The settlement law of surcharge preloading soft clay roadbed in high-speed railway was analyzed through observed data,its settlement developing experiences filling stage-dead load stage surcharge preloading stage-unloading stage,its settlement curve has some likeness with S-shaped growth curve.Using the least square method and the target function of the least square sum of the error,the optimum weighted coefficient is gained,the weight combination forecasting model is established.Gompertz curve and Logistic curve are fitted separately by using Origin software,and based on combination forecasti...