2D Finite Element Analysis For Pile-Strut Bracing Structure Of Unbalanced Excavations

With the development of urban construction, more and more large scale and deep excavations appear, the conditions of excavation are also complex. There are two kinds of excavations in current engineering: balanced excavations and unbalanced excavations. Four situation of the unbalanced excavations will be studied as following: first, the different heaped load; second, the different excavation depth; third, the different location of excavation separatrix;last, the different soil mass properties.The current researches mainly concentrate on the balanced excavations,but few on the unbalanced part.In this dissertation,on the base of the studies so far available,the unbalanced excavations is studied in-depth.The main work is as following.Considering the soil's mass properties and the relations of pile-soil, a 2D finite element analysis model built on Ansys is proposed in the paper. Solid,beam and link element are used to simulate soil, retaining pile and strut.Using the Drucker-Prager elastoplastic model as soil's constitutive model,establishing pile-soil contact element, and applying Ansys's advanced technology such as nonlinear analysis,element birth and death,all of these will improve the calculation accuracy to a great extent.Then,an example is used to verify the reliability of the process.By the method and procedure in this paper, the stress and strain of supporting structure are studied under the condition of different heaped load,excavation depth, excavation separatrix location and soil mass condition.The result shows that there is the great difference between the stress and strain of supporting structures on two sides with the same design parameters.So,it's necessary to calculate and analyse supporting structures on two sides separately while design the unbalanced excavation. Meanwhile, through the calculation and comparison, the paper summarizes some rules which are useful for the design and construction of the unbalanced excavation.Finally, an engineering case is simulated by the method and program developed in this dissertation.Comparing the theoretical results with the measured data shows that the calculation method developed in this dissertation is feasible, and the design by this method is more economical than traditional's.So it's valuable to the practice.