The mechanisms of consolidation by horizontal jet grouting, the selection of the jet grouting parameters, the matching of the horizontal jet grouting equipment and the key technologies of horizontal jet grouting are studied on basis of the horizontal jet grouting used in the construction of a tunnel in waterrich immature fine silty sand strata on LanzhouChongqing railway. The study results are applied in the construction of the tunnel, i.e., horizontal interlocking jet grouting piles are installed along the perimeter of the tunnel crosssection and anchoring horizontal jet grouting piles are installed in the tunnel face. In this way, quick sand at the tunnel crown, tunnel collapse and tunnel face instability are avoided, the excavation efficiency is improved and successful tunnel construction is achieved. 