The W–D, F–T, and W–D–F–T cycles si

The W–D, F–T, and W–D–F–T cycles significantly affect the macroscopic and microscopic characteristics of the swelling mudstone. With an increasing number of cycles, the volume of the samples decreases after W–D cycles, but increases after F–T cycles and W–D–F–T cycles.The stress–strain curves of untreated samples display strain-stabilization or strain-hardening behaviour, but they exhibit strain-softening behaviour after cyclic climatic treatments. The greatest reduction in shear strength is observed in samples treated by the greatest number of climatic cycles at the lowest confining pressure. In addition, with an increasing number of treatment cycles, the cohesion of the samples decreases, whereas the internal friction angle slightly increases, which can be caused by the formation of cracks and large voids, and the increasing aggregate size and density. The shear strength parameters are influenced more by the W–D–F–T cycles than by the W–D cycles or F–T cycles. The variations in the shear strength parameters due to W–D–F–T cycles are less than the superpositions of those due to W–D and F–T cycles.The variations in the electrical resistivity subjected to different cyclic treatments exhibit distinct trends. The electrical resistivity significantly increases with increasing number of W–D cycles, while the electrical resistivity decreases due to the effects of F–T and W–D–F–T cycles. This phenomenon is likely related to the various volume changes during cyclic treatments. The relationship between the electrical resistivity and porosity can be effectively expressed by a power function, which suggests that electrical resistivity can be used to assess deformation.With an increasing number of cycles, the P-wave values of the samples treated by the three cyclic processes decrease and the variation due to the W–D–F–T cycles are more significant, which is attributed to the cracks and voids induced by the cyclic treatments. Strong correlations between the shear strength parameters and P-wave velocity are obtained by exponential regression. Notably, the P-wave velocity can be used to predict the shear strength of weathered mudstone after rainfall events and to assess the slope stability.