Metro Trenching

CLEANFAST™ has been designed to eliminate all the previous problems associated with burying new services or utilities in the road sections of metropolitan areas.

Designed specifically for trenching in built up urban areas the CLEANFAST™ includes many unique design features. CLEANFAST™ vehicle are equipped with a patented mini rock saw tool, complete with a noise-reducing shield and a powerful self-contained vacuum unit for the extraction of waste and debris as a result of the trenching process.

The rock saw cuts through the asphalt or concrete surface and subsurface materials quickly and easily to make a consistent and continuous trench of 60mm to 150mm wide and 160mm to 450mm deep. The trenching process of the CLEANFAST™ is designed in such a way that minimal, if any, damage to the road construction and its integrity occurs. The integral vacuum cleaning and air-filter system minimizes and debris at the worksite and eliminates any dust from the cutting process.

The end result is a clean accurate trench ready for the insertion of any ducts, cables or utilities.

The City-Trencher Trenching Process

The City-Trencher process is very similar to the Cleanfast process with the same end result and benefits. The fundamental difference is that the City-Trencher is equipped with the Duct Laying and Back Fill process as part of the Trenching machine.

The City- Trencher cuts a trench of the same dimensions into the existing asphalt roadway and deposits the excavated debris alongside the trench. The Duct is then fed over the City-trencher straight into the newly excavated trench and the trench immediately backfilled. A Super- Sucker, or vacuum truck, follows close behind cleaning up the excavated debris. The City-Trencher process is in many ways therefore an all – in – one process, bar the vacuum cleaning action.

This process is unique in that the City-Trencher is entirely remote controlled.

Benefits of CLEANFAST™ & CITY-TRENCHER

Due to the nature of the design and width of the trench the system provides numerous benefits to both the operator and municipal authorities.

Speed of deployment for the Operator, means quicker time to market and revenue generation

Deployment in the asphalt provides access to areas not previously accessible, mainly due to utility congestion in the sidewalks. Minimal disruption to any utility services, i.e. Water, Electricity etc...

Controlled trenching process resulting in minimal disturbance to the existing road structure and no future problems for the road agencies.

Minimal disruption to traffic, the resultant trench of 120mm does not restrict traffic flow as vehicles can safely, and freely, pass over the open trench. Minimal pedestrian disruption as pedestrians can easily step over the narrow trench. No pedestrian disruption on the sidewalk.

Duct or Cable Laying Process

Laying of the ducts and/or cables follows the CLEANFAST trenching and cleaning operation. A light vehicle tows a reel trailer closely behind the CLEANFAST™ vehicle supported by a field crew which supervises and controls the reel ensuring that the required duct configuration is laid true to form on the bottom of the clean trench.

Typical duct configurations consist of up to four 40/32mm HDPE ducts or 7-way bundled 12/10mm micro ducts. Direct burial telecommunications, power cables and other utilities can also be laid in the trench if required.

The City Trencher TRS300 has the cable laying process as an integral part of the Mini trenching and backfill process.

Backfilling and Re-Instatement

Once the duct configuration is installed in the trench a special ready mixed concrete mixture, known as Backfill, is poured into the open trench using a special concrete pouring sleigh.

This reduction of the size of the trench reduces the volume of excavated material thereby ensuring that none, or very little decompression, of the surrounding soil and road layers occurs. This reduced trench size, furthermore, also maintains the original design strength of the road structure and the integrity of the different road layers.

Backfilling is carried out with a Backfill mix that has been developed both in Europe and South Africa and adapted to South African conditions. The Backfill takes the full shape of the trench and envelopes the buried duct, protecting the duct and strengthening the road structure.

For the City-Trencher the backfill process is part of the trenching process, however the backfill mixture is the same for both. The Backfill is produced under strict quality control in a Volumetric Mixer plant on location. A Volumetric Mixer is a specialized mixing unit, which produces the backfill on demand. The mixture is strictly controlled, in order to guarantee its homogeneity, composition and required strength (1 to 2 MPa in 28 days).

The Backfill mixture anchors the duct configuration in position and settles around the ducts/cables protecting its integrity. The fluidity of the Backfill fills all the cavities in the trench minimizing any possibility of deterioration of the road structure and its integrity

Most importantly the Backfill retains the existing road structures strength and the integrity of the different layers.

The mixture is specifically formulated to avoid the formation of a "stiff beam effect" i.e. it is flexible and can move with the surrounding road materials. The composition of the Backfill is such that it expands slightly to form a solid bond with the excavated road layers maintaining the integrity of the layers and road strength. It furthermore allows easily excavating and autocompacting

The Backfill mixture can also brightly colored to visually indicate the presence of an underground cable or utility system.Where the City Trencher TRS300 is used, the backfill process is integral to the trenching and cable laying process.

Rehabilitation of the Road Surface

Re-Instatement of the road structure is the final process which takes place to return the tarmac to its original standard. This process can only take place 3 –4 days after the backfill process is completed. The delay is due to the fact that the backfill material does have a curing period before it settles to the required "hardness".

This operation involves grinding away a 200mm wide slot into the tarmac, across the trench and then refilling either a Cold, or Hot, Asphalt mixture, which sets extremely quickly. It is extremely important that this mixture adheres to the existing asphalt and backfill to form a homogenous continuous layer blending in with the road surface.

Typical Metro Mini Trench Structure

The contents within the Mini trench can be adapted to suit a specific operator’s requirement. The number and size of the ducts may vary, in some instances power cabling may be required. Although it is not recommended, Mini trenches can be utilized to distribute water pipes etc.

Metro Trench Fibre Capacity

For Ducting and Fibre cable requirements the Metro trench is typically 100mm wide and has a minimum of 300mm backfill above the utility. These dimensions may vary, depending on the operator’s needs and city council requirements.

Typical Trench Position in Roadway

Metro trenches are generally placed out of the direct heavy traffic lines and wherever possible within the parking lanes alongside the kerb.

Metro Trench Fibre Capacity

The DFA Metro trenches are designed to accommodate up to 28 Fibre Optic Cables in an array of microducts. Each fibre optic cable can consist of up to 144 fibres. With today's transmission technology each fibre pair is capable of supporting at least 80 Lambdas running at 40GBps.

	1. Route Planning and design, Followed by GPR route survey and marking
2. Route Planning and design, Followed by GPR route survey and marking
	3. Route Planning and design, Followed by GPR route survey and marking
4. Route Planning and design, Followed by GPR route survey and marking
	5. Route Planning and design, Followed by GPR route survey and marking