Study Of Duncan-Chang Model Parameters On Rockfill

The development of research on large-scale triaxial tests on rockfill and gravel is reviewed. Some aspects concerning their engineering properties are discussed. Then the research topic is proposed.Based on a large quantity of conventional triaxial tests, the properties of rockfill and gravels are studied extensively with particular attention to the model parameters of Duncan and Chang's hyperbolic elastic models. The ranges of the parameters are summarised on the laboratory experimental results. The influence of the void ratio, content of mudstone, and the properties of the rock are investigated and some valuable conclusions are drawn.The frictional angles φ is between 34⁴4 degrees and the failure ratio R_f is between 0.7 and 0.9. The deformation parameters k of dry specimens is generally higher than that of saturated one of the identical tested rockfill. The n and F ranges from 0.1 to 0.5, and 0.1 to 0.4, respectively. On average, G is less than 0.5 with the majority between 0.3 and 0.5, while D varies greatly from 1 to 8. k_b is approximately half of k varying from 100 to 300. The range of m is similar to n as between 0.1 to 0.5. φ₀ is roughly about 40⁶0 degree with the value of saturated rockfill larger than those of dry specimens and Δφ is about from 6 to 16 degrees, which is almost identical for all the tested rockfills.With the increase of void ratio, φ , n, k_b , m decrease and k, φ₀ and Δφ increase with minute variation of G and F . Some empirical values were obtained for the tested quartz rockfill with 0.77 and 0.80 for the saturated and dry specimens, respectively. The frictional angles increase with the growing coarse rockfill diameters. However, the higher content of the coarse grains does not necessarily mean larger frictional angles. The higher strength of the rock grains, the less compressibility of the rockfill specimens. The strength of rockfill from rounded gravels is higher than that of angular grains of the same properties. Meanwhile, the increasing content of mudstone generally results in a decrease in frictional angles.