This paper investigates the thermo-mechanical volume change behavior of municipal solid waste (MSW) by conducting drained heating–cooling tests at constant stresses and isothermal consolidation tests using a temperature-controlled triaxial apparatus. The experimental results show that the compression and swelling indexes of MSW specimen were temperature independent, and the heating-induced volumetric contraction was partially reversible upon cooling. Different from conventional soils, the thermally induced reversible and irreversible volumetric strains of MSW were much larger and stress level dependent. Apart from the experimental study, an isotropic thermo-elastoplastic constitutive model was developed in the framework of existing modified Cam-clay model, which allows the prediction of thermally induced volume changes of MSW. An important feature in this model was the derivation of thermally induced plastic volumetric strain based on the concept of equivalent stress. The capability of the proposed model was validated against the experimental results and showed good predictions. This paper serves as the first attempt to study the thermo-mechanical volume change behavior of MSW, and has provided additional data for the serviceability evaluation of existing pipes as well as settlement and capacity estimation of MSW landfills at elevated temperatures.

The exploration of gas pressure and its distribution in landfills is a principal concern for the design and management of municipal solid waste (MSW) landfills. A one-dimensional analytical model was proposed to simulate a vertical gas flow in a landfill with layered MSWs. The transient analytical solution was obtained by the method of superposition and eigenfunction expansion and verified by a semi-analytical solution and numerical simulation. According to the results of a parametric analysis by the transient analytical solution, a vertical gas flow in landfills can be simplified to a quasi-steady-state flow. A quasi-steady-state analytical solution for simulating a vertical gas flow in a landfill with layered MSW is proposed. The quasi-steady-state analytical solution showed good agreement with the transient solution. Both temporal and spatial variations of the gas generation rate in MSW landfills were considered in the transient and quasi-steady-state analytical methods. A comparison between the proposed quasi-steady-state solution and the previously described steady-state solution showed that using the average gas generation rate or the gas generation rate corresponding to the average age of the MSW layer in the steady-state solution resulted in an error in the estimation of the gas pressure in landfills. The proposed solutions are reliable and can provide a reference for the design, management, and subsequent restoration of landfills.

Due to the lack of knowledge of site-specific data and corresponding pile test results, the reliability of random finite element analysis (RFEM) on monopile and its findings remain questionable. This paper performed an RFEM on monopile in a specific offshore wind farm. The spatial variability of soil parameters in each seabed layer was carefully characterized based on both laboratory test results and calibrated in situ CPTU data. Statistical results demonstrated substantial variability in undrained shear strengths of two silty clay layers and insignificant variability in friction angles of three sandy soil layers, and all soil properties following lognormal distribution. RFEM incorporating the spatial variability of two silty clay layers was conducted to examine the probability distribution of monopile's bearing capacities. The monopile was wished-in-place to overcome the convergence difficulty induced by the deep penetration of pipe piles in the layered seabed. Monte Carlo simulation findings suggest that the spatial variability of soil strength resulted in an overprediction of the vertical bearing capacity, comparison between the statistical results of monopile capacities from RFEM and 43 pile test data in the field proves the reliability of the numerical method. Finally, a quantitative relationship between the safety factor and failure probability was developed to improve monopile design.