基于空间滑移线场性状分析的竖向矩形锚板水平拉拔三维承载机理及极限承载力研究

The bearing mechanism research of vertical anchor plate under horizontal pullout has long-existing obscured understanding on some aspects, such as the definition standard of shallow and deep anchor, the symmetry of mechanical model and the relationship between the plane strain problem and the three-dimensional problem. This situation results to the existing calculation methods of ultimate bearing capacity couldn’t satisfy the design of new type of anchor plate structure. Therefore, the project presents the research on the bearing mechanism, mechanical model and ultimate bearing capacity of vertical rectangular anchor plate under horizontal pullout. First, the visual model test apparatus and digital photography measurement technology are used to qualitative examine the distribution and variation regulation of slip line field in vertical plane of strip anchor plate. Second, the characteristic of spatial slip line field of rectangular anchor plate is studied by verified finite element method to consider the influences of plate size, buried ratio and soil mechanical parameters. On this basis, bearing mechanism can be illustrated. And then, establish the mechanical model and deduce the theory solution of ultimate bearing capacity. At least three hundred datum of vertical rectangular anchor plate pullout test are collected to set up a database, which is used to do the comparison, verification and error analysis between the new solution and existing methods. At last, the regularity and charting research are carried out on the new theory solution. The fruit can deepen and unify the understanding of spatial bearing mechanism of vertical rectangular anchor plate, which can provide theoretical foundation for the revise of relevant specifications.

竖向锚板水平拉拔问题的承载机理研究长期在浅深锚界定标准、力学模型对称性以及平面应变问题与三维问题的关系等几个方面认识不清，导致现有的极限承载力计算方法无法满足当前新型锚板结构设计的要求。项目拟对竖向矩形锚板水平拉拔的承载机理、力学模型和极限承载力开展研究。首先，采用数字照相量测技术和可视化模型试验定性研究条形锚板竖直平面内滑移线场的分布和变化规律；其次，基于验证的有限元数值方法定量研究板的尺寸、埋深比及土体力学参数等因素对矩形锚板水平拉拔空间滑移线场分布特征的影响规律；在上述基础上，研究竖向锚板水平拉拔承载机理，构建三维统一力学模型，推导极限承载力理论解；建立三百个数据点以上的竖向矩形锚板水平拉拔试验数据库，广泛开展理论解、已有方法和试验数据的对比、验证和误差分析；最后，开展理论解的实用图表化研究。其成果可深化、统一竖向锚板水平拉拔的三维承载机理认识，为相关规范的修订提供理论依据。

竖向锚板水平拉拔问题的承载机理研究长期在浅深锚界定标准、力学模型对称性以及平面应变问题与三维问题的关系等几个方面认识不清。项目基于数字照相测量技术采用自制试验装置对砂土中14种埋深比下的竖向条形锚板开展了水平拉拔模型试验。采用ABAQUS数值软件对埋深比、土体力学参数等因素影响下竖向锚板水平极限拉拔下滑移线场的分布特征开展了研究。两者结果均表明：极限拉拔状态下，板前存在弹性核三角形（四棱锥）区域，其角度变化可反映板前滑移线场的对称性；随着埋深比的增大，弹性核的上角增大（φ至π/4+φ/2），上侧土体位移变形范围相对缩小，从延伸至地表收缩至板前附近；下角减小（π/2至π/4+φ/2），下侧土体位移变形范围则相对扩大，边界与竖向夹角在π/2至3π/4+φ/2间变化；上下角之和基本保持不变（φ+π/2），板前滑移线场由非对称逐步向对称发展。在此基础上，构建了可考虑埋深等因素变化的竖向条形锚定板的水平拉拔极限承载统一力学模型，并推导出极限承载力的统一理论解。结果表明：新的力学模型很好地反映了板前滑移线场的对称性随埋深比的连续变化规律，无需再人为区分浅埋和深埋；极限承载力统一理论解对砂土中竖向条形锚定板具有很好的适用性，计算结果与试验值符合的更好，较其它三种传统方法具有明显优势。通过板前四棱锥土核在垂直于板平面的竖直面和水平面投影三角形的形状演化来分别反映竖向和水平向破坏机制随土性、埋深比等因素变化的对称性；构建了竖向方形锚板水平极限拉拔的三维统一力学模型，并推导了相应的极限拉拔承载力三维统一理论解。与其他理论方法、试验数据的对比验证表明：新的力学模型很好地实现了一个模型来反映不同埋深比范围破坏机制的连续变化规律；统一理论解计算结果不仅与室内模型试验数据符合的很好，也和现场、大尺寸室内试验数据吻合，较三种国外方法计算结果更加接近于实测值。研究成果深化了对竖向锚定板水平拉拔承载机理的认识，并提出了新的承载力计算理论。