地铁隧道下穿历史风貌建筑影响研究

发布时间：2018-04-06 01:17

本文选题：历史风貌建筑　切入点：基坑　出处：《天津大学》2013年博士论文

【摘要】：大规模的地铁建设使盾构法得到了广泛的应用，同时也促进了地下工程的发展。软土地区进行深基坑和区间隧道的施工存在多种风险，特别是对邻近基坑的历史风貌建筑物的影响，不同的保护措施存在较大差别，研究不同施工阶段对建筑物的影响、注浆加固地层机理、盾构推力引起地层中的附加应力等非常必要。首先，基于对历史风貌建筑物的实测数据分析，考察了基坑开挖、降水、端头注浆与冻结加固、盾构掘进等方面对建筑物的影响，并在此基础上对注浆抬升过程进行有限元模拟，得到了与实测拟合较好的计算结果。结果表明，合理的盾构掘进参数可将建筑物的沉降控制在较小范围内，地下水通过冻结区盾尾间隙进入刀盘前方可引起建筑物的显著沉降；建筑物基础与隧道之间存在淤泥质土层时，在淤泥质土层下方进行注浆不能对自重较大的建筑物进行有效抬升，注浆在淤泥质土层中引起孔压的消散可导致建筑物在后期产生沉降。进而，采用通过实测验证的有限元参数计算盾构正面推力和盾壳摩擦在地层中产生的附加应力，研究了盾构正前方、侧方、上方和下方平面上不同方向附加应力的分布，并分析了附加应力对地下管线及构筑物等的影响。结果表明，盾构正面推力在正前方平面上产生的x向正应力随着距掌子面距离的增加影响范围逐渐增大，但附加应力值迅速减小。盾构摩擦力在地层中引起的附加应力分布与正面推力导致的附加应力分布规律相似，但整体影响范围更大，附加应力值相应衰减较慢。盾构推力在地层中产生的附加应力以土压力的形式作用在地下管线和构筑物上，过大的变形可能导致管线渗漏或者构筑物开裂，工程中需引起足够重视。基于实测验证的有限元模型，分析了不同土层中注浆和注浆位置相邻土层弹性模量对注浆效果的影响。结果表明，本工程中实际产生的注浆效果为注浆量的70%，注浆会导致注浆体周围土体中产生超静孔隙水压力，在注浆结束后超静孔隙水压力逐渐消散，建筑物会发生小幅度的下沉，注浆体上部土层弹性模量太大会对注浆体的膨胀有一定的约束作用，导致抬升效果不明显，而注浆体下部土层，弹性模量越大注浆对自重荷载较大的建筑物的抬升效果越明显，而对自重荷载较小的建筑物抬升效果越不明显。对天津地区的土层进行冻土实验，研究天津地区的冻土的物理力学特性，冻土的三轴试验结果表明，冻土在零下5度时，应力应变曲线体现出应变软化的特性，而温度为零下10度和零下15度时，冻土应力应变特性为应变硬化型。最后，对冻结法盾构进出洞进行研究，将盾构进出洞人工冻结简化为厚壁筒受内压，利用冻土弹性-线性强化模型推导出塑性状态下冻土冻结壁厚度。并结合工程实例，，对冻结法施工进行了实测分析，结果表明，冻结帷幕在早期的发展会很快，交圈后所形成的冻结壁为不均匀体，后期冻结壁趋于均匀。目前的冻结设计参数选择偏于保守，应结合冻土试验参数对冻结设计进行优化。
[Abstract]:Large - scale subway construction has made the shield method widely used , and also promoted the development of underground engineering . There are many kinds of risks in the construction of deep foundation pit and interval tunnel in soft soil area , especially the influence of different construction stage on buildings , the mechanism of grouting reinforcement formation , and the additional stress in the formation caused by shield thrust .

Firstly , based on the measured data analysis of historic buildings , the influence of foundation pit excavation , precipitation , end grouting , freezing and strengthening , shield tunneling and so on are studied , and the calculation results are obtained . The results show that the reasonable shield tunneling parameters can control the settlement of the building in a small range .
When the silt soil layer exists between the foundation of the building and the tunnel , the grouting in the bottom of the muddy soil layer can not effectively uplift the building with large dead weight , and the dissipation of the pore pressure caused by the grouting in the muddy soil layer can cause the building to generate settlement in the later stage .

In addition , the influence of the additional stress on the underground pipelines and structures is studied by using the finite element parameters verified by the measured finite element parameters , and the influence of the additional stress on the underground pipelines and structures is studied . The results show that the additional stress generated in the forward plane of the shield is similar to the distribution of the additional stress caused by the front thrust . However , the additional stress caused by the shield thrust in the formation is relatively slow . The additional stress generated in the shield is applied to the underground pipelines and structures in the form of earth pressure .

Based on the finite element model , the influence of the elastic modulus of the adjacent soil layers in different soil layers on the grouting effect is analyzed . The results show that the grouting effect in the project is 70 % of the grouting amount , and the pressure of the super - static pore water is gradually dissipated in the surrounding soil of the grouting body . The higher the elastic modulus of the upper soil layer of the grouting body , the higher the lifting effect is , the more obvious the lifting effect of the grouting body under the weight load is more obvious , and the less obvious the lifting effect of the building with smaller dead load .

The physical and mechanical properties of frozen soil in Tianjin area were studied . The results of triaxial tests of frozen soil showed that the stress - strain curve showed strain - softening characteristic when frozen soil was 5 degrees below zero , while the stress - strain characteristic of frozen soil was strain - hardening when the temperature was 10 degrees and 15 degrees below zero .

The frozen wall thickness of frozen soil under plastic condition is deduced by using the frozen soil elastic - linear reinforcement model . The results show that the frozen wall is not uniform in the early development , and the frozen wall in the later stage tends to be uniform . The current frozen design parameters are conservative , and the frozen design should be optimized in combination with the frozen soil test parameters .

【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU43;U231.3

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