Stress Distribution

Stress Distribution

1. Stresses created in soil mass

   • The total vertical stress acting at a point in the soil is due to the weight of everything that lies above that point including soil, water and any load applied to the soil surface.
     • In reality a soil profile is going to consist of a number of layers of different soils, which will differ in properties. If the soil is multi-layered, the total vertical stress is determined by summing the stresses induced by each layer of the soil.

2. Method of calculating soil mass

   • Total stress increases with depth and with unit weight.The total vertical stress at depth z in the soil due to only the weight of the soil acting above is defined as:

3. Principle of effective stress in soil mechanics

   • The stress that controls changes in the volume and strength of a soil in known as the effective stress. In soil properties chapter it was seen that a soil mass consists of a collectionof solid particles with voids between them. These voids are filled with water, air and water, or air only.

4. The effect of pore water pressure and groundwater table on stress at a point in soil mass

   • The water within the voids of a soil is under pressure. This water, known as pore water. Pore water experiences pressure known as the pore pressure or pore water pressure

5. Frost action in soils

   • As water freezes it increasesin volume by nearly 10% so there will be some heaving of the ground surface. If the cooling rate is high, then the soil water freezes before additional water can migrate through the soil to form ice lens and the amount of heave is limited.