| With the continuous development of highway tunnels,there are more and more long tunnels passing through complex geological conditions such as high ground stress,weak surrounding rock and rich water.Because soft rock often contains mineral components that swell with water,it is easy to cause bottom heave disease of inverted arch structure under the continuous action of ground stress,swelling force and soft rock rheology.Therefore,it is urgent to study the disaster-causing mode and control method of bottom heave disease.In this paper,based on the bottom heave disease section of Ningchan highway tunnel,the main research methods such as existing case analysis,influencing factor analysis,field measurement and numerical simulation are used to study the stress and deformation characteristics,influencing factors,disaster-causing mode and control method of inverted arch structure in the bottom heave disease section of Ningchan tunnel.On the basis of this research,two kinds of treatment measures,arch foot reinforcement + arch replacement and micro-pile reinforcement base,are put forward,and compared and analyzed by numerical simulation.Finally,the field monitoring data after treatment of Ningchan tunnel are verified.The main research contents and results are as follows :(1)Based on the statistical investigation and analysis of the characteristics,influencing factors and treatment measures of the floor heave of 42 tunnels in China,the characteristics,influencing factors,disaster-causing modes and treatment measures of the current tunnel floor heave are summarized.Based on the bibliometric method,it is studied that the current research hotspots of floor heave diseases are highway tunnels and floor heave prediction;the mechanism analysis of the main influencing factors of the tunnel provides a basis for the prevention and treatment of the tunnel floor heave.(2)Combined with the floor heave disease section of Ningchan tunnel,through the statistics of the support form of the floor heave section,it is found that the inverted arch sections on the left and right lines account for 55.7 % and 86.4 % of the whole line respectively.The inverted arch reinforced sections accounted for 44.04 % and 45.37 % respectively.The influencing factors and disaster-causing modes of the bottom heave of Ningchan tunnel were studied by using borehole coring,pit excavation and indoor expansion test.It was concluded that the main influencing factors of the bottom heave of Ningchan tunnel included groundwater,high ground stress,surrounding rock expansion,soft rock rheology and construction quality.(3)Based on the actual working conditions of Ningchan tunnel,FLAC 3D finite difference software is used to analyze the curvature of inverted arch and the deterioration degree of basement surrounding rock,and to explore its influence on the deformation of tunnel inverted arch.The results show that when the curvature of inverted arch changes from 0 to 1 / 12,the maximum floor heave of inverted arch decreases by 58.8 %.When the deterioration degree of surrounding rock increases from 0 to 70 %,the floor heave increases by 41.8 %.(4)Through numerical analysis,the orthogonal test method was used to select five influencing factors: lateral pressure coefficient,surrounding rock deterioration depth,surrounding rock expansion force,base water pressure and surrounding rock grade.The data analysis method used by the results of linear regression orthogonal test was used to establish the prediction model of the bottom heave of Ningchan tunnel,and the typical section of the bottom heave disease of Ningchan tunnel was verified.The results show that the order of the influence degree of each factor on the bottom heave is: H(surrounding rock deterioration depth)> F(soft rock expansion force)> D(surrounding rock grade)> A(lateral pressure coefficient)> P(base water pressure).(5)Aiming at the problem of the deformation of the inverted arch bottom drum of Ningchan tunnel,the measures of lining replacement,arch foot reinforcement + inverted arch replacement and micro pile foundation reinforcement are put forward,which are verified by the numerical model.Finally,the feasibility of the treatment measures is proved by the monitoring data of the inverted arch deformation after the on-site treatment.The analysis results can provide some guidance for the treatment of floor heave diseases in similar tunnel projects. |
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