Abstract:Taking the shield tunnel of Qingdao Metro Line 2 undercrossing the existing Jiaoji Railway as the background, the settlement law and deformation control of Jiaoji Railway subgrade were studied based on three-dimensional numerical simulation method. Firstly, in view of the existence of crushing zone in the project, the influence of shield crossing crushing zone on railway subgrade settlement was studied. Then according to the characteristics of the upper soft and lower hard strata in Qingdao, the upper soil grouting reinforcement scheme and the lower rock curtain grouting reinforcement scheme were used to study the deformation control effect of shield undercrossing the existing railway subgrade. The results show that the settlement of railway subgrade is too large when shield passes through the broken zone section, and there are safety risks in construction, which affects the safe operation of Jiaoji Railway. The settlement of the roadbed after stratum reinforcement is significantly lower than that of the stratum without reinforcement. The upper soil grouting reinforcement reduces the settlement value of the roadbed by about 40 %, and the whole section curtain grouting reinforcement reduces the settlement value of the roadbed by about 65 %. At the same time, the lower rock reinforcement is more significant than the upper soil grouting reinforcement. The influence of shield tunneling on railway subgrade reduces after stratum reinforcement, which can ensure the normal operation of Jiaoji railway.