Study On Ground Settlement Monitoring Due To Shield Construction In Metro Tunnel

Combining with the shield drive tunneJ of Nanjing metro, based on the analysis on ground settlement and surveying materials feedback quickly and reasonably, the several problems of g round settlement during shield tunnel construction are w idely studied in this paper. The primary contents are as follows:1. According to the feature and the theory of shield tunnel construction, based on the factors that cause effects on environment, the workable monitoring project is established, which include principles of design, the selection of monitoring cross section, the layout of monitoring points, monitoring content and materials feedback. Such as operation program, selection of earth pressure, wall-back grouting, rectification of shield machine, which are used to reduce the effect of construction on environment, are analyzed in detail.2. Based on some calculation methods on transverse ground settlement, the mechanics of ground settlement caused by shield tunnel construction are discussed. In combination with the shield driven section from XuanWu Gate station to New MoFan Road station of Nanjing Metro, the monitoring data are analyzed. Mainly zone and the subordinate zone of ground settlement caused by shield tunneling is summed up, and the influence zone are definite. Great economic and social benefits are gained. Compared w ith t he c alculated r esults and monitoring data, to verify i f the p resent parameters can accord with the real situation of Nanjing. The distribution of surface settlement trough is obtained by one-dimensional wave theory and calculation. The range of surface settlement trough coefficient is retrofitted. These conclusions are contributed to extend shield method in Nanjing.3. Longitudinal ground settlements caused by shield tunneling are analyzed by monitoring data. The settlements in different period are concluded. The settlements of different distance away from the incision are compared which possesses an important significance for construction. Compared with the cases of application between the dynamic model and static model, it is indicated that the method of time series analysis is an important and advanced forecasting method in statistical forecasting . It will be helpful to protect the environment , design of the succeeding engineering and experience accumulation.4. In order to evaluate the monitoring data quickly and timely, the database for shield tunneling monitoring are present which can dynamic display the ground settlement curve. It will be the means for manage shield tunnel construction normatively and scientifically. Besides, the engineers can inquire special information, predict or evaluation the environment, and make decision by this way.