| In recent years,with the rapid development of China’s transportation construction and the continuous improvement of technical level,China has become a major tunnel country with the largest number of tunnels,the largest construction scale and the fastest development speed.After the service of the tunnel,due to the complex environment and improper maintenance,serious tunnel diseases will occur.Rainfall infiltration is an important factor leading to the deterioration of surrounding rock,slope instability and tunnel cracking.In this thesis,aiming at the slope stability problem after rainfall and the mechanical behavior of tunnel structure,three rainfall models under crossing conditions are established to analyze the influence of rainfall on surrounding rock and slope stability.Based on this,the lining mechanical model of the soil-rock boundary section of the shallow-buried bias tunnel in service is established,and the mechanical characteristics of surrounding rock deformation and supporting structure under the condition of surrounding rock deterioration of the shallow-buried bias tunnel in service are analyzed.The interaction mode between tunnel and deteriorated surrounding rock is proposed under three positional relationships between tunnel and soil-rock interface.Taking the Arroube tunnel as the engineering background,the control measures are put forward according to the failure characteristics.The main contents and results of this thesis include:(1)Through the investigation of 26 disaster cases of tunnel crossing rock and soil structural plane,the tunnel deformation and failure characteristics of three crossing modes under orthogonal mode are summarized.The basic concept and formation mechanism of unsaturated soil matric suction,the basic theory of rainfall infiltration,the soil-water characteristic curve of unsaturated soil and the unsaturated permeability coefficient are introduced.(2)Based on the basic theory of unsaturated seepage under rainfall conditions,a two-dimensional unsaturated seepage model of soil-rock slope is established by using MIDAS GTX NX finite element software.The influencing factors of rainfall infiltration are analyzed.The variation of pore water pressure,soil volumetric water content,slope safety factor and rainfall duration,and the variation of slope safety factor and rainfall intensity are studied.(3)The soil-rock interface model of shallow-buried bias tunnel in service under three different crossing conditions is established.FLAC 3D finite difference software is used to reveal the variation of surrounding rock deformation(surrounding rock displacement,plastic zone)and lining mechanical behavior(maximum principal stress,minimum principal stress,bending moment,axial force)during the deterioration of surrounding rock.The failure characteristics and failure modes of the interaction between surrounding rock deterioration and tunnel structure are summarized,and the mechanism of the interaction between surrounding rock deterioration and tunnel structure is revealed from the time distribution and spatial distribution.(4)Taking the Aruber tunnel as the engineering background,the control measures are proposed for the two sensitive crossing modes of the tunnel crossing the soil-rock interface and the tunnel located on the soil-rock interface.The FLAC 3D finite difference software is used to establish two support models for numerical calculation,which further verifies the effectiveness and practicability of the control measures. |
