锚固类结构临界锚固长度作用效应、工作机理与优化设计方法研究

The critical anchorage length for anchorage structures refers to the ultimate anchorage length of anchor rods in a particular rock and soil medium beyond which the bearing capacity will not increase apparently any longer, while under which the bearing capacity will still have some potentialities to exploit. For the past decades, especially for the last decade, the issue of the critical anchorage length has been investigated in various ways and from different aspects in China, and several research findings have been obtained. However, there are very few direct researches up till now, and no systematic researches have been published. Also, there is not a distinct and clear concept about the critical anchorage length in foreign countries. After several exploratory researches, the applicant hold that the phenomenon of critical anchorage length is ubiquitous; and a thorough investigation into the issue will raise queries and challenges on the existing design theories based on the concept and method of average shearing stress as well as their theoretical basis - the anchor rod microstructure theory. An optimum design method will be established based on the critical anchorage length, and the conventional design concept will be altered radically. The applicant plans to carry out the research by a method combining numerical calculation, theoretical analysis with test study. Previous researches show that this program is feasible. The research findings will have extremely important scientific value and wide prospects of engineering application, and will promote further development and progress of anchorage technology.

锚固类结构临界锚固长度是指一定岩土介质中锚固类结构杆体的极限锚固长度，超过此长度，其承载力将不再明显增加；未达此长度，其承载力尚有一定潜力可挖。数十年来，特别是近10年来，国内以不同的方法，从不同的侧面对临界锚固长度问题进行了研究，取得了若干成果。但直接研究极为少见，系统研究未见发表。国外没有临界锚固长度的明晰概念。申请者在开展若干探索性研究后认为临界锚固长度现象是普遍存在的，对此问题的透彻研究，将对现行国内外基于平均剪应力概念和方法的设计理论及其理论基础锚杆微观结构理论提出严重质疑和挑战，并将建立基于临界锚固长度的优化设计方法，使传统设计理念发生根本改变。申请人拟通过数值计算、理论分析和试验研究相结合的方法对该问题进行深入研究。前期研究结果表明，该方案具有可行性，研究成果将具有极为重要的科研价值和广泛工程应用前景，它将促进锚固技术的进一步发展和科技进步。

摘要：本报告在查阅大量文献、研究成果和工程实践经验总结的基础上，论述了锚固类结构临界锚固长度的研究现状，分析了存在的主要问题，提出了拟解决的关键科学问题、主要研究内容、研究途径和技术指标，第一通过对8根土介质中拉力型和压力型锚杆现场原型试验，测得锚杆杆体上第一界面应变片读数410个，测得锚孔内第二界面应变砖读数470个，周边应变砖读数783个，周边应变片读数378个，锚杆位移读数83个，共计2124个数据。第二是通过对24根模拟均质岩体（高强、中强、低强混凝土）介质中拉力型和压力型锚杆原型试验，测得锚杆杆体上第一界面应变片读数1081个，测得锚孔内第二界面应变砖读数2303个，周边应变片读数1514个，锚杆位移读数262个，共计5160个数据。第三是通过对上述试验中4根拉力型锚杆1#、1-1#、2-1#、3-1#和4根压力型锚杆的2#、1-2#、2-2#、3-2#进行数值计算分析，得到了103条曲线。研究了①锚固类结构锚固体及第一界面和第二界面局部破坏特点、效应及其向杆体深部和孔口渐次转移的规律；②锚固类结构锚固体及第一界面和第二界面剪应力峰值点的特性及其转移规律；③锚固类结构锚固体及第一界面和第二界面剪应力零值点的特性及其转移规律；④上述三个“转移”的时空对应关系；⑤锚固类结构锚固体及第一界面和第二界面剪应力沿杆体轴向和垂直于该轴向的两个正交方向上的空间连续衰减规律，并在综合分析已有的研究成果、本课题试验和数值计算结果后得到了①锚固类结构临界锚固长度试验判别方法；②确定4种典型岩土介质中拉力型和压力型锚固类结构临界锚固长度指标值；③建立了锚固类结构优化设计方法。它将促进锚固技术的进一步发展和科技进步。