Evaluating the in-situ hydraulic conductivity of soft soil under land reclamation fills with the BAT permeameter

In-situ tests were undertaken with a BAT permeameter as part of a hydrogeological study to determine the horizontal hydraulic conductivity of Singapore marine clay at Changi. BAT permeameter tests were undertaken in marine conditions prior to land reclamation at a Test Site. An additional series of tests were undertaken after land reclamation and subsequent ground improvement works with prefabricated vertical drains after 23 months of surcharge loading. The BAT permeameter results were compared to laboratory test results carried out using a Rowe consolidation cell as well as hydraulic conductivity tests interpreted from other in-situ dissipation tests including Piezocone Penetration Test (CPTU), Dilatometer Test (DMT) and Self Boring Pressuremeter Test (SBPMT). The BAT permeameter was found to be suitable for horizontal hydraulic conductivity measurements. The BAT permeameter has the advantage that it measures horizontal hydraulic conductivity directly whereas other in-situ test methods require the introduction of additional parameters to evaluate the hydraulic conductivity indirectly. The horizontal hydraulic conductivity measured using the BAT permeameter was however lower than that expected which is attributed to smear effect. The horizontal hydraulic conductivity was found to decrease in the vertical drain treated area as compared to the prior to reclamation results which is attributed to the significant void ratio reduction at the vertical drain treated area.