复合单元法在地下厂房岩壁吊车梁中的 应用与验证

 针对某水电站地下厂房岩壁吊车梁,进行复合单元法和普通有限单元法的比较计算。研究的重点是岩壁吊车梁与围岩的接触面、锚杆与围岩的接触面以及锚杆穿越岩壁吊车梁与围岩接触面等部位,并且考虑地下厂房开挖施工、吊车梁安装和运行的过程。比较复合单元法和普通有限单元法的计算特点与计算效率,研究结果表明：在离散模拟加锚节理岩体方面,复合单元法和普通有限单元法的结果非常接近;复合单元法能给出更多应力–应变的细节,且前处理更加简便。研究结果还表明：由于复合单元法以大量的计算代替前处理工作,因此计算时间大为增加。     

加锚固体的三维复合单元模型研究

首先提出了复合单元的概念，然后将其应用于建立砂浆固结锚杆的分析模型。该模型考虑了岩体、砂浆、锚杆、岩体/砂浆接触面，砂浆/锚杆接触面等多重介绍，借助阶谱的概念，复合单元可以纳入常规有限单元法分析中去，当某单元不含锚杆时，即退化为常规有限单元。应用该模型进行加固布设优化分析，当单元内锚杆的数量与方向改变时，计算网格无需变化，从而为大规模三维复杂结构计算分析的前处理提供较大便利，模型在有限单元软件CORE3中实现，并提供了计算实例。     

Effect of grout properties on the pull-out load capacity of fully grouted rock bolt

This paper represents the result of a project conducted with developing a safe, practical and economical support system for engineering workings. In rock engineering, untensioned, fully cement-grouted rock bolts have been used for many years. However, there is only limited information about the action and the pull-out load capacity of rock bolts, and the relationship between bolt–grout or grout–rock and the influence of the grout properties on the pull-out load capacity of a rock bolt. The effect of grout properties on the ultimate bolt load capacity in a pull-out test has been investigated in order to evaluate the support effect of rock bolts. Approximately 80 laboratory rock bolt pull-out tests in basalt blocks have been carried out in order to explain and develop the relations between the grouting materials and untensioned, fully grouted rock bolts. The effects of the mechanical properties of grouting materials on the pull-out load capacity of a fully grouted bolt have been qualified and a number of empirical formulae have been developed for the calculating of the pull-out load capacity of the fully cement-grouted bolts on the basis of the shear strength, the uniaxial compressive strength of the grouting material, the bolt length, the bolt diameter, the bonding area and the curing time of the grouting material.     

加锚岩体的阶谱复合单元法研究

加锚岩体有着复杂的非线性的变形模式，常规的线性基函数不能满足成模拟这种非线性的要求，若进一步细分网格，又会增加前处理的工作。引入阶谱技术，建立阶谱复合单元法，其基本思想是在复合单元中增加虚节点，扩大容许函数容量，通过使用阶谱基函数，提高计算精度。在广义节点下分析复合单元，使用阶谱复合单元法模拟加锚岩体，随着升阶，能够从物理本质上更好的拟合加锚岩体复杂的力学性质；在粗糙单元网格下逼近真实值，减轻网格的束缚。对阶谱复合单元法进行理论推导和实例研究，通过与有限单元法和复合单元法计算结果的比较，发现在较粗糙计算网格情况下随着升阶，阶谱复合单元法计算结果有明显的改善。     

The influence of blasting on grouted rockbolts

Field tests and laboratory investigations have been carried out to evaluate the performance of grouted rock bolts subjected to close proximity blasting. The investigations comprised pull-out testing of bolts and vibration measurements on both the rock and the bolts. Laboratory work comprised compressive and flexural testing of the grout and analysis of polished thin sections of specimens consisting bolt, grout and rock. There is no observable decrease in pull-out strength for bolts installed close to the blast (3.4 m), compared to more distant installed bolts (22.0 m). Furthermore, there is no difference in pull-out strength for the bolts with the freshest grout compared to bolts with cured grout, when subjected to blast loadings. Anchorage length of the bolts was 125 mm, which gave an average pull-out strength of 140 kN, or 93 % of steel yielding load. Analysis of polished thin sections of the rock, grout and bolt does not show any variation in crack pattern or crack frequency between bolts with varying distance to the blast or varying curing of the grout when subjected to the blast loadings. Re-pulling of previously pulled bolts shows a healing effect of the grout. None of the tests carried out indicates any decrease of the bolt /grout performance. It can be concluded that fully grouted bolts can be used on or close to the face.     

