Study On The Influence Of Ground Surface Settlement On Adjacent Buildings Induced By Tunnel Shield Excavation

As urban population density is increasing, higher requirements of development for public transportation have been put forward. Urban rail transport, which is also called metro, is widely used since it is safe, clean and efficient. Since now our country is in a period of rapid development of urbanization, many cities are active in subway construction. Various factors taken into consideration, subway lines inevitably will be laid near or below the existing building. Thus strata subsidence caused by metro construction more or less has an impact on surrounding existing buildings. Therefore, pre-assessment of the safety of surrounding buildings is quite necessary. Thus we can get a conclusion about whether the surrounding buildings can work in good condition.At present, China has a limit that the settlement shall not exceed 30 mm caused by subway construction according to experience, but the criterion may seem not that applicable because geological conditions various while architectural structures differs.For good geological conditions or surrounding buildings has deep foundations, this limit may be too stringent, thus will increase the difficulty of construction. While for poor geological conditions and surrounding buildings are in bad working conditions thus they are historic buildings, this value cannot ensure the safety of the structure. Thus, to determine the settlement limit caused by subway construction to ensure the safety of surrounding buildings, geological conditions, building structures as well as foundation forms all should be taken into consideration. This paper adapts a nine-story frame structure as the study object; systematic study of such structures' respond to subway construction settlement has been done. Details are as follows:1. Current prediction methods for settlement due to subway construction have been systematically summarized, and a prediction model for Beijing, Shanghai and Guangzhou using the Peck empirical formula is put forward. The influence of tunnel depth, geological conditions, and the settlement trough width parameter on the model is been analyzed.2. A finite element model of the tunnel- soil- the frame structure is established, using the Deactivation method shield to simulate construction process, then the force and deformation characteristics of the structure are analyzed.3. Different settlement curves determined by Peck formula are input to the bottom of the structural basis as the initial load, then the structure's internal forces and deformation characteristics is analyzed. The result is compared with the method described above.4. In terms of structural stress analysis, cracking load of the structural frame column is selected as the structural safety indicator. Discuss the structure's safety performance under different settlement curves.5. In terms of structural deformation, systematically summarized indicators and evaluation methods to assess the settlement of subway tunnel construction influence of the structure of both China and abroad. Then use the indicators of our country to assess the safety of the nine-story frame structure under different settlement.The results show that: both the overall finite element method and simplified Peck formula method can be adapt in analysis of the impact of ground deformation caused by subway construction on the structure, apparently simplified formula method is more simple and practical; the evaluation result got from the structural internal force and deformation based on structural safety are the same, which means that the two methods indeed are unified.