Settlement Calculator – Loan calculator

Soil Settlement Calculator

Use this calculator to estimate the immediate (elastic) settlement of a shallow foundation on a compressible soil layer. This calculation is based on elastic theory and provides an approximation for preliminary design.

Applied Load (kN): Foundation Width (m): Foundation Length (m): Soil Modulus of Elasticity (kPa): Soil Poisson's Ratio (ν_s): Influence Factor (I_f):

Understanding Soil Settlement

Soil settlement refers to the vertical downward movement of the ground surface or a foundation due to applied loads. It's a critical consideration in geotechnical engineering to ensure the stability and serviceability of structures. Excessive or differential settlement can lead to structural damage, cracking, and functional issues.

Types of Settlement

There are generally three types of settlement:

Immediate (Elastic) Settlement: Occurs almost instantaneously upon the application of load, primarily due to the elastic deformation of the soil without any change in water content. This calculator focuses on immediate settlement.
Primary Consolidation Settlement: Occurs over time in saturated fine-grained soils (clays) as water is squeezed out from the soil pores under sustained load.
Secondary Consolidation (Creep) Settlement: Occurs after primary consolidation is complete, due to the plastic readjustment of soil particles under constant effective stress.

How the Calculator Works (Immediate Settlement)

This calculator estimates immediate settlement using a simplified elastic theory approach, often attributed to Janbu, Bjerrum, and Kjaernsli, or similar methods for flexible foundations. The general formula used is:

S = (q * B * (1 - ν_s²) * I_f) / E_s

Where:

S = Immediate Settlement (in meters, then converted to millimeters)
q = Applied Pressure on the foundation (kN/m² or kPa)
B = Foundation Width (m)
ν_s = Soil Poisson's Ratio (dimensionless)
I_f = Influence Factor (dimensionless, depends on foundation shape, rigidity, and depth of compressible layer)
E_s = Soil Modulus of Elasticity (kPa)

Input Parameters Explained:

Applied Load (kN): The total vertical load transmitted by the structure to the foundation.
Foundation Width (m): The shorter dimension of the rectangular foundation.
Foundation Length (m): The longer dimension of the rectangular foundation.
Soil Modulus of Elasticity (kPa): A measure of the soil's stiffness. Higher values indicate stiffer soil and less settlement. This value can be obtained from laboratory tests (e.g., triaxial tests) or in-situ tests (e.g., plate load tests, SPT, CPT correlations). Typical values for sands range from 10,000 to 50,000 kPa, and for clays from 5,000 to 20,000 kPa.
Soil Poisson's Ratio (ν_s): Represents the ratio of transverse strain to axial strain. For soils, it typically ranges from 0.2 to 0.4 for sands and 0.3 to 0.5 for saturated clays.
Influence Factor (I_f): A dimensionless factor that accounts for the shape and rigidity of the foundation, and the depth of the compressible soil layer. It is often obtained from charts or tables based on the L/B ratio (Length/Width) and the relative depth of the foundation. For a flexible rectangular footing on a deep elastic layer, I_f can range from 0.8 to 1.5 depending on L/B. A value of 1.12 is common for a flexible square footing (L/B=1).

Example Calculation:

Let's consider a scenario:

Applied Load: 1000 kN
Foundation Width: 2 m
Foundation Length: 3 m
Soil Modulus of Elasticity: 20000 kPa
Soil Poisson's Ratio: 0.3
Influence Factor: 1.12

First, calculate the foundation area: Area = 2 m * 3 m = 6 m²

Next, calculate the applied pressure: q = 1000 kN / 6 m² = 166.67 kPa

Now, apply the settlement formula:

S = (166.67 kPa * 2 m * (1 – 0.3²) * 1.12) / 20000 kPa

S = (166.67 * 2 * (1 – 0.09) * 1.12) / 20000

S = (166.67 * 2 * 0.91 * 1.12) / 20000

S = 340.39 / 20000

S = 0.01702 m

Converting to millimeters: S = 0.01702 * 1000 = 17.02 mm

This indicates an estimated immediate settlement of approximately 17.02 mm.

