ESTIMATION OF INITIAL VOID RATIO OF CONSOLIDATED CLAY BASED ON ONE-DIMENSIONAL CONSOLIDATION THEORY

Many stupas located within the sacred historical site of Ayutthaya, Thailand are inclined. It is important to understand their ground conditions and causes of inclination in order to design appropriate conservation countermeasures for these precious cultural assets. Soil investigations were conducted at four points around the inclined stupa of Wat Krasai, located outside the World Heritage Site "Historic City of Ayutthaya" in 2013 and 2016. Three key soil layers appear to be responsible for the inclination of this stupa: the second soft clay layer, the third loose silty sand layer, and the fourth hard clay layer. The inclination of this stupa increased as the thickness of the second soft clay layer. Thus, we assumed that the cause of stupa inclination and disproportionate settlement of the stupa was only the second soft clay layer. The amount of settlement and the initial void ratio of this second layer were estimated using the consolidation calculation formula based on Terzaghi's one-dimensional consolidation theory. The results of this study indicate that the amount of settlement is not exactly proportional to the thickness of the second soft clay layer, or that the void ratio is inhomogeneous in the layer. The calculation is conducted in four directions, north, south, east, and west, and the maximum settlement and the initial void ratio of the second soft clay layer are estimated at approximately 6.9 m and between 1.46 and 2.48 at the north side of the stupa, respectively.