Monitoring And Numerical Simulating On Deep Foundation Pit Support Structure For Yinchuan Tianxi International Center Project

Recently, the deep foundation pit supporting is much more fundamental when the tall and super-tall buildings have been constructing rapidly in the urban of Yinchuan, Ningxia. The deep excavation engineering located at Tianxi International Center of Yinchuan was studied as an objection and the research contents comprising of branch support structure, excavation slope deformation and monitoring data on-site were conducted in this thesis. The computer software of Lizheng and PLAXIS were employed to finish the calculating tasks for the multiple support structure form consisting of composite soil nailing wall and pile-anchor support structure. The math model was established by using the 15 nodes triangular element to simulate soil. According to the actual situation, soil body was divided into seven layers, and the concrete surface layer was simulated with grouting element, the row of piles was simulated with plate element and the soil nail was simulated by using the combination of point anchor and geo-grid. The deformation of multiple support structure for the deep excavation was calculated and the results were compared with the actual monitor data, which can provide the advice for the design and construction of deep foundation pit in Yinchuan.In this thesis, the main research work and results are as follows:(1) The soil nailing wall, composite soil nailing wall, and combined support structure of composite soil nailing wall and pile-anchor joint structure type, characteristics, mechanism and related calculating summarized and analyzed based on reading the existed literatures.(2) The numerical simulation process, different constitutive model characteristics and applicable conditions are analyzed and the Mohr-Coulomb model can be determined as a numerical simulating to deformation calculating for the deep foundation pit of Tianxi International Center project in Yinchuan.(3) After the summary of excavation deformation monitoring and the method of deformation estimation were discussed, the deformation and slope stability located in western of the excavation were calculated by using the Lizheng software which has been widely applied in our domestic. The results show that the deformation values of the joint support structure can meet the requirement of the excavation engineering.(4) The numerical model to the deformation on the western slope of the deep excavation which was supported by the joint structure was established by using PLAXIS geotechnical engineering software and the parameters for the model calculating was adjusted by comparing with the survey data on-site.(5) Using the numerical model built, the deformation of the deep excavation has been calculated and the simulating results show that has the large distortion at two supporting forms junction, where the rigidity of the excavation supporting material significant effects on the foundation pit deformation. Calculations analysis found that the stiffness exist mutation in the concrete interface between the soil nail wall and the crown beam on row of piles. So the reinforcement measures should be taken on the position to the design and construction of practice engineering.(6) The proposal of optimal design and construction are presented for the deep excavation engineering of Tianxi International Center project based on the comparing to actual monitoring data and the results of numerical simulation. Finally, the existing problems of the research work from the deep foundation pit engineering of Tianxi International Center project in this thesis are discussed and prospected.