## 3 Results  
### General Information Gathering and Document Selection  
The sample of 135 scientific documents consulted and obtained through the Scopus, Web of Science, and Google Scholar repositories was classified by similar topics according to their mechanisms of action about expansive soil improvement techniques and the materials typically used. The results are presented in Figure 6.  
An interpretation of Figure 6, which compares the number of publications by mechanism of action and type of technique, highlights the following:  
1. The chemical mechanism within sustainable and innovative techniques is the most studied (55 publications).
2. It is followed by the physical-mechanical mechanism and sustainable techniques (31 publications).
3. The biological category appears exclusively as a sustainable technique, with 11 publications.
4. Conventional techniques are much less represented in all categories.
5. The general theoretical introduction to the techniques is divided into the \"All\" and \"Sustainable\" categories.  
Regarding the occurrence networks, the fifth search string was chosen because it contained over 54% of the scientific documents consulted. It is filtered using the keywords \"expansive soil\", \"expansive clay\", \"stabilization\", \"improvement\", \"sustainable\", and \"innovative\", as shown in Figure 5. The main findings are as follows:  
* Presence of two thematic streams: The graph reflects two differentiated research streams, one focused on traditional materials and proven methods and the other oriented toward sustainable and innovative alternatives.
* Connection between clusters: The expansive soil node acts as a thematic bridge between both clusters, indicating that traditional and sustainable techniques focus on solving these soils' challenges.
* Importance of the term \"soil stabilization\": It occupies a central position with multiple connections, confirming its role as the thematic axis of the entire network.  
Figure 6: Comparative graph of the number of publications by mechanism of action and type of technique.  
* Emergence of alternative materials: The presence of rice husk ash alongside terms such as lime and compaction in a separate cluster demonstrates an emerging interest in residual and green materials with potential practical applicability.
* Relationship between geotechnical properties and admixture type: Key geotechnical properties such as strength, compressive strength, and swelling behavior are linked to the materials used, allowing for a comparative evaluation of the technical efficiency of each stabilization technique.  
Regarding the documents that were consulted with the sixth search string that included the keywords (\"expansive soil\" OR \"swelling soil\" OR \"problematic soil\") AND (\"soil improvement\" OR \"soil stabilization\" OR \"ground improvement\") AND (\"geopolymer\" OR \"line stabilization\" OR \"sustainable technique\" OR \"innovative method\") AND (\"coastal soil\" OR \"tropical soil\" OR \"Ecuador\"), results were obtained for Ecuador and its neighboring regions such as Peru and Colombia that present these expansive soils in some areas. However, the information was scarce and only in Spanish, with barely 11 scientific articles, which shows a potential topic for future lines of research.