Cohesion of Soil given Bearing Capacity for Local Shear Failure Calculator

Cohesion Formula:

\[ C = \frac{q_{fc} - (\sigma_s \times N_q + 0.5 \times \gamma \times B \times N_\gamma)}{\frac{2}{3} \times N_c} \]

Ultimate Bearing Capacity (kPa):

Effective Surcharge (kPa):

Bearing Capacity Factor (Nq):

Unit Weight of Soil (kN/m³):

Width of Footing (m):

Bearing Capacity Factor (Nγ):

Bearing Capacity Factor (Nc):

Cohesion in Soil (kPa):

1. What is Cohesion of Soil Calculator?

Definition: This calculator determines the cohesion of soil based on bearing capacity factors and other soil parameters for local shear failure conditions.

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

2. How Does the Calculator Work?

The calculator uses the formula:

\[ C = \frac{q_{fc} - (\sigma_s \times N_q + 0.5 \times \gamma \times B \times N_\gamma)}{\frac{2}{3} \times N_c} \]

Where:

\( C \) — Cohesion of soil (kPa)
\( q_{fc} \) — Ultimate bearing capacity (kPa)
\( \sigma_s \) — Effective surcharge (kPa)
\( N_q, N_\gamma, N_c \) — Bearing capacity factors
\( \gamma \) — Unit weight of soil (kN/m³)
\( B \) — Width of footing (m)

Explanation: The formula calculates soil cohesion by considering the bearing capacity equation for local shear failure conditions.

3. Importance of Soil Cohesion Calculation

Details: Cohesion is a critical parameter in soil mechanics that affects slope stability, bearing capacity, and foundation design.

4. Using the Calculator

Tips: Enter all required parameters with appropriate units. Default values are provided for common bearing capacity factors. All values must be > 0 except surcharge which can be 0.

5. Frequently Asked Questions (FAQ)

Q1: What is local shear failure?
A: Local shear failure occurs when only a portion of the soil beneath the foundation reaches the failure state, resulting in significant settlement.

Q2: How do I determine bearing capacity factors?
A: Bearing capacity factors depend on soil friction angle and can be found in geotechnical references or calculated using empirical relationships.

Q3: Why is the 2/3 factor used for Nc?
A: The 2/3 factor accounts for the reduced mobilization of shear strength in local shear failure compared to general shear failure.

Q4: What's a typical cohesion range for soils?
A: Clay soils typically have cohesion from 5-200 kPa, while sandy soils have little to no cohesion (0-10 kPa).

Q5: How accurate is this calculation?
A: Results are theoretical estimates; actual field conditions may vary by ±5% or more due to soil heterogeneity.