Abstract:

Before building a dam in a river, cofferdams are needed to be constructed in advance. The most commonly used method of filling a cofferdam is to dump granular materials into the deep water and let the particles pack together by gravity. Granular materials such as sand, sandy gravel and ballast are often used as the main packing materials, and the density formed by underwater packing of granular material is the key parameter for cofferdam design. Since the density cannot be obtained directly by sampling or calculation owing to the lack of theoretical or empirical solution, it has become an unsolved problem in the design and construction of cofferdam. In view of this, through analyzing the density’s influencing factors we conducted centrifugal model tests on 3 typical granular materials (sand, sandy gravel, and ballast) to measure the densities under different conditions, and investigated the influences of particle figuration, size and gradation on the density. On the basis of the test data, some insights about the particle packing underwater are summarized, and a tentative formula to estimate the particle aggregate density is proposed.

Key words: granular material, cofferdam, density, centrifugal model test