INVERSE ANALYSIS OF GEOTECHNICAL PARAMETERS ON IMPROVED SOFT BANGKOK CLAY

Deformation, strength, and flow parameters were determined by inverse analyses on geotechnical data obtained from two full-scale test embankments constructed on improved soft Bangkok clay. One site was improved with prefabricated vertical drains (PVD), and an adjacent site was improved with compacted granular piles (CGP). In the PVD site, the ratio of c(h) (field) to c(h) (lab) ranged from 1.5-4, and the c(h) value was 4.90 m2/year. The value of k(h)/k(s) was about 10, with d(s)/d(w) of 2.5. In the CGP site, the ratio of c(v) (field) to c(v) (lab) ranged from 1.3-12. The smeared zone was considered by reduction to CGP diameter by one-fifth. The ratio of E(u) to S(u) was determined to be 150. The observed final settlements in the CGP site was 30-35% lower than those in the PVD site. Using back-analyzed soil parameters, the settlements of the test embankments were predicted well. Both ground improvement schemes are effective in improving the soft Bangkok clay.