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Cohesion of Soil given Bearing Capacity for Purely Cohesive Soil Calculator

Cohesion of Soil Formula:

\[ C_s = \frac{q_{fc} - (\sigma_s \times N_q)}{N_c} \]

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1. What is Cohesion of Soil given Bearing Capacity for Purely Cohesive Soil?

Definition: This calculator determines the cohesion of soil based on the ultimate bearing capacity, effective surcharge, and bearing capacity factors.

Purpose: It helps geotechnical engineers and construction professionals evaluate soil strength for foundation design.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ C_s = \frac{q_{fc} - (\sigma_s \times N_q)}{N_c} \]

Where:

  • \( C_s \) — Cohesion of Soil (Pascal)
  • \( q_{fc} \) — Ultimate Bearing Capacity in Soil (%)
  • \( \sigma_s \) — Effective Surcharge in KiloPascal (%)
  • \( N_q \) — Bearing Capacity Factor dependent on Surcharge (%)
  • \( N_c \) — Bearing Capacity Factor dependent on Cohesion (%)

Explanation: The formula calculates soil cohesion by accounting for the bearing capacity and subtracting the effect of surcharge.

3. Importance of Soil Cohesion Calculation

Details: Proper cohesion estimation ensures stable foundations, proper slope stability, and accurate earthwork calculations.

4. Using the Calculator

Tips: Enter all values as percentages. The calculator will compute the cohesion in Pascals. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is typical cohesion value for clay soil?
A: Soft clay might have 5-25 kPa, while stiff clay can have 50-200 kPa cohesion.

Q2: How does surcharge affect bearing capacity?
A: Increased surcharge generally increases bearing capacity by providing additional confining pressure.

Q3: What are typical values for Nc and Nq?
A: For purely cohesive soils, Nc is typically 5.14 and Nq is 1.0, but varies with soil type.

Q4: Why measure cohesion in Pascals?
A: Pascals are the SI unit for stress and pressure, making them ideal for soil mechanics calculations.

Q5: How accurate is this calculation?
A: It provides theoretical values - actual field conditions may vary by ±5% due to soil variability.

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