| The contradiction between the increasing construction demand and the limited urban space has become more and more obvious with the rapid growth of national economy and urban construction,while the development and use of urban underground space effectively help relieve urban disease such as housing shortage and traffic congestion.The requirement of solving analytical problems existed in the underground construction project urged the emerge of deep excavation engineering,which has for a long time played an important role in structural safety as its stability not only decides its own safety,but also influences the structural distortion of the buildings surrounded.Stability analysis of foundation pit slope is the primary basis of deep excavation construction,and a framework of analytical process was constructed in the paper so as to reveal slope stability correctly.The engineering geology conditions of the foundation pit project and its relative soil parameters must be mastered at first in order to distinguish the main as well as the subordinate factors influencing slope stability,and the scientific analytical method was used to extract the most critical ones.The dynamical slope deformation was revealed through the analysis of monitoring data,which helped explain reason and tendency for building settlement deformation as well as provide suggestion for the risk management.In addition,taking reasonable forecast and control measures in line with the slope deformation tendency can effectively help prevent accidents related to deep foundation pits.In order to study the factors affecting the degree of contribution to the foundation pit slope instability.Taking the foundation slope of a university culture center as an example,the sensitivity analysis of the factors which influence the slope stability of the foundation pit including foundation soil cohesive force,internal friction angle,weight,height and slope was done.The quantitative evaluation of sensitive factors was done based on the combination of conventional orthogonal experiment,the calculation of soil mechanics safety coefficient by Sweden Circle and Bishop methods were done by Matlab software.The slope safety coefficient was calculated according to instance data,quantitative evaluation of the sensitivity of the factors was done by range analysis,variance analysis,interactive analysis and variation trend analysis of safety coefficient in order to find the main and secondary factors influencing the stability of foundation pit.The results obtained through the comprehensive analysis of a series of experiments,which were in accordance with engineering practice,showed that soil cohesive force,weight and height should be taken as the main factors whereas internal friction angle and slope as the secondary ones and could provide guidance for similar projects in the future.Analysis is the premise,monitoring is a means,forecasting is purpose.In order to define settlement deformation feature of ground surface caused by deep pit excavation of subway,refering to the construction process,data monitored of deep pit in Dalian city subway station is analyzed.It is concluded that common ground subsidence deformation characteristics of deep foundation pit,and put forward the risk management advice.At the same time,in order to forecast the settlement of two typical points of monitoring data,we used the grey GM(1,1)model which combined with C# software according to different construction stages.Prediction results show that the gray GM(1,1)model is reliable in the prediction of deep foundation pit settlement and the prediction in stages has higher reliability.It can be seen that the deformation of deep foundation pit is closely related to the excavation and construction,which can improve the forecast precision by combining with the construction schedule.It can provide reference for the analysis and forecast of the settlement monitoring data of Metro deep foundation pit in future. |
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