Study On Multi - Parameter Risk Assessment Method For Stability Of Deep Foundation

As the demand for underground space of the city gradually improve, deep foundation pit engineering more and more attention. How to evaluate the use of limited data monitoring of deep foundation pit in the health status of deep foundation pit, become the important research topic. The deep foundation pit of traditional risk assessment is mainly according to the specification requirement to develop monitoring parameters of the limit value, the original data and monitoring parameters and the limit value for comparison, evaluation of the stability of foundation pit; in the forecast, to take a mathematical model to predict a continuous monitoring data, and then the values were compared with the specification limits. The evaluation method of the deep foundation pit stability of this single parameter cannot have a full range of reflection of deep foundation pit’s health, but also for the deep foundation pit in complex, because there is no change in consideration of relevant parameters, the method of the evaluation results and the prediction results are not reasonable and scientific. To solve the above problem, this paper proposes the following three solutions:1. Grey BP neural network model is proposed, using this model to predict the deep foundation pit monitoring parameters, methods to provide the basic data for the multi parameter evaluation. Through analysis and comparison of cases can be obtained for the combined model prediction precision is better than that of grey model and BP neural network model, the forecast precision is high, the prediction results can be well applied in the deep foundation pit stability of single parameter and multi parameter in risk assessment.2. Proposed the multi parameters of deep foundation pit stability evaluation methods, through mechanical deformation of deep foundation pit support system and surrounding environment are analyzed and the change law of summary of the monitoring data, put forward the relationship between the five parameters including the retaining structure, the ground surface settlement, lateral displacement of supporting axial force of column pile, uplift and subsidence of the vertical displacement of the wall, etc. using this relationship, as to determine whether the stability of deep excavation standards, through the examples verify the evaluation method show that the multi parameters can be found in foundation pit risk not single parameter evaluation method of discovery, this method can better reflect the deep foundation pit supporting system and the surrounding environment and stress change pit risk evaluation method is a kind of single parameter good supplement, can give people the foundation pit construction to provide risk the stability of foundation pit of a more comprehensive assessment method.3.Put the data fusion technology is applied to the deep foundation pit stability of multi parameter evaluation, evaluation to improve the accuracy of multi parameter. The traditional deep foundation pit monitoring data processing method is to analyze and forecast a monitoring parameter data, for the analysis of other monitoring parameters can not be integrated processing, fusion, this forecasting method consideration factor is too single. To carry out comprehensive treatment of deep foundation pit of the monitoring parameter data with BP neural network as the core of the data fusion technology can, fitting out a most approximation of the actual situation of the linear or nonlinear function. Prediction method is superior to that of the single parameter method of the data fusion showed through the case study, higher accuracy, the prediction results more reasonable, can method and multi parameters to a single parameter assessment method provides basic data more scientific.Deep foundation pit stability evaluation method of multi parameters is derived through the study of deep foundation pit of mechanics characteristic and experience of data statistics, this method can comprehensively reflect the deep foundation pit of health, is a good evaluation method. In the multi parameter evaluation, prediction data of each parameter must be of high precision, and it must be scientific and reasonable, so as to play the advantages of multi parameter evaluation method, this paper puts forward the grey BP neural network model and data fusion technology can effectively solve this problem, can provide a more scientific and reasonable data to multi parameter evaluation method.