深厚覆盖层下锚碇沉井基础的极限承载力与长期稳定性研究

According to the analytical thinking of the theoretical modeling combined with model test, the ultimate bearing capacity and long-term stability of the anchorage caisson foundation in deep overburden layer are researched. Based on different size and different buried depth of the model test of anchorage foundation, and combining the corresponding numerical simulation experiments, the relations between the bearing capacity and the both of the foundation size and the buried depth are established. The computation model of the foundation bearing capacity reflecting the nonlinear effect is suggested. The computation method of the ultimate bearing capacity of the anchorage caisson foundation is given. Considering the load condition and the buried depth and the form and the geological conditions of the anchorage foundation, and combining the results in the engineering monitoring and taking in the deformation characteristics of anchorage foundation in the whole process of construction, the numerical computation model and the corresponding computation method of forecasting the inhomogeneous subsidence and long-term deformation are established. According with the control requirements of the foundation subsidence and horizontal displacement in the construction period and operation period, the theory of the design computation based on the deformation control requirements of the anchorage caisson foundation is suggested. From the standpoint of multi-level synthetic simulation and wide angle analysis, the deformation and long-term stability of the anchorage foundation are researched by the deterministic and uncertain models.The foundation ultimate bearing capacity and the deformation critical warning value are used as the quantization control indexes of the wide angle.The stability synthetical judging system and the corresponding critical warning indexes of the anchorage caisson foundation are given or predicted.

以理论建模和模型试验相结合的分析思路，针对深厚覆盖层下锚碇沉井基础的极限承载力与长期稳定性进行研究。基于不同尺寸和不同埋深的锚碇基础模型试验，结合相应的数值模拟试验，建立承载力与基础平面尺寸和埋深的关系，提出反映非线性效应的地基承载力计算模型，给出锚碇沉井基础极限承载力的计算方法；考虑锚碇基础受力、基础埋深、基础形式和地质条件，结合已有工程监测成果，计入锚碇基础施工全过程的各种变形特征，建立能够对不均匀沉降以及长期变形进行预测的数值计算模型与相应的计算方法；依据锚碇基础在施工与运行期对沉降与水平位移的控制要求，提出基于变形控制的锚碇沉井基础设计计算理论；从多层次综合仿真和广角度分析观点，以确定性和不确定性两类分析模型对锚碇基础的变形和长期稳定性进行研究，进而以基础极限承载力和临界变形警戒值为广角度量化控制指标，给出或预报锚碇沉井基础稳定性的综合评判以及相应的临界警戒指标。

深厚覆盖下锚碇沉井基础的极限承载力和长期稳定性是学术界和工程界极为关注的课题之一。本项目结合理论、试验和数值方法，系统深入地开展锚碇沉井基础的承载性能和稳定性研究，具体包含：锚碇沉井基础的模型试验，锚碇沉井基础的极限承载力计算，锚碇沉井基础长短期变位的计算模型，锚碇沉井基础超载安全度的分析方法。.围绕本项目的研究目前和研究内容，课题组四年来的潜心研究，取得以下成果：.（1）以泰州大桥的锚碇沉井基础为背景，制作了1：50的锚碇试验模型，设计了6种试验方案；探讨锚碇基础和周围土体的位移、应力变化规律，覆土以及地下水位对锚碇沉井基础变位和稳定性的影响。.（2）根据刚塑性体的平衡条件，在分别考虑粘聚力和重度的情况下，推导了方形深基础地基极限承载力的理论解，再结合条形深基础地基极限承载力的理论解，叠加得到矩形深基础地基极限承载力的通用解析解。.（3）提出将经典昆仑定律代替假想的弹簧模型，按Winker模型计算沉井基底井身水平反力，再根据接触面上的位移协调条件，推导得到沉井水平位移计算公式、滑移临界载荷以及沉井水平承载力增加系数与埋深的变化关系。.（4）在理论分析和数值模拟两方面，假设土体为Winkler弹性介质，给出了锚碇基础长短期变位的理论计算公式，基于Burgers蠕变模型，计算锚碇基础的长期变位。.（5）基于有限元数值模拟，假定锚碇的超载为大缆拉力按比例增加，研究锚碇基础变形和应力、基底反力以及抗滑移和抗倾覆稳定安全系数随大缆拉力超载系数的变化情况，确定锚碇基础的超载安全度。.（6）基于Winkler模型和数值模拟方法，结合具体工程实例，分别应用Winkler模型和数值模拟对沉井基础进行地震响应计算分析，验证了Winkler模型用于沉井基础地震响应计算的可行性。.研究成果为深厚覆盖层下锚碇沉井基础的极限承载力与长期稳定性评价提供了理论依据和分析手段，具有重要的科学意义和应用前景。