Slope instability occurs in landfills owing to increased internal temperatures. However, strength characteristic tests for solid waste (SW) and landfill slope stability (SS) calculations that consider temperature variations are scarce in the literature. In this study, we conducted triaxial tests on SW under a range of temperature conditions and proposed the circular slide method (CSM) for calculating SS in consideration of temperature effects. SW cohesion decreased linearly with increasing temperature, whereas the internal friction angle remained essentially unchanged. Our results showed that higher temperatures reduced the SW shear strength, changing the most dangerous sliding arc away from the slope toe. The landfill slope safety factor decreased by more than 20% with an increase of the maximum temperature from 20°C to 50°C. Reduction of the leachate level (LL) led to a decrease in the landfill high-temperature zone and the safety factor increased according to LL and temperature distribution. If cooling pipes are used to control the SW temperature, we recommend arranging the cooling pipes on the landfill liner. The proposed CSM can be used to analyse landfill SS.
The increase in landfill temperature often results in shear strength reduction of both the solid waste and the liner, which leads to slope instability. However, very few landfill slope analysis methods can simultaneously consider the effect of temperature on the shear strength of the waste solid and the liner. In this study, based on the strength parameters of the liner and waste with temperature, a wedge method for translational failure analysis of landfills considering temperature increase was established. The results showed that rising temperatures caused by biochemical degradation at the bottom and middle of the landfill reduced the anti-slide force of back slope more than that of bottom slope. With the leachate level increasing, the effect of temperature rise on landfill stability became obvious. The feasibility of the proposed wedge method was verified by the engineering case study of Xiaping Landfill, Shenzhen, China. This study probably provides important guidance for the design, operation and management of municipal solid waste landfills.
A novel multifunctional ring shear apparatus is introduced in this paper, which is developed for investigating the interface strength characteristics of liner systems in various waste containment and other facilities. Annular specimens with a 300-mm inner diameter and a 500-mm outer diameter are tested by the apparatus. This apparatus consists of four components: (1) the vertical loading system, (2) the torsional shearing system, (3) the multifunctional shearing box, and (4) the process control and data acquisition system. The advantages of this apparatus are as follows: (1) The specimen can be tested both in displacement control and stress control, during which the normal stress is maintained or varied as needed. (2) The maximum normal stress and shear stress that can be loaded are 2.39 and 2.59 MPa, respectively. (3) The shear displacement is unlimited and the real-time shear displacement of each interface in the liner system can be obtained. (4) Special nail plate panels are developed for clamping different types of geosynthetics. A new adaptive telescopic pressure plate device is also developed for testing other materials, such as the clay layer and sand layer, and adapting to its compression deformation without lateral deformation. The performance of the apparatus is comprehensively evaluated by the conventional shear mode experiment and mode switching shear experiment of the textured geomembrane/geotextile interface and the conventional shear experiment of the composite liner system.
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