Stiff overconsolidated clays

The recommended values of p are 500 for soff sensifive clays, 1000 for firm to stiff clay, and 1500 for very stiff clay. For fhe highly overconsolidated clays a value of p = 400 can be used. Poisson s ratio is taken as 0.5 for undrained condition. 

Merritt posey-San Antonio formation Pleistocene- e, very dense sand interbedded with overconsolidated stiff to very stiff clay. 

In stiff, overconsolidated clays, cyclic lateral loads may open a gap (slot) between the pile and soil. The slot may gradually grow wider and deeper because of erosion of soil caused by the squeezing of water out of the gap. This erosion, in addition to the seafloor surface erosion and scour, may significantly affect the pile design computations. 

Old bay mud/upper alameda formation Pleistocene- e, overconsolidated, very stiff to hard, h h plasticity clay. 

Consolidation settlement is usually significant in soft to medium stiff clayey soils. Creep settlement occurs most significantly in overconsolidated clays under large sustained loads and can be estimated by using the method developed by Booker and Poulos (1976). In principal, however, long-term settlement can be included in the calculation of ultimate settlement if the design parameters of soil used in the calculation reflect the long-term behavior. 

The fundamental problem involved is always one of data quality, and consequently the back analysis approach must be applied with care and the results interpreted with caution. Back analysis is of use only if the soil conditions at failure are unaffected by the failure. For example, back-calculated parameters for a first-time slide in stiff overconsolidated clays could not be used to predict subsequent stability of the sliding mass, since the shear strength parameters will have been reduced to their residual values by the failure. In such cases, an assumption of c = 0 and the use of a residual friction angle ip is warranted (Bromhead, 1992). If the three-dimensional geometrical effects are important for the failed slope under consideration and a two-dimensional back analysis is performed, the back-calculated shear strength will be too high and thus unsafe. 

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