Ground improvement by jet grouting and injection to control hydraulic conditions in the frame of Grand Paris Express Project, North-East section: methodology and quality control sequence

The main tunnels of Line 16 Lot1 the Grand Paris Express project are underway since 2019 using tunnel boring machines (TBM). They drilled entirely in permeable strata (fine/silty sands, marls, and limestones) at a depth 20÷30 m below groundwater level. Groundwater inflow with high pressure is major issue arrival/departure sections TBMs as well during excavation work connection galleries between maintenance or security shafts. located under dense urban areas requirement minimizing drawdown water civil engineering works; purpose to avoid excessive settlements on existing facilities dissolution reactivation process gypsum-rich strata. In order minimize these risks, different types ground improvement technics (jet grouting cement mixture injection) have been applied, where jet used fine sandy soil injection fissured marly-limestone. addition, both associated same site. From geotechnical point view, sands Beauchamp classified coarse-grained soils (60% SM 40% ML Unified Classification System ) Marly-limestone Saint-Ouen deep Marls soft medium-hard calcareous rock. This paper presents conditions, methodology quality control construction. sequence performed by vertical then horizontal drilling holes. method after (horizontal control) allows confirm treatment blocks specifically bonding block diaphragm wall.