ABSTRACT:

Citatah landslide was indicated at the section of Km 23, from Bandung Ð Jakarta main road, West Java, Indonesia. Its dimension is approximately 200 m long located at the medium to steep morphology. This present activity affects the roadway, which pass through the landslide body. The detail engineering geological and geophysical investigation have been done in order to study the behaviour of soil and rock creep at Citatah landslide. Resistivity analysis shows that the unstable soil layer has resistivity between 23 Ð 25 W m, the interlayer of clay, silt and sandstone have resistivity between 7 Ð 17 W m, claystone between 2 Ð 7 W m, and andesitic rock, as a sill, is between 40 Ð 85 W m. The rock analysis observed from shallow drilling hole shows correlation with the resistivity of the rock types. The layer of claystone found at the depth of 9 m, within bore hole 1, is indicated the value of resistivity between 3 Ð 7 W m. Within bore hole 2, claystone found at the depth of 14 m. These claystone layers are interpreted as sliding planes. This result of investigation could be considered for the mitigation of landslide around this area. So the proposed road is suggested to be placed on the andesitic rock which is situated in between the claystone layers belong to Batuasih formation.

INTRODUCTION

Most of Indonesian areas were covered by the youngest formation of the Quaternary deposits. Moreover, the volcanic belt passing through Sumatera and Java islands, Nusa Tenggara and Maluku archipelagos, and North Sulawesi, creates many unstable areas which may cause geological hazards including land movement. The Citatah area, in which the study was carried out, located at West Java Province, passed by road connecting Jakarta and Bandung. This area constitutes one of landslide zones in West Java.

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