Implications of Micro-Tunnelling on Wastewater Pipeline Constructions : a case study from Muscat Wastewater System: Al Khuwair Project

Kokila Ranasinghe

doi:10.4038/engineer.v48i2.6831

Abstract

Al Khuwair is a sub city located in Muscat in the Sultanate of Oman. It is presently growing rapidly with illustrious highways, modern housing complexes, commercial centres, hospitals, schools etc., being built. Even though the local population represents around 60% of the total population, developing infrastructure is an essential need in order to cater to the needs of both the local and foreign migrant population and also the tourists. The present trend of development of the city indicates that Al Khuwair would provide a considerable proportion of the Muscat's wealth. The yellow tankers roaming around the city are not uncommon in AlKhuwair even though it might surprise the visitors at their first glance. They enter every house and restaurant at least once a month in order to empty the septic tanks of those properties. It is also not uncommon to see overflowing septic tanks emitting in tolerable odours when tankers fail to arrive promptly to empty the overflowing septic tanks. The aim of the paper is to present the actual experience from Muscat Waste water Project that has been implemented in order to overcome the above mentioned most critical issue. It highlights the problems which surfaced with regard to pipe deviations, deflections and pipe cracking that occurred during the micro tunnelling of 1000mm diameter polycrete wastewater pipes. The attempts made to provide technical solutions for the deficiencies and possible alternatives to overcome the defective situations are comprehensively discussed in the paper.

Highlights

Horizontal Directional Drilling (HDD) and micro tunneling are two available "trenchless" construction methods used to install new pipelines and other facilities
To determine the sizes of the sewerage network pipes and their slopes, two more equations are recommended in the design code of practice. i.e Colebrook – White and Manning’s equations
The Al Khuwair component of the Muscat Wastewater Project reveals a number of important factors related to micro tunnelling of waste water pipes

Summary

Introduction

Horizontal Directional Drilling (HDD) and micro tunneling are two available "trenchless" construction methods used to install new pipelines and other facilities. One major advantage of trenchless pipeline construction is the freedom it provides to follow the most direct route between any two points provided the right-of way is available. Open-cut trench construction normally has to follow existing pipe utility easements, roadways or other unobstructed surface structures. Because HDD and micro tunneling are applied underground, these methods allow flexibility to go straight between any two points, even when this route traverses directly beneath utilities, structures, or other surface features. The applicability of HDD or micro tunneling for pipeline construction is primarily a function of the required pipe size and material, alignment tolerances, ground conditions and available staging areas. The selection of an appropriate method depends on the site conditions and project priorities

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Conclusion