được mô tả trong hình. 13,20, trong đó minh họa các đặc điểm thay đổi khối lượng phù sa không bão hòa, đầm. Khối lượng các chỉ số thay đổi (Le., C, Cm, D, và 0,) có thể được tính từ hình. 13,20. Thay đổi trong tỷ lệ vô hiệu và hàm lượng nước do sự gia tăng căng thẳng tổng số | 382 13 MEASUREMENTS OF VOLUME CHANGE INDICES Ỉ . Silt dry of optimum I _ _ WOG avg e0 avg. - ua - Uw 225 kPa 0 I IĨ in o Legend PP3DS ST1 X ST 2 Slope DmG. wGs vs increasing u - uw ST 3 ST 4 ST 5 10 102 103 10 10 10 Matric suction us uw kPa Figure Soil-water characteristic curve obtained from a pressure plate test on a silt compacted dry of optimum water content. Till dry of optimum w e 0 wGa b Figure Results from shrinkage tests on compacted silts and glacial tills a Shrinkage test data for the compacted silt b shrinkage test data for compacted silts and glacial tills. de d wGs or de d ua - uw d wGs d ua - uw is equivalent to the ratio of volume change indices . Cm DmGs The combined plot of Figs. and curve 2 . constructed from Figs. and a is depicted in Fig. which illustrates the volume change characteristics of an unsaturated compacted silt. The volume change indices . ct Cm D and m can be computed from Fig. . Changes in void ratio and water content due to an increase in total stress or matric suction can now be predicted using the computed volume change indices. The same test procedures were applied to other compacted silt and the glacial till specimens. Figure b summarizes the results of shrinkage tests on various compacted specimens. Typical volume change relationships for the compacted silt and glacial till are presented in Figs. and . The relationships are similar to that shown in Fig. . The computed volume change indices for the compacted silt and glacial till are tabulated in Table . These indices can be converted to other volume change coefficients such as mx and mì or a and b as explained in Chapter 12. In summary oedometer tests pressure plate tests and shrinkage tests are the experiments required to obtain the volume change indices corresponding to the loading of an unsaturated soil. .
