Evaluating Degree of Consolidation of Soft Soil by Using Asaoka, Hyperbolic and Back Analysis Method-Paper

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The study evaluates consolidation of soft marine clay beneath a 100-hectare reclamation project at Uran Creek, Maharashtra. The clay deposit is approximately 10–24 m thick and was improved using prefabricated vertical drains (PVDs) and surcharge preloading. Settlement was monitored with ground settlement markers, which record settlement in both clay and fill, and magnetic extensometers, which measure clay settlement.<br /><br />Field measurements from four instruments were analyzed using three methods: Asaoka’s observational method, the hyperbolic method, and back analysis, which adjusts geotechnical parameters so calculated settlement matches observed settlement. The measured settlements ranged from 625 to 1,006 mm.<br /><br />The estimated degrees of consolidation varied by method and instrument. Asaoka’s method yielded 93.7–98.7%, while the hyperbolic method gave lower, more conservative estimates of 87.5–91.2%. Back analysis estimated 93.6–95.1%. Asaoka’s and back analysis produced broadly comparable predictions of ultimate settlement, whereas the hyperbolic method generally predicted larger ultimate settlements and lower consolidation.<br /><br />The authors conclude that Asaoka’s method is a practical preferred approach for estimating consolidation from field settlement records: it is relatively quick and simple, and its predictions were close to those from back analysis. Back analysis can provide useful results but requires accurate clay-depth information at each instrument location, which may be difficult to obtain.

Keywords

soft marine clay

consolidation

reclamation project

prefabricated vertical drains

surcharge preloading

settlement monitoring

Asaoka method

hyperbolic method

back analysis

degree of consolidation