Finite difference analysis to obtain the rate of consolidation over a stress range below and above the pre-consolidation pressure

When a clay layer of uniform OCR is subjected to an external load that results in loading of a portion of the clay layer to within the normally consolidated range, there exists a boundary within the clay that separates the over-consolidated material from the normally consolidated material. This boundary changes as consolidation progresses. A finite difference solution based on Terzaghi's one dimensional consolidation theory incorporating this moving boundary between the over-consolidated and normally consolidated states Is presented. The coefficient of consolidation, c(y), and the compression indices, C-c, are updated to the normally consolidated values when the clay is loaded to the virgin compression range. The solution shows that the rate and magnitude of consolidation settlement varies considerably depending upon the magnitude of load and over-consolidation ratio, although other consolidation properties such as c(y) and C-c values being kept unchanged.