Merbein Railway Cutting Erosion Control

Background

In early 2017 V/Line experienced drainage issues within the Merbein railway cutting, 617.60 kilometers between the Dunolly to Yelta Freight corridor.

The engineering firm GHD was engaged to investigate the concerns during a site visit in August  2017. Reports from the visit revealed that the slopes within the cutting were showing signs of wind and water erosion. The erosion had formed large holes and scouring in the slopes, which had caused fine silt, sand, and clay particles to accumulate and create blockages in the crest drains.

This issue prevented water from displacing away from the train line, causing widespread moisture in and around the track ballast. The water had modified the structural integrity of the tracks by preventing its ability to bear the weight of oncoming trains. Due to this high-risk contingency, drivers reduced their speed by 10-15 kilometers per hour to ensure safe and effective movement across the train line.

This problem would be resolved by removing material build-up in the drains, followed by an erosion control solution on the railway cutting and embankment.

A revegetation approach would be a preferred solution for GHD to combat the reported problems. However, soil testing indicated that the sediment consisted of dispersive clay soil. This form of soil is prone to becoming airborne when dry. Due to the low rainfall in the area, revegetation would be a short-term solution; therefore, an erosion control blanket was the most viable alternative for the site.

Project Overview

V/Line approached Erizon in early October 2017 to stabilise the railway cutting in Merbein with low maintenance, long-lasting erosion control solution.

Erizon’s environmental consultants inspected the site location. During this visit, a 3D drone survey examined the land topography to determine the area measurements for optimal product coverage.

Erizon put forward a proposal aligned with V/Line’s industry commitment to maintaining the relevant Australian Road and Maritime Services (RMS) requirements for the embankment stabilisation.

The optimal solution for V/Line was:

• EcoArmour – applied at seven tonnes per hectare and accompanied by a ten-year guarantee.

Solution

EcoArmour is an Australian designed and manufactured erosion control solution, formulated for high-pressure, hydraulic application. Once sprayed, it sets and dries in a matter of hours, providing high-performance erosion control for up to 20 years, depending on the client’s specifications.

It is scientifically engineered with a blend of minerals, interlocking fibres, and specialty binders to form a durable, non-flammable crust. The binders incorporate themselves into the substrate to establish a flexible yet resilient cover, capable of moving with the ground without compromising the product structure.

Equipment

Erizon’s mine-compliant HydroRig equipment with extendable hose line was the ideal delivery vehicle for this project. The solution is mixed on-site in the HydroRig using in-built agitators to create and maintain a consistent slurry throughout each application.

Feature

This vehicle can store 7,000 litres within its holding tank, along with two in-built agitators designed to maintain a homogenous solution mix.

Scope

After extensive analysis and the implementation of safety procedures, works commenced with a 3D drone survey, scaling the area and determining the amount of product required for the project.

Data also indicated that the height of the 400-meter railway cutting ranged from one meter through to five meters, with angle gradients varying from 35 – 60 degrees. This process showed that 65.5 tonnes of EcoArmour was sufficient to protect the area successfully. The 9,350 m² project took four consecutive days to complete, from 6^th to March 10th, 2018.

Challenges

Safety and quality contingency procedures aided Erizon technicians during the following project challenges:

Location

• Access issues were evident early into the project’s first phase with hose equipment unable to maneuver within the corridor cutting. The team worked proactively to combat this problem by altering their application positions.
• The railway cuttings contained protected native plant species, which required the Erizon technicians to reduce the application rate and take additional care when applying EcoArmour around the plants.
• External contractors had not prepared and compacted the embankment located at the top of the railway cutting to Erizon’s company standards; therefore, the team had to resolve this issue with HydroBond, a product used to harden and prepare the surface for the erosion control blanket.

Weather

• On-site technicians were confronted with high temperatures and humidity. Eriozn’s fatigue and heat management plan under the ‘Vision Zero’ initiative triggered a change to break times and rehydration cycles to prevent dehydration and heat stress.

Results

V/Line was pleased with Erizon’s ability to deliver the EcoArmour solution to the RMS standards promptly. Routine communication also played a role in the quick recovery of the rain line, allowing for train travel to return to regulated speed parameters.