Velocity Method for Creep of Clayey Soils

Sudhir K. Tewatia et al.

MS Officer, New Delhi, India


Time-of-origin effects have been examined in relation to the creep settlement of clays, where it is shown that anomalous variations from a normal creep slope may arise as a result of incorrect assumptions, or lack of knowledge, of the true time of initiation of creep. Creep is the slow deformation of a body under constant stress, but in primary consolidation stress is being gradually but non-linearly transmitted from pore water to soil skeleton and hence for post-consolidation creep in clays, the real time of onset is obscure. There is, therefore, need to evaluate the coefficient of creep, a, without using the time of initiation of creep. Secondary or non-Terzaghian consolidation, also known as creep, generally exhibits itself as a straight line on d-log(t) and d-log(v) plots, where d is the experimental settlement, t is the experimental time and v (= dd/dt) is the experimental velocity of settlement. A few characteristics of this consolidation have been shown in this paper. A method for evaluating the coefficient of secondary consolidation, ca, when the time and settlement at the instant of load increment are not known is also proposed. The creep of the materials being the very slow process, it takes a long time to record the observations after load increment to evaluate the co-efficient of creep in the materials. A method is proposed to obtain d-log(t) plot from the d-log(v) plot. The velocity method is faster and better than the d-log(t) method.

KEYWORDS: coefficients, consolidation, laboratory test, slope, settlement, load, drainage, velocity, creep

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