Introduction:
The unconfined compression test is a widely used laboratory test in geotechnical engineering to determine the compressive strength and stress-strain behavior of cohesive soils. It was first designed by A. Casagrande and Goyal.

Explanation:
The unconfined compression test is a simple and quick test that does not require any specialized equipment. It involves applying a compressive load to a cylindrical soil sample without confining pressure. The test is performed on undisturbed or remolded cohesive soil samples.

Significance of the unconfined compression test:
The unconfined compression test provides valuable information about the strength and deformation characteristics of cohesive soils. It helps in studying the stability of natural slopes, designing foundations, and assessing the suitability of soil for construction projects.

Procedure of the unconfined compression test:
1. Sample preparation: A cylindrical soil sample with a height-to-diameter ratio of 2:1 is prepared. The sample is trimmed and capped to ensure parallelism and uniformity.
2. Sample saturation: The sample is saturated with water to mimic the field conditions and eliminate the effects of pore water pressure.
3. Sample placement: The saturated sample is placed in the compression machine, and the loading plates are aligned with the top and bottom of the sample.
4. Application of load: A constant axial load is applied at a specified rate until failure occurs. The load and corresponding deformation are recorded.
5. Calculation of stress and strain: The stress is calculated by dividing the applied load by the cross-sectional area of the sample. The strain is determined by dividing the change in sample height by the original height.
6. Plotting the stress-strain curve: The stress-strain curve is plotted to analyze the behavior of the soil under compression.

Importance of Casagrande and Goyal:
A. Casagrande and Goyal are renowned geotechnical engineers who made significant contributions to the field of soil mechanics. They designed the unconfined compression test, which has since become a standard laboratory test for cohesive soils. Their expertise and research have greatly influenced the understanding of soil behavior and the development of geotechnical engineering principles.