Performance and Cost Analysis of Two Component TBM Primary Grout

Chapter 8
Abstract
Two-component (A/B) grout systems are widely used in Tunnel
Boring Machine (TBM) tunnelling for annular gap backfilling. These
systems consist of a cementitious slurry (Component A) and an
accelerator (Component B, typically sodium silicate), which rapidly
react to form a gel, enabling quick setting and early strength
development. The performance and cost-effectiveness of such grouts
depend on mix composition, including cement, water, bentonite,
supplementary cementitious materials like fly ash, and accelerator
dosage.
This study evaluates the relationship between grout performance
parameters—such as viscosity, gel time, bleeding, and compressive
strength—and overall project cost. The use of industrial by-products
reduces cost and environmental impact but may affect early strength
and setting characteristics. Therefore, optimization of mix design is
essential to achieve a balance between performance, cost, and
sustainability. The study highlights the importance of laboratory
validation and techno-economic analysis for selecting suitable grout
compositions for TBM operations.
Keywords: TBM; Two-component grout; Sodium silicate; Fly ash; Cost
analysis; Tunnel grouting.