In the seven-year plan for development of the national economy of the USSR, bridge construction and the build- ing of hydrotechnical structures occupy a prominent place. One of the most importa. nt operations in such construc- tion is the laying of pile foundations. In recent years deep pile foundations have been developed, with heavy loads on the piling. This technique is necessary when penetrating dense sand-clay soils or when sinking the piles to hard rock. The operations are very laborious, requiring a. great expenditure of time and effort, and this Significantly low- ers the time of...