The new and definitive Terraforce Design Guide Consider low-volume concrete roads for

The new and definitive Terraforce Design Guide

The beautifully curved Terraforce block wall at the Salamanca Hospital development in Spain Partially based on the company’s original 1992 design manual, Terraforce’s new extended version involved the participation of professionals in three countries and takes note of their unique challenges and experiences in the design of segmental retaining walls (SRWs) in accordance with local and international standards.

Split into two sections, the Terraforce Design Guide deals with the theory and practice of gravity retaining wall design – with worked examples – as well as the design and installation of Terraforce reinforced soil retaining walls in accordance with BS 8006 and SANS 207:2011. All the procedural and sequential steps that need to be followed are covered to construct safe and sound SRW structures.

“Minimum requirements in the standards (SANS 207 and BS 8006) are sometimes questioned by engineers, such as the seemingly excessive minimum width of the reinforced soil structure. The reason for this is explained in depth, with guidance further provided for specifying shear resisting mechanisms,” says industry pioneer Holger Rust, founder of Terraforce, adding that another important topic covered includes the SANS 10400 National Building Regulations regarding balustrading above walls that exceed 1 m in height. “As with any structure, the design of Terraforce retaining walls should only be undertaken by suitably qualified and experienced designers with due cognisance being taken of the specific geotechnical conditions and vital soil parameters pertaining to the site,” Rust explains.

The Terraforce Design Guide also has builtin links to useful tools to assist in design, construction and supervision routines. Cautionary notes and notes for contractors are included, as well as a Table Creator to obtain design values for Terraforce’s range of precast concrete retaining wall blocks and allied products, and to help in estimating material costs.

“There will be a link to the Maxiwall Pro software for the design of composite retaining walls, as well as a link to Terrasafe, our in-house design service,” says Rust, adding that users can access the Design Guide by registering online at www.terraforce.com.

Maxiwall Pro

Terraforce launched Maxiwall Pro in August 2018 as a privately labelled version of the most comprehensive and widely used SRW design software in the industry, the Vespa MSE Design Suite (updated to the latest standards in 2020).

Maxiwall Pro allows SRW design professionals to easily produce complete wall designs utilising the award-winning Terraforce line of SRW products. With all block and geogrid information preloaded, designers can select from a wide range of proven Terraforce systems via easy-to-navigate drop-down menus.

Compared to other mechanically stabilised design software options, Maxiwall Pro increases design efficiency, improves accuracy and promotes a seamless flow of information between design stages and parties. It generates full wall layouts with accurate quantity estimates and comprehensive reports. The Calculation Engine can simultaneously run static, seismic and ICS analysis in accordance with NCMA,

A light gravity staggered SRW wall design

AASHTO (LRFD), AU (Australian Standard), and British Standards design methodologies.

“The Terraforce package is built around the understanding that the goal of the design engineer is to produce a set of clear, comprehensive construction drawings. With the DXF output feature, CAD cross sections and elevation views are automatically generated and ready to import into AutoCAD. “Users of the Maxiwall Pro package will also have an option to purchase a copy of the AWall CAD Tool, which allows the user to accurately represent the plan and elevation views of a retaining wall on their grading plan,” Rust explains.

AWall factors in the variable heights along the length of a wall, wall batter (inclination), and wall width to generate a plan view, representing the ‘real’ footprint of the wall, and can create elevations and generate quantities.

“Once the design is complete, Maxiwall Pro also allows you to export the wall geometry, soil conditions and loading conditions to Phase 3 settling tanks select Global Stability software programs,” Rust continues. in operation

A reinforced staggered SRW wall design using Terraforce Rock Face blocks Simple, easy-to-follow design tutorials are provided. These cover the generic version of Vespa MSE Design Software, but generally apply to Terraforce SRW.

“The Terraforce Design Guide is our contribution to setting the benchmark for SRW excellence both in South Africa as well as internationally where our Terraforce products are employed, and a special thanks goes to the various authors for their invaluable input in updating the 1992 version,” Rust concludes.

THE EVOLUTION OF RETAINING SYSTEMS

The practice of building retaining walls and barriers for various purposes, such as level platforms, dams and stabilised slopes, has been pursued on all continents for at least 6 000 years. Traditionally, rough or shaped boulders, rock-filled wicker baskets or clay mixed with reinforcing straw were used.

Early on, advances were made with burnt clay bricks, and then around 2 000 years ago with the invention of concrete by the Romans. With the demise of this empire, the know-how to make concrete was lost until its reinvention in the early 1800s in the UK by Joseph Asplin, inventor of Portland cement.

From the 1850s, mass concrete, in combination with reinforcing steel, became the preferred choice of material for building retaining walls. The first machine designed to manufacture hollow concrete retaining blocks was produced by a concrete pipe manufacturer in Germany.

Since then, many concrete retaining block designs have been developed to build segmental retaining wall systems. Some are interlinked with gaps between blocks, while others interlock on the vertical and/or horizontal plane. All systems rely – when used for mass gravity retaining walls – primarily on constructed mass (block weight and weight of soil, gravel or concrete contained within the blocks) and on inter-block friction to derive a measure of sliding resistance and, to a lesser degree, on interlinking or interlocking between blocks.

Soil reinforcement The concept of soil reinforcement was recognised more than 5 000 years ago. For example, ancient civilisations used straw and hay to reinforce mud blocks to create reinforced building blocks. The Great Wall of China serves as one of the earliest examples of reinforced earth using tree branches as tensile elements.

Woven geotextiles Woven geotextiles came into existence in the early 1960s (Huesker Synthetic). The modern form of soil reinforcement was first applied by Vidal (1969).

Geotextile reinforced retaining walls with wraparound facing were first built in France. Due to limitations on the design life of the wraparound geotextile facing, segmented retaining block walls were later used for this purpose.