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 Resources: Dredging and Offshore Engineering Lecture Notes



Home / Cutting of Sand, Clay and Rock / The Cutting of Clay /

    Lecture Notes Dredging Processes Clay Cutting (1210)

Clay Cutting

From literature on this subject it is known that the process of cutting clay is different from that of water saturated sand. Sand is often modeled as a continuum with an internal friction angle and a sand/steel friction angle but without cohesion and adhesion. Clay is considered to be a continuum with cohesion and adhesion, but with an internal friction angle and a clay/steel friction angle equal to zero. In this paper clay will be considered this way. It has been noticed by many researchers that the cohesion and adhesion of clay increase with an increasing deformation rate. It has also been noticed that the failure mechanism of clay can be of the "flow type" or the "tear type", similar to the mechanisms that occur in steel cutting. Previous researchers, especially Mitchell 1976 [5], have derived equations for the strain rate dependency of the cohesion based on the "rate process theory". However the resulting equations did not allow pure cohesion and adhesion. In many cases the equations derived resulted in a yield stress of zero or minus infinity for a material at rest. Also empirical equations have been derived giving the same problems. Based on the "rate process theory" with an adapted Boltzman probability distribution, the Mohr-Coulomb failure criteria will be derived in a form containing the influence of the deformation rate on the parameters involved. The equation derived allows a yield stress for a material at rest and does not contradict the existing equations, but confirms measurements of previous researchers. The equation derived can be used for silt and for clay, giving both materials the same physical background.

Miedema, S.A., "New Developments of Cutting Theories with respect to Dredging, the Cutting of Clay". Proc. WODCON XIII, Bombay, India, 1992.



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