A Laboratory Study of Soil Creep and Strain-rate Effects of Sands and Aggregates at the Micro-scale

Soil creep is the continuous deformation of soils with time under a constant effectivestress. Creep may lead to serviceability problems or even instability and catastrophicfailure of foundations, slopes and infrastructures. Even worse is that creep failures areoften progressive in nature, which may result in failure of geotechnical structures thatare deemed safe in their current state. Breakable sands and sands subjected to a largedeviatoric stress fall within the category of highly vulnerable soils against creepproblems. This phenomenon has been extensively studied in the literature, howevermajor mechanisms that govern the soil creep have not been systematically investigatedor fundamentally understood. Creep of granular materials, at the macro-scale, is linkedto the behavior of grains at their contacts including grain-to-grain sliding and graindamage and this behavior is highly strain-rate dependent. The aim of the project is toexplore experimentally fundamental aspects of creep of granular materials at the grainscale using novel micromechanical laboratory methods. This study will contribute todevelop, for the first time in soil mechanics research, high-quality laboratory data whichwill lead to quantification and analytical expressions of micro-quantities such as inter-particlesliding friction and stiffness and grain strength and damage against the loadingvelocity which expresses strain-rate effects. The project will incorporate studies on avariety of soil grain types including naturally occurred soils and aggregates and a varietyof load patterns. The first category of soils will predominately involve completelydecomposed sand grains and other types of weathered materials which are of majorgeological and geotechnical interest in Hong Kong as well as carbonate sand grainswhich find major applications in offshore engineering with particular interest inSoutheast Asia. The second category of soils will involve crushed rock and recycledconcrete aggregate with major applications in transportation and geotechnicalengineering which materials are of particular interest in Hong Kong infrastructure. Theproject will have a major contribution to the understanding of soil creep mico-mechanismsand will produce data and analytical tools of major impact in soil mechanicsresearch and practice.?