考虑时空效应的锚拉式挡土结构土压力理论及耐久性研究

For anchored retaining wall, because of lateral restraint of anchor bolt, the ability of anti-sliding and anti-overturning has been improved significantly. In addition, the section size of retaining wall can be decreased too. Therefor, the new type of retaining wall has been applied in many engineering successfully. Much test shows that the earth pressure distribution of the type of retaining wall have the obvious feature of spatial and age evolution effects, which can influence the structural mechanical features and durability seriously. However, these features could not be considered in normal calculation theory. To make up for the deficiency, test model of anchored cantilever retaining wall will be adopted to research the spatial distribution and main influence factors of earth pressure. According to test datum, 3D soil arching effects will be revealed by reference to the basic principle of unloading arch and lateral loaded pile. On the basis, by considering of arching effects and deformation influence, earth pressure model can be established by adopting the horizontal layer analysis method. In addition, during long term service time, because of long term traffic loading, anchor bolt will slip gradually lateraly, which can decrease the durablity and safety of retaining wall. Therefor, in order to reveal the progressive failure mechanism between anchor bolt and compacted soil under cyclic traffic loading, model test will be designed. According to test results, the mathematic relation between slipping value and load level can be put forward. Finally, much paper shows that the earth pressure distribution of anchored retaining wall can be influenced by many external effects during service time, such as the variation of soil strength because of water infiltration, lateral slip of anchor bolt, uneven settlement, failure of anchor bolt and so on. With the change of earth pressure, the mechanical feature of retaing wall will be changed seriously also. Thus, numerical simulation methods will be adopted to analyze the variation laws of earth pressure during service time, which can provide the reference for durability apprisal of anchored retaining wall. In a word, the research achivements can be benificial to the rapid development of the anchored supporting structure and ensure the long term traffic safety.

锚拉式挡土结构受注浆锚杆（索）侧向约束作用，土压力具有显著的空间分布特征，存在应力集中现象，并受外界因素影响呈动态变化，对结构受力的合理性及耐久性要求较高，但现有设计理论未予考虑，潜在安全隐患。为弥补理论不足，设计制作加锚悬臂式挡墙模型试验，结合数值模拟，研究土压力空间分布规律，并基于卸荷拱原理及横向承载桩效应等理论进行力学分析，揭示锚拉式挡土结构三维土拱效应，建立土拱力学模型。综合考虑三维土拱效应及非极限状态位移影响，采用水平层分析法构建土压力空间分布模型，并进行工程验证。为研究锚固体动态受力特征，设计制作重复荷载下注浆锚杆-土层渐进破坏模拟试验，揭示锚固体疲劳破坏机理，提出锚固体侧向滑移规律。考虑路基强度衰减、挡墙侧向变形、差异沉降等因素开展数值模拟，揭示土压力时间演变效应，提出锚拉式挡墙耐久性评价指标。研究成果对于完善锚拉式挡墙设计理论、保障交通安全具有重要的理论意义和工程应用价值。

锚拉式挡土墙作为一种新型支护结构，综合了传统挡墙与岩土锚固的技术优势，可提高挡墙稳定性，减少侧向位移量，适用于高填土路基支挡或避让重要建筑物等路段。但是，目前对于填土路堤中锚拉式挡土墙的支护机理、土压力分布模式及耐久性研究较少。本项目研究了不同挡墙类型（锚定板挡墙、锚杆挡墙、互锚式挡墙）、不同上覆荷载、不同预应力水平作用下锚拉式挡墙土压力、位移、锚杆拉力等指标的变化规律。研究结果表明，锚拉式挡土墙受侧向锚杆约束效应，其位移模式及土压力分布明显不同于常规挡墙，存在显著的空间分布效应，即空间土拱效应。无应力状态下，锚杆处挡墙位移量最大，墙背土压力类似梯形分布，即自上而下逐渐增大，靠近底板一定位置急剧降低，土压力值介于主动土压力与静止土压力之间；预应力状态下，挡墙位移呈现2次反弯点的挠曲变形特征，最大位移发生于锚杆下方。挡墙侧向土压力介于静止土压力与被动土压力之间，锚杆上方的墙背土压力逐渐增大，锚杆下方土压力急剧减小，至H/4处降为主动土压力。同时，挡墙墙背土压力沿路基纵向亦表现为土拱效应，主要影响范围为锚杆左右两侧D/4（D为锚杆横向间距）范围内。根据土压力的分布规律，构建了适用于锚拉式挡土墙土压力分布模型。本课题考虑挡墙不同工后沉降位移或转动模式以及行车重复荷载作用，研究了挡墙受力特征的时间效应。结果表明，受地基固结沉降影响，路基与挡墙会发生不均匀的沉降，从而引起挡墙与路基的相对竖向位移或挡墙的转动，造成挡墙墙背土压力及锚杆拉力的变化，无论何种位移模式，都会造成锚杆注浆体产生较大的弯矩效应，注浆体的拉压或压剪破坏及外界水侵入对锚固体的腐蚀耐久性非常不利；同时，车辆振动等重复荷载作用引起锚定板对受压土体产生累积塑性变形，造成锚杆（索）体预应力松弛，显著降低锚拉式挡土墙预应力值，一般仅为原设计值的40~50%，引起挡墙侧向变形增加，墙背土压力减小。本项目的研究为锚拉式挡土墙在土地节约技术中的高路堤支护打下了坚实的试验与理论基础。