砂性地层孔隙特征对泥水盾构泥浆成膜的影响

Influence of pore characteristics of sand strata on filter-cake formation under slurry shield

透水砂性地层开挖面上成膜特征是影响开挖面稳定性的关键因素,而地层孔隙特征与成膜特征量化关系的建立是进行相关分析的必要条件。通过在不同孔隙特征地层中开展渗透成膜试验,确定了地层孔隙特征和成膜特征的量化指标,基于二者量化关系的构建,研究了地层孔隙特征对泥浆成膜特征的影响规律。研究表明,地层滤失量曲线双参数模型可以描述地层滤失量变化特征,模型参数a,b可量化滤失量曲率特征、成膜时间和成膜阶段等成膜特征,具有明确的物理意义。基于参数a,b和孔隙体积v的幂函数关系,确定了地层孔隙特征和成膜特征的量化关系。研究成果可为泥水盾构穿越透水砂性地层合理确定泥浆配比方案和施工参数,保证开挖面稳定提供试验和理论基础。

The characteristics of filter cake formation on the excavation face of permeable sand strata are the critical factors for the growth and decrease law of the soil and water pressure in the strata as well as the stability of excavation face.Then the requirement of these analyses is to establish the quantitative relationship between the pore characteristics and filter cake forming characteristics.The quantitative indexes of pore characteristics and filter cake forming characteristics are raised by carrying out the slurry filtration tests in the strata with different pore characteristics.Based on the quantitative relationship between the both characteristics,the filter cake formation laws influenced by the pore characteristics are studied.The results show that the two-parameters model for the filtration curve can describe the variation characteristics of seepage discharge.Th model parameters own clear physical significances to quantify filter cake forming characteristics such as curvature characteristics of seepage discharge,formation time and forming stages of filter cake.Based on the relationship of power function between parameters a,b and the pore volume v,the quantitative relationship of pore characteristics and the filter cake forming characteristics is established.The research results can determine the reasonable slurry proportion and construction parameters and may provide experimental and theoretical support for guaranteeing the stability of the excavation face for slurry shield tunneling projects excavated in highly permeable sand soils.