Study On Reinforcement Techniques Of Enlarged Underground Chamber And Unloading Characteristics Of Segments For Shield Disassembly

With the rapid development of China's economy and society,many of the underground projects or facilities which are being and to be built are going deeper and deeper,and this makes the requirements of the construction of long distance inclined shaft on tunneling technique higher and higher.As the front terminal has been underground when the inclined shaft is constructed,the in situ disassembly is needed,and using terminal enlarged chamber to disassemble.The additional load of crane and other loads set a still high demand on the stability of the chamber while disassembling.At the same time,as removal of shield propulsion plant and longitudinal unloading,the structural mechanics properties of segments will be fundamentally changed.This paper aims at the safety and stability of enlarged chamber rock during shield disassembly and the mechanical behavior of segments after longitudinal unloading.Based on the long distance inclined shaft test project of Shendong Bulianta,it takes the way by combining numeric analysis and field test as the research method to study the strengthening technology of enlarged chamber during shield disassembly and the mechanical behavior of segments after longitudinal unloading.Its main research contents are as follows:(1)Based on the analysis of the engineering geological of disassembly section and the size of enlarged chamber,the supporting form is initially identified to reinforce the enlarged chamber of shield disassembly section,meanwhile,the deformation of anchor cable in the roof of enlarged chamber is analyzed.By using the finite difference software FLAC3 D,the influence of prestressed anchor cable with different length on the stability of surrounding rock is analyzed.Compared with the reinforcement scheme of enlarged chamber,the support parameters of the strengthening scheme are finally determined.(2)By using the finite difference software FLAC3 D,the numerical analysis model of the enlarged chamber for shield disassembly is established.Firstly,the stability of the enlarged chamber without reinforcement under the action of lifting load is analyzed.Then,the stability of the surrounding rock after reinforcement under lifting loading is analyzed,and compared with the results before the lifting load was applied.Finally,comparing and analyzing the field monitoring data and numerical simulation results of deformation of enlarged chamber.(3)By using the finite element software ABAQUS,a numerical analysis model of shield segments is established.The variation of longitudinal structural mechanics properties of segments is analyzed.(4)The method of reinforcement in the shield disassembly section released in this paper is reasonable and feasible,it can not only ensure the normal disassembly of the shield,but also play a guiding role in other similar projects,and the application of it will prospect well.