Mechanism And Disposal Technology Of Floor Heave In Horizontal Shale Tunnel

In order to analyze the mechanism,the influencing factors,the ultimate bearing capacity and the plastic zone depth of floor heave of horizontal layer shale in Mazui Tunnel left line of Nandao Expressway,.The method of laboratory experiment of rock physical and mechanical properties test,theoretical analysis,numerical simulation and field investigation were used comprehensively to study the floor heave of Mazui Tunnel of Nandao Expressway.On the basis of the correct understanding of the drum deformation mechanism of floor heave about the horizontal layered shale tunnel,the repair treatment schemes of floor bolt grouting reinforcement and the support capability of inverted arch are come up to control the floor heave efficiently,by using the numerical simulation software of FLAC3 D,the effect before and after treatment was used to analyze.The main conclusions are listed as below:(1)The floor heave of Mazui tunnel is:(1)The arch is not effective and timely support,closed into a ring after excavation(2)Inverted arch with poor stress conditions is not excavated,so it cannot form anti-arch(3)After the excavation,due to the thin rock layer,the developed horizontal bedding,the small adhesion,when the tensile stress is greater than its own tensile strength,the floor shale layer with the high level of stress grows to abscission layer and broken from the deep layer gradually.(2)The main reason for the occurrence of floor heave is: the low strength of the surrounding rock,the hydrological effect,the creep of the surrounding rock,the lack of support of the bottom rock,the above factors interact with each other to reduce the strength of the shale formation and eventually lead to the production of the bottom drum.The floor heave produced by floor strata bent is 62.31% of the total floor heave,which is the key factor to produce floor heave.(3)According to the theory of plates and shells,the mechanical model of the buckling and failure of the bottom plate is established.It can be seen from the expression that the failure of the floor strata is not only related to the length and width of the bottom drum,but also to the stratified thickness of the floor strata.What's more,the plastic zone of tunnel excavation is not only related to the cohesion c and internal friction angle,but also to the original rock stress.(4)The technology of bolt grouting reinforcement,invert arch and reinforced concrete is adopted to carry out field verification,the old and new schemes of surrounding rock displacement distribution,distribution of plastic zone is analyzed by using the numerical simulation software of FLAC3 D,and the field verification is carried out,that is nine monitoring sections were arranged in invert cracking segment,that is ZK18 + 370 ~ ZK18 + 410,and two sections were arranged in each section,and 18 sections were arranged in each section.The monitoring results show that the maximum amount of floor heave of each monitoring point,the two sides were reduced from 124.7mm,15.8mm to 17.2mm,9.45 mm respectively,reduced by 84.4%,40.2%,using the new program achieves the desired effect.