Prediction of grey system model on convergence of surrounding rock deformation of Longtan tunnel

Based on the convergence of surrounding rock of Long-tan tunnel during excavation,a grey forecast model of GM(1,1) is established by dealing with a list of data on time-dependent relative displacement with randomicity and undulation.It is used to predict the future convergence of surrounding rock deformation.The formula of velocity is gained by analyzing the prediction displacement.The time of stability of surrounding rock is forecasted by this formula.The forecast results of two sections are close to the data actually obtained from monitoring.