Optimization of plugging cement slurries using ultra-fine binders to reduce settlement deformations during tunnel construction

The most effective method of constructing underground rapid transit tunnels in dense urban areas is using a tunnel boring machine (TBM). However, it is necessary to take into account the problems of protecting buildings and structures in the underground construction zone. The most significant factor affecting the change in the stress-strain state of the soil mass during new construction is the presence of a gap between the soil and the reinforced concrete tunnel lining. This space is then filled with cement slurry, but various factors contribute to the settlement of structures of existing objects in the tunnel construction zone. TBM boring is often carried out in complex geological and hydrogeological situations, which in many cases requires the use of special processes. Conventional mineral-based backfilling systems do not allow high-quality filling of the space behind the lining, which negatively affects the settlement of surrounding buildings. One of the possible ways to minimize settlement is to introduce special ultra-fine binders (UFB), or micro-cements, into the backfilling mixtures. This allows for the injection of mineral-based mixtures even into highly water-saturated soils in the space behind the lining, maximally filling the annular gap. At the same time, fine fractions of UFB reduce the water loss of solutions and their tendency to stratification and washout under filtration conditions.