Probabilistic Analysis On Performance Of Suspended Waterproof-support System For Deep Excavation In Soft Soil

The continuous passive zone improvement area formed by construction process such as deep mix method can not only work as a horizontal support to control deformation,but also block groundwater effectively.However,the cement-solidified soil always has strong heterogeneity,and the effects of spatial variability of its parameter on deformation control and water-blocking performance of suspended waterproof-support system should not be underestimated.In this thesis,uncertainty analysis on holistic performance of suspended waterproof-support system for deep excavation in soft soil is conducted to clarify the influence of spatial variability of cement-solidified soil parameter.Firstly,the basic form of functional relationship between unconfined compressive strength and permeability coefficient of cement-solidified soil is derived and verified.Secondly,the random field is generated based on the K-L decomposition method to characterize the spatial variability of cement-solidified soil parameter,a typical model of deep excavation in soft soil is established by FLAC^3D,and reliability analyses on the ground surface settlement,horizontal displacement of diagram wall,bottom heave and water inflow are conducted.Thirdly,the strength reduction method is introduced into reliability analysis of deep excavation,and the impact of shear strength of cement-solidified soil on deep excavation stability against inrush is analyzed under different variation coefficients.Finally,an equivalent deterministic analysis method that can consider the influence of spatial variability of shear strength of cement-solidified soil on safety factor of deep excavation stability against inrush is proposed and then verified.The results show that there is an exponential relationship between unconfined compressive strength and permeability coefficient of cement-solidified soil,and the variation of permeability coefficient is much stronger than that of mechanical parameter.Deterministic analysis will overestimate deformation control and water-blocking performance of improvement area,and the impact of parameter variation on water inflow must be considered in design.The ratio of safety factor obtained from reliability analysis to that from deterministic analysis is irrelevant to the mean value of shear strength,but has a linear negative correlation with the variation coefficient of shear strength.The proposed equivalent deterministic analysis method for safety factor of deep excavation stability against inrush both can simplify analysis process and take the influence of spatial variability of cement-solidified soil parameters into reasonable consideration.