Evaluation of jet grouting efficiency as means of minimizing of the harmful effect of escalator tunnel construction

The article describes the escalator tunnel construction using tunnel boring machines in St. Petersburg. To reduce the harmful effects of underground construction on the Earth's surface in the mouth of the tunnel technology is used jet grouting rock mass. Based on the analysis of field data of the earth surface subsidence and rock strata proved the effectiveness of the jet grouting technology. Subsidence of the surface and within the grouting area, are approximately . The fact that the development of subsidence occurs mainly outside the zone of jet grouting soil is shown. A method of reducing subsidence by grouting additional unstable rocks in the massif, which will reduce the harmful effects of underground construction for an massif and the earth's surface, is offered. To assess the efficiency of the proposed method, a numerical modeling based on the finite element method is carried out. According to the modeling results it is revealed that the proposed method will reduce the subsidence at the surface by 2-3 times.