Effect of Preloading on Secondary Consolidation of Peaty Clay

Special consideration should be given to secondary consolidation settlements during service in the construction of high road embankments in lands underlain by thick layers of soft peaty clay. Usually a preloading design will be done to ensure that the peaty clay will remain in an over consolidated state during the operation of the road. At a stage of surcharge removal the in service settlement has to be estimated. In a preloading design the practically achievable over-consolidation ratios are in the range of 1.1 to 1.2. Effectiveness of such over-consolidation ratios (OCR) in keeping the long term in service secondary consolidation settlements within acceptable limits was studied in this research. Oedometer tests were done simulating the process of loading-unloading-reloading. Further tests were done on undisturbed samples obtained from preloaded peaty clay layers in two different projects. Results illustrated that the level of reduction of Cu is related to the achieved OCR