Research On The Ground Movement Induced By The Disturbance Of Multi-circular Shield Construction And Its Control Technology

With the further development of the urban underground space, the shield tunnelconstruction evolve to the large depth, small curve, long distance, large diameter andsection optimization.The various novelty non-circular shields appear to theconstruction of section tunnels and deeply buffed metro stations. The surfacesettlement induced by the construction disturbances of shield tunnel is one of thesignificant topics of the environmental soil engineering in urban area. The soildisturbance and movement of the Double-O-Tube(DOT) Shield tunnel is notadequately researched. It is of practice demand and of great theoretical significance toexplore the soil disturbance rule of the DOT shield tunnel.Bases on a DOT tunneling section of the Shanghai Rail Transit Line No.6, therules of ground settlement, the soil disturbance and the variation of pore waterpressure are brought forward through statistics analysis of the monitoring data, thedriving field test in experimental section and the 3-Dimensional numerical simulation.The construction controlling measures of decreasing the environmental geotechnicaleffect are summed up. The research can be reference for the futural application ofDOT shield, and other non-circular shields(Horizontal & Vertical Variation ShieldMethod, H&V, Multi-circular Face Shield Method, MF). The major works and resultsof this dissertation are as follows:(1) Based on the measurement data of ground settlement induced by the DOTshield, the characteristics of transverse and longitudinal settlement trench areanalyzed with the statistic method; the Quasi-Peck formula of forecasting the groundsettlement is established. The range of the influenced regions, the stratum loss ratio,and the settlement trench width is discussed.(2) Based on the driving test in-situ, the characteristics of the horizontaldisplacement, layered settlement, and pore water pressure, caused by the DOT shieldtunneling in soft clay region are monitored continuously. The characteristics ofregional and time-dependent of the DOT shield are brought forward. The zoningmaps of transverse and longitudinal disturbance are proposed. (3) During the construction, the parameters of working face pressure, groutvolume of shield tail, advancing velocity were rectified designedly. The layeredsettlement of transverse and longitudinal sections induced by the construction of DOTshield was monitored continuously in-situ. The correlation between the layeredsettlement and the shield operation parameters is carried out.(4) The computing method of additional stress field induced by propulsion ofDOT shield is established by means of the Mindlin's stress equations in elasticity. Thedistributing characteristics of additional stress and the extent of soil disturbance ofDOT shield construction are analyzed. In the analysis, the excess earth pressure andthe lateral friction between shield skin and the surrounding soil were taken intoaccount. The precedure is compiled adopting the program of Visual Fortran 6.0.(5) Adopting the classical mechanics solution, the computing methods of theground displacement field induced by the non-circular shield are established and thecomputational process is compiled with the program of Visual Fortran 6.0. Theanalytic formula contains the influence of the construction loads and the ground loss.The construction load is calculated by the Mindlin's displacement Solution, includingthe excess earth pressure and the lateral friction. The ground loss is estimated by themodified Sagaseta's formula, considering the soil Poisson's ratio and non-radialmovement patterns.(6) Based on the concept of the equivalent gap parameter, the modifiedLoganathan's formula of Multi-circular Face shied (DOT, MF) is established,considering the influence of internal friction angleφ. The characteristics of surfacesettlement, subsurface settlement and lateral displacement are revealed caused by theconstruction of the non-circular shields.(7) The ANSYS general finite element software is used to simulate mechanicsbehavior of the DOT shield construction. The process of layered settlement causedby the DOT shield is analyzed. Furthermore the results of numerical simulation arecompared with that of measurement to reveal the soil disturbance character.(8) The integrated numerical simulation techniques are put forward to thecomplex tunnel strucatures(cross connection structure,branch tunnel,special sections),which can actualize the rational combination of the preprocess modeling, computating, post-processing.The displacement field characters of DOT shield are carried out bythe FLAC^3D finite difference method. The contour characteristics of transverse andlongitude settlement induced by DOT shield are described.(9) The controlling methods of the environmental influence of soil engineeringinduced by the non-circular shield tunnel are generalized in this dissertation, and thecontrol construction techniques of the ground settlement caused by the DOT shieldare summarized. Furthermore, the deviation rectifying technology of the DOT tunnelis generalized. The concept of building the depth metro station with Multi-circularFace shield is brought forward. The strategy of domestically design and developmentnon-circular shield tunnel is proposed.