## 1 Introduction  
Expansive soils present a significant challenge for geotechnical engineering, as they are widespread in nature and their significant deformations are associated with changes in suction and the degree of saturation [1; 2; 3; 4; 5; 6]. In the unsaturated zone above the phreatic groundwater level, the soil moisture content varies significantly over seasons, necessitating a comprehensive understanding of expansive soil behavior and precise specifications for optimal characterization to mitigate risks [7; 8]. When facilities and roads are constructed on expansive soils, they can cause significant damage and high costs. For example, in the USA, losses resulting from cracks in buildings and roads built on expansive soils were estimated at about USD 10 billion in 1985 AD, with half of that amount spent on repairing roads [9]. Similar losses have been reported in [10; 11; 12]. According to [PERSON] and [PERSON] [13], the financial loss resulting from the devastating effects of expansive soils would be greater than the loss caused by earthquakes or floods. This highlights the importance of the continued deepening of research conducted on these types of soils to limit their damage. The objective of this study is to comprehensively examine the influence of the initial degree of saturation, initial dry unit weight, and the percentage of added sand on the swelling characteristics of expansive soils. This investigation entails experimental analysis through loaded swelling pressure tests and employs diverse machine learning algorithmic models implemented within the Python programming environment for predictive purposes. This paper introduces a new method that relies on ensuring that the weight of the structure is aligned with the properties of the expansive soil, such as dry unit weight, degree of saturation, and liquid limit. This approach aims to reduce the negative effects of expansive soils on structures and offers an alternative to traditional soil improvement methods. Sand is widely known as a granular material with a high bearing capacity that can alter the properties of cohesive soil, including plasticity, compactness, and resistance [14; 15; 16; 17; 18]. When mixed with cohesive soil in various ratios, sand replaces fine soil particles with coarser ones, creating a better gradient of soil grain that increases cohesion and friction and improves swelling properties. This research seeks to explore the swelling behavior of partially saturated expansive soils in response to variations in their sand content. Additionally, it endeavors to predict the optimal dry unit weight and applied stress parameters that result in minimizing swell amplitude, thereby contributing to the mitigation of associated risks. Despite previous studies that have explored the use of inert materials in expansive soils [17; 19; 20; 21; 22] and their contributions to improving expansive soils and reducing hazards, many questions and issues on the behavior of expansive soils remain unresolved. Within this framework, our objective is to assess the influence of varying proportions of sand under differing saturation levels and dry unit weights on the physical and swelling attributes of expansive soils. This study endeavors to optimize the applied stress to attain minimal swelling, thus contributing to a more comprehensive understanding of expansive soil behavior. The detrimental effects of expansive soils have been widely documented, and the poor evaluation of these soils can result in significant damage and financial losses [1; 2; 3; 4; 9; 10; 11; 12; 23]. Correctly classifying the degree of shrinkage and swelling of these soils is crucial for successful foundation treatment and ensuring the stability of structures built on them. However, expansive soils in different regions exhibit varying physical and engineering characteristics due to differences in their composition and environment [23].