【作者】 张欣；

【导师】 李术才；

【作者基本信息】 山东大学 ， 工程力学， 2008， 博士

【摘要】 锚杆是岩土工程中重要的支护构件。但由于锚固工程本身的复杂性和多样性,导致目前锚固机制、设计理论以及计算方法都不够完善。明确锚固力学传递规律、建立准确的界面应力分布理论模型以及采用合理的数值计算方法都是进行锚杆锚固研究的关键。本文在现有试验、理论的基础上,针对各种荷载作用和各种工程工况,对全长粘结式锚杆的受力特性、锚固界面力学模型以及数值模拟计算等方面展开研究工作。分析单根全长粘结式锚杆在张拉荷载作用下的受力状态,根据已有试验得到的锚固界面应力分布曲线和相关结论,用比较简单的数学表达式对复杂的剪应力分布情况进行描述,建立均质岩体锚杆应力分布理论模型和节理岩体锚杆支护理论模型。同时鉴于目前数值模拟计算中存在的问题,推导考虑锚杆与灌浆体之间剪切破坏作用的三维锚杆有限元计算程序,并借助Fortran编程语言得以实现,最后进行程序验证和拉拔试验数值模拟计算。结果表明,当拉拔荷载较小时,锚固界面没有解耦发生,杆端轴力最大,大小等于作用的拉拔力,随后轴力沿杆长呈“近似负指数”分布;随着拉拔荷载的增加,杆体前端界面出现解耦,解耦段的轴力恒等于峰值拉拔力,未解耦段的轴力依然服从“近似负指数”分布;当达到极限抗拉拔力时,锚杆前端界面解耦段长度的数值模拟结果与实测结果基本吻合。推导并验证剪切荷载作用下锚杆加固节理岩体系统的两种破坏理论模型。同时借助三维有限元计算,尝试采用新型数值计算模型来模拟全长粘结式锚杆以及锚杆与灌浆体之间的相互作用,进一步揭示某些锚固参数对锚杆加固效果的影响。得出以下结论:锚杆倾斜安装可以有效减小剪切位移、缓解锚固体系中应力的增加,最终提高节理岩体整体抗剪强度;当围岩抗压强度较小时,锚固系统最终发生拉弯破坏。采用合理的锚固体-岩土体界面力学模型来模拟锚固体与灌浆体之间的相互作用。结果表明,锚固段从加载到破坏分为弹性变形阶段、滑移变形阶段和脱粘滑动阶段,每一阶段应力的分布特征和演化规律都与理论分析结果一致;不同杆长的锚杆达到极限拉拔荷载时,其轴向应力分布、锚固界面剪应力分布非常相似,且界面应力主要分布在锚杆前端“临界长度”的范围内。以洞室开挖围岩位移为参量,建立并验证洞室围岩变形引起的锚杆界面剪应力分布的理论模型。最后,以大岗山水电站为背景,将上述研究成果应用到实际工程中,具体分析锚杆锚固前后围岩稳定性的变化以及锚杆的受力状态,为实际工程提供参考。更多还原

【Abstract】 Bolt is one important reinforcement, but the complicated project makes it difficult to learn bolt mechanism, design theory and computation. The keys of learning bolt reinforcement include ensuring the rule of mechanics transfer, setting the stress model of contact surface, adopting the reasonable numerical computation method. Based on the tests and theory, the study of mechanical characteristics of bolt, model of bolted surface will be made.Based on the mechanical state of single full grouted bolt under pull load and the stress curve of bolted contact surface, the stress theory model of homogeneous rock and the reinforcement theory model of jointed rock will be set with simple numerical equation. According to the question in numerical computation, the 3D bolt finite element program will be realized through Fortran and be applied in numerical computation after validation. The conclusion can be drawn that, there is no decoupling and the axial stress is equal to the pull load, and the following axial stress distribution is minus exponent. With the increase of full load, there appears coupling and the all axial stress distribution is minus exponent. At last, the length of decoupling from numerical computation is accordant to the result of examination.After deducing and validating two destroy models, with the 3D finite element method, the trying of using new numerical model will be made to simulate full grouted bolt and the interaction between bolt and grout and get some conclusion. For example, the incline of bolt installation can decrease the shear displacement, weaken the rise of stress, and enhance the shear resistance of jointed rock. Moreover, under the complex action of pull load and bend load, the bolted system will destroy when the compress resistance of rock is poor.Reasonable contact mechanics model between grout and rock can simulate the interaction well and make it clear that the course from load to destroy include elastic distortion phase, slippage distortion phase and decoupling phase. The distribution of stress in every phase is according to the theory result. Even if the length of bolt is different, the axial and shear stress will distort in forepart of bolt, called "critical length".Based on the displacement of excavation, the shear stress model of bolt contact will be set and validated.At last, background on hydroelectric power station, all above theory will be applied in practice project to study the change of rock stability and bolt mechanics. The results provide reference for project.更多还原