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| Box culverts used as flood guards  It is a frightening fact that most people who perish in the desert do not die of thirst but by drowning. While the scorching sun is shining from a cloudless sky it may be that far-away, and unnoticed a cloudburst happens in the mountains. Wadis are dry river beds with steep banks that may lie dry for years or even decades. They have always been used as a preferred traffic route to avoid the rough desert for the sake of convenience. When you are suddenly confronted with an onrushing wall of water, it may be too late already.Economic development is only possible with a suitable infrastructure. The capital of the Sultanate of Oman, Muscat, and Şuḩār, the country's two biggest cities, are lying in the north-east of the country on the Gulf of Oman and are to be connected via a multi-lane express way. The distance between the two is approximately 300 km. Construction begins at Şuḩār and runs to the south-east. There are many places where the future express way cuts across the alluvial deltas of wadis that run down from the mountain ranges; they are several kilometers across at their widest point. These pose a direct challenge to the construction companies. Soil conditions are irregular, future temporal and local variations of the rivers and their force are unknown and can only be determined statistically. A typical feature of these rivers is their varying bed load which includes all fractions ranging from giant boulders to fine sand plus any other objects that may be found in a wadi. This depends on the water's energy: It is at a maximum close to the mountains and at a minimum in the alluvial deltas. In the deltas several, up to a dozen wadis may be found running side by side. A typical construction site extends over 2-3 kilometers and employs up to 1400 workers which are housed in camps. There are two work shifts a day of 12 hours each, work is continuous round the clock. Due to high day-time temperatures concrete work is done mainly during night hours. Flooded roads are dangerous. The entire carriage way will cross the wadis elevated by several meters. The sub-structure consists of parallel tubular culverts made of on-site concrete, allowing the passage of water anywhere. The basis of the structure consists of base plates each 36 meters long and made of on-site concrete. Modular/GE Universal formwork from PASCHAL-Werk G. Maier with moving unit deployed as bridge formwork. write your comments about the article :: © 2011 Construction News :: home page |