## 3 Hysteresis Curve Characteristics of GRS
### Effect of D-W Cycles on the Hysteresis Curve Parameters  
The morphological parameters for four groups of soils with different fines contents soil under seven D-W cycles were plotted in Figures 7-10 to illustrate in detail the effect of D-W cycles. Since the compaction effect of soil is obvious in the first 20 loading cycles, these parameters change do not fully reflect soil properties. In addition, excessive loading numbers also affect soil properties (see the green and grey areas in Figure 7a,b), and the center offset \(d\) and residual strain \(\varepsilon_{sp}\) mainly occurs at \(N<100\), after which they are close to 0. Therefore, \(N=20\) to 90 (blue area) is the load-interval that best represents the influence of the D-W cycle on soil properties. Figures 7-10 plot \(S\), \(d\) and \(\varepsilon_{sp}\) versus the numbers of D-W cycles for different fines contents. \(S\), \(d\) and \(\varepsilon_{sp}\) have a similar variation. With the increase of D-W cycles, they first decrease slightly at T0-3, then increase slowly at T3-5, and finally reach a relatively stable state at T5-7. Smaller values are usually reached at the 2 nd or 3 rd D-W cycle. Besides, when the fines content is high, the \(S\), \(d\) and \(\varepsilon_{sp}\) values of the 7 th D-W cycle are similar to those without the D-W cycles. From Figures 7, 8, 9 and 10b, it can be observed that the \(k\) fluctuates at T0-3, while there is a significant decrease at T3-5, followed by a gradual stabilization at T5-7. Compared to \(S\), \(d\) and \(\varepsilon_{sp}\), \(k\) shows an opposite variation as the D-W cycles increase. The major axis gradient \(k_{\rm{ave}}\) under different D-W cycles are calculated and listed in Table 4. The value of \(k_{\rm{ave}}\) first increases and then decreases. Usually, the range of \(k_{\rm{ave}}\) is larger at the later load stage than that at the early load stage. Figure 7: Variation of hysteresis curve parameters with D–W cycles (C0). Figure 8: Variation of hysteresis curve parameters with D–W cycles (C10). Figure 9: Variation of hysteresis curve parameters with D–W cycles (C20). The above variation may be explained as follows. As shown by the schematic diagram of the initial state of GRS in Figure 11a, the grain sizes of GRS are mainly between 0.5 mm and 0.075 mm, and the total amounts of coarse and fine particles are close, while the content of medium particles is quite low. Due to the small content of medium particles, the macrospores are larger and are filled by fine particles and pore water. At the beginning of D-W cycles (T2\(\sim\)3, see Figure 11b), the fine particles are dispersed, and the cementitious substances in the fine particles are dissolved in the water and partly lost with the migration of water [1, 55]. However, during the drying process, the fine particles re-combine and aggregate to form a denser soil skeleton [56], resulting in a soil energy loss, a reduction of plastic deformation and an increase in stiffness. In the middle of D-W cycles (T3\(\sim\)5, see Figure 11c), the intrusion of water makes fine particles expand and disperse into finer particles, weakening the adhesion among the fine particles in the wetting process. On the other hand, finer particles continue to be lost with the water migration in the drying process [57]. Ultimately, the soil structure gradually loosens, so it shows more +energy loss and plastic strain characteristics. At the later D-W process (T5\(\sim\)7, see Figure 11d), some coarse particles are broken into fine particles after undergoing the previous D-W cycles, and with the further dispersion of fine particles, the fine contents filled in the pores increase.