Constitutive modeling for mechanical behaviors of geomaterials, new designs and techniques in geotechnical engineering
This Special Issue of the Journal of RockMechanics and Geotechnical Engineering (JRMGE) contains 13 papers prepared by international experts on various general topics in geomechanics, rock mechanics and geotechnical engineering. It represents a useful mix of theoretical developments, testing and practical applications. We present in the following brief details in the papers, alphabetically in accordance with the last name of the first author. Barla presents a review of tunneling techniques with emphasis on the full face method combining full face excavation and face reinforcement by means of fiber glass elements with a yieldcontrol support. This method has been used successfully in difficult geologic conditions, and for a wide spectrum of ground situations. The validation of the method with respect to the Saint Martin La Porte access adit along the LyoneTurin Base tunnel experiencing severely squeezing conditions during excavation is also included in the paper. The numerical modeling with consideration of the rock mass time dependent behavior showed a satisfactory agreement with monitoring results. A review of the disturbed state concept (DSC) for constitutive modeling of materials, interfaces and joints is presented by Desai. The DSC is a unified and hierarchical approach which allows many features ofmaterial behavior such as elastic, plastic and creep deformations, volume change, stress path, and microcracking leading to fracture, failure or softening, stiffening or healing under variousmechanical and environmental forces. The DSC has opened a new era for accurate and economic analysis and design for problems in geomechanics and geotechnical engineering. Its mathematical framework for solids can be specialized for interfaces and joints, thereby providing consistency in using the same model for both solids and interfaces. The DSC has been validated for geologic and other engineering materials. This study also provides a comprehensive list of publications that have employed the DSC based on elasticity, plasticity, elastoviscoplasticity, damage, fracture, and micromechanics. Behavior of modeled rockfill materials is studied through testing using a medium triaxial cell under drained conditions by Gupta. The effect of particle breakage is analyzed including the influence of size and confining pressure. Consolidated drained tests are reported for prototype rockfill materials for two dam projects in India by Honkadavadar and Sharma. An elastoplastic hardening soil (HS) model is used to characterize the material behavior. Procedures for prediction of shear strength and elastic parameters using the index properties and relative density are also included.