Coefficient of earth pressure at rest for normally and overconsolidated peat ground in Hokkaido area

Peat, which is widely distributed in Hokkaido, is a very soft and problematic soil. To perform an elasto-plastic Finite Element (FE) analysis, it is important to accurately determine the initial stress conditions, and among them, the value of the coefficient of earth pressure at rest (K0 value) is particularly important. A K0-consolidation test using triaxial testing apparatus and a flat dilatometer were performed to investigate the K0 value for peat ground in Hokkaido, Japan. It was found that the K0 value for normally consolidated peat and organic clay (K0NC) decreases with an increase in the ignition loss. The K0 value for overconsolidated peat and organic clay (K0OC) is more strongly dependent on the over consolidation ratio (OCR) than that of usual inorganic clay. That is, it is known that K0OC is empirically related to K0NC, as expressed by K0OC=K0NCOCRm, and in peat and organic clay the power of m increases with their ignition loss. An experimental equation to estimate K0 using a flat dilatometer for peat ground is also proposed.