软粘土结构扰动评价与地铁工程变形控制研究

The construction of subway will inevitably cause soil disturbance. The strength characteristics of soft clay, as well as the deformation characteristics and the compression characteristics, has a close relationship with the structure of the soil. Then the structure of the disturbed soil will be destroyed, its strength will be greatly reduced while its deformation and compression increases sharply, resulting in too large deformation or even failure of the subway project. The structural damage of soft clay and the construction disturbance may both lead to the increase of base deformation, and then affect the subway construction. Therefore, to control the deformation of subway project, the measurement and evaluation of both the construction disturbance and the disturbance degree must be studied. In this subject, the mechanical characteristic of the typical marine soft clay in coastal areas of Zhejiang will be studied. The study will reveal the influence of subway construction disturbance on the structure of soft clay, strength characteristics, consolidation characteristics, static deformation characteristics and cyclic accumulative deformation characteristics. The disturbance mode and a quantitative evaluation of disturbance degree for subway construction in soft clay will be proposed, the calculation methods for both static and accumulated settlement for disturbed foundation will be established to predict the long-term deformation, and measures to reduce the structural disturbance caused by construction and operation will be presented, which will provide a theoretical basis and technical support for subway construction and operation in soft clay foundation.

地铁施工不可避免地会对地基土造成扰动，软粘土的强度特性、变形特性、压缩特性等均与土的结构性有着紧密关系，受扰动后，土的结构性被破坏，其强度会大大降低、变形性和压缩性急剧增大，导致地铁工程变形过大甚至失效。结构损伤是软粘土地基变形增大的内因，施工扰动引起软粘土的结构损伤是外因，这两个因素共同决定了软粘土结构扰动及其对地铁工程变形的影响。因此，要实现地铁工程的变形控制，必须研究地铁施工扰动机理及软粘土地基扰动度的测定和评估。本课题以浙江沿海地区典型海积软粘土为研究对象，揭示扰动对软粘土强度特性、固结特性、静力变形特性、循环累积变形特性的影响规律；提出地铁施工对地基土的扰动模式和扰动程度评价方法；建立扰动土地基的静力沉降和循环累积沉降计算方法，预测地铁工程的长期变形；提出减少施工和运行对软粘土结构扰动的控制措施，为软粘土地基中地铁工程安全建设和运营提供理论依据和技术支撑。

我国沿海软粘土的强度特性、变形特性、压缩特性、固结特性均与土的结构性有着紧密关系。地铁施工不可避免地会对地基土造成扰动，受扰动后，土的结构性被破坏，其强度会大大降低、变形性和压缩性急剧增大，在施工期和运行期中产生过大的变形导致地铁工程失效。因此，软粘土地基中施工扰动是影响地铁正常建设和安全运营的重要因素。本项目以宁波市典型软粘土及其扰动土的力学特性研究为基础，通过揭示深基坑施工扰动和盾构隧道施工扰动对地铁工程和周边环境影响的内在本质，提出扰动度的测试和判断方法，深化软粘土及其扰动土的变形和沉降计算方法，确定运行期列车动荷载作用下隧道结构的动力累积变形，创新扰动土地基的加固方法和工程措施，为保障地铁工程建设的顺利实施、地铁工程的顺利运行、实现对周边环境的保护具有重要的理论意义和实践意义。.研究结果表明：（1）地铁基坑施工对周边土体的扰动较为明显。本项目综合采用位移监测、孔压监测、静力触探试验、十字板试验、剪切波速试验等多种土工原位测试技术研究了基坑开挖前后隧道周边土体的扰动情况，通过对每项试验结果的深入分析以及不同测试方法间的相互印证，初步得到了基坑开挖对周边土体产生扰动的机理、范围及程度。（2）盾构施工对周边土体的扰动较为明显。本项目综合采用位移监测、孔压监测、静力触探试验、十字板试验、剪切波速试验等多种土工原位测试技术研究了盾构施工前后隧道周边土体的扰动情况，通过对每项试验结果的深入分析以及不同测试方法间的相互印证，初步得到了盾构施工对周边土体产生扰动的机理、范围及程度。