Monitoring And Safety Evaluation On The Buildings Near The Foundation Pit Of The High-speed Railway

Along with the accelerating steps of urbanization in our country, in the constructions of high-rise buildings and high-speed railway tunnels, a large number of deep foundation pit have appeared lately, its scale and depth increase constantly. In addition, most of the foundation pit is in a group of dense buildings, so in construction of foundation pit, not only the safety and stability of the foundation, but also the adverse affects to the neighboring buildings, buried pipelines and other municipal facilities should be considered.The paper is supported by foundation pit in open excavation section of Long-Xia Railway Tunnel, according to the obtained site monitoring data and the buildings protection requirements, under the influence of foundation excavation, the changes of adjacent buildings absolute settlement, inclination and horizontal displacement were analyzed, then the rules of nearby buildings movement and deformation caused by excavation of foundation pit were summarized, and combining with the foundation excavation process and the support form in the project, the features of nearby buildings movement and deformation were further studied, the law of the use of the bolt and steel support in the foundation influence to nearby buildings movement and deformation were obtained.The paper evaluates the buildings safety under the influence of excavation by the basic principle of fuzzy comprehensive evaluation. The specific process of fuzzy comprehensive evaluation: the evaluation objects could be regarded as fuzzy set that is made up of many components (called the factor set u), and determine the evaluation grade of these factors to form fuzzy evaluation set (called the evaluation set v), then each single factor for different evaluation grade of degree of membership can be obtained respectively (degree of membership, judged by maximum subordinate degree, called the fuzzy matrix), finally, according to weight distribution of each factor in the evaluation objects, get the quantitative solution of the evaluation by computing (called as fuzzy matrix synthesis). In the paper, with the deformations of the absolute settlement, inclination and horizontal displacement, which affect the buildings' safety, as the evaluation factors, and accordance with the relevant specifications and requirements of the project construction safety, the control index of evaluation was established, then the evaluation model of buildings safety was set up, to the buildings safety which are affected by excavation was evaluated from the safety grade and comprehensive safety rating of buildings.From the analysis of the measured data and conclusion of buildings safety evaluation, we know that nearby buildings was less influence by excavation, and the buildings deformation was under control, did not affect its normal use.