Research On The Optimization Design And Reasonable Supporting Time Of Supporting Structure In Xiaobatian Dunnel

In recent years, highway and railway construction in China is developing quickly, at thesame time the soft rock tunnel project in the tunnel construction proportion also increasesgradually. However,soft rock tunnel design and construction is exposing more and moreproblems. For example, the supporting structure parameters are difficult to choose andsupporting construction time is difficult to determine, which have been plaguing theapplication and development of the soft rock tunnel supporting technology.Firstly, this paper summarizes the development of supporting theory of the soft rocktunnel and elaborates the construction characteristics,the deformation and failure mechanism,the supporting mechanism,the supporting optimization theory of the soft rock tunnel. Thispaper establishes the three-dimensional model to simulate the excavating and supportingprocess of soft rock tunnel according to before analysis by midas/GTS. The simulationanalyzes the effect of sprayed concrete strength grade and the bolt supportingparameters(length, diameter, spacing)and steel arch supporting parameters(spacing, type) onthe deformation of rock and the axial force of supporting structure. Then this paper analysesthe influence of secondary lining concrete strength grade and the thickness on the deformationof rock and the axial force of liner. The paper studies on how to optimize the supportingstructure on the base of before research, and puts forward the best supporting parameters andmode.Secondly,the paper elaborats criterion and determination method of the best time toconstruct secondary liner.Then the paper regards the displacement and stress as the maincontrol parameter and conducts on a deep study on the opportunity to construct secondaryliner acoording to actual monitoring data.The research gets the bset opportunity to constructsecondary liner under the conditions of original design of supporting structure. Based on thetheory of optimization of construction the paper ultimately determines the bset opportunitywith the optimal supporting parameters and methods by numerical simulation. the aboveresearch results can provide a theoretical basis and guidance for design and construction ofsimilar engineering in the soft rock.