The Long Term Settlement Calculation Of Soft Soil Ground Under Cyclic Loading

To predict the long-term settlement of soft soil foundation building scientifically and rationally is a key factor to ensure the safe use of the building.The distribution of soft soil is widely distributed in China,with the development of demand,it is inevitable to build lots of stored grain and oil and other material storage facilities in the soft soil foundation.The characteristics ofthese buildings is the loading and unloading process,besides the permanent load weight on multiple storage facilities at the end of the construction.This issue has attracted wide attention of scholars.Currently,much research of cyclic load resulted from traffic load is generated.And the method is relatively mature,but its frequency of changes is very high,while the frequency of cyclic loading resulted from storage facilities is low,and has relatively larger fluctuations.the settlement under cyclic load a mature method about prediction calculation of the settlement under cyclic load has not yet been formed.According to the complex engineering characteristics of soft soil foundation,the assume conditions of existing settlement method are not fully consistent with the conditions in practical engineering,so the calculation results and the measured results were quite different.Therefore,generally the empirical formula method based on measured data to predict the settlement of foundation is used,but whether this method applies for the low frequency cyclic loading remains to be studied.In this paper,the cyclic loading of storage facilities have been analyzed,then the introduction of domestic and international prediction methods for settlement calculation has been summarized.Many methods are proposed based on Terzaghi consolidation theory.Considering the irregularity of cyclic load,using the widely used empirical formula fitting based on measured datain which several curve fitting methods commonly used are analyzed separately,we list the advantages and limitations ofthem,taking the structural characteristics of the storage facilities into account,Origin software is used to put forward hyperbola,exponential curve method and three point method that can be used for settlement prediction of storage facilities.To verify the feasibility of the three methods by using engineering example,and analyze the fitting values by the three methods and the measured values comparatively,the results show that exponential curve fitting method that is more suitable for the long-term settlement of storage facilities.However this method is only for settlement prediction operation in operation period.Therefore,this paper also puts forward the method of superposition,settlement predicting by using the settlement observation data during the construction period.The principle of superposition method is based on cyclic loading and unloading of the processof warehousing facilities duringuse.After analyzing the cyclic load without regularity,classifying the load of similar size to a level,we can obtain settlement curve in exponential form under load of each level,then add all settlement curve together as the total settlement,so that using an example to verify the rationality and science of superposition can be achieved.Through analyzing cyclic load caused by soft soil properties and storage facilities,the index curve method and the superposition method based on the exponential curve to predict the long-term settlement of foundation are put forward,and their rationalities are verified,in order to provide the basis for reasonable settlement prediction effectively.