Short-term behaviour of propped walls at Doha airport station, Qatar

The New Doha international airport terminal station box in Qatar was constructed within the weathered Simsima Limestone where geotechnical properties relating to retaining wall design were not well understood. In order to reduce the construction programme to meet the scheduled airport opening, conservative geotechnical parameters, derived from available site investigation data within the region, were adopted for the preliminary design and subsequently revised as more comprehensive site investigation data became available. Accordingly, the structural instrumentation and monitoring programme was implemented to facilitate the design and construction verification process. This paper describes the performance of the instrumented diaphragm walls and props in the central section of the box. Permanent large-diameter reinforced concrete props were adopted at roof and mezzanine levels. An additional level of temporary strutting was required between mezzanine and base levels owing to the significant vertical span between these levels. Design predictions are compared with field measurements. Back-analyses have also been undertaken to permit a better understanding of the geotechnical properties and assist future design in similar ground conditions. These analyses demonstrated that wall deflections are sensitive to the assumed pore-water pressure conditions. Moreover, a Mohr–Coulomb model, with small strain stiffness for limestone/mudstone, is sufficient to capture the wall behaviour.