this topic is very hot. I am very interested in it. following is some of personal viewpoints. M4~^tML>Ey
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let's talk about the origin of the calculation of pile capacity. there are two methods to calculate the skin friction of piles, i.e. alpha method and beta method. alpha method is related to Cu, it is a semi-empirical method. beta method is related to effective overburden pressure, beta*sigma'v. as can be seen, the skin friction comes from the effective horizontal stress caused by vertical effective stress. whether the pile is static or sliding will not affect the existence of skin friction, as only can influence on the extent to which the skin friction has worked. 6Q"fRXM
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as for the pile toe resistance, it is originated from bearing capacity of the soil, i.e. Nc*Cu. generally the Nc is taken as 9, but it may vary with different soil conditions. )7f;FWI
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sometimes if the soil is sitting on soft soil, the skin friction may dominate. thus, the pile length may be long. but that does not mean the toe resistance is useless. Psm5J80}n
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but for some cases, the toe resistance may dominate, even negative skin friction may be considered. Y HSdaocp
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so the two parts of pile capacity components are not controdictory with each other. they should be considered together. at some special cases, one may play important role.
