Structural Design
Retaining Wall Design
On sloping ground and fill areas, we calculate cantilever, gravity, counterfort and piled retaining walls with geotechnical investigation data, and design them together with their drainage.
What we calculate in a retaining wall design
A retaining wall holds back the soil where there is a level difference on a site, so that the building, road or garden on the upper level can be used. If a wall is built without taking into account the earth pressure behind it, groundwater, building and traffic loads on the upper level and the earthquake effect, its stem cracks, it leans forward, overturns or slides on its base. Sometimes it slides as a whole together with the slope behind it. That is why we design a retaining wall not as a boundary wall but as a load-bearing element with its own geotechnical and structural calculation.
Gölcük and Kocaeli as a whole have many hillside settlements, sloping plots and old fill areas. On this ground a wall is needed for a building foundation, a car park ramp, an estate road or a plot boundary, and the wall is often part of the building design. In fills close to the shore, the groundwater level and the density of the fill change the calculation directly. Both the boundary wall of a single plot and a wall running along a long line are among the jobs we design for property owners, contractors and public bodies.
We take the soil parameters from the geotechnical investigation report prepared by authorized firms and approved by the relevant authority. If there is no report, or the depth it covers is not enough for the height of the wall, we state in writing at the start that further investigation is needed. Carrying out the geotechnical investigation and approving the report are not within our authority. Our responsibility is to use the data in the report correctly in the design and to write the assumptions we make plainly into the calculation report.
Scope
Reinforced concrete cantilever walls
In cantilever walls with a toe and heel and a stem fixed into the base, we set the toe and heel lengths according to the wall height and the space left on the plot.
Gravity and counterfort walls
For low walls a gravity wall is often enough. As the height increases, we move to a system where the stem is supported from behind by counterforts.
Piled retaining structures
On ground with low bearing capacity, we place the wall on piles or design it as a bored pile wall.
Soil nailing and anchored shoring
For deep excavations we prepare temporary and permanent excavation support designs together with our Geotechnical Design service.
Stability checks
We check overturning, sliding, base pressure and bearing capacity. A global stability analysis that takes in the wall and the slope behind it together is carried out separately from these.
Drainage design
We show on the drawings the weep hole spacing, filter material, drainage pipe and where the water is discharged.
Applicable regulations and standards
We take the earthquake effect into account with the equivalent static (pseudo-static) approach, following the provisions of the Turkish Building Earthquake Code (TBDY 2018) for retaining structures. We apply TS 500 (the Turkish standard for the design of reinforced concrete structures) to the reinforced concrete section and reinforcement design, and TS 498 to load values. We calculate active and passive earth pressure, the surcharge from buildings and traffic on the upper level and water pressure with the parameters in the geotechnical investigation report. If the wall is close to a building foundation or a neighboring plot, we look separately at the effect of the load coming from that structure.
One of the common causes of retaining wall damage is water building up behind the wall. If the weep holes and the filter layer are left out during construction, the wall is loaded by a higher water pressure than the one assumed in the calculation.
How we work
Site and data review
We review the existing site survey map, the level differences, neighboring buildings and the geotechnical investigation report. If needed, we go to site and look at the line the wall will follow.
System selection
We choose the wall type by looking at the height, the ground conditions, the space left on the plot and the cost.
Calculations and checks
We calculate earth pressures for the static and seismic cases and carry out the overturning, sliding, bearing capacity and global stability checks.
Reinforcement and drainage details
We draw the section reinforcement, joint spacing and drainage system on the sheets.
Quantities and delivery
We take off the concrete, reinforcement, excavation and fill quantities and deliver the design in a form ready for submission for approval.
Support during construction
If the excavation reveals ground different from the report, we reassess the design together with the contractor and the building inspection firm.
Deliverables
- Structural and seismic calculation report (with the results of the checks)
- Wall plan, longitudinal profile and typical sections
- Reinforcement detail sheets and reinforcement schedules
- Drainage details
- Quantity schedule for concrete, reinforcement, excavation and fill
Frequently asked questions
Is a geotechnical investigation required for a retaining wall?
Yes. The earth pressure and bearing capacity calculations rest on soil parameters, and we take these from the geotechnical investigation report prepared by an authorized firm. We do not calculate on assumptions.
Stone wall or reinforced concrete wall?
It depends on the height of the wall and the load it will carry. For low walls a gravity wall may be enough; as the height, the loads on the upper level and the earthquake effect increase, a reinforced concrete cantilever or counterfort wall is needed. We make the choice on the basis of the calculation.
Do you assess an existing wall that has cracked?
Yes. We inspect the wall on site and look at whether the drainage is working and at its stability. If needed, we prepare a replacement or strengthening design.
Can I see the construction cost in advance?
Yes. We deliver the concrete, reinforcement, excavation and fill quantities with the design. If you wish, we also calculate the approximate cost through our Quantity Take-off, Bills of Quantities and Cost Estimates service.
What backfill should go behind the wall?
A free-draining granular material and a filter layer. Clayey fill that holds water increases the earth pressure and clogs the drainage. We specify the properties of the material to be used in the design.
Examples from practice
Our projects in this field
Request a quote for your project
Write to us with the type of building, its location and the documents you have. We will agree the scope and timeline with you and send a written quote.