First paper published in the Chinese Journal of Geotechnical Engineering

Experimental research on compaction characteristics of gap-graded coarse-grained soils

This paper marks the beginning of Jidu’s research journey: his very first journal publication, completed under the supervision of Prof. Sihong Liu at Hohai University and published in the Chinese Journal of Geotechnical Engineering (岩土工程学报).

Coarse-grained soils with discontinuous (gap) gradations are common in geotechnical engineering, but their compaction behavior was not well understood. Through a series of laboratory compaction tests, we examined the main factors controlling the compaction of gap-graded coarse-grained soils.

The tests showed that, compared with continuously graded soils, missing particle sizes below d30 hinders compaction, while missing intermediate sizes can actually aid it. The dry density increases with the fractal dimension of the base gradation, with the best compaction at D = 2.5–2.7, and first increases then decreases with fines content. The optimal fines content depends on the packing densities of the coarse and fine fractions and on how they interfere with each other. Based on these findings, we proposed a model that predicts the maximum dry density of gap-graded soils from only a small number of tests, greatly reducing the testing effort required.