Multilevel schemes for the layout of temporary and permanent spillways are presently used in the construction of high-head hydrodevelopments.Such schemes, corresponding to the technical level attained by Soviet gate construction, provides the release of considerable flows over a wide range of heads up to 100-130 m. The number of levels of spillway structures at high-head hydrodevelopments can be reduced by using high-head gates.This can effect a considerable economy, especially in the case of spillway tunnels, since the cost of each level amounts to 10-20 million rubles.At present designs have been developed for deep, mainly vertical-lift and radial gates which can operate satisfactorily under heads to 200 m for opening areas of up to 30 m 2. However, if the temporary discharges during construction are great, the spillway is built with a large number of openings, which adversely affects the hydraulics and leads to an increase in the spillway face, rock excavation, and capital expenditures. Therefore, the need for creating high-head gates covering openings greater than 30 m 2 at heads to 200-300 m is quite pressing.
This article gives a general idea of the design and method of static calculation of the foundation of a mediumhead spillway dam on shell piles constructed on a nourock base.*The design of a dam on shell piles which guarantees its static stability is depicted in the following form (Fig. i). The upstream face, rigidly joined with the spillway slab, consists of shell sheet piling which is placed along the entire length of the upstream face of the dam. All locks of the sheet piles are cemented with the exception of those in the axial plane of the piers, where they are not filled with mortar but with a bituminous material for independent movement of the wall sections. The sheet piling is embedded into the ground and is nowhere directly connected with the pier foundations; it transmits the load on them only through the spillway slab, projections of which freely pass into the grooves of the piers. This design permits assuming the sheet piling undergoes plane bending, which protects the lock joints.The bottom on the lower pool side immediately beyond the dam is reinforced with rock fill. The calculated surface of the base (CSB) is taken with consideration of local scour and possible zones of shear and heaving of the soil. The spillway slab over the length of the upstream face also has two joints on the axes of the piers. It is made with a nose to divert the stream from the structure. The upstream edge of the spillway dam is made monolithic with the sheet piling and its end projections rest on the foundation parts of the piers. Asphaltic filler blocks are placed in the joints on its upper-pool side.The foundations of the piers are tall pile grillages composed of separately standing vertical and batter shell piles which permit a fuller utilization of the bearing capacity of the foundation. The piles are connected by a single pile superstructure passing into the pier, in the base of which are grooves for the projections of the spillway slab. This permits us to regard the pier and foundation as a single disk, which is taken to be rigid in the calculation.The static calculation of the foundation of the spillway dam on shell piers can be reduced, with certain assumptions to a plane problem with forces collected within one span. The calculation scheme represents a tall pile grillage connected by a rigid spillway slab with the sheet piling perpendicular to the working axis of the grillage.
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