MODEL TEST AND 3D NUMERICAL SIMULATION STUDY ON EXCAVATION OF DOUBLE-ARCH TUNNEL

Recent years,more and larger,even huge underground projects are under planning,designing and construction in China,as well as in the world.Besides the numerical simulation,physical and geomechanical model tests have been putting on the agenda to meet engineering request.As a new structure form of highway tunnel,the theory of double-arch tunnel is still primary up to now.According to the similar principle of elastic theory,a model test simulating the excavation stage of double-arch tunnel was carried out with the background of a double-arch tunnel being constructed in the Yuanjiang—Mouhei Expressway,Yunnan Province.The model tests for double-arch tunnel,in the past,were mostly two-dimensional or three-dimensional in small size.In those model tests,the displacements were not measured in real deformation field,or even used simply dial indicator,displacement sensor,strain-gauge transducer,etc.,which is incomplete because the full deformation field can not be obtained by those methods.In present paper applied with earth-pressure cell,digital camera and settlement plate,the distributions of stresses and displacements in the wall rock mass were measured during the tunnel excavation.3D fast Lagrangian element method is applied to simulate the excavation of double-arch tunnel.The distributions of stresses,displacements and plastic zones in the wall rock mass of double-arch tunnel were obtained;and the result is in good agreement with that of model test.Some valuable results were concluded finally.