# Stability of MSW Landfill Slopes Reinforced with Geogrids
## 1 Introduction
As a result of the study, it was stated that the determination of suitable shear strength parameters and the solid waste composition, grain diameter, degree of deterioration, and moisture content in the field are very important in the analysis. [PERSON] [5] carried out three-dimensional numerical analyses to model the slope failure occurring in the Kettleman Hills Landfill. It was shown that the internal friction angle and cohesion values obtained as a result of the back-analysis carried out for the post-failure slope and the values obtained by the laboratory experiments were compatible. [PERSON] et al. [6] investigated the shear strength of MSW landfills by back-analysis of failed waste slopes using laboratory tests and field experiments. Using the results obtained from the study, suggestions were made for modeling the shear strength of landfills in analyses. [PERSON] and [PERSON] [7] analyzed the stability of landfill slopes as a function of time and decomposition. In the study, numerical analyses were carried out using FEM and LEM. At the end of the study, they compared the obtained results from the numerical analyses. In the study carried out by [PERSON] and [PERSON] [8], the shear strength parameters of waste landfills were investigated using back-analysis of failed waste slopes. They presented the back analyses of the failed waste slopes in four landfills. Each of the landfill slope failures was reviewed, and the results of the back-analyses were presented. At the end of the study, the obtained and recommended parameters were compared with other studies. Because the tensile strength of the soils is low, the slopes can be made more stable with materials such as metal reinforcements, geotextiles, or geogrids placed inside the slope. High-strength elements are used in these structures, which are defined as reinforced slopes. While metal strips or reinforcements were used in the first applications, today such materials have been replaced by geosynthetic materials. In slopes that are reinforced to increase stability, a solution is realized by including the geogrid forces in the limit equilibrium or finite element analysis as known forces. Geogrids are high-strength, polymer-structured, geosynthetic materials with sufficient space and different grid structures to ensure interlocking with the soil. In its chemical structure, polyethylene-, polyester-,or polypropylene-type polymers are available. Geogrids have an important role in the reinforcement of soils with their high tensile strength and are often used to reinforce slopes. Although there are many studies in the literature on the stability of slopes in landfills, investigations on the stability behavior of reinforced landfill slopes are limited. Today, increasing the stability of slopes using geogrid materials has become a routine and standard practice. However, their use for the reinforcement of landfill slopes is rare. The few studies that have been carried out on reinforcing solid waste slopes using geogrids usually include field applications. [PERSON] and [PERSON] [9] investigated the integrity of geogrid-reinforced landfill slopes subjected to differential settlements and seismic loadings experimentally and numerically. According to the results obtained from the study, it showed that the critical reinforced region corresponding to different loading mechanisms occurred at different elevations within the reinforced soil structure. [PERSON] et al. [10] performed finite element analysis to investigate the failure mechanism and FS values of a geotextile-reinforced extended berm in a MSW landfill slope of 45\({}^{\circ}\). [PERSON] et al. [11] performed a one-year field monitoring of a MSW landfill slope reinforced by geogrids. Using the results obtained, suggestions were made for future studies on the subject. While the reinforcement of MSW landfill slopes using geogrids is available at existing landfills, the interactions between the solid waste material and geogrids have not yet been clearly demonstrated.