Subsurface monitoring of P.79 – P.82 LUSI embankment using GPR method to locate subsidence and possible failure

LUSI (Lumpur Sidoarjo) mud volcano has been erupting solid and liquid materials for more than 7 years since its birth. The sudden nature of this phenomenon and land subsidence observed around the big hole requires immediate and precise management. Embankment built around it needs proper monitoring to observe the subsurface condition in order to avoid sudden failures. GPR monitoring, being non-destructive and easily applicable is conducted continuously in P.79-P.82 embankment since it collapse in December 2010. The research shows subsurface cross section during the timeline of March 2011-October 2013 which displays the difference of embankment condition, notably at rainy season in December 2012 when the embankment at its weakest where subsidence was observed at the surface. Correlation with Standard Penetration Test (SPT) data gives initial input for data acquisition. Comparison with other part of embankments shows that though essential, rain water permeating into the embankment is not the only deciding factor of the failure.