| Knowledge of saturated clay shear strength with floating rock particles is very limited for design purposes. Landslide rehabilitation designs for particle rich colluvial slopes in eastern Kentucky are generally inadequate because of difficulties in determining shear strength values from standard laboratory tests and understanding how floating particles interact in saturated soil. Existing engineering practices by their very nature produce conservative designs resulting in higher cost and sometimes failed stabilization efforts.; This research proposes a conceptual model specifically for floating rock particles contained within a matrix of lean, saturated clay that identifies the effects of stress, pore pressure, and strain changes on shear strength. A prototype saturated, soil representative of the most typical conditions observed within eastern Kentucky landslides was mixed with marble spheres separated by five different distances. A consolidation process was devised to produce two initial pore pressure conditions. Twenty-two large scale direct shear tests showed that shear strength in low initial pore pressure tests followed a two-phased relationship for floating particle concentrations. The shear strength measurements for high initial pore pressure conditions indicated that particle concentrations had little effect.; Because pore pressure measurements could not be measured during testing, numerical simulations were used to examine stress changes adjacent to stiff particle inclusions in response to assumed pore pressure dissipation. As water flowed from regions of high to low pressure, patterns of failure developed from the particle at angles ranging from {dollar}pm 30spcirc{dollar} to {dollar}pm 45spcirc{dollar} to the axis of the minor principal stress. In the low initial pore pressure tests, failure zones propagated approximately 1/2 particle radius from the edge of the particle; while in high initial pore pressure test, failure was widespread. Therefore for material with low initial pore pressure conditions, local failures were assumed to have little affect on shear strength until particle separation was reduced to approximately one radius (a floating particle concentration of approximately 16%). Conceptual models were developed to explain possible relationships between the shear strength of saturated clays and the concentration of floating rock particles. Future slope remediation efforts within the colluvium slopes of eastern Kentucky should consult these models to consider what impact local clay-rock mixtures may have on shear strength. |
