3 Results
3.1 Shear resistance
The direct shear results shown in Fig. 3 demonstrate that the peak shear
stress of mudstone granules decreased with an increasing number of
dry-wet cycles when tested under both dry and wet conditions. Notably,
the variation in the original direct shear data was smoothed with the
fast Fourier transform method. Strain hardening behavior was observed
for the dry specimens: the shear stress increased rapidly and remained
constant near the peak strength without significantly decreasing with
increasing shear displacement. Although a wide normal stress range from
200 kPa to 1400 kPa was applied, dependance of the strain softening
behavior on the normal stress observed in Ma et al. (2019) was not
revealed within 20 mm of shear displacement. With increasing weathering
intensity, the drop in the peak shear stress of the dry specimens
increased at a higher normal stress. Compared with the mudstone, the
sandstone exhibited a greater reduction in the peak shear stress between
different normal stresses in the strain hardening curves after 6 dry-wet
cycles (Fig. 3 d).