Determine and locate proper base size for each section of the retaining wall. Verify that the correct type and color of block has been ordered and delivered to the job. Verify that the foundation soil and retained soil conform to design requirements. Verify that infill soil meets design standards.
It is recommended retaining walls be inspected four times a year, that is, before or after each season. Heavy rains or soil frost movement can have a significant effect on a retaining wall in a short time. At the very least, someone should perform an annual inspection and compare those findings with the year before.
The basic principle for the design of the Retaining Wall is that the reinforced concrete stem and footing flexure and shear design strength must e at least equal to the factored moment and shears determined from the analysis. The wall stem is designed as a cantilever, fixed at the footing.
There are two checks to consider the stability of the retaining wall. One is the check for an overturning moment and the other one is the check for sliding. The weight of the retaining wall including the gravity loads within it plays a vital role in performing the stability check. Refer to Figure A.
Absolutely! Even a 2-foot retaining wall needs an effective drainage system. Without it, water can build up behind the wall, leading to pressure that might cause the wall to lean or even collapse. All walls need systems to manage water effectively, preventing damage over time.
Signs of a Failing Retaining Wall
Sagging or bowing: Chances are, if it looks like your retaining wall is beginning to bend, there may be a problem with the structure itself or what it's holding back.
A Building Permit and engineering calculations are REQUIRED when: The wall is greater than 4'-0” measured from bottom of footing to top of wall.
Depending on the material, soil, and groundwater, a permanent retaining wall can last anywhere from 25 to 100 years. However, consider the material used to build a retaining wall and any necessary maintenance for the structure's longevity and performance.
In addition to the three types of failures i.e. sliding, overturning and bearing failure, a retaining wall may fail in the following two modes if the soil underneath is weak. Shallow Shear Failure: This type of failure occurs along a cylindrical passing through the heel of the retaining wall.
Shape Arrays are installed on the backside of the wall or on slopes above the wall to monitor lateral displacement, deformation, and rotation. Load cells or strain gauges monitor anchor performance. Piezometers monitor pore-water pressure. Crackmeters can monitor movement at joints.
The most common ones are the limit equilibrium method and the finite element method. The limit equilibrium method assumes that the wall and the soil are rigid bodies that can be divided into slices, and calculates the factor of safety against sliding, overturning, and bearing capacity failure.
A cinder block retaining wall can last a very long time, typically between 50 to 100 years, depending on the quality of materials used and the conditions it's exposed to. Proper construction and maintenance are crucial for longevity.
Rules of thumb commonly used by designers to establish the geometry of the wall include (refer to diagram): Base width = 1/2 to 1/3 of the height of the wall. Base thickness = 1/8 of the height of the wall but not less than 12 inches. Stem thickness = 6 inches + ¼ inch for each foot of wall height.
Concrete block retaining walls must be stronger than freestanding walls. Insert rebar in the footing when you pour it; this should be done every three blocks or at intervals specified by your local codes.
With the permission of both property owners, a retaining wall can be built on property lines. But it's worth noting that the two parties still have responsibility for any of their actions that destabilises the wall's structural integrity.
The maximum slope for the soil you can safely go without having a retaining wall is 35 degrees. This is especially important to keep in mind if the soil is granular. If the slope of your angle is steeper than 35 degrees, you will need a retaining wall to keep the landscape in place.
Retaining walls that are built between 3 to 4 feet high also don't require any structural support, as they can hold their own weight and the soil without collapsing.
Here's how to inspect your retaining wall: Visual Inspection: Walk along the length of the wall and look for visible signs of damage, such as cracks, leaning, or bulging. Check Drainage: Ensure that the wall's drainage system is functioning correctly. Look for water pooling or seepage.
So, if soil and ground issues are not covered by homeowners insurance, are retaining walls covered by insurance? Because retaining walls are frequently considered a detached structure, damage to them can be covered under your homeowners policy under the right conditions.
Bulging or leaning retaining walls indicate significant structural issues that need immediate attention. Poor drainage or clogged drainage pipes often cause soil to shift, leading to these problems. When you notice a leaning retaining wall, the situation requires quick intervention to avoid severe property damage.
Hydrostatic Pressure and Wall Failure
When water isn't properly drained, it can accumulate behind the wall, exerting pressure on the structure. This pressure can prompt the wall to shift, crack, or even collapse. To avert such failures, it's crucial to have adequate drainage behind the retaining wall.
Excavation
Dig a trench for the bottom row of blocks. They should be buried about 1 inch deep for every 8 inches of wall height. This provides strength and stability to your retaining wall. Make sure that your trench is level and compacted.
Proper drainage is critical to prevent water buildup behind the wall, which can lead to pressure and eventually cause the wall to fail. For effective drainage, the choice of gravel is paramount. Fractured rock is often the preferred choice for the drainage layer of retaining walls.