Terraced Walls can Tackle and Unruly Hillside – Building a new home can be exciting and often challenging. This hillside lot was indeed a challenge for the homeowners building in a new development. They needed to reshape the slope in front of their home and gain more usable land for a driveway leading to the front entrance. Read all about it:
Terraced Ashlar Blend Retaining Wall
The Wall Inspector Certification Program is designed to give building officials and inspectors the proper training and tools to ensure top quality retaining walls are built. As a leader in the industry, Allan Block Corporation has developed these tools and training programs to help building inspectors get the knowledge and the resources they need to inspect Allan Block projects.
With the help of our vast network of trained Allan Block representatives, building officials now have the opportunity to take advantage of our installation training, technical support, and the many tools we have available to help them properly inspect and verify installation of the Allan Block products. Learn more…
I just wrapped up helping an engineer with his design and thought to myself “this is a great wall to blog about.” The wall was nothing spectacular, in fact, it was quite ordinary. All too often we get excited about those monster walls and forget that most of the walls built are less than 10 ft (3 m) tall. What made this wall interesting was the slope below the wall, a parking lot above the wall, and a very tight jobsite. For a detailed look at some of the conditions you need to watch for, see the Conditions page on the Allan Block website.
The first thing we addressed was the slope below the wall. A general rule of thumb is to bury additional block when there is a slope below the wall so you have a minimum level area, or bench, of 5 ft (1.5 m) extending from the toe of the wall horizontally to daylight.
In relation to this slope below the wall, we discussed the potential for a global stability problem. A global stability failure can be defined as the entire hillside slipping and sliding to the bottom of the slope which would obviously take the Allan Block wall with it. Global stability can also be a concern when building terraced walls, working in poor soil conditions, or building near water.
Wall Setback
Improper water management is a leading cause of wall failures. To help mitigate this potential problem, proper water management is critical throughout the life of your retaining wall. In February, Danelle touched upon the planning that must be done in order to direct water away from your retaining wall using swales, berms, and other grading.
Water Management
Once the wall is built correctly with proper drainage, the owner must assume responsibility for the water management for the life of the structure. If future site improvements involve grading the site differently, keep in mind how water may flow and ensure that it does not flow directly toward the wall. If new gutters are put on the house, or a new sprinkler system is installed, avoid having this water pool near the top of the wall. Taking care to avoid water management issues will prolong the life of the retaining wall and keep it maintenance free.
Tom
Last time I discussed what geogrid reinforcement is and how it benefits your retaining wall, but what is really going on behind that Allan Block façade? For an overview of internal stability with pictures, take a look at the Reinforced Soil Walls Analysis page on the Allan Block website.
We recommend 2-course spacing when constructing your retaining wall. This helps to tie the reinforced soil mass together one cohesive mass to retain the soil behind. Typically, this 2-couse spacing will allow a lighter weight grid to be used because the forces are shared among more layers of grid. The closer the grid is placed together, the less each layer of grid needs to work to keep the wall standing tall.
When designing a wall using geogrid, there are three main factors that need to be reviewed:
Using geogrid reinforcement in your retaining wall design is a way to build taller walls that can support tremendous loads. When designing, keep in mind the wall’s internal stability by considering all of the forces acting on the individual layers of grid.
Tom
For information on how to plan design and build Allan Block Segmental Retaining Walls and Allan Block Courtyard Walls go to
www.allanblock.com
