###### Abstract
Indeed, according to some authors ([10; 11; 12; 13; 14; 15; 16; 17; 18; 19]) the use of lateritic soils in the subballast layer has demonstrated satisfactory performance. Figure 1: Railway track cross-section with highlighted components, [PERSON] et al. [4]. [PERSON] [10] conducted a study using fine lateritic materials collected in western Maranhao, which yielded excellent results and was validated using this material for the subballast layer. The layer tended to accommodate the permanent deformation shakedown, indicating that the material classified as LG' (laterite clayey soil) is suitable for use in this layer. [PERSON] [11] assessed the mechanical performance of tropical soils from the Carajas railway (EFC) region, which were previously considered unsuitable for railway pavement according to conventional criteria. However, his study showed that these soils exhibited favorable behavior when used in the subballast layer. [PERSON] [12] conducted a study where he measured the resilient modulus of 53 soil samples collected along the Estrada Ferro Carajas. The lateritic samples exhibited a predominantly medium-to-high resilient modulus, indicating their potential suitability for use as subballast material. [PERSON] [13] conducted a study to assess the suitability of four types of tropical soils (fine and granular, lateritic and non-lateritic) as subballast material for a permanent railway track, taking into account their hydraulic and mechanical properties. Based on laboratory tests and numerical modeling of infiltration using the IVFlow model, the author concluded that the lateritic soils under investigation had high suction, low permeability, and were prone to water-induced damage. [PERSON] [14] conducted a comparative analysis of the performance of five soil types used in the subballast layer, as a capillary barrier to protect the subgrade of a railway platform under the impact of rainfall. The study revealed that sandy lateritic soil and lateritic sand exhibited a superior performance compared to other soil types. [PERSON] [15] carried out a study that involved laboratory testing on cohesive soil samples collected from different locations in South China. The researchers measured the resilient modulus and soil suction under various moisture conditions using specialized equipment and testing procedures. The findings indicate a significant correlation between the resilient modulus and soil suction for cohesive soils. As soil suction increased, the resilient modulus decreased, indicating a softer and more deformable material. This relationship has implications for pavement design and performance, as it helps in predicting the resilient behavior of cohesive soils under different moisture conditions. [PERSON] [16] and [PERSON] et al. [2] observed in the field the satisfactory performance of a fine sandy lateritic soil used as a subballast material in a railway section built in 2015. The section has been monitored and is still in good condition. [PERSON] et al. [17] declare that when the subgrade lacks adequate mechanical properties, it contributes significantly to the overall deterioration of the geometry. Therefore, it is important for the subballast layer to function as a capillary barrier to safeguard the subgrade. Supporting this argument, the climate is considered one of the most relevant factors that lead to issues in railway subgrade. The adverse weather conditions, coupled with the high axle loads of heavy haul railways, significantly impact the soil saturation levels, resulting in fluctuations in its bearing capacity, as highlighted by [PERSON] and [PERSON] [18]. Considering the above, it is evident that conducting an in-depth study on the utilization of tropical soil as a subballast layer is necessary. This layer can act as a protective shield against water's detrimental effects on the subgrade, particularly because there is a vast abundance of tropical soils available in Brazil.