盾构隧道双道密封垫防水增强机理研究OA北大核心

Rubber gasket is the core structure of joint waterproofing of shield tunnel.With the increase of shield tunnel diameter and design water pressure,the double gasket mode has gradually become the mainstream waterproofing design scheme of shield tunnel.In order to explore the mechanism of waterproof enhancement of double gasket compared with single gasket,the waterproof test of double gasket was carried out under the normal working condition without inner cavity water pressure and the special working condition with inner cavity water pressure.The water pressure time-history curves of central cavity and inner water cavity were recorded.The leading factors of waterproof enhancement were obtained under the two conditions.The results show that under the action of viscous resistance,the pressure drop caused by the pressure water flowing from the central cavity into the inner water cavity is the main factor affecting the waterproof enhancement of the double gasket under normal working conditions.The smaller the porosity of the gasket under compression,the more significant the viscous resistance pressure drop effect.By introducing porosity influence coefficient,a calculation method of viscous resistance pressure drop effect based on porous media seepage theory is proposed,and the acquisition methods of three key parameters,porosity,fluid velocity and average particle diameter of porous media,are given.Under the reaction of the water pressure in the inner cavity,the additional contact stress of the external gasket is the main factor affecting the waterproof enhancement of the external gasket under special working conditions.The greater the compression degree of the gasket,the more obvious the waterproof enhancement effect under the action of inner cavity water pressure.By evaluating the equivalent Poisson's ratio of gasket with the aid of compactness index,the calculation method of waterproof enhancement ability under the action of inner cavity water pressure is put forward.The waterproof enhancement mechanism of viscous resistance and inner cavity water pressure on double gasket is studied and proved,and two calculation methods of enhancement effect are given.The results can provide reference for waterproof design of double gasket.