This dissertation details research into the shear strength and stiffness of dry, granular soils. The shear strength and stiffness properties of large, crushed granular soils are examined by use of the parallel gradation model. The issue of a representative volume and scale effects in typical experimental apparatus is examined. The second focus was research on the possibility of modeling broadly graded soils using a matrix density model. In this physical model, the "matrix" (the material left after oversized particles are removed) is tested at the same density that it had in situ, when the oversized particles were still in place. This research also sheds interesting light on the influence of inclusions on the shear strength and deformability of an otherwise uniform soil matrix. Klosky (1997) referred to these geotechnical materials as composite soils.; Use of a parallel gradation of crushed granular soil made from the same source as the prototype material to predict the shear strength of oversized crushed granular materials has been shown to be successful. Use of the matrix density model to predict the shear strength of broadly graded soils has also been shown to be successful, provided that the oversized particles are from a natural source and comprise less than 50% of a full oversized skeleton. Predictions of elastic properties using either model were poor, with the exception of the E{dollar}sb{lcub}50{rcub}{dollar} secant modulus.; Numerical modeling of a composite soil shows that it is possible to predict the peak strength trends of soils with inclusions using a finite element approach. Additionally, the numerical model gives insight into the mechanisms that govern the behavior of the peak shear strength trends of composite soils.
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