Limitations:

This calculator provides an estimate for immediate settlement. Actual settlement can be more complex and influenced by factors not included here, such as:

Soil layering and heterogeneity
Time-dependent consolidation (for clays)
Groundwater conditions
Foundation rigidity (this calculator assumes a flexible foundation)
Stress history of the soil
Construction sequence

For critical projects, a detailed geotechnical investigation and analysis by a qualified engineer are always recommended.

.settlement-calculator-container { font-family: 'Arial', sans-serif; background-color: #f9f9f9; padding: 20px; border-radius: 8px; max-width: 800px; margin: 20px auto; box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1); color: #333; } .settlement-calculator-container h2 { text-align: center; color: #0056b3; margin-bottom: 25px; } .settlement-calculator-container h3 { color: #0056b3; margin-top: 30px; margin-bottom: 15px; } .settlement-calculator-container h4 { color: #0056b3; margin-top: 20px; margin-bottom: 10px; } .calculator-inputs label { display: block; margin-bottom: 8px; font-weight: bold; color: #555; } .calculator-inputs input[type="number"] { width: calc(100% – 22px); padding: 10px; margin-bottom: 15px; border: 1px solid #ccc; border-radius: 4px; box-sizing: border-box; } .calculator-inputs button { background-color: #007bff; color: white; padding: 12px 20px; border: none; border-radius: 4px; cursor: pointer; font-size: 16px; width: 100%; margin-top: 10px; transition: background-color 0.3s ease; } .calculator-inputs button:hover { background-color: #0056b3; } .calculator-result { margin-top: 25px; padding: 15px; background-color: #e9f7ef; border: 1px solid #d4edda; border-radius: 4px; font-size: 1.1em; font-weight: bold; color: #155724; text-align: center; } .calculator-result.error { background-color: #f8d7da; border-color: #f5c6cb; color: #721c24; } .calculator-article p { line-height: 1.6; margin-bottom: 10px; } .calculator-article ul, .calculator-article ol { margin-left: 20px; margin-bottom: 10px; } .calculator-article ul li, .calculator-article ol li { margin-bottom: 5px; } .calculator-article code { background-color: #e0e0e0; padding: 2px 4px; border-radius: 3px; font-family: 'Courier New', monospace; } function calculateSettlement() { var appliedLoad = parseFloat(document.getElementById("appliedLoad").value); var foundationWidth = parseFloat(document.getElementById("foundationWidth").value); var foundationLength = parseFloat(document.getElementById("foundationLength").value); var soilModulus = parseFloat(document.getElementById("soilModulus").value); var poissonsRatio = parseFloat(document.getElementById("poissonsRatio").value); var influenceFactor = parseFloat(document.getElementById("influenceFactor").value); var resultDiv = document.getElementById("settlementResult"); resultDiv.className = "calculator-result"; // Reset class for potential error messages if (isNaN(appliedLoad) || isNaN(foundationWidth) || isNaN(foundationLength) || isNaN(soilModulus) || isNaN(poissonsRatio) || isNaN(influenceFactor) || appliedLoad <= 0 || foundationWidth <= 0 || foundationLength <= 0 || soilModulus <= 0 || poissonsRatio = 0.5 || influenceFactor <= 0) { resultDiv.innerHTML = "Please enter valid positive numbers for all fields. Poisson's Ratio must be between 0 and 0.5 (exclusive of 0.5)."; resultDiv.classList.add("error"); return; } // 1. Calculate Foundation Area var foundationArea = foundationWidth * foundationLength; // 2. Calculate Applied Pressure (q) var appliedPressure = appliedLoad / foundationArea; // 3. Calculate Immediate Settlement (S) // S = (q * B * (1 – ν_s^2) * I_f) / E_s // Note: B is typically the characteristic dimension, often the width for rectangular footings. var settlementMeters = (appliedPressure * foundationWidth * (1 – Math.pow(poissonsRatio, 2)) * influenceFactor) / soilModulus; // Convert settlement from meters to millimeters var settlementMM = settlementMeters * 1000; resultDiv.innerHTML = "Estimated Immediate Settlement: " + settlementMM.toFixed(2) + " mm"; }