The coupling effects of rainfall, earthquake, and complex topographic and geological conditions complicate the dynamic responses and disasters of slope-tunnel systems. For this, the large-scale shaking table tests were carried out to explore the dynamic responses of steep bedding slope-tunnel system under the coupling effect of rainfall and earthquake. Results show that the slope surface and elevation amplification effect exhibit pronounced nonlinear change caused by the tunnel and weak interlayers. When seismic wave propagates to tunnels, the weak interlayers and rock intersecting areas present complex wave field distribution characteristics. The dynamic responses of the slope are influenced by the frequency, amplitude, and direction of seismic waves. The acceleration amplification coefficient initially rises and then falls as increasing seismic frequency, peaking at 20 Hz. Additionally, the seismic damage process of slope is categorized into elastic (2-3 m/s2), elastoplastic (4-5 m/s2) and plastic damage stages (>= 6.5 m/s2). In elastic stage, MPGA (ratio of acceleration amplification factor) increases with increasing seismic intensity, without obvious strain distribution change. In plastic stage, MPGA begins to gradually plummet, and the strain is mainly distributed in the damaged area. The modes of seismic damage in the slope-tunnel system are mainly of tensile failure of the weak interlayer, cracking failure of tunnel lining, formation of persistent cracks on the slope crest and waist, development and outward shearing of the sliding mass, and buckling failure at the slope foot under extrusion of the upper rock body. This study can serve as a reference for predicting the failure modes of tunnel-slope system in strong seismic regions. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Bedding slope is a typical heterogeneous slope consisting of different soil/rock layers and is likely to slide along the weakest interface. Conventional slope protection methods for bedding slopes, such as retaining walls, stabilizing piles, and anchors, are time-consuming and labor- and energy-intensive. This study proposes an innovative polymer grout method to improve the bearing capacity and reduce the displacement of bedding slopes. A series of large-scale model tests were carried out to verify the effectiveness of polymer grout in protecting bedding slopes. Specifically, load-displacement relationships and failure patterns were analyzed for different testing slopes with various dosages of polymer. Results show the great potential of polymer grout in improving bearing capacity, reducing settlement, and protecting slopes from being crushed under shearing. The polymer-treated slopes remained structurally intact, while the untreated slope exhibited considerable damage when subjected to loads surpassing the bearing capacity. It is also found that polymer-cemented soils concentrate around the injection pipe, forming a fan-shaped sheet-like structure. This study proves the improvement of polymer grouting for bedding slope treatment and will contribute to the development of a fast method to protect bedding slopes from landslides.

The undisturbed soil in the slip zone is highly water sensitive. Elucidation of its strength properties and degradation mechanism is important for assessing the stability of slopes with bedding planes parallel to the slope. For this purpose, a series of direct shear test, ring shear test, scanning electronic microscope (SEM) test, and nuclear magnetic resonance (NMR) test were conducted on undisturbed slip zone soil samples sourced from a typical bedding slope along the Mabian River. Finally, an evaluation method of the bedding slope stability was investigated. The results show that the shear strength of undisturbed slip zone soils under saturated softening degrades sharply within the first hour. During this period, the moisture content of slip zone soil increased by 79.6%, and the cohesion and internal friction angle decreased by 45.0% and 36.2%, respectively. The occlusion of coarse grains in the slip zone soil hinders the formation of the shear plane, thus transforming the occlusal friction into sliding friction under saturated softening, leading to an obvious characteristic strain softening. The decreasing shear strength of the slip zone soil is caused by the shear failure of its internal structure. Under saturated softening, cementation between solid grains is destroyed when clay minerals are swelled by water absorption. Furthermore, the NMR shows the increase in the volume of small pores in the samples under submerged conditions, indicating a more losing structure, which provides a reasonable explanation for the significant strength degradation of undisturbed samples. A quantitative relationship is proposed for the bedding slope stability considering the effect of saturated softening.