ABSTRACT
Large-scale construction of metro lines and stations has been underway in Moscow for many years. Transit tunnels are constructed by mechanised method, and station complexes — in deep excavations. The jet grouting geotechnology is used in the places of tunnel and excavation fence interfaces, drilling piles interlocking, and inter-tunnel joints. Its advantages: versatility, no need to open the place of work, time saving, possibility to perform several types of works on the construction site in parallel, equipment of acceptable size, etc. The peculiarities of using jet grouting are revealed. The peculiarities of using jet grouting at depths over 15...20 m have been revealed when forming a backfill for TBM entry into the excavation, making a bottom-hole chamber for replacement of TBM cutting tools, forming a mass of consolidated soil for mining method of inter-tunnel joints. The main difficulties in performing the works are the use of jet-grouting in floating ground, at great depths, large shrinkage of the ground concrete, non-compliance of the ground concrete strength with the project. The report analyses the main risks of using jet grouting and suggests ways to reduce them. Risks are recommended to be taken into account in the design and execution of jet grouting works and in the general choice of construction technology.
