Challenges & Solutions

Conventional tunnel construction has always represented a significant engineering challenge. Success depends not only on careful planning and execution, but – critically – on ensuring optimum interaction between the machine technology and speciality chemistry of the supporting systems. Depending on the rock and soil encountered, problems can arise during excavation even with the best possible planning, high-performance technologies and optimum construction execution. To ensure that your tunnelling project is successful, MC offers system solutions individually tailored to your requirements and covering everything from driving to repair. With decades of experience across major international projects, our effective, project-specific product systems are designed to ensure your full satisfaction.

Soil conditioning for EPB shield TBMs

Ensuring efficient mechanical tunnelling

The inherent safety and efficiency of mechanised tunnelling makes it particularly suitable in difficult geological formations and inner-city projects. Aside from the gripper and slurry methods, EPB technology (earth pressure balance) is especially effective as it offers certain economic advantages in tunnel boring.

The efficient use of EPB shields in TBMs (tunnel boring machines) offers even-pressure support of the work face. Soil conditioning has to be carried out in order to meet the requirements placed on the excavated soils serving as the support medium. With MC-Montan Drive, MC offers conditioning agents specifically adapted to geological conditions, enabling you to achieve high tunnelling advance rates with a good degree of reliability and environmental compatibility.

Annular gap grouts for backfilling and stabilisation

Individually formulated grouting mortar systems for reliably bedded tunnel profiles

The annular gap that results during tunnel driving between the shield and the in-situ material is backfilled with grouting mortar to minimise surface subsidence and stabilise loose rock. Injected into the annular space over the full area, the mortar is formulated for stiffness and strength values aligned to those of the surrounding rock material. MC has a number of one-component and two-component annular gap grout formulations within its MC-Montan Grout range that can be aligned to the in-situ rock conditions specific to your tunnel construction project. This means that every tunnel profile is provided with the optimum bedding solution for minimum subsidence.

Speciality chemicals aligned to machine technology

Integrated systems from a single source

In tunnel construction, compatibility between the mechanical hardware and speciality chemicals is as essential to success as careful planning and execution. MC offers complete, integrated systems comprising both the equipment and the speciality chemistry, helping to achieve exceptionally high performance in soil conditioning and shield tail sealing operations. With HDT-Montan Device CT, you can create optimum-quality foam for outstanding conditioning results, even under difficult geological conditions. For shield tail sealing, it is also essential to have both high-performance sealing compounds and optimised pump and conveying technology. With our speciality pump and tailored sealants, you can ensure the shield tail remains impermeable.

Quality of the highest standard

Tunnel segments offering maximum concrete quality and durability

Tunnel segments are required to withstand not only the forces imposed upon them by the in-situ rock but also the pressures generated during the tunnel driving operation. Properly reinforced designs based on high-performance concrete are therefore essential.

MC is able to offer you a comprehensive product portfolio comprising superplasticisers, hardening accelerators, retarders, stabilisers, air-entraining agents, concrete admixtures and release agents. Together with our concrete technology experts, you will be able to put together a complete system solution individually tailored to your project, ensuring your tunnel segments are of the highest quality and durability.

Shotcrete solutions for shoring, sealing, reinforcing, smoothing and waterproofing

Quality and reliability in conventional tunnel construction

Conventional tunnelling using “hand mining” techniques is still employed in infrastructure projects around the world, with methods ranging from soft ground tunnelling to blasting with explosives. Here, shotcrete is used primarily as a temporary means of consolidating and sealing the in-situ material and for smoothing the excavated sections. As a means of rock edge reinforcement, it also serves to close gaps and prevent small cavities from forming as a result of the arching effect in the profile. With the MC portfolio comprising superplasticisers, retarders, concrete admixtures and hardening accelerators, you can formulate the ideal shotcrete for your application, whether for the wet or dry spray process.

Sprayable sealing membranes for reliable tunnel waterproofing

Permanently watertight and highly resistant

Sealing in conventional tunnelling is provided by plastics waterproofing sheet or sprayable waterproofing membranes. Both systems have a common objective – to ensure that the tunnel remains dry over its planned service lifetime exceeding 100 years. This objective places particularly high requirements on the sealing systems. These are expected to protect the support structure and technical installations while ensuring disruption-free operation. Hence they need to be able to both withstand chemical attack and resist mechanical stress phenomena.

With the highly flexible dry-spray waterproofing membrane MC-Montan Shot Seal, MC offers a high-performance solution for your tunnel construction project. It is particularly suitable where geometries become difficult, for example in the area of station structures, galleries or access tunnels.

Attendant measures for stabilisation, waterproofing and repair

Minimising risk during the drive

Despite the best possible planning, high-performance technologies and optimum construction execution, problems can still arise during excavation, depending on the rock and soil encountered. In such cases, attendant measures need to be implemented to sustain the required rate of advance while maintaining maximum safety. MC-Montan Injekt and MC-Injekt offer high-performance, fast, reliable and sustainable special-purpose injection systems for rock stabilisation and sealing, surface and joint waterproofing and crack and cavity filling. Damage and leakage in the tunnel lining or shell can be repaired immediately by attendant systems following cutting or excavating operations. Other attendant concrete repair and surface protection measures, promptly implemented following the drive, minimise the risk of structures failing or degrading. This not only reduces repair and maintenance costs in the future but also has a positive effect on the durability of the entire tunnel system.