ANALYSIS OF SETTLEMENT CAUSED BY SHIELD TBM EXCAVATION WITH DISCRETE ELEMENT METHOD

초록

Ground subsidence can be minimized, due to tunneling with mechanized tunneling method. Especially, shield TBM tunneling has been used to build cable tunnel in Korea. However, ground subsidence cannot be avoided during shield TBM tunneling. In this study, the settlement caused by Shield TBM excavation is simulated by using Particle Flow Code (PFC) 5.0 in three dimensional models. Above all, uniaxial compression rock test model is conducted to calibrate the micro-parameters of weathered soil and weathered rock. The properties of grounds are taken from the technical reports of cable tunnel in Korea and calibration was done through trial and error until Young’s modulus and uniaxial compression strength are close to the values presented in the technical reports. The shield TBM excavation is analyzed in two different ground conditions. The tunnel is excavated through 50 stages. To measure the settlement of ground, monitoring points of settlement were set up along both longitudinal and transversal direction of the tunnel. The settlement obtained from DEM analysis was compared with the measured data. Volume loss of model was also calculated and reviewed. The result shows that the simulation can replicate realistic ground behavior due to tunneling. The tunnel model is validated with monitoring data and the settlement of model is within the range of monitored settlement. Also, volume loss of model is evaluated and verified with reasonable accuracy.