Measuring production rate for the construction of the subgrade layer of a road

Abstract

The performance of the pavement is highly determined by the subgrade layer of the road due to the fact that it’s the lowest component of a road and it supports the load carried from the upper layers of the road laid on top of it. With the increasing investments by the government of Uganda in the road sector, it is therefore important to determine accurately the production rate of a road subgrade for accurate budgeting and scheduling purposes by the management. This research therefore focused on measuring work undertaken during the construction of the subgrade layer in order to come up with its production rate. A number of five construction sites were visited in Kampala metropolitan to measure the production rate of activities carried out for the construction of aa road sub-grade layer. The most major activities measured on site were excavation of the ground, laying and levelling of the soil and its compaction and their production rates computed for the different horizontal road profiles for a given section of a road. Probability distribution functions for the different activities was obtained using Easyfit and Monte Carlo simulation was then carried out on the probability distribution functions in Mathematica to obtain the total production rate. The study revealed that the total production rate proves the central limit theorem. A relative importance index was then assigned to the different road profiles and probability distributions fit to the RII values and Monte Carlo simulation carried out on the PDF. A linear regression model was then built with the road profile as the independent variable and the total production rate as a variable to predict the production rate for the construction of a road subgrade for the different horizontal road profiles.