# Cantilever Retaining Wall Example (Metric)

September 1, 2020

ASDIP RETAIN is a structural engineering software for design of retaining walls. It includes the design of concrete cantilever retaining walls based on the latest ACI 318 provisions. This document is a step-by-step overview of a design of a concrete cantilever retaining wall example using ASDIP RETAIN in metric SI units.

The design of retaining walls may become cumbersome and time-consuming, since it involves an iterative process to calculate the stability ratios, and the application of the Code provisions to design the reinforcement. ASDIP RETAIN supports the following systems of units: US (kip, ft, in, ksi), SI (KN, m, cm, MPa), MKS (Tn, m, cm, kg/cm2).

## Cantilever retaining wall example (metric units)

As an example, letâ€™s consider a cantilever retaining wall with a flat backfill, subject to the surcharge load shown below. Design the optimum dimensions and find the required reinforcement.

## Design Steps

Enter the geometric dimensions of the wall. In this case, the stem height is 7.20 m. Let's try a stem thickness of 65 cm. and also let's specify a footing thickness of 65 cm. The rebars will be selected as necessary per the flexural requirements. Enter initial values of toe and heel, say 1.0 m and 3.5 m. Note that the design is an iterative process and the final dimensions may vary slightly. A shear key is required to increase the sliding resistance. The At-a-Glance tab shows a summary of the design for a quick overview of your work as you go. Note that the soil bearing pressures are less that the maximum allowable value.

Click to enlarge

Enter the loads on the wall. The backfill will be a select material with density = 19 KN/m3 and internal friction angle = 30 deg. In this example the backfill is flat with a uniform surcharge on top. Enter the surcharge load given as part of the problem statement. The water table is 1.0 m above the bottom of the footing. Use the Coulomb active lateral pressure theory. The Condensed tab shows a more complete set of results grouped by topic, great for a more detailed overview of your design.

Click to enlarge

Enter the material properties. In this example the concrete strength is 30 MPa and reinforcing steel yield is 500 MPa. This will affect the shear strength, and will control the thickness of the stem and footing. Use a friction coefficient between the footing base and the underlying soil of 0.50. The internal friction angle of the natural soil is 28 degrees, which is used to calculate the passive pressures. The image below shows the Materials tab, and a graphic view of the Stability pressures and forces. Note that all stability safety factors are larger than the minimum allowable.

Click to enlarge

Specify the rebars for the wall. ASDIP RETAIN has multiple options to customize the reinforcement. In this example the stem main rebars are 32 mm diameter. If we want to use a smaller rebar size we will need to increase the stem thickness. The image below shows the Reinforcement tab and a construction view of the retaining wall design example rebar sizes and spacing. Note that alternate vertical rebars at the backfill side have been cut off in order to optimize the stem flexural capacity.

Click to enlarge

## Takeaway

ASDIP RETAIN includes the design of cantilever retaining walls in different systems of units. This example in SI metric units shows that the design can be completed and optimized in minutes, which otherwise would be very cumbersome and time-consuming.

Detailed information is available about this structural engineering software by visiting ASDIP RETAIN. For engineering background, please see the blog post Cantilever Retaining Walls: Overview of the Design Process. For our collection of blog posts about retaining walls please visit Structural Retaining Wall Design.