The West Trunk Sewer Project Contract 2 stands as a testament to innovation and efficiency – one remarkable feature that has contributed significantly to the project’s success is the use of compressible grout. Compressible grout is a revolutionary material that has been making waves in underground construction, particularly in projects like West Trunk Sewer Project Contract 2.

This article explores the advantages of this unique material and its application in Contract 2 where Technicore Canada played a pivotal role, providing insights into how it has revolutionized the construction of a 3.8 km-long tunnel with a minimum internal diameter of 2.4m, a mid-tunnel drop shaft, and challenging geological conditions. From providing stability to minimizing water leakage and gas penetration, compressible grout has proven to be a game-changer in tunnelling projects.

The Unique Composition of Compressible Grout

Compressible grout’s effectiveness lies in its innovative and unique design. It is a patented blend of cement, bentonite, foam particles, and admixtures. This composition results in a material that, when hardened, can withstand the expected time-dependent deformation of rock, making it an ideal choice for tunnelling projects with challenging geological conditions.

To understand why compressible grout is so effective, it’s crucial to look at its material characteristics. Tests were conducted using steel cylinders to measure lateral confinement and confined compression strength. These tests were performed under controlled conditions, providing valuable insights into the material’s properties. The results reveal a material capable of accommodating significant deformation while maintaining its structural integrity.

Innovations on West Trunk Sewer Contract 2

In West Trunk Sewer Project Contract 2, compressible grout played a vital role in overcoming the project’s unique challenges. With a 3.8km tunnel, varying geological layers, and stringent requirements for stability and corrosion resistance, this project required innovative solutions. Compressible grout rose to the occasion, meeting the project’s demands and ensuring its success.

Enhancing Stability and Performance with Compressible Grout

In the construction of underground tunnels, ensuring the stability of the surrounding soil or rock is paramount. This is where compressible grout shines. It offers several advantages that make it an ideal choice for projects like the West Trunk Sewer Project Contract 2:

Accommodating Deformation

One of the standout features of compressible grout is its ability to accommodate deformation. In the context of tunnelling, deformation refers to the changes in the shape and size of the annular space surrounding the tunnel lining. Compressible grout can handle deformation of up to 16%, and this percentage can be adjusted by altering the mix design. This flexibility is invaluable in scenarios where the surrounding geological conditions are prone to shifts and changes.

Minimizing Overstress

Overstressing the tunnel lining can lead to structural issues and potentially catastrophic failures. Compressible grout acts as a safeguard against such overstress. It helps distribute forces evenly and prevents undue pressure on the tunnel lining. This ensures the long-term structural integrity of the tunnel, even in the face of geological movements.

Water and Gas Leakage Prevention

Water infiltration into tunnels can be a major problem, causing damage and affecting the overall functionality of the structure. Compressible grout, when used as a backup to the gasket, helps minimize water leakage. Additionally, it serves as a barrier to the penetration of gases like methane, which can be hazardous in tunnel environments. This dual functionality enhances safety and reliability in tunnel projects.

The Unique Composition of Compressible Grout

Compressible grout’s effectiveness can be attributed to its innovative composition. It is a proprietary blend that combines various elements to create a material with exceptional properties:

This carefully balanced combination results in a material that is not only strong but also flexible, making it well-suited for tunnel construction in varying geological conditions.

Material Characteristics and Testing Methodology

Understanding the material characteristics of compressible grout is crucial for ensuring its performance in demanding tunnelling projects. Rigorous testing by Technicore was conducted to evaluate its properties, including lateral confinement and confined compression strength. Tests involved the use of steel cylinders to simulate the conditions in which the grout would be used. These tests were performed under controlled conditions, including specific rates of axial deformation. The results provided valuable data, including:

The testing process also involved allowing the grout to undergo significant axial deformation before completion, simulating real-world scenarios where the material needs to adapt to deformation without compromising its integrity.

These tests confirmed that compressible grout possesses the necessary characteristics to excel in challenging tunnelling projects like West Trunk Sewer Project Contract 2.

Innovations on West Trunk Sewer Contract 2

The West Trunk Sewer Project Contract 2 presented several unique challenges that demanded innovative solutions. Let’s explore how compressible grout played a pivotal role in this project’s success.

Project Description

Compressible Grout – Requirements

The project’s requirements were stringent, necessitating a solution that could provide stability, accommodate deformation, prevent overstressing of the lining, and minimize water and gas infiltration. Compressible grout proved to be the ideal choice, meeting all these requirements effectively.


Compressible Grout


Integrated Corrosion Resistant Lining

Another unique aspect of this project was the need for a corrosion-resistant lining. The client specified the use of AGRUSAFE SureGrip® HDPE lining with a minimum thickness of 5mm. This lining was required for a specific section of the tunnel, encompassing 150m upstream and 100m downstream of the drop shaft. Also, Herrenknecht Combisegments® were used for this 250m length, providing a reliable and durable lining solution.


Compressible grout has emerged as a revolutionary material in the realm of tunnel construction, and its advantages were vividly demonstrated in the West Trunk Sewer Project Contract 2. Its ability to provide stability, accommodate deformation, prevent overstressing, and act as a barrier against water and gas infiltration makes it a valuable asset in challenging tunnelling projects.

With its unique composition and favourable material characteristics, compressible grout is set to continue transforming the way we approach underground construction. In the ever-evolving field of civil engineering, innovations like compressible grout are essential for building a safer and more resilient infrastructure.

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