ANALYSIS OF CBR VALUES BASED ON DCP TESTING ON THE PENUMANGAN–UNIT VI ROAD SECTION

Abstract

The subgrade is an important component of the pavement structures as it receives and distributes the traffic loads thru the pavement layers. The bearing capacity of subgrade is low, which can accelerate the deterioration of pavement and reduce the service life of pavement. The objective of this research is to analyze the value of California Bearing Ratio (CBR) estimated from Dynamic Cone Penetrometer (DCP) testing and to evaluate the variation of subgrade bearing capacity in the Penumangan–Unit VI Road Section, West Tulang Bawang Regency. DCP testings were carried out at 24 observation points by using 8 kg hammer and 60° cone. The penetration data were converted to CBR values by using the appropriate DCP–CBR correlation provided in the Indonesian DCP testing guideline. The results indicate that the estimated CBR values are in the range of 5.87% to 8.26% with average value of 6.83%. The evaluation criterion of 6% indicates that there are 21 observation points (87.50%) that have a CBR value of at least 6% and there are three observation points (12.50%) that are below the criterion. The lowest values were recorded at STA 13+000 (5.87%), STA 14+600 (5.92%) and STA 16+600 (5.94%), while the highest value was observed at STA 14+800 (8.26%). These results indicate that the subgrade condition is generally adequate based on the chosen criteria, but there are still localized weak spots throughout the road section. Thus, DCP testing can be used as a rapid, low-cost field screening procedure to identify spatial variations of subgrade bearing capacity and to help prioritize further investigation and road maintenance.