PREDICTION OF THE PARTIALLY DRAINED BEHAVIOR OF SOFT CLAYS UNDER EMBANKMENT LOADING
キーワード:
vertical drain(IGC : E2/E3)
1992 年 32 巻 1 号 p. 41-58
詳細
1992 年 32 巻 1 号 p. 41-58
Partial drain behavior of soft saturated clay foundation is discussed under embankment loading. The partial drain effect both on a consolidation settlement and on a bearing capacity is totally examined in terms of both soil permeability and load intensity, the latter of which is shown to be normalized by the undrained bearing capacity that should be evaluated at the stage just before embanking execution. Through a series of numerical computation and the case record study, the following findings are obtained : (1) The range of soil permeability which yields the variation of partial drain behavior has been found 10-7cm/sec<k<10-4cm/sec when a clay deposit of about 25 meters thick is considered. This is also corresponding to the usual loading rate of embanking in engineering practice of soft clay. Out of this particular range of parmeability the clay foundation will behave almost in a perfectly undrained manner or in a fully drained manner. (2) When soil permeability lies on this particular range the bigger the load intensity, the more the partial drain effect should be expected. (3) The soil permeability representative of a clay foundation, sometimes referred to as mass permeability, can be evaluated inversely based on the observation of consolidation settlement when a load intensity is normalized with the undrained bearing capacity of the foundation. The procedure is shown to be still applicable, through a case record study, even for a clay foundation that is improved by a number of vertical sand drain piles. In this context, the inference is also made in the present study that the efficiency of sand drains is to be observed in a limited range of soil permeability and under a particular magnitude of load intensity.