任意岩石锚杆计算模型及其算法

针对目前岩土工程中锚杆数值模型存在的局限性,提出了任意岩石锚杆的计算模型,该模型能考虑任意方向穿过岩体单元的锚杆,且岩体单元的划分不需要考虑锚杆的具体位置,锚杆信息可由已形成的岩体单元信息自动生成,可以适应岩石边坡、复杂地下结构支护分析以及加锚参数优化设计。应用表明,该模型方便可行,提高了加锚岩体数值模拟的适用性。     

A new analytical solution for the displacement of fully grouted rock bolt in rock joints and experimental and numerical verifications

This study proposes a new analytical solution to predict displacement of a fully grouted rock bolt intersected by single rock joint. The main characteristics of the analytical model, consider the bolt profile and joint movement under pull test condition. The anchorage capacity of fully grouted bolts has been studied for many years; however, the bolt profile and its effect on bolt shear resistance are poorly understood. Investigations of load transfer between the bolt and grout indicate that the bolt profile shape and spacing play an important role in improving the shear strength between the bolt and the surrounding strata. Rock displacement is a sum of elastic part and a jump part due to the presence of joints planes. The performance of the proposed analytical model is validated by experimental method and comparison with numerical modeling. The results showed that there is a promising agreement between analytical and numerical methods. Studies indicate that the displacement rate between the bolt and the rock declines exponentially. Which is dependent on the bolt characteristics such as: rib height, rib spacing, rib width and thickness grout, material and joint properties.     

加锚节理面抗剪性能研究

本文通过室内模拟试验和理论分析,着重探讨了锚杆对节理面抗剪性能的影响,以及杆体阻止节理面发生相对错动的“销钉”作用机制,提出改进了的估算加锚节理面抗剪强度公式。试验结果表明:加锚节理面的抗剪强度随剪切位移的增加而增大。试验和理论分析都表明,即使不大的剪切位移就已使杆体的抗剪作用得到充分发挥。试验研究还充分显示出锚杆倾角对加锚节理面抗剪强度的重大影响。 本文在给出了用于描述加锚节理面抗剪性能的分析模型和理论分析方法的基础上,导出了计算锚杆最佳安装角的公式。用此算式求得的最佳安装角与实验结果十分吻合。本文还分析了当前在有限元分析中经常使用的一些锚杆单元模型的不足之处,并指出了改进的方向。     

基于复合岩体法的锚杆支护隧道收敛修正分析

基于复合岩体方法考虑锚杆与围岩的相互作用,在引入加锚效应不均匀性基础上,根据对围岩变形约束程度修正复合岩体等效计算刚度,获得了锚杆支护作用下圆形隧道收敛变形的修正解。对比既有解及数值结果验证了本文解的正确性,修正解合理地降低了既有计算方法对锚杆约束效果的过高估计。结果表明:锚杆通过提高复合围岩等效刚度降低隧道收敛变形;增加锚杆密度比增加锚杆长度对降低隧道收敛更为有效;在常规锚杆布置参数条件下,锚杆支护对隧道最终收敛的降低幅度不会超过20%,难以完全依靠系统锚杆来限制软岩隧道的收敛大变形。本文提出的修正解能合理反映锚杆对围岩收敛变形的约束作用,可为锚杆支护下隧道收敛变形的量化分析提供简洁准确的计算方法。     

Systematic numerical simulation of rock tunnel stability considering different rock conditions and construction effects

This paper outlines the construction process mechanics (CPM) principle for analysing the stability of rock tunnels and presents finite element method (FEM) numerical simulation and prediction on the deformation and failure of the rock masses surrounding tunnels under various rock mass properties and excavating and support conditions. Based on numerical modelling, a series of predicting curves for rock mass response and deformation are obtained, which provides the basis of guiding the design and construction of rock tunnels in Taiwan.     

宜兴抽水蓄能电站地下厂房锚杆承载力现场试验研究与计算方法

简要介绍了一次大型洞室锚杆支护设计现场拉拔试验的研究成果，内容包括所采用的拉拔试验方法和主要试验结果。给出了锚杆体轴应变测试方法及其测试结果、岩体层面夹角对锚杆受力状态的影响、岩体表面及杆端位移特征、锚杆注浆体与孔壁之间的粘结力等试验结果，并根据试验结果提出了锚杆承载力峰值剪应力计算方法。与传统方法相比，所提出的方法建立在现场试验测试结果基础上，计算中考虑了锚杆体上剪应力不均匀分布的特点，锚杆长度按张拉段与锚固段之和计算，锚杆承载能力按杆体上的峰值剪应力计算，计算结果可较好地反映锚杆的实际受力状态。     

不连续岩体渗流的复合单元法初步研究

基于复合单元法的原理，提出了不连续岩体三维渗流的新算法。该算法具有以下3个主要特点：（1）不连续面（如断层或节理）含于复合单元之中，在划分网格时不予考虑，使网格的生成大大简化：（2）复合单元中可含有由不连续面分割而成的任意形状的子单元，每个子单元各有一组用于插值的映射节点水头。子单元的水头势、流速由相应映射节点水头计算得到，而复合单元中不连续面上的水头势、流速则由其相邻的2个子单元的映射节点水头计算得到；（3）复合单元中映射子单元的节点水头求解过程与传统有限元法类似，不含不连续面的单元自动退化为常规有限单元，因而复合单元法计算程序可以方便地与传统有限元分析程序融合。简单模型算例验证了该算法的正确性，而重力坝算例则表明该算法的有效性和在前处理上的优越性。     

