Dytap - Design

Design
The information in this brochure is intended to give guidance in the preliminary selection of the Dytap system. Ruthin Precast Concrete offers comprehensive advice on design and installation, including detailed drawings, full work schedules and on-site advice.

Flexible (hand laid)
Where a flexible form of construction is required the actual design will depend on the application, the nature of the formation and environmental conditions which the system will be subjected to.

For example, where the bank of a major river is to be protected and the formation is of a cohesive nature the following will be a typical form of construction:
The bank should be graded to required line and level. Soft spots and voids filled with suitable material and the surface regulated if necessary with a granular material such as quarry scalpings at a grade of 20mm to dust. It may often be necessary to regrade the river bank in which case selected gradings of material must ensure long term stability. The final layer should generally be a nominal 100mm thick capping of compacted DOT type 1 sub-base. The surface thus prepared should be covered by a carefully selected geotextile filter membrane to prevent loss of fines from the underlayers. A 150mm thick drainage layer of DOT type B clean stone is laid and screeded to an acceptable tolerance (say + or - 15mm over 3m). The Dytap blocks are then laid dry jointed. For minor streams and watercourses, the drainage layer may be omitted.

Foundation and Boundary restraint
The provision of an adequate toe support is recommended for all non-articulated revetments. Various types of foundation detail can be adopted. An additional information sheet is available to assist in selection.

The free edge, particularly upstream, should be protected against scour and mechanical damage. An additional information sheet is available to assist in selection of an appropriate detail.

Flexible (articulated/underwater)
Where adverse ground conditions or water levels make provision of a toe support or dry laying impractical, it is possible to form articulated panels of Dytap blocks. Dytap units with holes through the short axis can be assembled into panels using flexible non-corrosive tendons. These panels are generally factory assembled and can be laid onto a prepared surface, below water level if necessary. The panels form completely interlocked and articulated protection which will accommodate minor settlement without disjointing or material loss. The panels are supported by terminating the tendons into an in situ concrete anchor at the top of the revetment slope. Underlayer preparation should generally be as for flexible hand lay, however, tidal and underwater working may dictate some alternative procedures. Full details are available from Ruthin Precast Concrete Environmental Engineering.

On-site fabrication extends the choice of panel length and width to suit individual design requirements, However, under most circumstances factory assembled panels are the preferred option.

Please contact us for details of this and practical panel sizes which are available.

Toe details Although the articulated panels are not supported by the toe construction, it is prudent to consider a form of construction which will protect the toe of the panel from erosion and mechanical damage.

Underlayers The selection of underlayer materials is of paramount importance to the performance of the installation. In most circumstances it is advisable to contact our design advisory service where our long experience in river and coastal engineering can be used to the designer's advantage. Semi rigid This from of construction may be necessary where total flexibility is not feasible. For example, where a transition from a normal embankment slope to a vertical structure is required. In this situation it is possible to lay the Dytap blocks on to a nominal 100m thick screeded layer of 'lean mix' or 'no fines concrete'. The Dytap blocks can be laid with either dry or grouted joints. At slopes of greater than 1:1 and approaching vertical, proprietary ties or slot anchors and mortar joints should be used to give additional stability to the Dytap units.

Wall Cladding When used for walling and cladding Dytap blocks can be built as a permanent shutter or lining for concrete surfaces. They may be attached to structures with slot anchors or built as free standing walls reinforced or unreinforced.

Deterrent/underbridge paving It is often necessary to utilise a form of paving which will accept minor deformation and settlement of the formation and yet remain attractive and functional. This can be achieved by adopting a flexible form of construction. The surface should be prepared with a nominal 100mm of compacted hard core with Dytap blocks bedded on course sand or gravel. The blocks can be laid dry jointed or a dry grout can be brushed in.



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