【作者】 谢小松；

【导师】 徐伟；

【作者基本信息】 同济大学 ， 结构工程， 2007， 博士

【摘要】 逆作法施工在建筑密集的城市基坑工程中得到了越来越广泛的应用，其原理简单、经济和社会效益明显，但是施工组织复杂、工序繁多，在理论计算和施工实践中均有大量的问题需要解决。因此，对深基坑逆作法的施工技术与结构分析进行系统研究，对于指导工程的顺利进行、确保施工安全具有重要的理论意义和实际应用价值。本文以上海目前最大的基坑工程——仲盛商业中心基坑工程为研究背景，对逆作法施工中的若干关键技术及结构计算进行了深入研究，得到了一些可用于指导施工实践的结论。首先，本文对逆作法深基坑的设计计算理论作了探讨，主要包括水土压力的计算、地下连续墙的承载力、深厚比及沉降量的确定；并对不同形式的中间支承柱的荷载取值及承载力计算、地下室楼层内支撑梁的设计和底板的厚度进行了讨论。其次，对大型深基坑逆作法施工中的若干关键技术难点进行了专题研究，主要包括对地下连续墙的接头构造及施工质量控制、逆作条件的土方开挖方式及组织、逆作条件下地下室结构的各种连接节点构造和施工、逆作法施工中差异沉降的产生及控制、地下室底板浇筑施工中底板钢筋支撑体系及后浇带的处理；并重点讨论了决定支承柱承载能力的三个因素，即：立柱与立柱桩的连接方式、支承上部荷载的方式及支承柱垂直度。针对大型深基坑逆作法施工中的盆式开挖工艺，本文利用有限元法分析了预留土体坡肩宽度对地下连续墙变形的影响，并据此对上海地区软土中的经济坡肩宽度给出了建议取值；提出采用强度折减法对盆式挖土中预留土体土坡的稳定分析，并以具体工程为算例验证了本文方法的正确性；采用多场耦合的有限元法对底板大体积混凝土养护过程中温度裂缝的产生机理进行了理论研究，结果表明混凝土内外最大温差的出现时刻出现在第4～5天，并提出了相应的控制措施。对逆作法基坑工程信息化施工中的监测—反演—预测—控制四个环节进行了探讨，提出了基于遗传算法的土体参数反分析理论并结合通用的有限元软件ANSYS二次开发技术，尝试编制了计算程序BATDCM，根据反分析得到的参数正演计算进行预测并根据预测结果提出了有针对性的控制措施。本文总结了深基坑逆作法施工全过程模拟的三维非线性有限元理论，重点探讨了考虑流变效应的上海地区软土本构模型及参数的确定方法；围护墙的模拟方法；土-结构界面接触的模拟方法；土体初始应力场的模拟方法；土体开挖过程的模拟等进行了研究。最后，采用上述方法对“中间顺作、周边逆作”的仲盛商业中心基坑工程进行了施工全过程数值模拟，计算结果与实测数据较为吻合。为今后类似工程提供了理论支持和实践参考。更多还原

【Abstract】 More and more high rise buildings and large-scale public structures are beingbuilt in recent years. A lot of deep foundation pits are appeared and the size and depthare increasing. The building construction meets problems of restrict control on sitearea and circumstance protection. There are dense buildings, large number of urbanground pipes around most of these pits. In result, Top-Down Construction Method(TDCM) is getting more and more application, as an effective method. However, theTDCM has complex construction organization, and many courses. Whether on theoryor practice, there are quite lot of problems and questions in TDCM need to be solved.There are important theoretical significance and practical value to study on thetechnology and calculation of structure in TDCM, in order to ensure the safety ofengineering and people’s lives. This dissertation is carried out research andinvestigation on the base of the largest deep pit engineering of Shanghai—thefoundation pit of Zhongsheng Commercial Center. Some conclusions and resultswhich can be used to guide practice are made.Firstly, some design theories of TDCM are discussed. They are calculation ofpressure of soil and water; the confirmation of level and vertical bearing capacity, theratio between depth and thickness, settlement of diaphragm wall; calculation of loadand bearing capacity of different formal pillars; the design of the sustain beam andsolepiece.Secondly, some key techniques of TDCM are studied in this dissertation. Ondiaphragm walls that are used as a part of main structures, the structure of joints andquality control were extensive analyzed. On pillars, joint structures between pillarfeet and pile cap, the supporting load ways and the uprightness are researched. On theexcavation construction, the dissertation discusses the excavation method and theorganization of construction. On the joint structures between beam and pillars,diaphragm and basement beam or plate, diaphragm and upside wall, pillars andsolepiece are researched.Thirdly, the basin opening excavation method and the temperature crack areresearched by FEM. On the excavation construction, the influence of width ofobligating soil slope shoulder on deformation of diaphragm is extensively researchedand the economical and rational width of soil slope shoulder in soft soil is obtained.In addition, stabilization of obligating soil slope is analyzed by strength reductionfinite element method and the safety factor is calculated. The creating mechanism oftemperature crack in solepiece constructing is researched by multi-physical fieldcoupling FEM and the time of the most difference in temperature between inside and surface in concrete is calculated. Some interrelated control treatment is broughtforward.Fourthly, the computer simulation theory that can simulate TDCM constructionsequences is discussed and successfully applied. It chooses the nonlinear rheologicalconstitutive relation of soft soils, determines corresponding parameters, uses 3-Dplate elements to simulate diaphragm wall, adds contacting elements between soilelements and diaphragm wall elements, adds simulated initial stress in soil, andapplies nonlinear rheological FEM theory to simulate 3-D excavation andsuperstructure construction progress.Fifthly, four processes in information-based construction (monitoring-reverseanalysis-predicting-control) are investigated. The reverse analysis of soil parameterbased on genetic algorithms, forward calculation to predict and pertinence control bypredicted result are discussed.At last, the full course construction of Zhongsheng Commercial Centerfoundation pit that adopt "normal centrally and top-down around" constructionproject is analyzed applying the 3-D nonlinear FEM theory introduced above.Through contrasting between calculated result and actual measured data, someconclusions that can provide theoretic basis are obtained.更多还原