Abstract The water content of loess layer of the tunnel body with a large section in the rear distribution area of Donggang station of Lanzhou rail transit line 1 is about 28.5% and the saturation is over 95%, which induces large settlement of primary support and long time to get stable for the surrounding rock. Based on the data of laboratory geotechnical test, a three-dimensional finite element model was established, the mechanical and deformation charac?teristics of primary support, ground surface settlement and pore water pressure distribution during construction by CRD method and double side drift method were compared and analyzed based on fluid-solid coupling and uncoupling effects. The results show that the ground surface settlement, vertical and horizontal displacements and their increase rates of primary support considering the effect of fluid-solid coupling are larger than that without considering the effect of fluid-solid coupling, there is no significant decrease in the later period and they are closer to the measured values at site, while there is no big change of mechanical behavior; it is more favorable to adopt the construction method of CRD with six excavation sections to control ground surface settlement and tunnel deformation based on fluid-solid coupling effect and the force applied on primary support are approximate under the two construction methods but the distribution forms is different; under the effect of fluid-solid coupling, the places with large hydraulic gradient of groundwater are mainly located at tunnel sidewall and invert, which is prone to leakage during construction, and compaction of shotcrete at crown and backfill grouting should be carried out to prevent the seepage field from shifting.
Abstract：
The water content of loess layer of the tunnel body with a large section in the rear distribution area of Donggang station of Lanzhou rail transit line 1 is about 28.5% and the saturation is over 95%, which induces large settlement of primary support and long time to get stable for the surrounding rock. Based on the data of laboratory geotechnical test, a three-dimensional finite element model was established, the mechanical and deformation charac?teristics of primary support, ground surface settlement and pore water pressure distribution during construction by CRD method and double side drift method were compared and analyzed based on fluid-solid coupling and uncoupling effects. The results show that the ground surface settlement, vertical and horizontal displacements and their increase rates of primary support considering the effect of fluid-solid coupling are larger than that without considering the effect of fluid-solid coupling, there is no significant decrease in the later period and they are closer to the measured values at site, while there is no big change of mechanical behavior; it is more favorable to adopt the construction method of CRD with six excavation sections to control ground surface settlement and tunnel deformation based on fluid-solid coupling effect and the force applied on primary support are approximate under the two construction methods but the distribution forms is different; under the effect of fluid-solid coupling, the places with large hydraulic gradient of groundwater are mainly located at tunnel sidewall and invert, which is prone to leakage during construction, and compaction of shotcrete at crown and backfill grouting should be carried out to prevent the seepage field from shifting.
LI Ming YAN Songhong PAN Chunyang ZHANG Xubin
.Analysis of Fluid-Solid Coupling Effect during Excavation of the Water-rich Large-section Loess Tunnel[J] MODERN TUNNELLING TECHNOLOGY, 2019,V56(4): 81-88
2019, Vol. 56 