| With the development of urbanization,urban traffic is increasingly crowded recently.In order to solve the problem of crowded urban traffic and citizen traveling,more and more cross-sea and cross-river tunnel projects are being constructed,and large-scale slurry shield applications are widely used in these cross-sea and cross-river tunnels.Due to the complex conditions of crossing the stratum,the construction is difficult and the risk is high,especially for cross-sea shield tunnels,.In order to be able to complete the construction operation safely,a dense filter cake need to be formed at the excavation surface to maintain the excavation face stability.Therefore,it is meaningful to study the slurry mixing proportion of the working stratum,so that it can penetrate into the film to maintain the stability of the excavation face.This article relies on the Qingdao Metro Line 8 cross-sea tunnel project,the single factor control and the comparative analysis method are adopted for the high-permeability sand soil layer to carry out slurry preparation test and slurry penetration and formation test in the seawater environment,on the basis of analyzing and grasping the micro-mechanism of filter cake formation and the relationship between the filter cake and maintaining the excavation face stability.The characteristics of the slurry and its influence on the filter cake formation were studied,and the following research results were obtained:(1)The micro-mechanism of filter cake formation and the relationship between filter cake formation and excavation face stability are revealed.The effect of slurry pressure on the filter cake balances the water and soil pressure at the excavation surface to support the stability of the excavation face;(2)A large number of slurry preparation experiments were carried out,the slurry materials on the basis of bentoninte,CMC,sodium carbonate and clay particles and slurry characteristics on the basis of slurry specific gravity,slurry viscosity and water filtration.A single factor control variables method is adopted to study the effect of different slurry materials on slurry characteristics one by one,especially the slurry characteristics under seawater conditions,which laid the experimental foundation for the study of slurry penetration test of cross-sea shield engineering;(3)Designed and developed a slurry penetration membrane forming test device that can have good airtight performance under high pressure.According to the test device,it can better simulate the infiltration film formation process of the mud in the slurry shield machine under the action of slurry pressure to form the filter cake.The test results show that the specific gravity of the slurry is the main factor affecting the amount of water filtration.Increasing the content of bentonite can increase the specific gravity of the slurry and reduce the amount of filtered water effectively in the sea-slurry,a higher slurry viscosity is beneficial for the filter cake formation in the high-permeability formation with large pores,and the film formation effect is better;(4)According to the characteristics of seawater environment and high permeability sand soil layer,on the basis of a large number of slurry preparation tests and filter film formation tests,comprehensively considering the adaptability and economic cost of slurry and working strata,the optimal slurry proportion have suggested to adapting to this stratum.The ratio(mass ratio)is m(bentonite):m(CMC):m(sodium carbonate):m(seawater)=100:3:6:700.Figure[39]table[16]reference[64]... |
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