GPR application to investigate soil crack persistence in Cianjur landslide

Cianjur region, located in West Java, is one of regions in Indonesia with high intensity of rain, where medium land movement may be inevitable. The presence of joints on sandstone outcrops conducts as water access and accelerates weathering process. The survey aims to study the continuity of the soil cracks that develop in the body of slope its density. This survey used Ground Penetrating Radar method to study landslides in both favorable and unfavorable light. Ground Penetrating Radar, GPR, is the method that adopts electromagnetic wave propagation to map subsurface properties. GPR is one of the effective methods to delineate subsurface with the highest resolution in the shallow depth, even it has highly variation results corresponded to complex of geological features and clay-rich materials. The result section showed soil crack continuation into deeper part of the layer with GPR's frequency 40MHz, most of section then showed the crack occurrence is dominated in the upper 200 ns. Crack density could be affected by mineral composition and other factors. This study resulted two lines GPR data which has different altitude. Line A which is lower than Line B has loose crack density rather than B, about approximately 40%. The area was approximately affected by landslides that usually exhibited dramatic spatial and temporal variations of lithological and hydrogeological conditions. It will need further survey to know the effect of soil crack toward the sliding surface of the landslide from other surveys.