| In recent years, with the economy and transportation developing, 2 lane road tunnel did not meet increasing demands of traffic, resultly,3 lane road tunnel and above is shown rapid development.But for the large section tunnels, there is a few practice and no mature experience for the struction to be referred ,and there are fewer design calculation methods to be used. At presnt, there are no standard and specifications to be referred for design and construction of large section tunnel, the analogy is the frequent method in the design and analysis.For the present study state and difficulty in the large section tunnel that there is no unified know of suppor form and its charameter, the standard to judge stability of the rock is still uncertain, rock pressure ,design caculation methods and consruction schemes and etc are undeeply studied, combining several ways of site test and mechanism with numerical analysis and etc methods. The paper puts up stress path design method of rock load on the large section tunnel.The paper studies many stress paths’effects on stress and displacement of rock and support for 3 lane,4 lane and 5 lane tunnel, and studies many digging methods’effects on stress and displacement of rock and support for biasing and unbiasing 5 lane tunnel. The paper also proposes some safety gurantee ways of constrution of the large section tunnel and some exploratory jobs are carried out on accout of the effect on the varaity and character of stress and displacement brought by the stress path and space effect, and the study results are successfully used in the project.The main innovations of this study are list as follow.(1) According to the measured results of rock deformation throughout the construction process, this paper analyzes the displacement variation feature during the excavation process, generalizes the extending scale and laws, and based on the influence of the stress path on the load, the calculation formula of rock load of large section tunnel is put up.(2) Based on numerical analysis results of the influence of stress path on stress state and deformation properties of rock and supporting strctures in many different construction conditions of large sections tunnel, the paper analyzes thoroughly the stress path effect mechanism and laws of rock and supporting structure, and provides a new method to study the more safe and lower risk construction scheme of large section tunnel.(3)Based on the numerical results of rock stress and deformation with different excavation methods and speed which is carried out under the space of large section tunnel, this paper analyzes the influence of rock stress and deformation disribution with different excavation methods and the influence of space effect about construction safety state, and explores space effect’s influence scale and rules of large section tunnel, and studies the influence of construction safety of excavation method and speed to provide good refernece to construct the tunnel.(4) This paper takes large section bias tunnel with 5 lane as the research object, analyzes the influence of landform on stress and displacement of rock and the supporting structure, identifies angle bias of large section tunnel, studies the stress path’s effect, displacement path’s effect and laws and etc ,and suggests best construction shcmes to provide reference and consult of safe analysis about the exit and entrance construction of large section bias tunnel.(5) Based on the stress path and space effect on the large section tunnel, the study results are applied in the studied tunnel project and are compared with site monitoring results. It proves reasonable that the calculation formula of rock load of the large section tunnel on account of the stress path and space effect. |
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