Profiles of displacement caused by seasonal creep of an expansive silty clay soil were measured at several times of the year with a tiltmeter and flexible pipes installed in two areas near Stanford University in central California. The displacement profiles typically are convex upward and net creep displacement at the ground surface of an undisturbed slope with a gradient of 12 to 14 per cent is about 0.4 in/yr (1 cm/yr) for a layer of soil of five feet (1.5 m) thickness The soil apparently expands and creeps on wetting of the soil and while the soil is at a high moisture content, but the creep rate diminishes with time, as predicted by laboratory tests by Mitchell and Singh. On drying, a point on the surface of a slope contracts roughly along a normal to the slope but directions of horizontal displacements during drying appear to be random and to depend on the location of the point with respect to local shrinkage cracks.

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