EVALUATION OF THE PVD PERFORMANCE AT THE SECOND BANGKOK CHONBURI IDGHWAY (SBCH) PROJECT

Abstract

The soft Bangkok clay foundation  at the Second Bangkok Chonburi  Highway Project   (SBCH)  was   improved   using  prefabricated   vertical   drains   (PVD).   Monitoring instruments such as surface settlement plates, deep settlement plates, inclinometers and piezometers were installed in the subsoil in order to observe the deformation behavior of the embankments   under  loading.  The  Department   of  Highways,  Thailand,  arranged  for  the monitoring and documentation of the deformation behavior. These monitored records, supplemented  with  the laboratory  test  results,  were  analyzed  in order  to verify the in-situ horizontal coefficient of consolidation  of the soil as well as the rate and amount of settlement. The maximum surface settlement was calculated using one-dimensional consolidation  theory, Skernpton-Bjerrurn method, as well as Asaoka's method. In addition, a one-dimensional  FEM computer  software,  capable  of  calculating  the  consolidation  of  multi-layered  soil,  named PVD-SD was also used successfully to predict the rate and amount of settlement. Finally, the monitored deformation behavior was compared with the predictions during the design stage of SBCH to evaluate the performance of PVD. The amount of settlement predicted by Asaoka's method was in excellent  agreement  with  the observed  values, whereas  the one-dimensional consolidation  method,  Skempton-Bjerrurn  method  and the  PVD-SD  FEM  method  showed some overprediction. The  PVD performance  at SBCH  Project confirmed  and validated  the ground improvement by preloading and drainage on soft Bangkok clay.