How are dams built over the rivers? How pillars of dams are protected from the gushing water?
Rivers small enough are simply diverted around the construction site. Once the dam is built the river is re-diverted back to its original or nearly original course. In larger projects a combination of diversion and coffer dams are used. Coffer dams are temporary dam used to help shape the diversion. SOmetimes a section of the river is dammed on on side by a coffer dam and dikes, pushing the flow to the other side while construction is done. When possible the coffer dam is included in the final dam in some way. Pillars are protected by the forms built to hold the concrete while it is curing. THe forms, steel or wood, are forced down and anchored. The concrete poured into the form displaces the water up and out (or through side holes, pushed sideways) until the level need is reached. Having water in contact with the curing concrete actually helps it cure slower and better. Because the concrete is so dense there is no problem with mixing, the water stays out naturally. Of course, th concr
