【作者】 向安田；

【导师】 朱合华； 丁文其；

【作者基本信息】 同济大学 ， 结构工程， 2007， 博士

【摘要】 本文结合一些工程案例及其现场试验资料、部分室内试验资料,采用理论分析和数值模拟的方法,对锚索格梁支护体系的承载机理及其设计计算中的一些关键问题进行了系统深入的研究,为锚索格梁支护工程的设计提供了重要参考依据。主要研究内容和成果如下:1、通过理论分析和数值模拟,研究了锚索锚固段的相互影响规律和边坡表层附加压缩应力的横向衰减规律,为锚固间距控制标准的提出奠定了相应的理论基础;2、锚索的主要破坏机制是:在拉拔力较大的情况下,锚固外端附近发生塑性变形,峰值剪应力向坡内转移,注浆体周围岩土体因拉裂而抗剪能力遭到削弱,锚索因接触面的渐进性剪切破坏而逐步失去承载能力。对自由型锚索而言,边坡表层附近的锚墩失稳也不可忽视;3、根据锚索的荷载传递原理和破坏机制,将接触面塑性硬化和软化本构关系简化为三折线本构模型(破坏阶段的接触刚度按零处理)。基于荷载传递原理、接触面的本构关系假设以及不同的边界条件建立的锚索P—S理论关系与现场抗拔试验、室内抗拔试验和数值模拟结果吻合良好。理论的P—S曲线在初始阶段为线性关系,当接触面部分进入塑性阶段后为非线性关系,但仍为似线性关系;4、针对现有设计方法的不足,在承载机理及设计参数研究的基础上,提出了基于荷载传递原理和现场抗拔试验所获得P—S曲线的新锚索设计方法,并给出了相应的实现过程。该方法的简单设计参数能通过现场试验获得,可综合反映实际工程条件,有良好可靠性,并能进行允许塑性变形的定量化设计;5、针对锚固间距过大,浅层锚杆等被动支护措施也可能难于防止松散边坡的表层坍滑这一问题,从土拱效应的角度,推导了最大临界锚固间距的理论表达式并进行了算例分析;6、算例分析表明,在几种传统的解析算法中,Winkle弹性地基梁法对格梁内力的计算适应性相对较好。针对Winkle梁解析算法不能考虑格梁与锚固介质之间的脱离、地基刚度非线性的问题,在格梁内力影响因素的系统分析中,通过基于MARC的二次开发克服了这些缺点。将Winkle梁“植入”边坡中,研究了施工过程和施作位置对格梁内力的影响作用;7、通过参阅文献和大量监测资料,分析了锚索预应力损失的一般规律及其影响因素。在MARC计算平台上对能考虑预应力变化耦合作用的广义KELVIN蠕变模型进行了二次开发,通过算例分析研究了蠕变对预应力长期损失的影响作用。依据灰色系统原理,编制了等时距和不等时距GM(1,1)预测模型的计算程序,通过算例分析明确指出了其适用范围。更多还原

【Abstract】 Study on supporting mechanism of pre-stressed cable with beam frame and its design&calculation method are delayed greatly than their applications, and is being in urgent need of further improvement. Aiming to solve the problem, several aspects such as load transfer mechanism、design parameter and method、computation method of internal force for beam frame and prediction of pre-stress loss, are comprehensively studied by means of numerical simulation and theoretical analysis, combining with some in-situ testing and indoor testing data. The main research content and results are as follows:1) Through theoretical and numerical analysis, rules for prestress’s transverse attenuation and interaction of anchorage part, are gotten. These rules can provide theoretical base for stipulation of anchorage spacing;2) There are two simulated mechanisms for cable with free part: one is that the grouted cable slip along the interface after the progressive failure of ambient rock because of the action of pull press, the other is that the rock fail under the anchor pier and lose bearing capacity;3) Based on load transfer principle、hypothesis upon interfacial constitutive law and different boundary condition, the P-S relationship of cable, which is well accordant with that gotten from numerical simulation、indoor or on-site pull-out test, is derived and analyzed. P-S curve from pull-out test is still approximately linear while part of the interface is in plastic state, and linear at the initial stage;4) To the shortcomings of present cable design methods, a new design method and its realization procedure are put forward after load transfer mechanism and computation method of design parameters are ascertained. In this method, the simple design parameter with better reliability can be obtained from on-site P-S curve and embody the syntheticalengineering condition, plastic-zone length near the interface can also be designated;5) As for disintegrated or loose slope, it may collapse if the anchorage spacing is excessively big even with shallow anchors in it. So, in this thesis, some control conditions are provided to calculate the "biggest critical anchorage spacing" between parallel and adjacent beams according to soil arch theory and the formula is got; 6) Through computational examples and comparative analyses based on theoretical analysis, several traditional methods for assessing the internal force of beam frame, are respectively examined and their suitability discussed. For the Winkle elastic foundation beam method, finite element computation model, which can consider the seperation and nonlinearity of p-y relationship between beam and slope by MARC’s secondary development, are put up and utilized to analyze the influence factors of internal force. To study the effect of slope construction and beam position on internal force, Winkle beams were embedded into FEM model of a practical slope for numerical analysis and the gained result is that-internal force of beam may augment greatly with the proceeding of construction and be obviously affected by beam position;7) By referring to large amount of field test data and pertinent literatures, the general law of prestress loss after lock-off and its affecting factors are extensively analysed. Coupled by prestress change, a general Kelvin rheological model is established and incorporated into MARC to analyse the effect of rock rheology on prestress loss. Meanwhile, two forecast model named equal interval GM(1,1) model and non-equal interval GM(1,1) model, are presented and programmed according to grey system theory respectively. Suitability and reliability of the two models are explicitly demonstrated by computational examples.更多还原