| With the development of cities,the use of underground space has become more and more important as space above ground has become more and more constrained.Underground tunnelling is being carried out on a larger and larger scale,with the consequent emergence of sudden ground loading around tunnels,leading to frequent safety accidents and failure of lined pipe sheets.The development of underground engineering has also led to the rapid development of full-section tunnel boring machines(TBMs),which have been widely used in recent years in practical projects such as transportation,municipalities,water and electricity due to their advantages such as fast digging speed,high safety and good construction quality.This has a great impact on the service life of the hob.This thesis firstly investigates the impact of lining support on the tunnel structure during the tunnel boring process using a 3D physical model,and analyses the soil settlement and tunnel deformation pattern under the influence of the opposite stack load.The main research elements of this thesis are as follows:(1)Using the 3D physical model test method to study tunnel excavation and soil settlement,we establish the geometric similarity ratio of the model test according to the actual project,prepare the soil similar materials,make the test model box,design the soil settlement observation scheme,make the lining support tube sheet,determine the tunnel excavation process,make two types of tunnel models according to the excavation process: gross tunnel and lining tunnel,apply loads to the two columns of models to carry out soil settlement The results show that both types of tunnels are subjected to a high level of soil settlement during excavation.The results show that for both types of tunnels,the settlement of all layers of soil in the settlement test was located at the top of the vault,when it was closest to the loading position,and the further away from the loading distance,the smaller the settlement.The comparison between the two types of tunnel settlement tests shows that the lined tunnel is subjected to a higher ultimate load compared to the buried tunnel,the soil settlement and the depth of the collapse pit are significantly reduced,and the tunnel structure remains stable after the ultimate load is reached in the lined tunnel,with no damage occurring,indicating that the lined support tube piece significantly improves the stability of the tunnel structure.(2)Using the finite element simulation calculation method to study the 19" single-edge hob tapered roller bearings,the detailed parameters of the hob structure were determined according to the existing drawings combined with the current hob and bearing specifications,a full-section rock-breaking model of five hobs was established,rock-breaking simulations of the hobs were carried out,and the data were extracted as the boundary conditions for the bearing analysis.A finite element model of the bearing was established to carry out static and transient dynamics analyses respectively,to analyse the interaction and motion of the bearing components,and to investigate the law of stress changes in the rollers and the inner and outer raceways,and the motion of the rollers.The results show that the vertical force plays a major role in the rock-breaking process of the hob,and the values of the lateral force and the hobbing force are small and basically do not affect.Hobs bearing in the radial force and axial force,the roller two ends of the stress change is the most concentrated,the roller and the inner and outer raceway contact position stress is larger,and the roller and the outer raceway contact stress is greater than the contact stress with the inner raceway,increase the radial force found that the roller stress is a linear growth trend.Bearing in the radial force,axial force and speed,the roller appeared bias load,the axis appeared obvious distortion,roller vibration is the most violent,increase radial force can be known radial force on the role of roller vibration is non-linear. |
PDF Full Text Request