concrete encased conduit duct bank crossing

CONCRETE ENCASED CONDUIT DUCT BANK CROSSING INSTALL
CONCRETE ENCASED CONDUIT DUCT BANK CROSSING FREE

If these minimum cover heights cannot be met, additional protection of some form should be provided, eg., concrete slab or concrete encasement. Subject to construction equipment loadings Subject to vehicle loading, not in roadways Minimum cover over the top ducts should be in accordance with AS/NZS 2032 and AS/NZS 2033 recommendations, repeated here for reference: Again, lower quality surround material may be used with increased spacing and higher stiffness ducts, but this play off is unlikely to offer a more economical solution. Low fines sand is the most commonly chosen material. Single sized crushed gravel offers the best support, but infiltration over time of soil from above may have longer term undesirable consequences.

CONCRETE ENCASED CONDUIT DUCT BANK CROSSING FREE

The material used for surround of multiple ducts must be readily compatible and free flowing.

Compaction should be carried out layer by layer, and spacer jigs used to maintain alignment. Whilst alignment may not be functionally critical, displacement in one direction will detract from the ability to compact on the other side. This requires somewhat more care than for single duct installations. The other obvious difficulty with multiple ducts is maintaining alignment during the compacting process. Spacers should be used to control depth of sand, removed before compaction and placement of the next layer. The height between each layer must be sufficient to enable a uniform bed to be achieved. The requirement will vary somewhat with particular circumstances and size of pipe, but 40 mm could be considered a minimum convenient gap for a 100 – 150 mm duct to allow access with a hand compacting tool. There must be sufficient space between the ducts to allow placement of surround material and its compaction. A preferred method is to use sub-duct inside a larger duct. If this type of installation is necessary, part compensation is possible using a stiffer pipe. Conduits installed in this way will distort, possibly quite severely.

Clearly, ducts cannot be installed in contact with each other with any expectation of support all round. The requirements for support are no different for multiple ducts, but the practicalities of achieving it are somewhat more tricky. General guidance for the installation of PVC and PE pipes are given in AS/NZS 2032 2 and AS/NZS 2033 3 respectively. Proper support is obtained by the use good surround material and compaction practice.įor single pipes or conduits, the relationships between surround material properties, compaction levels, and pipe stiffness are well established and design procedures are covered by Australian Standard AS/NZS 2566.1 1. All flexible pipes, regardless of material, require adequate support from the surround material to control vertical deformation due to soil loading. This property enables them to accommodate strains from soil movements, expansion and contraction, seismic and other loadings that would rupture rigid pipes. This note provides guidance on preferred installation practice.

CONCRETE ENCASED CONDUIT DUCT BANK CROSSING INSTALL

It has been common practice for many years with PVC and PE Telecommunications and Electrical conduits to install multiple duct banks in a single trench. Installation of conduits in multi-duct banks (VX-TN-12G) Introduction

Concrete encased conduit duct bank crossing