Probabilistic Models Of Excavation Static Load Effects For Tunnels Based On Bayesian Method

The static load caused by excavation is one of the main load forms of tunnel lining structure.Because of the complexity of underground engineering,the scientific evaluation of tunnel excavation load effect is one of the difficult problems in the field of civil engineering.It is difficult to estimate the excavation load of tunnel accurately either by field measurement or model test.At present,China’s tunnel engineering has made great progress with the construction of infrastructure.Systematic and scientific estimation of the excavation static load is significant to ensure the safety of tunnel structure.In the study of excavation load effect and engineering practice,the analytical method based on mechanics principle and the numerical simulation method based on finite element software are mainly adopted.In the existing analytical methods,due to the low accuracy of formation pressure calculation and insufficient consideration of soil-structure interaction,the calculated excavation load effect usually has obvious deviation from the real value.The finite element method can usually give more accurate estimation of load effect,but it is not convenient for engineering practice,and it is difficult to comprehensively consider the randomness of each factor.In view of this,this paper systematic research the circular lining tunnel under excavation load effect of bending moment,axial force and deformation,based on the finite element simulation results,three probabilistic models of load effects are proposed by adding correction terms on the basis of analytical method,and the model parameters are estimated by using Bayesian method.the concrete research content is as follows:(1)In order to make the model have a clear physical meaning,the load effect probability model in this paper is obtained by adding a correction term on the basis of the analytical method based on the mechanics principle,and the model parameters are calibrated with the finite element simulation results as the basic data.Therefore,this paper systematically discusses and compares the analytical methods for calculating tunnel lining load effects based on different theories,and presents the finite element numerical simulation methods used in this paper,such as material properties,soil structure interaction and boundary conditions.(2)In order to comprehensively consider the influence of different factors,this paper systematically compared and analyzed the influence law of construction method,buried depth and material properties on the load effect of tunnel excavation,and selected a group of parameters that have significant influence on the load effect,combined with the design The norms and actual tunnel engineering give the value ranges of these parameters.Based on the uniform design method,a set of sample points that need finite element simulation calculation are designed,and finite element calculation and result extraction are performed.(3)to obtain unbiased estimate of the effects of load probability model,based on the finite element calculation results of sample points as the benchmark data,the bayesian method is used for tunnel excavation load effect probability model for optimization and parameter estimation,and considering the bending moment,axial force and deformation of the lining of road tunnel effect of three kinds of load,each kind of load effect are separately presents a probability model,An application example of the probabilistic model in this paper is given based on a practical tunnel engineering example.