Assessment Of Construction Methods The Cover And Excavation Top-down And Cover And Cut-bottom Used In Wuhu Underground Commercial Street

The contrast between the rapid development of urbanization and urban land resources tension prompts people to develop urban underground space, more and more underground commercial streets and subway stations sprang up. Although the development of underground space is beneficial to alleviate the urban land resources tension, construction of underground structures is inevitably accompanied by the emergence of various problems. In order to control the negative influence of the underground structure construction, higher technical requirement for underground structure construction is needed. Therefore, selecting a reasonable construction method is particularly important. The judgement of construction methods'quality can't be relied solely on previous experience, but should take construction difficulty, construction period, construction cost, the impact on the surrounding environment and structure stress into consideration. Last but not least, concrete project concrete analysis.Based on the underground commercial street construction of Changtong Project in Zhongshan Road, Wuhu, the subject analyses the construction process of top-down method and cover and cut method with finite element software MIDAS/GTS. And through analysising the impact of the structure itself and surrounding environment during construction process to offer some reference for the similar projects. The main contents and achievements are as follows.Firstly, introduce finite element software and project overview, and then introduce the basic assumption of the numerical model, model size, the model domain boundary constraints, unit attribute definition and the division of construction process in details;Secondly, the subject analysis the displacement of site surface and foundation, the horizontal displacement of frame column and supporting piles, the vertical displacement of the roof and floor by different construction methods. The results tell that the soil excavation in foundation pit is the main reason for the large changes of displacements of site surface, surrounding buildings and underground structures. During the process of top-down construction method, the roof and floor can slow the impact to surrounding environment, but during the process of cover and cut-bottom method, the displacements change obviously because the retaining piles don't have enough lateral support. Last but not least, the top-down construction method has an advantage in controlling the displacements over the cover and cut-bottom method, but the pit deformation index of the two methods satisfy the specification requirements.In conclusion, different construction methods of underground structures have different characteristics. Only selecting the appropriate construction method can guarantee the safety of construction.