In this paper, earth pressure balanced （EPB） shield tunneling projects as themain object of study. Studied the instability mechanism of shield一tunneling faces,disaster evolution characteristics of instability of shield一tunneling faces underseepage action and its control technology system of instability in depth bylaboratory experiment, theoretical analysis, numerical calculation, model test andfield test. The result has theoretical significance and practical value in engineering project, mainly includes:
（1）Summarized and proposed the construction method and equipmentselecting. The equipment selecting suitability obtains from the permeabilitycoefficient of formation, grain composition, characteristics of geotechnical andgroundwater state. Developed the software system which had a good man一machineinterface with shield construction method. The rules to select the shield methodunder complex geological environment especially the water一rich sand stratum isconducted in一depth study.
（2） By sorting and analyzing the cases of surface subsidence and water inrush,caused by excavation surface instability, the disaster environment and evokedfactor are analyzed. The basic characteristics of disaster sources were introducedin the paper. And set up a system of evaluation indexes of excavation surfaceinstability. The attribute recognition model is established. It provided a dynamicassessment of the high risk period of tunnel based on the software system. Putforward the prevention and control measures of excavation surface instability byearth pressure balance shield construction.
（3） Based on the limit analysis upper limit theorem, the 3D revolving bodydamage model is built. The formula of ultimate supporting force of excavationface is derived by the critical failure power of doing work by external forces isequal to the internal dissipation of soil.The critical failure supporting force ofexcavation face in homogeneous formation and complex strata is solved by thecomputer program. The computer program is compiled by MATLAB.For complexstrata, this paper respectively analyzed the influence factors such as tunnel depth,characteristics of soil, groundwater level under two working cases. They are thecasing soil and crossing layer. Compared with the calculated results with thepredecessor's results, it verify that the validity of the theoretical model.
（4） Based on the 3D revolving body damage model, introduced thegroundwater seepage action to the limit analysis of excavation face stability. Thenthe seepage force formula deductions of collapse of the soil and excavation faceare demonstrated. The relationship between seepage force and groundwater levelwas obtained. The upper limit solution of supporting force of excavation face under complex strata was finally solved.
（5） The construction mechanics process of earth pressure balance shield undercomplex strata is calculated by numerical method considering the effect ofgroundwater seepage. The relationship between the damage forms of excavationface, deformation of excavation face, surface deformation, limit supporting forceand tunnel buried depth, mechanical properties of rock and soil, groundwater stateare studied in the paper respectively earth pressure balance shield constructionunder homogeneous formation and complex strata.
（6） In order to study the change rule of excavation face supporting force andfailure mode of shield tunnel excavation face under seepage force, then shieldtunneling construction model test system was developed. It includes visual testplatform, waterproof automated monitoring system. Take shield tunnel that crosslimestone and sand layer of Jinan Metro line R1 as engineering backgrounds, andcarry out model test about the excavation face stability in complex ground, tostudy the problem for stability of excavation face of shield construction incomplex ground under different buried depth and water head height, analyzeinfluence law that buried depth and water head height affect ground settlement,limit supporting force and soil deformation of excavation fare, reveal theevolutionary mechanism about excavation face unstable failure.
Key words:shield tunnel; excavation face stability; compound strata; limitanalysis; groundwater seepage; control measures.
盾构毕业论文英文摘要三：
论文题目：盾构隧道管片内力分布特性数值模拟分析
ABSTRACT: In recent years, a lot of tunnel projects were built in the world greatly promote thetechnology of shield tunnel, and the fixed methods are forming in most country about thedesign of shield tunnel segment structure. But there are no definite rules about the computingmodels or computing methods of load on deferent soil, so many numerical methods are springup about tunnel and underground project.
In this paper, taking a shield tunnel in Shenyang Metro as an example, three internalforce computing methods of shield tunnel are reviewed and analyzed. A new load-structuremodel of calculating the segment internal force is proposed based on earth pressurecalculation method in soil mechanics. Analyzing the factor of segment internal force, such asthe different joint type, tunnel depth, the diameter of segment, the elasticity modulus andPoisson's ratio of soil. The distributions of internal forces on segments are simulated by usingfinite element method while the ground stress release rates induced from shield tunneling areconsidered. The practical ground stress release rate of a tunnel is determined by comparingsettlements computed by finite element method with in-situ observed data. The numericalsimulation shows that the maximum settlement of ground surface is proportional to groundstress release rate. Based on plane assumption of beam in bending state in material mechanics,the analytical expressions of bending moment allocations on double-layer linings of shieldtunnel are deduced. Two examples for double-layer linings of shield tunnel are numericallysimulated with FEM in order to compute moment allocation ratio. Analytical solutions forallocation ratio of bending moments agree well with numerically simulations. Analyzing therelationship between the first lining and second lining; Analyzing the influence of internalforce on shield tunnel segment by soil relaxation pressure on the example subsea tunnel ofQIONGZHOU strait with high water pressure and great depth.
Key Words: Shield Tunnel segment; internal forces; ground stress release ratedouble-layer linings; soil relaxation pressure.
