Standards related to underground services are governed by 55 territorial authorities and a myriad of water service providers, local lines companies, and gas distributors. As such standards and requirements are different in your local area. This document is based on Auckland and National standards and is intended to provide a general guide only.
Stonebloc is a residential gravity retaining system. At the heart of the system are a series of interlocking mass concrete blocks ranging in weight from 300kg to 900kg. In general, the blocks are stacked on top of eachother in a running bond pattern. In good ground conditions simple foundations of leveling fines are required.
One of the unique benefits Stonebloc offers is the ability to non-destructive dismantle walls to access utilities for maintenance purposes, and then reconstruct the walls with ease.
Some councils do not require segmental retaining walls to have a bridging design as the wall can be non-destructively dismantled to access the underground pipe in the event maintenance is required. This should be discussed with council before undertaking structural design work.
Bridging, in a technical sense, is required when a retaining wall is within a defined ‘Zone of Influence’ in relation to an underground [water] pipe. The assumption is that the retaining will exert pressure on the pipe and may damage it. Therefore a ‘bridging’ design is required to ensure the force of the wall is directed to a point outside the Zone of Influence.
There are two core scenarios where bridging may need to be considered:
