The study of rainfall thresholds is vital in understanding the factors that trigger landslides, being one of the criteria applied to landslide early warning systems that aim to mitigate their consequences. These thresholds enable the prediction of landslide occurrences as a function of rainfall measurements. This work presents an overview of the parameters involved in defining rainfall thresholds based on scientific articles published between 2008 and 2021 that discuss the subject through statistical or physical methods. These articles provided data such as publication information, threshold types, details on the data used in the works, methodology, and application of the threshold in early warning systems. There was a significant increase in research papers on this theme during this period, possibly due to the strategies advocated by the Sendai Framework. However, some regions of the world severely affected by landslides are barely mentioned in these studies. The results indicate specific trends, such as those found in the methods used to define rainfall thresholds and the parameters relating to the database when a statistical approach was used. Certain deficiencies were found, such as those concerning geological-geotechnical conditions for categorizing thresholds, the time scales of rainfall data, rain gauge density, and the criteria to define the accumulated rainfall period to be considered.

Shallow tunnels induce surface displacements which can cause damage to existing structures; an adequate evaluation of their settlement trough is of paramount importance. Nowadays, it becomes even more critical when dealing with an underground occupation where the green stress field has already been disturbed by previous excavations. Since the end of the last century, many researchers have explored the subject. Some empirical methodologies have been developed based on data from actual cases, sometimes associated with numerical analysis. The present work used plane strain numerical analysis of different geometric arrangements of side-by-side twin tunnels for different depths and distances between tunnel axes to evaluate its compatibility with some of the proposed methods to adjust the settlement profile of the second cavity. It was observed that the discussed methodologies have similar results for maximum settlement and its eccentricity. Nevertheless, the behavior of the trough width parameter from the semi-empirical methods has shown discrepancies.