Study On Pre-support And Comprehensive Construction Technology Of A Concrete Lining In Loess Tunnel

Loess is a kind of soil with unique engineering characteristics therefore construction of loess tunnel has many important problems.The surrounding rock at the mouth or body of many tunnels is weak.In excavating most of tunnels,the self-stability of surrounding rock of tunnel face is poor,requiring pre-reinforcement namely pre-support.As one of methods with simple construction process,obvious reinforcement effect and strong economic efficiency in several pre-support,the small duct is widely applied in engineering practice.In the meantime,for more effective,safe and fast construction,it studies pre-support and comprehensive construction technologies.This paper,relying on No.2 tunnel in Dingyuan of ‘Lianyungang-Huoerguosi Highway'and targeted as the analysis point of engineering construction of V level surrounding rock of loess tunnel,studies the above two problems.The main work of this paper is as follows:(1)Analyzing deformation situation and characteristics of reinforcement force of surrounding rock in Dingyuan tunnel via on-site monitoring data.Analyze variation relation between these two systematically,the analytical results show that deformation duration of surrounding rock is long and the preliminary deformation rate is fast.(2)Systematically analyzing grouting reinforcement mechanism of advanced small pipes and their action effect,and then discussing briefly various parameters of pre-support of advanced small pipes,using MIDAS/GTS software for numerical calculation simulation,analyzing influence of pipe diameter,of grouting pipes,circumferential distance,pipe length,grouting length and other factors on reinforcement effect.(3)Putting forward different deformation control measures purposefully,analyzing methods of reserving core soil in circumferential excavation of second step one by one under different heights and lengths of step and excavation progresses.Finally,select optimal control measures to inhibit deformation of surrounding rock.(4)Comparatively analyzing adopting of different excavation forms that labor and oil costs account great proportion in total expenditure.The oil costs change with the degree of mechanization.The more the mechanical equipment is used and the higher the degree of mechanization is,the higher the oil costs are.Compared with dear labor costs,the total expenditure will reduce.So it shall select supporting machinery with high work efficiency as much as possible.