Grouting at Lonato tunnel

The planned Brescia-Verona high-speed/high-capacity railway line is a key project of the Milan-Verona railway link. Between Brescia and Verona, the new line is about 48 km long, running mostly alongside the A4 highway. Near Lonato (south of Garda Lake), the line goes under A4 and other buildings and structures, through twin tunnels bored by the tunnel boring machine (TBM). The soil consolidation project is deemed necessary to protect the road from subsidence before the TBM is deployed. On site, the soil is extremely heterogeneous but always characterized by a silty sand matrix. The poor capacity of the soil to be permeated led to reshaping the borehole mesh and selecting both cementitious and silicate-based grout mixes designed to obtain rheological features leading to better permeation capability. The operation to prevent subsidence involved injecting some 10,000 m3 of grout mixture, through about 90, 000 m of sleeved pipes, in multi-directional geometries.