Evaluation of Surface Settlement due to Tunnelling Works using Numerical Method

The rapid urbanization in India has resulted in an increase in dependency on underground spaces for the major issues like space constrains and transportation infrastructure. This further required the assessment of impact of underground construction on the safety of superstructure. The present study evaluates the surface settlements induced by tunnelling activities in Delhi Metro. The numerical method using MIDAS GTSNX finite element software is used for the analysis. The settlement results from the finite element method are compared with the field data obtained through settlement monitoring points. It was observed that there was an increase in the surface settlements in transverse and longitudinal directions until the lining was provided. After placing the tunnel lining, the rate of change of settlements was negligible. The increase in settlement is noticed up to 2.5D from the tunnel centre at which the maximum settlement is 3mm, hence the zone of influence of settlement can be considered as 2.5D from the tunnel centre. Further settlement comparison using semi-empirical relationships is also carried out to bring out the best method for assessment of surface distortions due to tunnelling.