某工业厂房岩石锚杆基础抗拔性能的分析

发布时间：2018-12-15 06:44

【摘要】：某工业厂房柱基础由于直接建在岩石上,厂房本身较高,基础受到较大的弯矩和水平力作用,基础采用岩石锚杆基础,锚杆的设计采用钢结构柱脚基础螺栓的设计方法进行设计。对厂房柱基础的抗拔力进行了实验研究和有限元分析,以确保工程的顺利实施,为后续类似工程提供理论和实践指导意义。本文以该工程G列部分锚杆基础的抗拔承载力试验为例,按锚杆总数的5%抽取检测试样,共抽测37根锚杆,对单根锚杆抗拔承载力进行现场监测,经检验单根锚杆的轴向抗拔承载力均能够达到所给出的特征值160kN设计要求。对单根锚杆继续加载,除个别锚杆被拔出以外,其余均能够承受260kN的抗拔力,并未出现明显破坏的特征。运用ANSYS有限元数值模拟软件建立有效的三维模型,对锚杆的抗拔力进行了分析计算,并将现场试验值结果对比,实验值和分析值基本一致,说明所选有限元模型的有效性。在此基础上,利用有限元对锚杆抗拔力的影响因素做了具体研究。首先,对不同岩石的弹性模量进行研究,通过岩石弹性模量与锚杆自由端抗拔承载力位移曲线可以看出,弹性模量在15~35GPa时位移变化较大,表明在岩石弹性模量较小时锚杆对岩体锚固尤其重要。岩石弹性模量达到60GPa以后锚杆自由端位移趋于稳定,说明岩体材质刚度较大时,锚固效果不明显。其次,讨论了混凝土—锚杆摩擦系数对锚固系统的影响:当摩擦系数较小时,随着外荷载的增加,锚杆被拔出,在此过程中锚杆处在弹性阶段,此类破坏主要是因为接触面摩擦力不足产生的破坏;当摩擦系数较大时,在外荷载作用下,钢筋锚杆首先处在弹性阶段,然后锚杆进入塑性阶段,继续增大外荷载,锚杆被拔出,锚固系统破坏。在现场试验过程中发现锚固抗拔承载力富余量很大,因此最后对锚杆的锚固深度做了进一步的研究,当锚固深度为2.5m时抗拔承载力为194kN,达到原设计值160kN的1.2倍,满足原设要求。最后通过分析得到了锚杆直径与锚固深度的关系式。总之,研究表明提高锚杆抗拉强度及界面的摩擦,可以改善锚固系统的抗拔承载力,选择合理的锚固深度可以有效节约工程成本和项目建设时间。
[Abstract]:Because the column foundation of a certain industrial factory building is built directly on the rock and the factory building itself is relatively high, the foundation is subjected to greater bending moment and horizontal force, so the foundation adopts rock anchor foundation. The design of anchor bolt adopts the design method of steel structure pillar base bolt. In order to ensure the smooth implementation of the project and to provide theoretical and practical guidance for the subsequent similar projects, the experimental study and finite element analysis of the pull-out force of the foundation of the factory building column are carried out in order to ensure the smooth implementation of the project. In this paper, taking the test of uplift bearing capacity of G row partial anchor foundation as an example, a total of 37 anchors are extracted according to 5% of the total number of anchors, and the uplift bearing capacity of a single anchor rod is monitored on the spot. It is proved that the axial pull-out bearing capacity of a single anchor can meet the 160kN design requirements of the given eigenvalues. With the exception of individual anchors being pulled out, the single bolt can withstand the pull-out force of 260kN without obvious damage. ANSYS finite element numerical simulation software is used to establish an effective three-dimensional model, and the anti-pull-out force of anchor rod is analyzed and calculated, and the results of field test are compared. The experimental value is basically consistent with the analytical value, which shows the effectiveness of the selected finite element model. On this basis, the finite element method is used to study the influence factors of bolt pull-out force. First of all, the elastic modulus of different rock is studied. The displacement curve of rock elastic modulus and free end tensile capacity of anchor can be seen that the displacement of elastic modulus changes greatly when 15~35GPa. It is shown that the anchor rod is especially important for rock mass anchoring when the elastic modulus of rock is small. When the elastic modulus of rock reaches 60GPa, the free end displacement of rock bolt tends to be stable, which indicates that the anchoring effect is not obvious when the material stiffness of rock mass is large. Secondly, the influence of friction coefficient of concrete-anchor rod on the anchoring system is discussed. When the friction coefficient is small, the anchor rod is pulled out with the increase of external load, and the anchor is in the elastic stage in the process. Such failure is mainly due to the failure caused by insufficient friction on the contact surface; When the friction coefficient is large, the reinforcement anchor is first in elastic stage, then in plastic stage, and then increases the external load, the anchor rod is pulled out and the anchoring system is destroyed. In the course of field test, it is found that there is a great amount of surplus of anchor pull-out bearing capacity. Finally, the anchoring depth of anchor rod is further studied. When the anchoring depth is 2.5m, the pull-out bearing capacity is 194kNs, which is 1.2 times of the original design value 160kN. Meet the original requirements. Finally, the relationship between anchor rod diameter and anchor depth is obtained by analysis. In a word, the study shows that improving the tensile strength and the friction of the interface can improve the uplift bearing capacity of the anchoring system, and selecting reasonable anchoring depth can effectively save the project cost and the project construction time.
【学位授予单位】：辽宁科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU476

【参考文献】