Abstract:

Material grading design, dam zoning and filling design criterion are the basis for dam material design and evaluation in gravel dam projects, which currently rely heavily on engineering experience. In this paper, the typical gradation envelope range of actual engineering dam sand and gravel materials are first analyzed based on the statistics on gravel grading envelope and field dry density from typical engineering dams. Then, the distribution intervals of key gradation characteristic parameters are given, and the influence of gravel gradation characteristics on compaction properties is studied. The results show that: i) The maximum particle size of typical dam-building sand-gravel grading is 400−600 mm; the gravel content of the common grading envelope is 70%−88%; the curvature coefficient is 1−10; the non-uniformity coefficient is more than 5; and the parameters b and m in the gradation equation range from 0 to 0.9 and 0.2 to 1.0, respectively. ii) The gradation of sand-gravel material that can obtain higher filling dry density should satisfy: the gravel content is 70%−85%; the curvature coefficient is 1−10; the inhomogeneity coefficient is greater than 5; and the b-value and m-value of the gradation equation parameters are 0.7−0.9 and 0.6−0.9, respectively. iii) Gravel content, curvature coefficient, inhomogeneity coefficient and maximum particle size all have significant influences on the dry density, and the degree of effect decreases in order.

Key words: gravel dam, grading envelope, grading characteristic, compaction characteristic