With the increase in rainfall, landslides occur on many gentle slopes in the mountainous areas of southeast China. Gentle slopes have a particular dual geological structure, i.e., the lower part is a gravel soil layer with good water permeability, and the surface layer is clay soil with relatively poor water permeability. Under conditions of heavy rainfall, a gentle slope with this structure is likely to collect temporary confined water. The intermittent creep of the upper slope is caused by the floating force of the temporary confined water, which causes landslide disasters. The conditions that bring about temporary confined water are related not only to the stratum structure, but also to the rainfall intensity and the initial height of the water table level. On the basis of the characteristics of the stratum of the gentle slope landslide on the front of Fanshantou Mountain, we constructed a hydrological model in GEO-STUDIO. We investigated the effect of different rainfall intensities and initial water table levels on confined water under continuous rainfall conditions and conducted a corresponding stability analysis. The results show that when both the initial water table level and the rainfall intensity are high, temporary confined water is formed rapidly, increasing the chance of a landslide disaster. The research results provide a theoretical basis for the treatment of landslides on similar gentle slopes in the mountainous areas of southeast China.

We propose a plasmonic waveguide comprising a single-layer graphene, a silica dielectric layer, and a silicon grating substrate to realize dual-channel slow surface plasmon polaritons. The dual-channel results from the introduction of two kinds of periodic structures with defects in the waveguide. According to the Bragg equation, we match the appropriate structure parameters to ensure the slow light dual-channel working around λ 1 = 9369.1 n m (32 THz) and λ 2 = 7138.2 n m (42 THz). The influence of the structure parameters on the slow light effect is discussed, and the largest value of the normalized delay bandwidth product (NDBP) is up to 7.38. Then, by shifting the gate voltage, obvious linear blueshift of the dual-channel is achieved. In this process, the slow light performance of the dual-channel exhibits good stability, and the average values of the NDBP are 4.5 and 4.4. Due to the flexible tunability, the waveguide may pave the way for the design of slow light devices.

Siphon drainage, which is applicable in engineering as one of the effective methods to maintain slope stability, has many advantages, including no additional power requirements, simple construction, and low construction cost. However, due to topographic constraints and high farmland occupation costs, most projects inevitably use pipes with a total length of more than 100 m and horizontal sections of more than 50 m for drainage. The increase in pipe length has serious adverse effects on the siphon drainage process, limiting its drainage capacity and long-term applicability. Therefore, in slope siphon drainage, drainage efficiency and long-term effectiveness are critical factors in determining whether a particular pipe size can be used effectively for slope drainage management. This paper investigates the performance of different pipe diameters in drainage capacity, flow regime, and restarting ability under different head and pipe length combinations through theoretical analysis and extensive foot-scale model tests. It was found that a 5 mm pipe diameter, as a transitional pipe diameter between capillary and typical pipe diameter, has both capillary and gravity-dominated characteristics under different capillary and Reynolds number conditions, which can form a stable segmental plug flow while maintaining the presence of liquid film and preventing increased frictional losses along the course.

Slope siphon drainage is a convenient and efficient above-ground drainage method that is free of manual power and can effectively maintain the stability of potential landslides and prevent the loss of life and property. The complex engineering topography inevitably requires the use of siphon drains with a total length of more than 150 m and a horizontal section length of more than 80 m, which significantly increases the difficulty of calculating the drainage capacity and thus affects the actual utilization of the project. The traditional siphon flow rate equation does not apply to long-pipe siphon conditions, especially when the lift is close to the limit, and there are significant errors in the calculation results, for which we propose a new calculation method. The proposed method considers both air release and flow-pattern classification. Thirty-six sets of experiments were conducted to validate our proposed calculation method. The results showed that our method not only calculated the siphon flow velocity well but also predicted the main flow pattern in the siphon in the experiment well. Furthermore, the equation for calculating the siphon flow velocity was extended to the siphon operation mode with long horizontal sections.