The Effect Of Grouting And Settlement Prediction Of Pile Foundation In Soft Soil

Piles are widely apply to high-speed railway foundation construction, which requires high standards of bearing capacity and settlement, owing to their high bearing capacity, small and uniform settlement. However, the end bearing and shaft resistance loss a lot, because of the inherent defect of piles cast in place (mud in the end and side of piles). All of these will arouse adverse impact on the control of settlement. In order to eliminate the bad influence caused by the mud in the end and side of piles, some kinds of methods, such as end grouting, side grouting and end-side association grouting, could be used. Through the interaction of filling and cementing, reinforcing, pressuring and solidifying, the physical and chemical characteristics of the soil in the end and side of piles could be enhanced, so that the bearing capacity could be improved and the settlement remarkable decreased. Based on on-site test data and comparative analysis of the program effectiveness of a variety of grouting, this dissertation draws that the 501# cap with whole pile grouting program has the following characteristics.1. The minimum total settlement; 2. The rapidest to reach a stable settlement; 3. Rapid development of early settlement, which is very beneficial to reduce post-construction settlement; 4. Large volume of injected slurry. Overall, this program of grouting works best and is considered as the optimal solution under a combination of factors. Therefore, this paper recommended the whole pile grouting program as a deep soft soil grouting program areas.The settlement of foundation usually is one of the most important controlling factors for the high-speed railway construction in deep soft soil. That is because the excessive settlement or uneven settlement will deteriorate the road condition, reduce the comfort of passengers, and even endanger traffic safety. Therefore, it is vital to get the settlement data of the pile foundation. On the one hand, it ensures safety during construction. On the other hand, it forecasts the post-construction settlement correctly to control it under the permit of the range of the design. Hence, forecasting the settlement deformation is of significance to the actual engineering. At present, there are many forecasting methods for the pile foundation built in the deep soft soil. Each method has its shortcoming and virtues and its suitable condition. This paper will forecast the long-term developing law of settlement and the final settlement by hyperbola, exponent curve, BP neural network and grey theory method based on measured data. After the comparison of these methods, the following conclusions are drawn. The predicted final sedimentation values using above methods are very close, which illustrate predicted values are credible.2. Owing to the great random selection of the initial calculation points (t0,S0) in it, hyperbolic law and exponential curve of methods are not convincing enough, so this two predictions can only be as references.3. Gray system theory is an effective prediction method in relatively short-term forecasts but in long-term settlement prediction.4. BP neural network method, which can remember the development of the original settlement curve patterns correctly, is the most reliable. Therefore, BP neural network is recommended as the forecasting method for the long-term developing law of settlement and final settlement of the pile foundation by the post-grouting, which is built in soft soil in this dissertation.