Study On Stabality Of Cavity Caused By Shield Tunneling In Sandy Cobble Stratum

The characteristics of water rich sand pebble layer are particle large discreteness, pebble particle, high uniaxial compressive of single rock, high permeability the stratum and so on. Because of sandy pebble layer itself characteristics and influence of shield tunneling construction, shield tunneling in sandy pebble watery stratum will inevitably produce hole formation. The hole formation will develop to the surface under formation gravity stress conditions and external disturbance, as a result of which will cause large area of subsidence, even surface subsidence. In order to study the above situation, the author of this paper has carried on the rich water sandy pebble cases, shield tunneling formation causes of hollow and hole formation in the diffusion process in the formation mechanism of hollow structure analysis and carried out indoor model test of the hole formation spreading in the formation. Then, Put forward the proposal of prevention measures of appearing hole formation and treatment measures of the hole formation after the hole formation appeared.The main research results are as follows:(1) From the perspective of the sandy pebble formation characteristics and the basis of the shield machine driving way analyze the cause of hole formation. Analogy loose strata in tunnel hole stress mechanism analysis methods to analyze the mechanism of hole formation in sandy pebble (temporary); The evolution of the hole in the sand pebble formation model is analyzed.(2) Carrying out indoor model test for hole formation in the formation of the development situation, mainly from the stratigraphic hole size, hole depth, formation, groundwater seepage hole position disturbance, the vibration disturbance on the surface, groundwater seepage and the development of vibration under the action of coupling hole formation on qualitative description.(3) Based on the above theoretical analysis and experimental results, combining with the current domestic construction as an example, has carried on the shield tunneling process hole formation prevention measures and treatment measures after the appearance of hole formation analysis.