Study On The Influence Of The Bias Of Tunnels In_weak Inercalation By Benching Stepping Methods

In tunnel construction,the geological structure bias problem often arises from the tunnel excavation methods and weak intercalated layer.In order to study the characters of tunnel bias is caused by the geological strcuture,it is necessary to study on the influence of the bias of tunnels in weak inercalation by benching stepping methods.Therefore,this paper based on the bias deformation phenomenon by three-bench seven-step method in the high-speed passenger railway of Jiling-Hunchon engineering.Analysis the deformation characteristics in each stage after bias settlement.It used finite element software FLAC^3Dto build a calculation model of tunnel and simulated in this condition,the feasibility of numerical simulation is validated,once more to build a calculation model of Shangbuluo and Haibaluo deep-buried tunnel in the high-speed passenger highway of Xianggelila-Lijiang engineering,simulated the process of tunnel excavation in the weak intercalated layer with different inclination angles by the three-bench seven-step method and two-bench method respectively,and studied on the conditon of bias,the main research achievements are as following.Firstly,a study of the bias deformation phenomenon in shallow JIaoxi tunnel with weak interaction by the process of three-bench seven-step excavation method,by analyzing a field measure data and the result of numerical analog computation,the comparison research indicates that the largest settlement value is monitoring point-2 in the upper bench stage and the right of middle bench stage.The maximum settlement position is move to carve the arch line and the magnitude decreases in the left of middle bench stage and the right of lower bench stage,the largest settlement value is monitoring point-8 in the left lower bench stage,the largest settlement value is monitoring point-6 in the invert stage;the cumulative settlement value from largest to smallest,it goes:the right of middle bench,the left of middle bench,the upper bench,the right of lower bench,the left of lower bench,invert,the simuluated results in good agreement with the experimental data,which demonstrates that the feasibility of FLAC^3Dnumerical simulation is validated.the two-bench method is less than three-bench seven-step method when the angel is 55o?90o,the two-bench method is better than three-bench method at this point.Thirdly,the change of the dip angle of the weak interaction layer has great influence on the difference of bending moment in the deep geognostic bias tunnel,the maximum range of bending moment moves from the position of the arch shoulder to the arch line in the three-step method,and the maximum value,and the maximum value of the difference is the monitoring point 2 in the left of middle bench when the dip angel is 50o,the maximal value even reaches 70.438k N.m,the difference of bending moment in the monitoring 1 is considerably fluctuant by two-bench step method,the minimum value is-6840.2k N.m and the maximum is 20104.2k N.m when the dip angel is 60o,the unfavorable regarding force applied on structure,which makes it necessary to take effective measures to improve the strength;The axial force difference in the three-bench step method is less than the two-bench step method,it is beneficial to stress of tunnel liner.Lastly,the plastic zone of surrounding rock increases first and then decreases with increase of the dip angle of the weak interaction layerin the deep geognostic bias tunnel by the three-bench seven-step method and two-bench method.The plastic zone of surrounding rock is the largest when the dip angel is 60o;The plastic zone of surrounding rock is not only breakthrough weak interaction layer and influence tunnel bias but also the plastic zone grows in the left of tunnel arch bottom,the instability of surrounding rock leads to cracks in the inverted arch of tunnel.