Effect of elevated temperature on solid waste shear strength and landfill slope stability

Abstract

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.

Effect of gas pressure on municipal solid waste landfill slope stability

“…Larger amounts of kitchen waste are received by landfills in Asia than by landfills in Europe and North America, meaning that leachate is generated more quickly in landfills in Asia than in Europe and North America (Gao et al, 2015). The LL is, therefore, generally high in MSW landfills in Chinese and other Asian cities (Jayaweera et al, 2019;Merry et al, 2005;Shi et al, 2020;Somani et al, 2020;Zhan et al, 2008). In this study, the LL was set to 10 m from the landfill top and 40 m from the landfill bottom.…”

Wedge method for landfill stability analysis considering temperature increase

“…According to the temperature-controlled triaxial test results of the degradation-limited synthetic waste, the composition of which is referred to the on-site waste (the dry density 0.66 g cm -3 , the specific gravity 1.982, and the void ratio 2.0; containing 24% kitchen waste, 12% paper, 5% bamboo, 4% fibre and 12% plastics), Shi et al (2020) provided linear relationships between strength parameters and temperature at different axial strains. This article adopted these hypotheses and set ε a = 15% as the failure strain (Towhata et al, 2004), in which case the cohesion of MSW decreases with an increase in temperature by 0.483 kPa/°C.…”

“…Compared with the passive wedge, the active wedge is easier to slide along the back slope because β > θ; thus, the friction angle of back slope slip surface is more critical to wedge stability than that of bottom slope slip surface; as a result, the ratio of back slope inclination to the frictional coefficient, tanβ/tanδ 20 , can be chosen to represent the mechanical property of the slip surface. In the case of the active wedge sliding through the waste fill, the study of Shi et al (2020) has revealed that ϕ sw changes little with temperature; thus, δ 20 = ϕ sw . The change of tanβ/tanδ 20 reflects the effect of different liner materials or the waste composition change due to degradation on the mechanical property of slip surface.…”

“…Stark et al (2010) analysed the stability of a hypothetical MSW landfill with shear strength parameters of thermally degraded MSW and found that thermal degradation and elevated gas and leachate pressures create a positive feedback loop, resulting in a significant reduction in the factor of safety (FS). Shi et al (2020) proposed a circular slide method for calculating landfill stability in consideration of temperature effects. Kumar and Reddy (2021) studied the effect of the temperature along the bottom liner on the short-term and long-term stability in a composite bottom liner system in MSW landfills using numerical analyses.…”

“…Effectively analysing temperature variation inside a landfill will not only contribute to a good understanding of the ongoing biochemical reaction in the landfill but also help designers and operators assess the landfill stability properly (Jafari and Stark, 2016; Jafari et al, 2014; Shi et al, 2020; Stark et al, 2010). The temperature in a landfill is affected by factors such as landfill process, climate condition, municipal solid waste (MSW) composition and water content (Yeşiller and Hanson, 2003).…”