Composite element method for the seepage analysis of rock masses containing fractures and drainage holes

The composite element method (CEM) is formulated for the seepage analysis of rock masses containing fractures and drainage holes. Each fracture or drainage segment is treated as a special sub-element having definite seepage characteristics, and is located explicitly within the composite element. The governing equation for the composite element containing both fractures and drainage holes is established using the variational principle. By the CEM developed in this paper, the fractures and drainage holes can be simulated explicitly but do not intervene in the discrete of the calculation domain concerned, in this way the generation of the computation mesh is not restricted strongly by the position and the orientation of the fractures and drainage holes, which is important in the optimal design of seepage control system. If there are no fractures and drainage holes, the CEM will automatically be degenerated to the conventional finite element method (FEM). The validity and reliability of the CEM is verified by a numerical example. The application and comparative study for the Baozhusi dam foundation is presented.     

锚杆单元及其在黄土隧道计算中的若干问题

隧道设计施工中考虑围岩的自承作用是新奥法的核心思想之一，而采用锚喷支护是技术上的关键。如何考虑锚杆的作用至今仍存在值得探讨的问题。介绍了一种弹塑性锚杆单元，给出了黄土隧道考虑锚杆作用的数值分析结果，对锚杆的合理长度以及提高锚固区围岩力学参数模拟锚杆作用方面提出了合理的建议。     

3D Behaviour of bolted rock joints: experimental and numerical study

Rock bolting is the most effective and also the most economical means of supporting excavations in rock. Various types of bolts are used today, and an understanding of the way in which these bolts work is essential for an optimal, safe, and economical use. Fully grouted, untensioned bolts have been commonly used in rock mechanics (i.e., mines, rock fall stabilisation, underground works) for many years. In the 1980s a new type of bolt, called Swellex, was developed, becoming more and more widespread because of their easy and fast installation. However, regardless of the type, the mechanical behaviour of the bolted rock joint is not fully understood, and only the experience accumulated on rock bolting gives the know-how for the reinforcement calculation and execution. In this paper the different mechanical responses of full steel bars as opposed to the frictional Swellex are discussed. The study was done through experimental tests coupled with numerical simulations. The analysis of the results obtained both from finite element (FEM) modelling, and from large-scale (1:1) shear tests on rock joints, reinforced with fully grouted rods and Swellex bolts, clearly shows that the two bolt types deform in dissimilar ways, responding very differently to shear load.     

预应力锚杆作用机制研究

针对预应力锚杆作用机制研究方面存在的问题，根据弹性理论轴对称问题的基本理论和方法，在引入锚杆影响范围内岩体平均轴向应力（平均轴向应变）假设的条件下，推导锚杆在完全黏结条件下界面剪应力分布公式；以此为基础，在考虑界面本构关系情况下，研究界面脱黏段的剪应力分布及脱黏段长度，阐述预应力锚杆的荷载传递特性，从而为预应力锚杆设计提供理论依据。     

不连续岩体温度场的复合单元模型初步研究

 基于复合单元法原理和不稳定温度场的隐式解法,提出针对不连续岩体温度场的复合单元法。该算法的特点是每个复合单元可以含有任意的不连续面,如断层或节理,且当结构中含有需在计算中离散处理的不连续面时,网格的生成不受不连续面的数量、位置和方向的影响。初步研究针对含1条节理的复合单元模型展开,假定岩块中无对流和辐射影响,推导岩块子单元和不连续面的热传导计算式,得到不连续岩体温度场的复合单元算法基本方程组,然后将该算法整合到传统有限元分析程序中。分别采用传统有限单元和复合单元法模拟热水流过单条裂隙时岩体温度场的变化过程,二者的计算结果非常接近,表明不连续岩体温度场的复合单元算法是合理和有效的,但其配套的温度场等值线后处理程序有待进一步完善。该算法的提出为深部岩体的多场耦合研究提供又一思路。     

任意岩石锚杆计算模型及其算法

针对目前岩土工程中锚杆数值模型存在的局限性，提出了任意岩石描杆的计算模型，该模型能考虑任意方向穿过岩体单元的锚杆，且岩体单元的划分不需要考虑锚杆的具体位置，锚杆信息可由已形成的岩体单元信息自动生成，可以适应岩石边坡、复杂地下结构支护分析以及加锚参数优化设计。应用表明，该模型方便可行，提高了加锚岩体数值模拟的适用性。