Gabion Wall Design Spreadsheet

Gabion Wall Design

The design of gabion walls and other modular retaining  wall systems can be extremely time consuming. This is mostly because of the fact that there are no bonds between the layers in the gabion wall. This means that the stability calculations need to be repeated for each layer in the gabion wall. For a high gabion wall this can lead  to dozens of calculations. The requirements of BS EN 1997 further complicate matters with two design combinations which need to be checked for every level. If an optimised gabion wall design is required, the whole process may need to be repeated multiple times.

The CivilWeb Gabion Wall Design XLS completes these time  consuming calculations automatically every time the designer alters any of the input parameters. The designer can see instantly the effects of changes on any of the parameters making optimisation of the design quick and simple. Unique design analysis tools also show the designer graphically the effects of changes to the main design parameters, allowing the designer to optimise the design at a glance.

Compared to completing the calculations by hand, the CivilWeb Gabion Wall Design Spreadsheet will save the designer hours of work on every single design.

Gabion Wall Design - Inputs

The CivilWeb Gabion Wall Design Spreadsheet works by completing a design analysis for a proposed gabion wall design input by the designer against three failure modes. This is the approach required in BS EN 1997. The three failure modes are bearing capacity failure of the underlying soils, overturning failure of the gabion wall or sliding failure of the gabion wall caused by the forces acting on the gabion wall from the retained materials. As described above, the overturning and sliding failure modes must be completed both for the whole structure and for each level of the gabion wall. This is because there are no bonds between  the levels in a gabion wall, just the friction between the courses.

The first step in gabion wall design is to input a proposed retaining wall geometry. The main considerations for the designer are usually the width of each course of gabion baskets and whether the front face of the gabion wall is to be stepped or sheer. This is usually an aesthetic consideration though stepped gabions are generally more stable than sheer face gabion wall designs. The overall height of the gabion wall is usually set by the site conditions and the height of each course is set by the standard height of the gabion units which is usually 1.0m.

The initial geometry of the gabion wall can often be approximated from experience of similar height gabion walls. The CivilWeb Gabion Wall Design XLS includes a handy tool which shows the designer the geometry of the input gabion wall which allows the designer to instantly see any mistakes and to judge whether the gabion wall looks reasonably stable.

Next the designer must input the gabion wall parameters such as the density of the units and the friction between courses. This information can be taken from the manufacturer. Different densities of rock fill can be used in some cases, a denser fill material will produce a more stable design though it will also exert a  larger force on the underlying soils.

Finally the designer must input the soil characteristics such as soil density, internal friction angle and bearing capacity. The CivilWeb Gabion Wall Design Spreadsheet calculates the maximum bearing pressure which the gabion wall will produce and compares this with an allowable bearing capacity input by the designer. The bearing capacity of the soil can be determined from insitu or laboratory testing of the underlying soils or from experience. A detailed bearing capacity analysis can be undertaken using software such as the CivilWeb Soil Bearing Capacity Spreadsheet.

Note in some conditions the settlement of the gabion wall may also be significant. Usually the allowable bearing capacity method of analysis will limit total settlement to less than 25mm and differential settlement to even less. This is usually more than sufficient for gabion walls. However in some soils significant consolidation settlement can occur so a settlement check may be prudent. This can be undertaken using software such as the CivilWeb Foundation Settlement Calculation Spreadsheet.

Gabion Wall Design - Stability Calculations

The CivilWeb Gabion Wall Design XLS now completes the stability calculations and presents these instantly in a summary table. The spreadsheet completes the calculations in accordance with BS EN 1997 which requires calculations to be undertaken with two sets of partial action and material factors. These are the Design Approach 1, Combination 1 and Combination 2. These partial action and material factors are preset into the spreadsheet but can be changed by the designer if required.

The spreadsheet presents the results of the calculation instantly in a unique design summary table which allows the designer to see exactly where the proposed gabion  wall design is valid and where it is not. It also allows the designer to see which parts of the gabion wall design are overdesigned and can be optimised.

CivilWeb Gabion Wall Design Spreadsheet

The CivilWeb Gabion Wall Design Spreadsheet includes unique analysis tools allowing the designer to complete and optimise a fully BS EN 1997 compliant gabion wall design in minutes.

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