The Study Of Soil Improvement Technology On Nanchang Metro Underwater Tunnel

With the rapid development,shield tunneling method has been widely used in many large and medium cities for its high degree of mechanization, low labor intensity, high security, little effect on the surrounding environment and other competitive advantages. However, many accidents were caused by poor improvedresidue soil or unproved residue soil. To avoid the above problems.In this study, some technical problemsoccurred in the process of shield tunnelingwere investigated based on the metro construction of the first underwater tunnelbetween the east station of Aixi lake and the west station of Aixi lake in Nanchang, such as mud cake, spewing, occlusion, wear.To figure out the practical problems,laboratory tests were carried out by utilizing the orthogonal experimental design method and field tests were conducted to verify the experimental results.The microscopic mechanism and stratum adaptability of different additiveswere studied systematically, and the indexes of permeability coefficient, friction coefficient, slump etc. wereused to evaluate the cohesiveness and water retention of modified residue soilto obtain aflow plasticity state similar to toothpaste. The optimization scheme for shield tunneling in sandy-gravel layer and stand-pebble layers was determined according to the experimental results. Trialtunneling was applied to assess the improvement effects in field and the parameters of shield tunneling and the changes of the surrounding environment were analyzed. The parameters of total thrust, tunneling speed, cutter torque, rotation speed of screw conveyor, torque and field measurements before and after modification were compared.It indicates that the improved method proposed in this paper is helpful to solve some technical problems occurred inthe shield tunneling section between the east station of Aixi lake and the west station of Aixi lake. For its lower risk of going under the lake within a long distance, less wear of the cutter and the machine, lower cost, the project was carried out in safety and order, to some extent, providing references for similar projects.