Black cotton soil is a typical swelling soil, which loses its strength when it comes under contact with water thereby increasing its volume. Likewise, in an absence of water, it shows multiple cracks resulting in shrinkage. This volumetric change causes distress to the structure located in the areas containing expansive soils and leads to structural failure. Therefore, the proposed study aimed at developing a stabilized black cotton soil surface for the construction of RESA (Runway End Safety Area) with a California bearing ratio (CBR) value greater than 15%. Prosopis juliflora ash was used as an additive in stabilizing the expansive soil. The ash contents were added in different percentages such as 0%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, and 4% by weight of the soil. The characteristics of the ash-treated soil were tested under three criteria such as gradation, physical parameters, and strength characteristics. Gradation includes wet sieve analysis, physical parameters include field density, swell index, Atterberg’s limit, modified proctor compaction, specific gravity, moisture content, and strength characteristics including California bearing ratio (CBR) and unconfined compressive strength. The targeted CBR value of more than 15% was achieved when 3.5% of ash content was added.

黑棉土是一种典型的膨胀土，遇水会失去强度，从而增加体积。同样，在没有水的情况下，它会出现多处裂缝，导致收缩。这种体积变化会对位于含有膨胀土壤的区域中的结构造成困扰，并导致结构失效。因此，拟议的研究旨在开发一种稳定的黑棉土壤表面，用于建造 RESA（跑道末端安全区），加州承载比 (CBR) 值大于 15%。七叶木灰分用作稳定膨胀土的添加剂。灰分含量按土壤重量的 0%、1%、1.5%、2%、2.5%、3%、3.5% 和 4% 等不同百分比添加。在级配、物理参数和强度特性等三个标准下测试了灰分处理土壤的特性。分级包括湿筛分析，物理参数包括场密度、膨胀指数、Atterberg 极限、改进的普洛克特压实度、比重、水分含量和强度特性，包括加州承载比 (CBR) 和无侧限抗压强度。当添加 3.5% 的灰分含量时，可实现超过 15% 的目标 CBR 值。