency of shear strength of infilled rock fractures on the hydraulic hysteresis
  9. Keywords:
  10. Shear Strength ; Unsaturated Soil ; Soil Mechanics ; Drying ; Wetting ; Hydromechanical Behavior ; Infilled Joins ; Rock Fracture ; Infill Materials

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