1. A 3m x 3m square footing is constructed at a depth of 2m in a 26m deep clay layer with following soil properties: I =16.5kN/m', Normally Consolidated Clay, e,= 0.65, Cc = 0.25,s=0.5 and Es= 6.0 MN/m2. If there is a 1000KN structural load on the footing, calculate the consolidation

Structural Analysis
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ISBN:9781337630931
Author:KASSIMALI, Aslam.
Publisher:KASSIMALI, Aslam.
Chapter2: Loads On Structures
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### Example Problem: Calculation of Consolidation Settlement

**Problem Statement:**

A 3m x 3m square footing is constructed at a depth of 2m in a 26m deep clay layer with the following soil properties:

- Unit weight (γ) = 16.5 kN/m³
- Soil Type: Normally Consolidated Clay
- Initial void ratio (e₀) = 0.65
- Compression index (Cc) = 0.25
- Settlement factor (βs) = 0.5
- Modulus of elasticity (Es) = 6.0 MN/m²

If there is a 1000 kN structural load on the footing, calculate the consolidation settlement of the footing.

**Solution Guide:**

1. **Determine the Stage of Settlement:**
   - Since the clay is normally consolidated, we focus on the primary consolidation settlement.

2. **Identify Parameters and Conversion Factors:**
   - Load on footing (P) = 1000 kN
   - Area of footing (A) = \(3 m \times 3 m = 9 m²\)
   - Depth of the clay layer (H) = 26m

3. **Calculate the Increase in Stress:**
   \[
   \Delta \sigma = \frac{P}{A} = \frac{1000 \, kN}{9 \, m²} = 111.1 \, kN/m² (\text{additional stress on the soil layer due to the load})
   \]

4. **Compute the Initial Effective Stress (\(\sigma'_0\)):**
   \[
   \sigma'_0 = \gamma \times (depth - depth of footing) = 16.5 \, kN/m³ \times (26 \, m - 2 \, m) = 16.5 \, kN/m³ \times 24 \, m = 396 \, kN/m²
   \]

5. **Determine the Final Effective Stress (\(\sigma'_f\)):**
   \[
   \sigma'_f = \sigma'_0 + \Delta \sigma = 396 \, kN/m² + 111.1 \, kN/m² = 507.1 \, kN/m²
   \]

6. **Calculate the Settlement (S):**
   - Using the formula for consolidation settlement:
Transcribed Image Text:### Example Problem: Calculation of Consolidation Settlement **Problem Statement:** A 3m x 3m square footing is constructed at a depth of 2m in a 26m deep clay layer with the following soil properties: - Unit weight (γ) = 16.5 kN/m³ - Soil Type: Normally Consolidated Clay - Initial void ratio (e₀) = 0.65 - Compression index (Cc) = 0.25 - Settlement factor (βs) = 0.5 - Modulus of elasticity (Es) = 6.0 MN/m² If there is a 1000 kN structural load on the footing, calculate the consolidation settlement of the footing. **Solution Guide:** 1. **Determine the Stage of Settlement:** - Since the clay is normally consolidated, we focus on the primary consolidation settlement. 2. **Identify Parameters and Conversion Factors:** - Load on footing (P) = 1000 kN - Area of footing (A) = \(3 m \times 3 m = 9 m²\) - Depth of the clay layer (H) = 26m 3. **Calculate the Increase in Stress:** \[ \Delta \sigma = \frac{P}{A} = \frac{1000 \, kN}{9 \, m²} = 111.1 \, kN/m² (\text{additional stress on the soil layer due to the load}) \] 4. **Compute the Initial Effective Stress (\(\sigma'_0\)):** \[ \sigma'_0 = \gamma \times (depth - depth of footing) = 16.5 \, kN/m³ \times (26 \, m - 2 \, m) = 16.5 \, kN/m³ \times 24 \, m = 396 \, kN/m² \] 5. **Determine the Final Effective Stress (\(\sigma'_f\)):** \[ \sigma'_f = \sigma'_0 + \Delta \sigma = 396 \, kN/m² + 111.1 \, kN/m² = 507.1 \, kN/m² \] 6. **Calculate the Settlement (S):** - Using the formula for consolidation settlement:
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