外海大回淤沉管隧道软基沉降特征与控制计算研究

发布时间：2019-05-09 17:07

【摘要】：外海大回淤沉管隧道软基沉降特性及计算目前尚无比较成熟的经验可资借鉴，但其地基的沉降计算方法及参数取值、沉降控制对隧道设计和施工都具重要意义。论文通过现场试验测试与室内模型试验相结合的方法，提出一套有效应用于沉降计算的参数取值方法；建立了符合施工工序的沉管隧道地基沉降计算方法；通过离心试验的定性分析与沉降的定量计算，，揭示了沉管隧道天然地基的回弹再压缩沉降特性；结合蒙特卡罗概率有限元方法，进行岩土参数变异性、施工偏差及回淤量对沉降影响的敏感性分析；建立考虑不均匀土层下的弹性地基梁计算力学模型，推导了沉管隧道沉降控制计算方法，为沉管隧道的基础方案设计与优化及施工工艺改进提供了重要支撑。 1.基于现场测试数据资料分析，依据模型相似理论和渗透固结理论，提出了模拟完整施工工序的小比尺离心模型试验方案；结合工程实际及离心力场特性，确定了离心模型试验中离心机加速度；选用特种有机玻璃为沉管材料，对其几何尺寸进行部分修正，实现了模型与原型承力的相似；布设高灵敏度及高精密测试元件。试验结果揭示了不同垫层厚度下基底应力变形变化及沉管应变分布规律，也为下一步小探头CPTU试验及室内常规试验提供土样条件。 2.地基参数的确定决定沉降计算结果精度，为能快捷的获取准确计算参数，且减小土样采集制备过程产生的误差，论文分别开展了2cm2和15cm2探头CPTU原位测试，并借以2cm2探头CPTU测试结果，拟合出CPTU原位测试数据与土性参数间的回归公式，由此建立了由CPTU原位测试确定的海底特殊地层土性参数指标的计算方法，用以确定后期的计算参数。 3.基于计算参数确定方法，考虑沉管隧道基槽开挖、垫层铺设、隧管沉放、管顶回淤、航道开挖等整个施工过程，建立模拟施工过程的有限元计算模型及沉降简化计算模型，揭示了沉管隧道天然地基沉降特性，明确了回填-沉管-地基间的相互作用机理，确定纵向地基刚度变化较大区段。 4.结合传统的有限元计算分析方法及蒙特卡罗理论，基于Spearman秩相关系数的灵敏度分析方法，对沉管隧道下卧土层的岩土参数变异性、可能的施工偏差及回淤量等因素对地基横向及纵向沉降的影响敏感性进行分析，确定了敏感性较大的影响因素，得出了对沉降影响的最不利工况组合及分布形式，为施工控制提供参考。 5.结合弹性地基梁理论，建立考虑不均匀土层情况下的弹性地基梁计算力学模型，计算出隧道纵向位移曲线方程及隧道某一位置截面的剪力，推导沉管隧道沉降控制标准计算公式，为基础方案设计优化及施工工艺改进措施提供条件。
[Abstract]:At present, there is no mature experience to learn from the settlement characteristics and calculation of soft foundation of large silting pipe tunnel in the outer sea, but the settlement calculation method, parameter value and settlement control of the foundation are of great significance to tunnel design and construction. Through the combination of field test and indoor model test, this paper puts forward a set of parameter value method which is effectively applied to settlement calculation, and establishes a settlement calculation method of immersed pipe tunnel foundation in accordance with the construction process. Through the qualitative analysis of centrifugal test and the quantitative calculation of settlement, the springback and compression settlement characteristics of natural foundation of immersed pipe tunnel are revealed. Combined with Monte Carlo probabilistic finite element method, the sensitivity analysis of geotechnical parameter variability, construction deviation and siltation amount on settlement is carried out. The computational mechanical model of elastic foundation beam considering uneven soil layer is established, and the calculation method of settlement control of immersed pipe tunnel is deduced, which provides important support for the design and optimization of foundation scheme and improvement of construction technology of immersed pipe tunnel. 1. Based on the analysis of field test data, according to the model similarity theory and osmotic consolidation theory, a small scale centrifugal model test scheme is proposed to simulate the complete construction process. Combined with the engineering practice and the characteristics of centrifugal force field, the acceleration of centrifuge in centrifugal model test is determined, and the geometric size of special plexiglass is partly modified to realize the similarity between the model and the prototype. High sensitivity and high precision test elements are arranged. The test results reveal the variation of foundation stress and deformation and the strain distribution of sinking pipe under different cushion thickness, and also provide soil sample conditions for the next step of small probe CPTU test and laboratory routine test. 2. The determination of foundation parameters determines the accuracy of settlement calculation results. In order to obtain accurate calculation parameters quickly and reduce the error caused by soil sample collection and preparation process, 2cm2 and 15cm2 probe CPTU in situ tests are carried out in this paper. Based on the CPTU test results of 2cm2 probe, the regression formula between CPTU in situ test data and soil property parameters is fitted, and the calculation method of soil property parameters in special formation of seafloor determined by CPTU in situ test is established. Used to determine the later calculation parameters. 3. Based on the method of determining the calculation parameters, considering the whole construction process, such as foundation groove excavation, cushion laying, tunnel pipe subsidence, pipe top silting, channel excavation and so on, the finite element calculation model and the simplified settlement calculation model are established to simulate the construction process. The settlement characteristics of the natural foundation of the immersed pipe tunnel are revealed, the interaction mechanism between the backfill, the sinking pipe and the foundation is clarified, and the section with large variation of longitudinal foundation stiffness is determined. 4. Combined with the traditional finite element calculation and analysis method and Monte Carlo theory, based on the sensitivity analysis method of Spearman rank correlation coefficient, the variability of geotechnical parameters in the underlying soil layer of immersed pipe tunnel is studied. The influence sensitivity of the possible construction deviation and siltation amount on the transverse and longitudinal settlement of the foundation is analyzed, the sensitive factors are determined, and the most unfavorable working condition combination and distribution form of the influence on the settlement are obtained. Provide reference for construction control. 5. Based on the elastic foundation beam theory, the computational mechanics model of the elastic foundation beam considering the uneven soil layer is established, and the longitudinal displacement curve equation of the tunnel and the shear force of a section of the tunnel at a certain position are calculated. The calculation formula of settlement control standard for immersed pipe tunnel is derived, which provides conditions for the design optimization of foundation scheme and the improvement of construction technology.
【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U452.11;U459.5

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