Field verification of a stochastic model of soil creep
The research investigates random soil movement as suggested by Culling (1963), concentrating on the development of a technique for testing this theory. The technique employed dispenses with the need for continuous monitoring and avoids the inherent problems of soil disturbance arising from the use of soil probes. The theory assumes random and diffusive soil movement leading to a distinctive pattern of soil densities, through time, about obstacles of varying shapes. Solutions for circular and elliptical cylindrical obstacles have been calculated (Culling, 1981). The existence of a soil density pattern has now been investigated for circular obstacles by examining soil from around telegraph poles using photo-microscopy and image analysis to facilitate rapid calculation. Soil samples were removed in brass tubes, dried with acetone, impregnated with resin, made into thin sections, photographed and analysed. From the soil:void ratios of each picture the changing micro-density of soil around an obstacle can be determined. Results indicate significant variations in the density values. Detailed inspection of the two-dimensional information reveals that under sloping site conditions there is a coherent pattern of soil density which reflects that predicted by the theory. Flat sites are also consistent in that there is no identifiable trend in the horizontal plane. The conclusion considers the adequacy of the research undertaken to evaluate the theory.