STOCHASTIC COST INCREASE IN ROAD PROJECTS BY GEOTECHNICAL CAUSES AND COUNTERMEASURES AS AN INFRASTRUCTURE MANAGEMENT SCHEME

Abstract

 Generally, it is said that costs in road construction are increased from original budget plan by mainly geotechnical causes due to these uncertainties. However, the characteristics of cost increase by geotechnical causes has rarely been analyzed quantitatively. Therefore, in this study, the purpose is to clarify the characteristics of cost increase by geotechnical causes in road construction by means of statistical analysis with project evaluation reports (518 cases). The result of the analysis showed that 1) Two thirds of cost increase is caused by geotechnical causes, 2) The characteristics of cost increase by geotechnical causes is approximated by lognormal distribution, and 3) Two thirds of geotechnical causes are misestimation of geological conditions. Lastly, from case studies about geotechnical judgement and literature research about project evaluation method in England, proposals about the concept of countermeasures are suggested that 1) Statistical analysis about cost increase prospects should be positively implemented and 2) Geotechnical information should be more utilized by civil engineers.