Longevity of stepped spillways and their adaptability to installation

Abstract

Stepped spillways are a modern and promising technical solution from positions of longevity and adaptability to installation.Stepped spillways and water outlets have been known for some time, and have been constructed in various countries under various climatic conditions. The stepped shaped of the spillway surface has been predetermined primarily by the tendency to prevent destruction of river channels beyond the spillways and damages sustained by buildings and structures located near them downstream along the rivers.Longevity of stepped spillways. In countries with a warm climate, some of these structures, which are formed from stone masonry in a limestone grout, have existed and operated for hundreds of years, despite the fact that they have been frequently subjected over time to percussive effects from floating bodies and drift. In Iran, for example, a stepped spillway of a hydroproject constructed almost 1000 years ago is still in service [1].At the turn of 19 th century, a number of hydroprojects were established in southern countries for the construction of cement-concrete and reinforced-concrete dams. On the island of Cyprus, in addition to masonry dams, several concrete gravity dams 30 -40 m high were built with stepped spillways. With their vertical thrust faces, the downstream faces of these dams have a slope of 1:0.70 -1:0.75, despite the fact that a significant portion of the load on the dam is created by drift that settles in the low-volume reservoirs. These dams are already more than 50 -60 years old, and, moreover, although they are situated on mountain rivers fed annually by freshets carrying drift, and brush and trees, they have never been repaired during that time [2].A number of different modifications of stepped spillways and weirs, many of which are still in service, had been constructed long ago in our country. For example, moreover, more than ten of these structures are situated in St. Petersburg and its environs alone. The spillway dam built in the 18 th century at the reservoir impounded for the Sestroretsk Armament Plant (Fig. 1), the three-and five-step spillways, which were constructed between 1820 and 1822 at the reservoir for the Izhora Plant, and finally, the multiple-step weir for the Great Cascade of Petergof Fountains, which was built by order of Peter I in 1709 -1720, i.e., 300 years ago, are most familiar. During WWII, the fascists destroyed and pillaged the whole of Petergof. As early as 1947 -1950, however, the Great Cascade of Fountains, including the multiple-step weir with its reinforced-concrete structures, had been completely restored. As before, it is still considered one of the most beautiful of similar structures in the world, and has already existed for more than 60 years in its restored form.The fact that the above-enumerated long-servicing spillways are operating under extremely unfavorable climatic conditions is deserving of mention. With a mean-annual air temperature of +3 -4°C in the neighborhoods of St. Petersburg and the Leningradskaya Oblast', the number of ...

Determination of Adhesive Strength Layer’s Roller Compacted Concrete the Method Axial Extension

“…Одной из основных проблем, возникающих в процессе роликового уплотнения бетонной смеси, является необходимость обеспечить требуемую прочность сцепления слоев бетона между собой [12][13][14].…”