COFFERDAMS WITH SPECIAL REFERENCE TO SRISAILAM PROJECT IN ANDHRA PRADESH

Abstract

This dissertation "Coffer Dams with Special Reference to sailam Project in kidhra Pradesh" deals with the various types 1 Hof ` coffer dams, the conditions under which each type is to . be /Jadopted and design aspects of these various types. The causes , ;/ / for failure of cofferdams have also been given. Some recent / texamples of coffeardam construction adopted elsewhere under condi- ~`~ % ! similar to that at Srisailam Project have been covered in bons this work. The eonv :ratio ,, types of, cofferdams were not suitable in evoivdng the type as finally adopted at Sr&sailam iroject. !geophysical investigations ,conducted in the deep channel. portion at Srisailam Damette rave ale that the thickness of the bouldary fill was about 120 . ft. (36 .8 M), near the 'Location of the up-stream cofferdam i.e 650,ft (198 Ma. upstream of the dam site) and reduced to about 10 ft (3,0 M) at 8o ft (2 9 I') downstream of the dam axis. _ The cofferdams were of the underwater type with standing .pool of water, of about 32 ft ( ► 75 14) on the up-. stream side and, about 46 ft. (f1,03 . on the downstream of the foundation . area of the dam in the deep channel portion. The optimum diversion discharge which would give maximum work .g period, while at the same time not involve too costly coffer-dams required overtopping of coffer dams during floods. AU these factors ultimately led to the adoption of under water construction of. eolerete coffer dams. The protective arrange-ment for overtopping of cofferdams required exhaustive model experiments which were carried out at Central Water and Power Research Station, Poona! The appects which required Careful consideration at various stages of design$ construction treatment and protection of cofferdams in order to keep the amount of see Page in the foundation area of the main dam to within the limits of dewatering by reasonable Dumping capacity have also been dealt in this dissertation.