基于熵值法的砂卵石地层深基坑开挖安全可拓评价

为客观评价富水砂卵石地层中深基坑开挖的安全稳定性，根据结构变形、受力、地下水以及周边环境等因素选取地面沉降、建筑物沉降、地下水位等8个评价指标进行开挖安全性评价，以成都某地铁车站深基坑工程为例，根据基坑开挖4个月内的实测数据，采用熵值法对所选评价指标进行赋权，基于物元理论与可拓集合的关联函数，建立深基坑开挖安全可拓评价模型，并将评价结果与模糊综合评判结果进行比较. 研究结果表明:熵值赋权计算中，混凝土支撑轴力、桩顶沉降和支护结构水平位移是本案例中最重要的三项指标，对安全评价影响最大；对地面沉降与管线沉降的可拓评价结果比模糊综合评判结果高一个等级，与实际监测数据的评判结果相符，有利于施工过程中对潜在风险的防控；基于熵值赋权的可拓评价模型能够对基坑开挖安全性进行单因素分析与综合分析，所构建的可拓评价模型可以在成都地区富水砂卵石地层基坑工程安全评价中推广使用. 

Extension Evaluation on Excavation Safety of Deep Foundation Pit in Sandy Cobble Stratum Based on Entropy Method

In order to objectively evaluate the safety and stability of deep foundation pit excavation in watery sandy pebble stratum, eight evaluation indexes, such as ground settlement, building settlement and groundwater level, are selected to evaluate the excavation safety according to the structural deformation, stress, groundwater and surrounding environment. A deep foundation pit project of a metro station in Chengdu is used as an example, and according to the measured data within the four months of foundation pit excavation, the entropy method is employed to assign the selected evaluation indexes. Based on the correlation function between the matterelement theory and extension set, the extension evaluation model of excavation safety for the deep foundation pitis established. Comparing the evaluation results with those of fuzzy comprehensive evaluation, it is concludedthat the axial force of concrete support, pile top settlement and the horizontal displacement of support structure are the most important three indexes in the entropy weight calculation of this case, which have the greatest impact on the safety evaluation. For the safety evaluation of ground settlement and pipeline settlement, the extension evaluation result is one grade higher than the fuzzy comprehensive evaluation result, which is consistent with actual monitoring data and is conducive to the prevention and control of potential risks in the construction process. The extension evaluation model based on entropy weight can accurately improve the safety of the foundation pit excavation through single factor analysis and comprehensive analysis, and the extension evaluation model can be applied in the safety evaluation of foundation pits in watery sandy cobble strata in Chengdu.