Question

The soil profile at a site consists of:

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The water table is initially at a depth of 1m below the surface. The water table is to be rapidly lowered to a depth of 6m and maintained at that level permanently. Consider two points in the soil profile, Point A at a depth of 4m and Point B at a depth of 10m. Determine the effective vertical and horizontal stresses at Points A and B for two cases:
Initial conditions where the water table is 1m below the surface.

Answer 1

I understand the problem you've described. To determine the effective vertical and horizontal stresses at Points A and B for the initial conditions where the water table is 1m below the surface, we'll use the following principles:

1. Effective Vertical Stress (σ'v) at a given depth:

σ'v = γ' * depth

where γ' is the effective unit weight of the soil and is calculated as (γ - γw) where γ is the total unit weight of the soil and γw is the unit weight of water.

2. Effective Horizontal Stress (σ'h) at a given depth:

σ'h = K * σ'v

where K is the coefficient of earth pressure at rest.

Given:

- Depth to the water table (h) = 1m

- Depth to Point A (depth_A) = 4m

- Depth to Point B (depth_B) = 10m

- Coefficient of earth pressure at rest (K) = Assumed value based on soil properties

- Total unit weight of the soil (γ) = Known value

- Unit weight of water (γw) = Known value

Calculate the effective vertical stress (σ'v) at Points A and B using the equation provided above. Then, use the calculated σ'v values to find the effective horizontal stress (σ'h) at Points A and B using the equation for σ'h.

Keep in mind that the coefficient of earth pressure at rest (K) depends on the soil properties and stress conditions. You may need to use typical values or provided data to estimate K for your calculations.