The Many Faces of SRWs

By Kurt Mee Commercial Wall Specialist Pavestone Company ?EUR??,,????'??+ Denver, Colorado

One of the newest technologies eliminates the split face look and replaces it with the look of stacked rock. This process involves specialized production capabilities. With the ability to make multiple blocks in one mold, each block can have its very own unique look.

Natural Impressions??????oe Ashlar Stone

Presently, the concrete segmental retaining wall blocks available display several distinctive faces. Due to various factors driving the necessary changes our industry is seeing, future faces of the retaining wall block offer countless possibilities. A look back in time reflects how the concrete segmental retaining wall has evolved to what it is today.

Retaining wall construction dates as far back as 5000-6000 B.C. Surrounded by soil, tree branches were placed in horizontal layers to help maintain the structure. Practice, at that time, instructed facing the mass with sun dried mud ?EUR??,,????'??blocks?EUR??,,????'?? or rock. Historic examples include the Persians who built great cities on top of retaining walls. The Pyramids of Egypt, the Ziggurats of ancient Mesopotamia (modern day Iraq), and even parts of the Great Wall of China were built on this principle. These construction practices developed the mechanically stabilized earth (MSE) construction commonly used today.

Today, segmental retaining wall (SRW) block systems are designed and engineered under conservative design principles. The ancient rock facings have been replaced with prefabricated concrete manufactured to achieve high levels of compressive strength. For stability, geosynthetics interact with the retained soils behind the block facing. These blocks can be designed to create walls exceeding 70 feet in height and can carry substantial surcharge loadings such as bridges, buildings, and roadways. This type of wall is an MSE wall using high strength modular blocks.

The SRWs have many ?EUR??,,????'??facing?EUR??,,????'?? personalities. The vertical height of the individual block establishes its overall scale, making it available in three dimensions. The first is the four-inch tall block, sold primarily through home improvement stores and specialty garden centers. These blocks are primarily for the do-it-yourself homeowner who is working on a ?EUR??,,????'??backyard lifestyle?EUR??,,????'?? project. Work on these projects involves small series of walls for planter beds or level sloping ground in minor applications. The second is the six-inch tall block used for larger landscaping projects. These six-inch systems can actually achieve heights of over fifteen vertical feet, when engineered and designed properly. The third face is the eight-inch tall block. The principle concept of the SRW system is to stabilize the earth behind the block, therefore reducing the lateral loading pressure naturally created by the soils. This provides for less weight in the face mass and allows use for more aesthetic facings.

Multiple grades, expansive on-site soils, poor site drainage and site accessibility are typically encountered. All of these issues involve more capital expenditures in order to make the land usable.

Replacing the old singular block style with the new multiple shape products creates a much less appealing structure to be painted on by graffiti ?EUR??,,????'??artists.?EUR??,,????'?? The surface looks irregular to the ?EUR??,,????'??tagger?EUR??,,????'??, thereby taking away the smooth canvas appearance created by a straight block system.

SRWs Today

SRWs were introduced to the United States in the 1970s and, until recently, solution designs have been created mostly by the engineering community. An engineer is contracted by the owner/ developer to design a retaining wall. The engineering of SRWs is principally concerned with the structural capabilities of the product and not the aesthetics. This structural design premise did not lend itself to block face aesthetics. For many years the standard 8-inch by 18-inch straight face block became the status quo for the entire industry.

According to the Bureau of Justice, graffiti is the most common type of public property vandalism. The web site, www.graffitihurts.org, states graffiti attracts crime, drains tax dollars, decreases property value and even reduces business growth. Since many retaining walls are in new metro development areas, they become easy targets for graffiti artists. Annually, communities are spending millions of dollars trying to remove this blight.

Working closely with developers, designers, and municipalities, the block manufacturers are creating new looks that are less appealing to the ?EUR??,,????'??would be?EUR??,,????'?? graffiti artist. By utilizing multiple faced products and colors together, designers can achieve new high quality looks for the walls while reducing the incidence of graffiti.

With the site developmental challenges before us in most communities, the SRW future is on solid ground. In addition to this growth, there have been exciting new facing designs to enhance SRW projects. Most SRWs are an integral part of today?EUR??,,????'???s developments providing wonderful resources for the private and public sector.