Three-dimensional Formation Structure Simulation Considering Spatial Variation And Its Application

The distribution of stratum structure is the basic data for the foundation design of buildings and structures.However,the variability of stratum exists widely in practice.The complexity of stratum distribution,the scarcity of borehole data and the lack of geological exploration work make it difficult to predict the distribution of stratum structure.At the same time,in order to simplify the calculation,most studies on the response of geotechnical structure do not consider the influence of stratum variability.Therefore,based on the basic principle of Markov chain,three-dimensional stratum structure simulation considering stratum variability and uncertainty analysis of foundation pit excavation deformation are carried out.The main research results are as follows:(1)From the perspective of probability and statistics,based on the basic principle of Markov chain and.two-dimensional Markov chain theory,a three-dimensional stratigraphic structure model considering the spatial variability of strata is established.T he corresponding program is developed by using MATLAB language,and the rapid uncertainty modeling of 3D formation based on geological borehole information is realized.The accuracy and convenience of the program are verified by a numerical example.(2)A similarity calculation method is proposed.Through a practical engineering to simulate the formation structure,the results show that the similarity values of the models are higher than 85%when they are stable,which verifies the accuracy and scientificity of the three-dimensional formation structure simulation method.The influence of the number of boreholes on the accuracy of characterization of formation variability is discussed.It is concluded that with the increase of the number of boreholes,the increase rate of similarity is getting smaller and smaller,which shows that considering the engineering economy,the number of boreholes is not the more the better,but there is an optimal number of boreholes.According to this law,a method to reveal the true formation distribution with the least geological boreholes is proposed,which improves the probability of finding weak interlayer in the formation and reduces the redundant arrangement of Engineering boreholes.(3)Through the construction of the three-dimensional Markov chain random stratum simulation method,combined with a foundation pit engineering example,the stratum distribution in the study area is simulated,and the stratum random field is mapped to FLAC 3D to establish a numerical model.The finite difference calculation is carried out,and the calculation results of the vertical displacement of the foundation pit excavation are obtained.The results are compared with the deterministic calculation results without considering the stratum variation,The deterministic solution of the vertical displacement of foundation pit excavation is in the middle of the random solution considering the variation of the stratum,and the random value higher than the deterministic calculation result accounts for 49%of the total,which indicates that there is a risk that the displacement and deformation are estimated too small.Therefore,the random analysis method can more comprehensively consider the impact of layer variation,grasp the possible range of deformation displacement,and has higher practical value.