Measurement of production rates for manual trenching on construction projects

Abstract

Trenches,a preliminary activity in construction for foundations, road drainage, laying utilities etc in most developing countries, particularly Uganda is done manually using tools such as hoes, pick axes, and spades. Production rates for various manual trenching techniques are essential for effective planning before commencement, however, there is still a lack of proper benchmarks. In response to this, a field measurement study was conducted with the main aim of finding factors affecting production rates for manual trench excavation in construction work and developing a simulation model to compute overall production rates. The study implemented factor analysis using Principal Component Analysis to develop a relative importance ranking of factor relevance using Minitab and provides a benchmark production rate for excavating trenches generated using Monte Carlo Simulation run in Wolfram Mathematica.PCA-factor analysis revealed three principal factors significantly affecting production rates: crew configuration, as the most significant, followed by weather conditions, and ground type with Euclidean distances of 0.845, 0.750, and 0.689 respectively. The less significant factors were soil type at the fourth position followed by the horizontal alignment, and the longitudinal slope category with Euclidean distances of 0.682, 0.626, and 0.624. The findings emphasize the importance of considering these factors to perfect manual trenching operations. The highest average production rate of 0.860 m3/hour/person was achieved by a 2-man crew under straight-flat alignment, with soft sandy-clay soils and a skilled crew. On the other hand, the lowest average production rate of 0.447 m3/hour/Person was seen for a crew working under straight-steep alignment, with hard gravel soils and dry weather conditions. The results from the Monte Carlo simulation identified the most probable production rate as 0.738 m3/hr/Person, with a standard deviation of 0.032 m3/hr/Person, kurtosis of 2.983 m3/hr/Person, and skewness of 0.379 m3/hr/Person.This study contributes to improving trenching processes, resource allocation, and decision-making in construction projects. On the business perspective, production rates are a key performance indicator andtracking them enables the business owners to analyse their performances, establish targets while setting standards for success and identifying areas of improvement.