Preliminary analysis and solution for collapsed road embankment due to drought in Pak Phanang, Nakhon Si Thammarat

Abstract

The Bureau of Rural Roads 11 (Surat Thani) and the Bureau of Test, Research and Development, Department of Rural Roads, conducted the failure investigation of road embankment of Rural Highway NS4045 at Highway 4103 Ban Ban Ya, Pak Panang District, Nakhon Si Thammarat, where subsidence occurred along the edge of the road for a certain distance. This study aims to find the cause of the road failure and to give suggestion on an appropriate solution. The investigation made to use of geophysical surveys that included the Resistivity Survey and a Screw Driving Sounding test in order to evaluate the subsurface ground condition and to estimate the soil strength. The Plaxis 2D software was used to analyze the factor of safety for the slope stability of various conditions. The results achieved from the simulation demonstrated values of 1.10 for critical condition that the water level in the canal along the road is low with water pressure remains in the road embankment; and 1.30 for the condition that there is no canal presented along the road. The latter is considered stable and safe from road failure. This is also true and can also be seen in the area where there is no canal running along the road.