Analysis Of Influence Factors Of Shield Excavation Face Stability And Research On Rensitivity

Because of its unique advantages,shield tunneling has become a popular method in urban underground space,especially in tunnel construction,and geostatic shield is one of the most pop methods.In the actual construction process,due to the complexity of groundwater,soil conditions and construction parameters,so that the excavation face of the larger fluctuations in the supporting force and thus affect the stability of the excavation face.At the same time,the influence of various factors on the stability of the excavation face is diffirent so much,so it is useful in practical project to carry out the sensitivity ranking of the factors affecting the stability of the excavation face.1)The formula of the limit supporting force of the excavation face is deduced by using the wedge theory,and in this paper,the stability of the excavation face is discussed theoretically,and the parameters affecting the ultimate supporting force of the excavation face are analyzed.2)Based on Shenyang metro line two shield project,the soil mass of shield tunnel was tested by three axial test.The saturated and unsaturated shear strength parameters of silty clay are obtained by the stress-strain curve and the shear strength envelope.3)The criterion of the shield excavation surface instability is improved and the Fish language program is written in FLAC3 D,and simulating the corresponding question.It is concluded that the law of surface settlement,the change law of soil stress,the volume change law of the plastic zone in front of the excavation face and the change rule of the damage range under the limit of the supporting force are obtained.4)Based on the simulation analysis of the factors-the thickness of overlying soil layer,water level,shear strength parameters of soil and so on-that affecting the stability of the excavation face,the influence of various factors on the ultimate stress ratio,the settlement law of the ground surface and the influence range of plastic failure are obtained.5)Based on the theory of grey correlation degree,the ultimate stress ratio of the excavation face is taken as the reference sequence and the influencing parameter as comparison sequence to calculate.The correlation degree ordering of each influence factor is obtained.