Abstract: The basic characteristics of the gravel-sand binary structure such as Guilin was evaluated by sampling at the first terrace of Lijiang River and the collected samples were divided into nine different grain size groups throughout the sieving analyses. By using the in-house developed erosion deformation test device, the samples with the same gradation were prepared with the compaction in lifts. Under the condition of the same degree of compaction, the influence of different moisture contents on the seepage erosion failure of in the gravel-sand binary structure was evaluated by controlling the moisture content of sand samples. The test results show that the moisture content has a great influence on the erosion speed, and when the fine sand and the gravelly sand are at the optimal moisture content, the erosion speed is relatively low. At the same time, the test results show that the influence of the moisture content on the stability gradient of the erosion velocity is not obvious.

Key words: gravel-sand binary structure, moisture content, degree of compaction, erosion speed