Soil Bearing Capacity Calculation Excel

Soil Bearing Capacity Calculation

Soil bearing capacity is very commonly used in foundation design as a way of simplifying the soils reaction to the foundation. The soil bearing capacity calculation is designed to be very conservative so that the designer can be certain that if the soil bearing capacity is not exceeded, the foundation will be stable and will not settle excessively.

It should be noted that some soils can continue to settle due to consolidation for many years after the foundation is built. In these cases a separate settlement analysis should be undertaken along with the bearing capacity calculation. A simple design spreadsheet such as the CivilWeb Settlement Analysis Suite can be used. Note a special bundle of the CivilWeb Soil Bearing Capacity Calculation and the Settlement Analysis Suite worth £40 can be purchased together for just £25 at the bottom of this page.

There are many different  methods of completing soil bearing capacity calculations. The first popular method of calculating soil bearing capacity was derived by Terzaghi. This method assumes a shear failure plane and then calculates the pressure required to create this failure plane using soil strength parameters. The Terzaghi method has subsequently been revised many times but is still occasionally used today.

This method of shear failure plane analysis remains the basis of modern soil bearing capacity calculation methods. Several modifications to the Terzaghi method have been proposed either to improve accuracy or to extend the method to other design conditions such as foundations  on slopes. The most commonly used methods today are based on the Meyerhof method in the US or the Hansen or Vesic methods in Europe.

Several national and international design standards have also proposed variations on the soil bearing capacity calculations. The CivilWeb Soil Bearing Capacity Calculation Excel Suite includes the Eurocode 7 Method and the BS 8004 method which are variants of the Hansen method.

There are also methods of calculating the soil bearing capacity from site investigation information. This is especially useful for preliminary design where only general site investigation results are known. The CivilWeb Soil Bearing Capacity Calculation Excel Suite includes methods of calculating the soil bearing capacity from three different site investigation results, SPT data, CPT data and plate bearing test results.

For preliminary foundation design it is common for the designer to choose a typical soil bearing capacity based simply on the soil type. Please see our articles on Bearing Capacity of Rock, Typical Soil Bearing Capacity and Safe Bearing Capacity of Soil for further information.

CivilWeb Soil Bearing Capacity Calculation Excel Suite - Inputs

The simplest analytical method developed by Terzaghi requires the designer to input  the length, width and depth of the foundation, and the density and shear strength parameters for the soil. The soil strength parameters can be taken from testing of the soils.The designer should input a trial size for the foundation which can then be adjusted iteratively to optimise the foundation design.

The geometrical foundation size parameters affect the bearing capacity of the soil and will also affect the bearing pressure underneath the foundation. A larger foundation both increases the soil bearing capacity and decreases the bearing pressure. This effect is often neglected in foundation design but can have a significant effect on the required size of the foundation. The unique analysis tools provided with the CivilWeb Soil Bearing Capacity Calculation Excel Suite show the designer at a glance exactly how the soil bearing capacity is altered by a change in the size or depth of the foundation. This makes optimising the design simple.

Other methods were developed to include wider ranging site conditions and so require a few more input. These include the eccentricity of the loading, the inclination of the load, the tilt of nearby slopes and the tilt of the base of the foundation. All these factors will affect the soil bearing capacity calculation and different methods are suitable for different site conditions.

The bearing capacity spreadsheets based on site investigation results obviously require the designer to input these results. The results can be from an SPT, CPT or a plate bearing test undertaken on the proposed foundation site. Ideally this  test should be on the exact spot for the foundation.

CivilWeb Soil Bearing Capacity Calculation Excel Suite

The CivilWeb Soil Bearing Capacity Calculation Excel Suite includes the following spreadsheets;

1. Terzaghi Soil Bearing Capacity Calculator
2. Meyerhof Soil Bearing Capacity Calculator
3. Hansen Soil Bearing Capacity Calculator
4. Vesic Soil Bearing Capacity Calculator
5. BS 8004 Soil Bearing Capacity Calculator
6. Eurocode 7 Soil Bearing Capacity Calculator
7. SPT Soil Bearing Capacity Calculator
8. CPT Soil Bearing Capacity Calculator
9. Plate Loading Test Soil Bearing Capacity Calculator
10. 74 page detailed Ultimate Design Guide for soil bearing capacity calculations including instructions for use of all the spreadsheets and comprehensive typical soil bearing capacity values for every soil and rock type.

The CivilWeb Soil Bearing Capacity Calculation Excel Suite includes all the tools required to complete a detailed analytical soil bearing capacity calculation. The spreadsheet includes unique tools which assist the designer in seeing the effects of different sized foundations on the bearing capacity. When used alongside a foundation design spreadsheet such as our Pad Footing Design Spreadsheet, this allows the designer to complete a fully optimised foundation design in minutes. This saves the designer from  completing multiple time consuming soil bearing capacity calculations by hand.

Buy the CivilWeb Soil Bearing Capacity Calculation Excel Suite now for only £20.