In a direct shear test, the soil load is subjected to more stress at the edges. This is because the edges are where the shear stress is concentrated due to the confinement of the soil sample.

- Direct shear test:
The direct shear test is a common laboratory test used to determine the shear strength parameters of soil. It involves applying a constant normal stress to a soil sample and then shearing the sample horizontally along a pre-determined plane. The test provides valuable information about the shear strength, friction angle, and cohesion of the soil.

- Stress distribution in direct shear test:
When the soil sample is subjected to a normal stress, the stress is distributed throughout the sample. However, the stress distribution is not uniform, and certain areas of the sample experience higher stress than others.

- Stress concentration at the edges:
In a direct shear test, the soil sample is confined within a shear box. The edges of the shear box restrict the lateral movement of the soil particles, causing the stress to concentrate at these locations.

- Effect of stress concentration:
The stress concentration at the edges of the shear box affects the behavior of the soil sample during the test. The concentrated stress causes the soil particles to mobilize and rearrange, leading to shear deformation along the predetermined plane.

- Shear failure:
The soil sample in a direct shear test fails along the predetermined shear plane when the shear stress reaches a critical value. The failure occurs due to the sliding and rotation of soil particles along the shear plane.

- Importance of stress concentration:
Understanding the stress concentration at the edges is crucial in interpreting the results of a direct shear test. It helps in determining the shear strength parameters of the soil and predicting its behavior under different loading conditions.

Therefore, in a direct shear test, the soil load is subjected to more stress at the edges due to stress concentration caused by the confinement of the soil sample within the shear box.