Abstract: The unit weight of earthwork backfills is the key index to evaluate the backfill quality. It is both time and labor consuming to estimate the unit weight by the traditional method, and the test results are significantly affected by the operation factors. In this paper, a large-scale earthwork backfills test results of Ezhou Huahu airport project are presented. The wave velocity of the multi-channel transient surface wave of the compacted backfill material and the dry density results obtained by the traditional irrigation method are compared and evaluated. It is found that there is a good linear relationship between both methods. Therefore, a new method and its calculation formula for estimating the unit weight of the backfill material by the transient surface wave velocity are proposed. Meanwhile, based on the results of many fields screening tests, the applicable boundary conditions for the new method are also recommended. The results of this paper provide an experimental basis for the application of transient surface wave method in the accurate determination of the earthwork quality.

Key words: transient surface wave method, earthwork backfills, dry density, grain size distribution