基于突变理论的盾构下穿危旧房屋及河流段风险评价与控制方法研究

为了综合评价盾构下穿危旧房屋及河流段风险,结合软土土质特点,在对已有评价模型分析的基础上,针对风险评价普遍存在的问题,借鉴突变理论,确定盾构施工风险突变评价法步骤,将各因素归纳为工程地质、勘察设计施工、周边环境和水文地质四大指标,并对其进行分解,构建风险评价指标体系及等级标准,利用突变理论对工程实例进行评价,得到该区间盾构施工风险等级为极高风险,评估的结果较好地反映了工程的实际情况。基于风险评价结果,在盾构下穿过程,采取合理设定土压力、调节盾构推进速度和注浆压力等措施,实时动态监控地表沉降的变化和盾构施工关键参数,所得成果验证了突变理论风险评价的实用性和有效性。

On the risk evaluation and control method of the shield tunneling under the hazardous buildings and rivers based on the catastrophe-forecasting theory

The article intends to present its results of the risk evaluation and control measures of the shield tunneling under the hazardous buildings and rivers based on the catastrophe-forecasting theory.For this purpose,the paper has established the procedures of catastrophe theory based on the soil properties,physical and mechanical parameters as well as the analysis of existing evaluation models.In order to evaluate the risk of the shield tunneling under the hazardous buildings and rivers more comprehensively and accurately,all the influential factors can be divided into the following four categories:the engineering geology;the survey,design and construction work of such buildings,the evaluations of the surrounding environment and the hydrological statusin-situ.Careful study of the aforementioned factors may allow us to establish an index system for the risk evaluation and the risk hierarchical criteria of the shield tunneling under the risk-involving buildings and rivers.The study of the above comprehensive factors involved can help us to understand the potential hazard degree embodiment whereas the different hierarchical factors can be taken into consideration in a logical order.Referring to the conventional risk categorization method and the different risk classification approaches,such risk factors can be divided into 5 levels from low to high,that is,levels from Ⅰ,Ⅱ,Ⅲ to Ⅳ and Ⅴ.And,finally,we have brought the catastrophe theory model into the risk evaluation practice of the shield tunneling under such buildings and rivers in the Ningbo metro line 2 between Li-she Airport and Li-she Village station,whose risk level ranks level Ⅴ.And,later,we have proposed the corresponding risk control measures based on the risk evaluation results,which can be said faithfully reflecting the actual geo-physical conditions of the project.The engineering practice of Ningbo metro project proves that such measures have all been taken successfully as the setting of the reasonable soil warehouse pressure,adjusting the shield machine advancing speed and determining the grouting pressure,in addition to the real-time dynamic monitor of the surface subsidence and key parameters of the shield,indicating that the risk assessments they have done are well in accord with the availability and applicability of the engineering practice based on the catastropheforecasting theory.