What is trenchless technology?

Trenchless technology is a type of subsurface construction work that requires few trenches or no continuous trenches. It is a rapidly growing sector of the construction and civil engineering industry. It can be defined as “a family of methods, materials, and equipment capable of being used for the installation of new or replacement or rehabilitation of existing underground infrastructure with minimal disruption to surface traffic, business, and other activities.”

SASTT Award of Excellence 2024

ROLKON - Winner of the 2024 SASTT Award of Excellence

Stormwater Drill – Innes Road Durban

Project Detail

The aim of this project was to upgrade the stormwater network in the area to prevent the micro flooding that was constantly occurring between the properties. The drill required the installation of the main stormwater trunk which was a 630 diameter HDPE Pipe PN10 of 85 meters in length.

BLOC was the main contractor and they undertook the project for the eThekwini Municipality. Rolkon was contracted by BLOC to provide horizontal drilling skills and equipment. BLOC and Rolkon have a long history in project
partnerships where collective solutions to technically challenging HDD projects are required.

Location and Constraints

The project site was located along Innes Rd in Morningside, an affluent suburb in Durban KwaZulu Natal overlooking the Moses Mabhida Stadium.

One of the most hilly areas of Durban, not only did the topography pose grade challenges, but a series of other site constraints that had to be carefully
understood and planned around. These included:

Tight space behind the construction site itself which posed a challenge when it came to fitting the drill rig onto site.
Drilling under the ablution facilities that had been established for the construction site we found ourselves located on. This meant we had to enter the drill point at approximately 15 degrees to ensure we could get under the building.
Ensuring we drilled under the foundations and footing of the very old outbuildings on the property
Ensuring we drilled under the cantilever foundation of the retaining wall that ran adjacent to approximately 80% of the drill line.
Drilling under both a pool house and tennis court and avoiding a garage.
Tying up the levels at the entry and exit pits across the 17m fall of the drill grade.

Technical Aspects

There were some interesting technical challenges on this drill which required some innovative thinking from all members of the team and the application of an array of skills to ensure the job was delivered. Some of the challenges included:

The drill length itself which was in the order of about 120 meters in length
The drill grade which was down a slope of approximately 10%
The drill time required and the need to keep the drill head lubricated
The excessive mud that was produced as a result of a drill of this nature and the management of this mud.
The management of the traffic on busy Innes Rd.

Some of the solutions applied to manage these challenges included:

The design of a vertical and horizontal site profile by Rolkon to help manage the drill line
The 4m deep pit was constructed by BLOC for the changing of reamers and removal of the pullers.
A 315mm puller specially engineered and manufactured by HDD Engineers
A 630 mm to 315 pipe reducerdesigned and bulit by RHO -Tech.
A 10,000 litre water tank installed to ensure a constant supply of water to make the drilling mud
Mud management using a combination of a TLB, 5m3 tipper lined with plastic and a vacuum pump for sewage – used to pump mud in this instance.

What are the Benefits of Trenchless Technology?

Environmentally Friendly

Using specialized equipment underground infrastructure is installed, repaired or replaced with minimal ecological disturbance. Infrastructure can be installed under buildings, under forests, under wetlands and bodies of water.

Minimal Disturbance to Surroundings

No one likes their home, business or morning commute to be affected by construction. The footprint for a trenchless construction zone is smaller and often times done in an existing right of way.

Decreased Rehabilitation Time

Because trenchless construction methods require little digging, the time to rehabilitate the work area to as-found or better condition is decreased.

Saves Time

With decreased disturbance, projects using trenchless methods take less time to complete. Less time means less inconvenience associated with a construction project.