Traffic & Loading
When selecting enclosure type, designers and end users must determine if enclosure will be placed in trafficable application; whether traffic is deliberate (e.g. along driveway) or accidental (e.g. along footpath); and whether traffic is vehicular or pedestrian nature. In addition, consideration must be given to ground topography, soil conditions, and building location.
Pits positioned in a long cable route can typically cross various types of load scenarios. Each pit location should be individually considered.
Footpaths
Enclosures located in footpaths are generally exposed to a high volume of pedestrian traffic but can be subjected to non deliberate vehicular loads. Good practice requires enclosures are selected so only minimal surface area of footpath space is occupied - particularly along cycleways, pedestrian alignments, wheelchair access paths or ramps. It's recommended that cable pits are located outside ‘drip lines’ of footpath vegetation.
Landscaped Areas
Enclosures installed in landscaped areas are generally exposed only to pedestrian traffic. Plastic pits are ideal for this application as long as sand/soil is stable and vehicles in close proximity do not surcharge soil and introduce side loads to pit. Designers must aim to locate cable enclosures at high points along terrain so they do not become significant drainage collection points.
Rigid pavement cable enclosures (e.g. vehicle paths, driveways, cycleways, ramps) are generally subjected to deliberate vehicular traffic. Pit bodies need to be strong enough to support traffic rated covers and be encased in cement concrete (base and surround). ACO does not recommend use of plastic pits in these applications.
For these applications, AS/NZS 3084 specifies minimum distances for access holes with respect to each other, roadway corners and other highly trafficked zones.
Unless enclosures are designed for heavy duty applications, they must not be placed in locations where heavy loading is anticipated. Guards or barriers that prevent entry are recommended. If heavy duty cable pit is required, or where constant deliberate vehicular traffic is anticipated, ACO recommends Rhinocast®, ductile iron access covers are installed in slab/pavement above enclosure. If surface cable ducting is required use ACO CS System.
Cable pits should not be installed in fast moving road applications, unless certified by qualified engineer and approved by relevant roads authority. Austroads document: AP-G72 provides further guidelines for cable pits and access holes located on/near urban/rural roads.
Load Standards
There is no Australian standard that tests for cable pit strengths. AS/ACIF S008 provides basic performance criteria for communications pits. Some telecommunications carriers have their own criteria.
To give assistance in selecting correct enclosure, table below is based on loadings outlined in AS 3996 (Access Covers & Grates). This is cross referenced with international standards, EN 124 and EN 1433, the latter, best suited for surface cable ducting.
ACO has NATA accreditation (No. 15193) for its testing laboratory and can provide NATA certified test reports for load tests set out in AS 3996, EN 124 and EN 1433.