Optimum Design And Finite Element Simulation Analysis Of Foundation Pit Support Works About A Project In Beijing

Because urban land for the construction of the limitation, surrounding environment is tough, excavation and the supporting is complexity and uncertainty. Building pit is a challenging, high-risk, and advanced geotechnical engineering issues. In engineering practice, due to improper design and construction of deep excavation works, caused major economic losses of excavation accidents still occur from time to time; and the design is too conservative, resulting in recessive waste of engineering example is not uncommon. Therefore, the foundation works of design theory and method for a more in-depth study is necessary. Contrast optimization design method, achieve the best economic purposes and achieve cost-effective as well as social and environment benefits.Every theory is a certain simplifying assumptions under the premise established and have certain limitations. To prevent the design and construction mistakes, Design Foundation Pit workers in the use of a theoretical analysis issues, the need to consider it had not included the impact of other factors, and comprehensive analysis and judgment. Excavation deformation and failure mode has a very close relation with the evolution of stress and strain when excavation supporting, thus it is necessary to study the evolution of stress and strain when excavation supporting, which makes the numerical simulation method. This requires the help of numerical simulation method. Therefore, the deep excavation support system simulation is particularly meaningful. This paper gives design program of a real foundation pit, carries out numerical simulation using Ansys finite element software and comprehensive analyze impact factors of foundation pit design. It studied foundation pit of Yunnan Tobacco Corporation liaison complex building in Beijing, the key content and study as follows:First, the foundation pit advances to 10.5m depth. The surrounding environment of the construction site is complex. The distance from the west side to residential buildings is only 5m. The other three sides are close to road, along the road laid underground pipeline. When the program is designed, this design use single anchor pile program, in light of the actual situation of the project, on the basis different conditions for a variety of support structures.Second, weighing all the pros and cons of structural endogenous force calculation, this paper count the length of pile and internal force through traditional simply supported beam and equivalent beam method, count the supporting structure displacement through "m" method. Through analysis two ways on the basis of fully considering the site geotechnical conditions and environmental conditions, we selected a suitable calculation for the project—equivalent beam method, thereby using it to get the anchor power and the greatest moment, the imbed depth etc.In single anchor pile design, the location of anchor has a great influence of supporting structure. It should be considered the impact bolt position to the biggest moment of pile, the anchor power and the imbed depth, thereby this paper research the optimal location of anchor, and raise a method which use multi-objective optimization methods for the best anchor position in this paper. The best anchor position which under the top of the pile 4.2m is calculated. Four, based on the design principles and formula of the anchor, we given preliminary results of the fixed length, the free length, inclination, distance, anchor diameter. In E. Kranz-replacing-walls the stability of anchor is calculated to correct the initial design strictly. And it showed the design is stable. Using the results calculated steel for the five anchors.Five, Based on length and parameter of the pile, calculated the cross-sectional area, number the steel etc.Six, According to the size and other data, combining the design result of pile and anchor, got the number of the overall number of piles, gave the furnished set the anchor, the layout map of the pile, the profile map of the supporting structure.Seven, checking the resist-rise stability and the overall stability of the pit, certificated fully the pit is stable and the design is reasonable. Eight, the basic principles of finite element numerical simulation methods are introduced. The Ansys is given a brief statement. And use the Ansys to do the numerical simulation for the excavation and support of the foundation pit. Analysis its findings, conclusions:With further increase the load supporting structure of the lateral displacement has been increased. The lateral displacement of pile top is not large, but the lateral displacement of pile is lager. So the monitoring to the supporting structure should be strengthened. It should be taken the necessary measures to reinforce when find the continuing dramatic increase of the lateral displacement.With the increasingly deep excavation,anchor began to play role and suffered growing tension. The anchor axial force peak is transferred to the inside of the trend. This illustrates the potential pit slope sliding in the face inwards occur, the potential sliding soil growing. The end of anchor it's axial force close to zero. It note the anchor length is sufficient to this work. It is meaningless to increase anti-pullout power through increasing the anchor length.When wall strength, anchor stiffness meet the requirements, it is little to reduce the displacement through the increased wall thickness and anchor area. Therefore, it is unreasonable mainly through increased wall thickness and anchor stiffness to reduce the displacement. From an economic of view, the small-diameter pile should be used as far as possible in meeting deformation control requirements. The anchor area proposed should not exceed 2000 mm2.