Transforming Underground Construction with Swissloop Tunneling

Microtunneling is a trenchless construction method using a remotely controlled, steerable tunnel-boring machine for underground pipeline installation. It minimizes surface disruption, making it ideal for urban and sensitive areas. This technique ensures precise pipeline alignment and involves simultaneous excavation and pipe installation, enhancing safety and efficiency. Widely used for utilities, microtunneling's precision and reduced environmental impact make it a preferred choice for constructing water, sewage, and other infrastructure systems in congested settings.

This article highlights the progress a young engineering student team from Switzerland has made with its self-developed micro tunnel boring machine. It describes the project on its way to revolutionizing the tunneling industry with specific regard to its innovative 3D-printing-like tunneling mechanism.

The Journey of Swissloop Tunneling

Swissloop Tunneling is a student group from ETH Zurich that focuses on developing innovative tunneling technologies. This team, composed of students, works on designing and testing tunnel boring machines that incorporate advanced technologies and methods. Their efforts aim to enhance the efficiency and reduce the costs of tunneling processes, contributing to the broader goal of revolutionizing tunneling to facilitate ambitious infrastructure projects, including proposed systems like the Hyperloop transportation system.

Further reading: Swissloop Tunneling: Revolutionizing the Tunneling Industry

Throughout the last 3 years, over 100 Swissloop Tunneling members have made contributions to a common goal: unleashing the potential of time-, cost-, and resource-efficient tunneling. In this regard, innovation is needed to accelerate the infrastructural progress to benefit society by supporting the rapid expansion of connected underground systems. Therefore, Swissloop Tunneling aims to contribute to advancements in technology, demonstrated by its two iterations of prototypical tunnel boring machines since its founding in 2020. 

Building upon its first model named Groundhog Alpha, the team has maintained the first machine components’ strengths while further extending it with technological add-ons, designing certain subsystems from scratch, conducting tests, and optimizing for higher reliability. Those efforts have now led to the current model Groundhog Beta.

The Groundhog Beta

The current model of the association’s (micro) tunnel boring machine named Groundhog Beta consists, among others, of these functions:

Erosion

Extracts and processes the underground material during the boring phase. At the front of the machine, where the cutterhead is placed, a special soil-conditioning foam is used to help decompose the sticky clay ground in Bastrop (TX), where the prototype was being tested. The erosion subsystem can further handle small to medium-sized rocks by crushing them into smaller pieces. A suctioning mechanism then transports the eroded material through and out of the machine. At this point, an external sedimentation system is ensuring a constant circulation of used water and the removal of the extracted material.

Fig. 1: Groundhog Beta tackling clay using soil conditioning foam

Navigation

Consists of a two-component system. The steering component allows for angled digging and enables withholding stronger vibrations. It consists of a comprehensive sensory system to achieve an accurate autonomous movement of the machine. The propulsion component gets the machine moving forward by coordinated gripper plates that push the machine forward through the tunnel wall.

Fig. 2: Swissloop Tunneling's hydraulics-powered propulsion component

Starting platform

Placed in the launching area or on the surface, the starting platform enables the machine to launch from various angles.

Tunnel liner

One of the most innovative aspects of Groundhog Beta is its tunnel lining mechanism. The liner mechanism simultaneously builds the interior tunnel wall while continuously moving forward with the tunnel boring machine, acting like a 3D printer. As it stands right now, a mechanism of this type has not been tested in tunneling yet and provides an ecologically sustainable solution regarding the reusability of the wall material. By using a pneumatic system, a polypropylene granulate to later build the tunnel wall gets transported into the machine. It then gets extruded by melting it and steering the viscous material into the right shape, finally being cooled down to achieve its intended tunnel wall structure. This mechanism has been optimized since last year - especially in terms of reliability. Additionally, an external testing system was designed to make isolated testing of this subsystem’s functionality possible. In the end, a 15mm thick tunnel wall is produced, being able to withhold the intense forces of machine and earth pressure.

Fig. 3: Polymer starting to come out of the tunnel lining component on the right

Achievements Over the Years

In addition to refining the engineering processes, the Swissloop Tunneling team has consistently participated in every Not-a-Boring Competition an event aimed at fostering innovation in tunneling technologies. Not-a-Boring Competition is organized each year in the USA by The Boring Company, founded by Elon Musk.

The team has exhibited its excellence by winning awards for innovation and design at the first two competitions, held in Las Vegas (NV) in 2021 and Bastrop (TX) in 2023. Ahead of the 2024 competition in Bastrop, the team dedicated significant efforts to optimizing their machine and making key adaptations. These efforts paid off spectacularly at the Not-a-Boring Competition 2024, where Swissloop Tunneling triumphed by winning 1st Place Overall and the Champion Award.

Fig. 4: The Swissloop Tunneling Team

With these achievements, the team remains committed to pushing the boundaries of innovation. Swissloop Tunneling will continue to enhance and refine its machinery, further developing its capabilities to fully realize the remarkable potential of advanced tunneling technology.

Conclusion

The advancements in tunneling technology showcased by the recent developments of the micro tunnel boring machines are reshaping the landscape of construction and infrastructure. By integrating innovative 3D-printing-like methods for tunnel lining, these machines are setting new benchmarks for efficiency, cost-effectiveness, and environmental sustainability in tunnel construction. 

Such technological breakthroughs promise to revolutionize urban development and the future of transportation, making the once-distant dreams of projects like the Hyperloop increasingly attainable.