Reliability Analysis Of Deep Excavation In Soft Soil Considering Variability Of Soil Property Parameters And Uncertainty Of Construction Parameters

The variability of soil property parameters and the uncertainty of construction parameters have an important influence on the mechanical behavior of deep excavation in soft soil.However,most previous studies only focused on the influence of variability of soil property parameters and did not consider the influence of uncertainty of construction parameters on the mechanical behavior of deep excavation.Therefore,this thesis takes into account the influence of both variability soil property parameters and uncertainty of construction parameters at the same time.The main research content in this thesis is as follows:(1)Based on the statistical analysis of deep excavation accidents,the type and cause of accidents are investigated.It is concluded that the mistakes in design and construction are the main reasons of excavation accidents.(2)By finite difference numerical analysis,the influence of soil property parameters and construction parameters on mechanical properties of deep excavation is investigated.It is concluded that the modulus of soil,compared with the internal friction angle and cohesion,has a greater influence on the mechanical behavior of deep excavation.The axial stiffness of steel braces,the vertical position of braces and the load around the excavation have a great influence on the mechanical behavior of deep excavation.(3)Uncertainty analysis of excavation is performed.The influence of the variability of sensitivity parameters(e.g.,the modulus of soil,the axial stiffness of steel braces,the braces vertical position,etc.)on mechanical properties of excavation is investigated.It is concluded that with the increase of coefficient modulus variation and horizontal correlation distance,the variation of maximum underground diaphragm wall horizontal displacement and maximum axial force of braces increase.For the construction parameters,the uncertainty of support vertical erection position has the greatest influence on the support axial force,the coefficient of variation of maximum support axial force is 5.66%.The uncertainty of load around excavation has the greatest influence on the maximum horizontal displacement of diaphragm wal.(4)Based on the investigation of uncertainty analysis with the effect of the variability of soil property parameters and the uncertainty of construction parameters separately,the comprehensive influence of variability of soil parameters and uncertainty of construction parameters on mechanical properties of excavation is performed.It is concluded that the safety of excavation will be overestimated without considering the uncertainty of construction parameters.The maximum horizontal displacement of diaphragm wall and the maximum axial force of support obey normal distribution.