Bearing Capacity of Cohesive Soil for Circular Footing Calculator

Ultimate Bearing Capacity Formula:

\[ q_f = (1.3 \times C \times N_c) + \sigma_s \]

Ultimate Bearing Capacity:

kPa

1. What is Bearing Capacity of Cohesive Soil?

Definition: The ultimate bearing capacity is the minimum gross pressure intensity at the base of the foundation at which the soil fails in shear.

Purpose: This calculator determines the bearing capacity of cohesive soil for circular footings, which is crucial for foundation design in civil engineering projects.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ q_f = (1.3 \times C \times N_c) + \sigma_s \]

Where:

\( q_f \) — Ultimate bearing capacity (kPa)
\( C \) — Cohesion in soil (kPa)
\( N_c \) — Bearing capacity factor dependent on cohesion
\( \sigma_s \) — Effective surcharge (kPa)

Explanation: The 1.3 factor accounts for the circular footing shape. The formula combines the soil's cohesive strength and the additional load from surcharge.

3. Importance of Bearing Capacity Calculation

Details: Proper calculation ensures foundation stability, prevents excessive settlement, and avoids structural failure in buildings and infrastructure.

4. Using the Calculator

Tips: Enter the soil cohesion in kPa, bearing capacity factor (default 9), and effective surcharge in kPa. The bearing capacity factor has ±5% uncertainty.

5. Frequently Asked Questions (FAQ)

Q1: What is typical N_c value for cohesive soils?
A: For circular footings, N_c is typically 9, but can range from 5.7 to 9 depending on soil conditions.

Q2: How is cohesion determined?
A: Cohesion is measured through laboratory tests like unconfined compression tests or field vane shear tests.

Q3: What affects the bearing capacity factor?
A: Soil type, footing shape, depth, and loading conditions all influence N_c.

Q4: What is effective surcharge?
A: It's the vertical pressure from soil or other loads above the footing base level.

Q5: Does this consider safety factors?
A: No, this calculates ultimate capacity. Apply appropriate safety factors (typically 2.5-3) for allowable bearing capacity.