Top-Down Construction Method: A Case Study For Underpass Structure in Qatar
الملخص
The Cut and Cover construction method has been applied to build several underpass structures within the expressway programme of the Highway Projects Department, Public Works Authority, Qatar. Booming in the construction industry contributes to increasing existing traffic in Qatar. This subsequently failed existing road junctions and required updating the road network parallel to the traffic studied. Underpasses and bridges were planned across many locations in Qatar to increase the level of service at road junctions, enhance the traffic capacity, reduce traffic congestion, and improve the free flow of traffic. This paper discusses the design and construction challenges of the underpass structure constructed by top-down construction method located on D ring Road in Doha, Qatar. The top-down construction method has been suggested by the construction contractor as an alternative to the conventional cut-and-cover construction method to minimize the traffic disruption and meet updated temporary traffic management (TTMs) due to underpass construction works, restore traffic at the junction on top of the underpass prior to the completion of construction works and overall optimize the construction duration. A numerical modelling research was carried out to study the change in arrangements. The site-specific challenges, such as modification in the structural arrangement of the underpass, change in ground conditions, lateral displacement of pile walls and dewatering challenges, are discussed in this paper.