Abstract
We focused on soil properties that appear to affect the strength of a surface and bed of a strip road. In addition, we clarified whether the properties of different soils caused differences in the strip road strength. The study area was a place covered by pyroclastic fall deposits in Numata City, Gunma. Two plots that were set in the same strip road were compared, and plot 1 was found to contain a lot more gravel but less clay and silt than plot 2. A difference in the Nd-values or dry densities was observed when a penetration test and a soil density test were performed. The difference in the values was attributed to the amount of gravel included in the soil. Further, a smaller difference in the compaction degree was observed between the two plots. This is because the operator increased the working hours for compaction in plot 2 so that the compaction degree in each plot was identical. In terms of bearing capacity using a simple instrument, plot 2 had a higher value than plot 1 in the cutting-side rut. The tendency observed in this case was opposite to that observed in other tests, but plot 1 had higher values in the fillingside rut, similar to the tendency observed in other test results. When the soil properties are unsuitable for compaction, it is important not to construct the road the strength of which is partly low by improving the poor soil properties through the use of soils suitable for compaction.
