Study On Stability Of Surrounding Rock For Shallow-buried And Unsymmetrically Loaded Loess Tunnels With Small Interval

The small interval tunnel has been widely applied and development due to therestriction of topography and geological conditions in site area of the tunnel,construction technology, quality control, project cost and many other advantages.However, what is different from ordinary small interval tunnel is that the shallow-buriedand unsymmetrically loaded loess tunnels with small interval could lead mishap-proneto construction safety accident, and brought great losses to our people, due tocomplicated and variable geological conditions and the construction environment and soon. Therefore, the further and systematically studies on stability of surrounding rock forshallow-buried and unsymmetrically loaded loess tunnels with small interval has veryimportant significance.This paper was written on this condition, and use realistic project as background,through theoretical analysis, field measurement and numerical simulation method, thecurve of the displacements of surrounding rock varying with time, reserved deformation,the development law of surrounding rock deformation of tunnel with the slope of theground and buried depth, and the main factors influencing the stability of surroundingrock for shallow-buried and unsymmetrically loaded loess tunnels with small intervalwere studied. Main contents and results are as follows:Firstly, this article summarizes the current research situation on discrimination andclassifying methods for shallow-buried and unsymmetrically loaded tunnels with smallinterval, and systematically expounds on the calculation method of the surrounding rockpressure, and the deformation character and classification of the surrounding rock wereanalyzed and summarized.Secondly, through coordinating and analyzing the data based on the actualmeasurement engineering data, displacement curves of surrounding rock duringexcavation was concluded. In addition using regression and function fitting analysis, thecurve of the displacements of surrounding rock varying with time was obtained.Furthermore, the final deformation scale and the time required of stability ofsurrounding rock can be drawn by induction.Thirdly, based on the actual situation relying on the project, two-dimensionalelastic-plastic finite element numerical model is built. The stability of the surroundingrock and the mechanics characteristic of support structure and its change rule for shallow-buried and unsymmetrically loaded tunnels with small interval were calculatedand analyzed as the slope angle and buried depth of tunnel changed.Fourthly, based on the factors influencing the stability of surrounding rock forshallow-buried and unsymmetrically loaded loess tunnels with small interval, thesequence of construction, the size of interval, the method of construction, the propertiesof middle rock wall and the distance of excavated face are main research object.Fifthly, the contrast between the results of field measurements relying on theproject and the numerical simulation results, the general regularity on stability ofsurrounding rock for shallow-buried and unsymmetrically loaded loess tunnels withsmall interval is presented. In the end, combined with the engineering practice, somesuggestions and expectation on the future work are appreciated.