ESTIMATING UNDRAINED SHEAR STRENGTH OF
SOFT CLAY GROUND IMPROVED BY PRE-LOADING WITH PVD
 -CASE HISTORY IN BANGKOK-

SATORU SHIBUYA  and L. T. HANH

 ABSTRACT: The installment of pre-fabricated vertical drain (PVD) combined with pre-loading is an efficient way to gain the prescribed strength and compressibility of very soft clay over a short period of time. This note describes case histories of such improvement performed in Bangkok. The change in undrained shear strength, s_u, before and after the ground ns of field vane test (FVT) and fiat dilatometer test improvement was investigated at two sites in Bangkok area by mea (DMT). The results of FVT showed that the s. value of soft Bangkok clay increased over nearly the full depth down to the tip of the PVDs. It is also demonstrated that DMT may be a useful tool for promptly assessing the change of s. in soft clay due to pre-loading. Applicability of the SHANSEP method in estimating the profile of s. with depth in recently overconsolidated clay ground after pre-loading is also discussed.

 Key words: case history, clay, dilatometer test , field vane test , ground improvement , shear strength (IGC:D5/D6/D7/C2/C6/Bl)