软土地层地铁盾构施工风险可拓评估方法研究

On the risk evaluation of the metro shield construction in the soft soil condition background with the extension method

为了综合评价软土地层地铁盾构施工风险,结合软土地层土质特点,选取地质复杂情况、地下水状况、最小覆土厚度、最小曲率半径、掘进长度、与临近周边环境距离和施工管理水平7个风险影响因素作为评价指标,采用简单关联函数法计算得到各评价指标的权重,避免了主观因素的干扰,运用可拓学理论建立了风险可拓评估模型,并将该模型应用于宁波轨道交通工程2号线栎社机场站-栎社新村站盾构区间的风险评估,得到该区间盾构施工风险等级为中度风险,评估结果较好地反映了工程的实际情况。

The article is aimed at making an evaluation of the metro shield construction risk under the soft soil condition.To make such risks evaluation more scientific and accurate,the paper has chosen the following seven evaluation indexes as the key ones while full account has to be taken into the geological features of the soft soil.Or to be more specific,it is necessary to carefully put thoughts on the complexity of geological conditions,the groundwater conditions,the minimum thickness of overburden layers,the minimum radius of the tunnel curvature,the excavation length,the distance access to the surroundings and construction management level.And,then,it is also of great significance to analyze and clarify the different influential factors on the risks of the aforementioned indexes.Therefore,it is necessary to work out an evaluation index system of all the risks to be involved in the metro shield tunnel construction.To achieve all the above said construction goals,we have proposed a entirely novel method for such comprehensive and objective evaluations,in hoping to broaden its available prospective areas,that is,to identify and work out all the weighing factors of the risks in the metro shield construction in the soft soil.In doing so,it is believed that the rationality and the reasonability of defining the index weight system should be taken as a trustful and confident system to ensure the trustfulness of the estimation results.What is more,it is also necessary to get rid of interference of the subjective factors in the process of decision making by integrating the objective weighing methods and the simplex correlation function method.Therefore,we have decided to establish the extension evaluation model based on the extension theory.And,finally,we have managed to apply the evaluation model we have made to the risk evaluation practice of the shield tunneling construction of Ningbo metro line 2 between Li-she Airport Station and Li-she Village station.As a result,we have managed to enable the risk level of the metro shield tunnel construction to be reduced to a moderate grade.And,we have also proposed a series of the related risk control measures.Thus,as a matter of fact,the evaluation result has fully reflected the actual conditions of the risks in the tunnel construction fully,showing that the model can serve as an important guide to the risk evaluation and the safety management of such metro shield construction under the soft soil condition.