Abstract:
Use of PVDs and preloading on the ground can significantly reduce the time it takes for ground to consolidate. Many soils in situ are lightly overconsolidated, with overconsolidation ratios (OCR) ranging from 1.0 to 2.0 due to various reasons such as glaciation, ground water level fluctuation, aging, isostatic uplift, cyclic loading, creep, erosion, cementation, etc. The phase transition from overconsolidated to normally consolidated occurs in lightly overconsolidated clays due to an increase in effective stress beyond the preconsolidation stress during the consolidation process under external loading. The effects of overconsolidation ratio are analysed in this study. Compression index and consolidation coefficient are important parameters in determining time – settlement response of soft soils under preloading and with PVDs. These parameters are typically estimated using oedometer tests on samples, with the assumption that the results represent the entire deposit. The in-situ time-settlement plots at different depths are used in the back analysis for estimating compressibility and consolidation parameters of in situ ground, resulting in more representative values that reflect the deposit's overall behavior. From observed time versus settlements plots, variations of compression index and coefficient of consolidation with depth of a deposit are presented. Estimation of compression index with depth is possible based on different OCR values as shown in this study. Asaoka method is used to estimate the coefficient of consolidation with flow in the radial direction.
Key words: Lightly overconsolidated soil, overconsolidation ratio, compression index, coefficient of consolidation, Time-settlement plots, Radial consolidation, Asaoka method.
Abstract: Theme 6