The FEM Analysis Of Composite Soil Nailed Wall In Construction Process And Earthquake Action

As a deep excavation technology which is easy and celerity to implement, safe and less cost, soil nailed wall is getting more and more application to deep excavation construction. However,soil nailed wall cannot be used in soft soil such as loose layer, mucky soil and saturated soil or for cases which deformation of the soil nailed wall has to be strictly limited. To cope with these more difficult situations, composite soil nailed wall, i.e.a combination of soil nailed wall with ground anchors, soil-cement mixing piles or mini-piles, is recently developed. However the research on the theory of behavior and mechanism of the structure lags behind the application in the engineering practice. For example, many finite element analysis methods of composite soil nailed wall regard it as a 2-D problem or a partial spatial one, not the whole 3-D analysis method. The model can not analysize spatial effect of the foundation pit. Besides,many finite element software do not care for transitional time of element's "birth and death" in process of excavation of foundation pits. These factors will affect analysis results of FEM.Furthermore, the study of the behavior and mechanism of the composite soil nailed wall of the excavations in northwest loess zone should be strengthened. Especially the FEM analysis of the dynamic response of the soil nailed wall which subjected to earthquake, the retaining structure coupled pore pressure are studied rarely.With above stated situation, a whole 3-D finite element model on composite soil nailed wall connected with soil-cement mixing piles is established for deep foundation pit based on the nonlinear finite element software ADINA.Spatial action of foundation pit and transitional time of element's "birth and death" are considered in the model.Firstly, deformation of soil and soil-cement mixing piles, the axial forces of soil nails and the corner effect of foundation pit with the staged excavation are analysized,and then are compared with the actual test data.Subsequently, the paper has a further research on the influence of composite soil nailed wall behavior in the perspective of the horizontal distance of nails, pile diameter of soil-cement mixing piles, the inserting depth of soil-cement mixing piles and small prestress.At last, the dynamic response of the composite soil nailed wall is analyzed and discussed. And the variation principles of the composite soil nailed wall which subjected to the earthquake, and the earthquake coupled with pore pressure, are demonstrated respectively.Based on the above analysis, some valuable conclusions which can be refered for engineers in design and construction of composite soil nailed wall are obtained.