ISBN:  Unavailable

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Page count: 32

A micromechanical theory of cone penetration in granular material is developed that takes into account the effects of soil/penetrometer friction, material compaction, and the statistics of microstructural element failure. Microstructural elements (elements) consist of particles connected to each other by cohesive or friction contacts. Soil/penetrometer friction and the deformation and failure of elements in contact with the penetrometer effective surface (PES) cause cone penetration resistance (penetration force divided by the cone base area). The PES is the interface surface between the compacted material that forms around a cone penetrometer and the surrounding elements. The cone half-angle and the volume strain at which granular particles from failed elements lock up determine the PES area. The failure of elements during penetration produces a random roughness surface of elements next to the PES. Consequently, a finite probability exists that each element next to the PES will be in contact with it at any time. The probability of contact, dimensions, and failure strength of the elements determines the percentage of elements next to the PES that contribute to penetration resistance. The statistical interaction of elements with the PES causes the maximum penetration resistance to decrease with increasing penetrometer base area, asymptotically approaching the average value. The effects of decreasing soil/penetrometer friction and the increasing PES area as a function of cone half-angle produce a minimum penetration resistance at a cone half-angle of about 15 degrees. Element failure strength is described in terms of elastic-brittle and Mohr-Coulomb models.