Safety Assessment Of Shield Tube Disease And The Influence Of Cavity Grouting Behind Tube

As a major force component of shield tunnel, tube bear jacking force, rock pressure, grouting pressureand groundwater pressure in the construction and operation. It is a comprehensive guarantee of waterproof,fireproof and durability. Because of the effects on technology, pressure and environment, there will becavity, cracks, breakage, upward movement and other diseases. To ensure the safety and summarize cavitygrouting influence of the tunnel, the paper assesses the ill tubes and analyzes four different conditions ofcavity and grouting behind tube through theoretical analysis, numerical analysis and on-site monitoring andother methods. With the engineering project, the paper draws the conclusions as follows:1Through the numerical simulation of tunnel mechanical characteristic and the safety factor calculationprogram, we obtain the axial force, moments, safety factor and other parameters, and then assess the safetyof structure according to the safety factor, the carrying capacity and crack width.Then the law of the cracksdevelopment were studied by SOLID65, research shows that: When the load between2.5and4times of thedesign load, the relationship between the load and number of cracks close to the S-curve.2Through the numerical simulation of different cavity behind tube and analysing its affection, this paperdraw that the hole of different location with the same size affected the structure mostly when it is locatednear the middle of the tunnel. In addition, the tube’s safety factor is small and decreased rapidly thereafterwhen the hole size is larger than0.5*0.5m, while the hole size is larger than1.5*1.5m, the structure willdamage.3Deriving hemispherical diffusion equation of slurry in clay based on modified Darcy’s law. Throughnumerical simulation, we get the results as follows: For grouting in different places, the affection is largerwhen grouting in the top or bottom of the tube. For grouting in different pressure, axial force, moments andupward movement will decrease with the reducing of grouting pressure. When the grouting pressure is0.3MPa, the mechanical characteristic of tube is same as design conditions except a small rotatory angle ofcontrol-section.4By comparing monitoring results with numerical simulation, we obtain that surface displacement ofsimulation results is difference with the actual project, while the results is consistent between numericalsimulation and actual displacement. When change the simulation method, we reach a similar results.