| Since the 21st century,China's urban construction projects have developed at a high speed,and the number of high-rise and super-high-rise buildings has increased,and the corresponding foundation pit projects have also increased.At the same time,the city building foundation pit is located in a complex environment with dense houses,criss-crossing roads and underground pipe networks.Therefore,the safe risk of foundation pit projects is getting higher and higher.How to judge and ensure the safety of foundation pit projects has become urgent questions to be solved in the construction industry.At present,in the safety evaluation of foundation pit engineering,most only check whether the monitoring data of a certain monitoring content exceed the alarm value set by the relevant code or design to judge its safety state.But sometimes although a monitoring content exceeds the alarm condition,but from other characteristics do not see the foundation pit there is a safety problem,so the foundation pit construction often will not take measures and persist to the end.It shows that this single indicator evaluation method plays a very limited role,although there are many monitoring contents,but it can not be internally and organically linked to the evaluation.This paper mainly explores how to conduct effective foundation pit information monitoring through literature survey and field test research,and studies the risk assessment method of foundation pit engineering for effective graded early warning.The research contents include as following:(1)Through the analysis of the monitoring data of a large number of foundation pit projects in Ganzhou,based on the characteristic points of the monitoring data with a 95%guarantee rate,the horizontal displacement at the top of the supporting structure,the displacement of the surrounding surface,the settlement of the surrounding buildings and the characteristic values of the displacement rate are given respectively.On the one hand,the current situation of foundation pit engineering is found out,most of which meet the requirements of the current code.In addition,it solves the difficulty that the Level ? early warning control value is determined by the designer in the previous 4-level alarm strategy.(2)Through the comparative study of automatic monitoring and manual monitoring on the foundation pit engineering of a middle school experimental teaching building in Ganzhou,the advantages and disadvantages of the two monitoring methods are made clear,and it shows that automatic monitoring can not completely replace the traditional manual monitoring.Especially in the automatic monitoring of the internal force of the anchor cable,the temperature has a great influence on the anchor cable meter,and the monitoring value fluctuates greatly in one day because of the large difference between day and night temperature in summer.It is worth paying attention to the influence of monitoring value draw on.It is suggested that the two methods should be combined to monitor the construction of foundation pit in order to complement each other,to improve the monitoring level of information and to ensure the safety of foundation pit.(3)The entropy weight-AHP fuzzy comprehensive evaluation method are combined to make a perfect 4-level warning strategy,so as to better quantitatively evaluate the safety state of the foundation pit and surrounding environment.Based on the safety evaluation of the foundation pit engineering of a middle school in Ganzhou,the results show that the method proposed in this paper is feasible and provides a new idea for the safety evaluation and analysis of the foundation pit engineering(4)Using MTLAB to compile the entropy weight-AHP fuzzy comprehensive evaluation method into interactive program software,and realized the multi-level warning strategy of foundation pit based on the measured data.The case calculation shows that the effect is obvious and the operation is simple,help to achieve timely analysis,evaluation and decision-making. |
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