Analysis of subsidence zone of the village access road in Jatirunggo, Semarang Regency using microtremor data

The rehabilitation of the subsidence phenomenon in Jatikurung sub-village, Jatirunggo village, Pringapus Subdistrict, Semarang Regency, Central Java, has been carried out for a long time however, it has never been successful. Every time an embankment is made, it is only a matter of time before another subsidence occurs. This research aims to investigate the subsurface structure of the subsidence sites. It is proposed to be used as a reference for structural planning in the treatment of road subsidence. Subsurface information is very useful in addressing the subsidence problem more effectively and precisely. The method used was by recording microtremor data and analyzing shear wave velocity and Poisson ratio as parameters to determine the type of subsurface layer. The obtained results are in the form of clay layers to bedrock layers at a depth of 35m. The movement occurred because of the soft or loose soil below and at the edge of the road above the impermeable clay layer. In addition, to the north side of the collapse point is a fairly deep cliff, which is a burden on the bedrock. When it was raining, the soil filled with water and there was even a flow of water in the soil deposits (piping) resulting in the ground movement toward the lower part.