【作者】 贾嘉陵；

【导师】 王梦恕；

【作者基本信息】 北京交通大学 ， 桥梁与隧道工程， 2008， 博士

【摘要】 西安地铁是地铁工程界首次在湿陷性黄土地层中进行的城市地铁建设,湿陷性黄土地层复杂性使黄土地层盾构掘进施工存在“问题多,难点多,数据少,参数缺”。对于湿陷性黄土地层,至今盾构施工没有系统的盾构施工技术参数,直接构成湿陷性黄土地层盾构施工系统安全风险,直接影响隧道穿越西安古城墙、钟楼、护城河的安全,直接影响隧道穿越陇海铁路和地裂缝的安全,直接影响城市市政地下管线的安全,所以,提出“湿陷性黄土地层盾构施工引发地层变形特性的研究”课题。围绕课题研究,首先对湿陷性黄土进行研究。在大量查阅黄土资料基础上,针对黄土盾构施工,提出“湿陷性新黄土地层二元结构”。以此作为课题基础平台,研究盾构施工黄土地层变形规律。结合地铁工程‘西安轨道交通地铁二号线盾构施工沉降监测数据’进行统计分析,采用数值模拟计算和理论分析,得到湿陷性黄土地区盾构施工的成果如下:1.湿陷性新黄土地层二元结构在分析湿陷性黄土Q₃、Q₄地层的物理力学性质基础上,针对地铁隧道盾构施工,提出“湿陷性新黄土地层二元结构理论”,系统地研究黄土二元结构的组成结构、应力路径、本构关系和上下元结构位移变形的耦合。指出:新黄土二元地层结构上元非饱和黄土结构是结构性黄土,具有节理性,弹性脆性破坏,在浸水情况下发生湿陷突变;下元饱和黄土类似一般的软粘土,但仍具有湿陷性黄土的特殊性质（高含水率、高灵敏度和低强度,塑性变形破坏）。黄土二元地层结构耦合,在外力作用下上元将外力传递下元,下元结构受力作用下发生弹塑性变形;上元结构在下元变形作用下,沿自身节理裂隙发展产生剪切破坏。2.上元非饱和黄土结构地层变形在新黄土上元非饱和地层中盾构施工,与一般地层比较地层变形具有五个阶段。地层沉降变形主要影响因素是地层损失、盾尾注浆黄土湿陷和固结变形。地层变形存在湿陷突变属黄土脆性破坏;“盾尾注浆黄土湿陷”导致黄土湿陷9¹5mm,地层损失沉降15²3mm,固结变形2⁵mm。同时,拟合湿陷性黄土上元结构盾构施工地面沉降的修正Peck曲线,其中修正系数k是综合系数,与地质勘察、隧道埋深、盾构机状态、盾构施工水平和盾尾注浆相关,对西安黄土地层k的取值范围k=1.30¹.45。3.下元饱和黄土结构地层变形与上元非饱和黄土结构相比较,下元饱和黄土盾构施工地层变形是地层损失,不存在盾尾注浆黄土湿塌的沉降突变。在下元饱和黄土结构盾构施工中,在上元非饱和黄土结构稳定区域产生“压力拱”,约束下元结构的沉降变形。4.掌子面稳定状态及其控制在分析施工掌子面稳定极限状态基础上,通过数值计算分析和施工监测,认为在盾构施工过程中,盾构施工围岩地层存在三区（挤压区、剪切区和松动区）。沿盾构隧道地层基本处于弹性状态,主要是因为黄土的大孔隙、节理性和结构性的结果,使黄土盾构施工影响范围在10³0%D。在上元非饱和黄土结构盾构施工时,盾构对土体的扰动范围为10%D,而下元的扰动范围为30%D,同时考虑上元结构的压力拱作用。更多还原

【Abstract】 XiAn metro construction is first metro engineering in collapsed loess in the world, in that there are many questions to be solved such as "many studies,much difficulties, little parameters and no data ",which could be risk resource of metro engineering in crossing under old wall,tower and river directly,so that the "study on deformation of collapsed loess in metro construction by shielding" is put forward here.Firstly,the collapsed loess is studied by information,and put forward the dualistic structure of collapsed loess for shielding in loess.Based it,the law of loess settlement in shielding was found out by analysis of data of shielding settlement by supervision and demonstrated by digitally in theory.After study on deformation of loess by shielding,innovation achievements have been gotten as the following.1.Against metro influence in other cities,there is special properties of metro in Q₃,Q₄,collapsible loess of XiAn city.With change of water content w and saturation degree S_r,there is differences of physical and mechanical properties of Q₃,Q₄ collapsible loess,and therefore the dualistic structure of loess are formed naturally. After analysis of loess,theory of dualistic structure of collapsed loess is gotten.The above block of unsaturated loess in the structure has relationship with water content w and degree of saturation S_r,and the other one,saturated loess under water,does properties of general weak clay with collapsible loess.There is coincidence of deformation in dualistic structure.when one dualistic body is forced,the above block delivers the action to under one,in coincidence the deformation of under block is plastic deformation,making the above settlement in elastic along fissure.2.Settlement when shielding in above block of dualistic structure,the are 5 phrases in settlement under construction,in which the loss of clay by shielding and collapsed loess after jetting are two main factors,loss of body for 15²3 mm,collapsed loess for 9¹5 mm and consolidation for 2⁵ mm.Based deformation from shielding, the improved formula Peck is gotten in,kis synthetic to contain factors,k = 1.30～1.45.3.When shielding under block of dualistic structure,against shielding in above block,the settlement curve is flatter more,there is one factor impacting deformation-loss of clay.Maximum settlement by the loss is 16.88～30.71 mm,and one pressure arch appears in above block,which restrains deformation of under block.4.Stability of clay face and shielding knife face pressure,after analysis of stability of clay face,get the critical pressure of shielding face,which has influences in 10～30% of diameter of face.The shielding is kept on stability by the financial pressure.更多还原