Poor subgrade soil conditions can result in inadequate pavement support, shortened pavement life, and various pavement distresses, especially in expansive soil (Black cotton soil), which is exceedingly brittle and insufficiently stable for any kind of construction activity. It is well known that not all soils can be used to create high-quality paving because they lack certain qualities. A variety of modification techniques should be employed to enhance the subgrade performance of such soils because they cannot be modified. This is achieved by using soil quality improvement methods that are unsuccessful in their natural form. For subgrade soil to remain stable, its engineering qualities must be improved. In this study, the fundamental engineering and geotechnical properties of poor subgrade soils reinforced by geosynthetic materials, such as geotextiles, were investigated. A geotextile used between the base material and the subgrade can serve as drainage, a filter medium, a water permeability layer, reinforcement with a specified tensile strength, and a layer of separation. In this study, the subgrade soil is strengthened using coir geotextiles. The improvement in CBR value is assessed when coir geotextile is put into a CBR mold at different depths with single layer (H/2, H/3, & H/4) and multi-layers. The CBR values of soil has been observed to increase with the addition of multi-layer geotextiles compared with the single-layer coir geotextiles.