【作者】 张爱民；

【导师】 胡毅夫； 张栋材；

【作者基本信息】 中南大学 ， 采矿工程， 2009， 硕士

【摘要】 锚固工程是岩土工程领域中非常重要的分支,而锚杆内锚固段锚固特性研究是锚固工程中的核心问题之一。本文采用弹性力学模型和剪滞-脱粘模型对锚杆的内锚固段锚固特性进行了研究,基于软岩的锚固特性设计出新型的内锚固段结构,并通过室内物理结构特性试验和数值模拟试验验证其锚固特性。主要有以下几个方面的内容:1、运用弹性理论空间模型,对拉力型、压力型预应力锚杆内锚固段剪应力沿长度方向的分布规律进行模型研究,得出两种锚杆内锚固段外界面上的剪应力分布都不是均匀分布,其剪应力峰值点都不是在端点位置。拉力型锚杆剪应力峰值发生在距锚固段起点10cm左右,而压力型锚杆剪应力峰值发生在承载板附近。2、分析预应力影响周边岩土体质点位移变化时发现,拉力型锚杆预应力在岩土体中的分布是以杆体轴线为对称轴,以锚固段顶部为界面,呈半圆形向四周空间传递。而压力型锚杆是以承载板为中心,呈现似“U”形向四周波形传播。3、建立锚杆外界面滑移-脱粘模型,对其变形—破坏过程的力学分析得出:锚固段从加载到变形破坏可分为弹性变形、塑性滑移变形、脱粘变形三个阶段;根据静力平衡方程结合Coulomb屈服条件及非关联的流动法则,推导出了锚注段外界面上的位移微分方程,并求解出锚注段其三个阶段的剪应力表达式;4、考虑外界面剪滞-脱粘破坏过程,提出了锚杆内锚固段长度的确定方法:当施加的预应力P₀小于最大预应力P_max时,界面处于弹性变形阶段,可采用已建立的弹性公式求解;当施加的预应力P₀大于最大预应力P_max时,界面处于三种变形阶段,可以根据等积分法确定其锚固段长度。5、基于软岩的锚固特性,结合岩层控制的关键层理论和组合梁协调变形的思想,提出对软岩锚固作用机理描述的内外锚固墙理论。将结构工程中的底部锥形结构引入到岩土锚固工程中,设计出底部为锥形的压力型锚杆。6、通过软岩相似试验、室内物理试验及数值模拟,得出压力型锚杆与锥形锚杆的位移均从孔底向孔口渐进式传递,而拉力型锚杆则相反,由孔口向孔底扩展;比较锚杆拉拔过程的应力矢量图或位移矢量图可以发现,锥形锚杆的锥形结构对应力的方向有分散作用,但分散的作用范围有限。更多还原

【Abstract】 Anchor engineering is a very important branch in the field of geotechnical engineering , and Study on anchoring characters of interior bond section is one of the key issues in anchor engineering. In this paper, anchoring characters of interior bond section in bolt are studied with elasticity model and shear lag debonding model. Based on the anchoring characters of soft rock, a new type of structure about interior bond section is designed, and is validated with pull-out tests and numerical simulation in laboratory. The main contents are as follows:1、Based on the elastic theory, Model research on distribution regularity of shear stress on anchorage end of prestressing bolt is carried out in both tension-type and pressure-type prestressing bolt. The non-uniform distribution of shear stress is obtained, and their peak shear stress points are not in the location of the endpoint. The shear stress peak point of tension-type anchor occurred in about 10cm away from the starting point of bond section, and the shear stress peak point of pressure-type anchor occurred in the vicinity of the bearing plate.2、Analysis of the displacement changing result from the impact of pre-stressed physical point of the surrounding rock, in pull-type bolt, prestressing force is transferred to the surrounding space with the semi-circular shape by the symmetry axis of bolt and the top interface of bond section in rock and soil. However, prestressing force is transferred to the surrounding space with the ’U’ shape in the pressure-type bolt.3、Setting up the shear-lag debonding model in external interface of bolt, analysing in the mechanics in the process of destruction and studying on bonding length, the following is obtained. From the loading to the damaging on anchor section, there are three phase, including elastic deformation, plastic-slip deformation, debonding deformation. According to the static balance equation, Coulomb yield conditions and non-associated flow rule, the shift differential equations about the external interface of bolt-grouting section is deduced and the expression of Shear stress in the sliping part of bolt-grouting section is solved out.4、Considering the process of shear-lag debonding, the method of the length of interior bond section is proposed. When prestress is less than the largest prestress, the interface is in elastic stage, and bonding length is solved through the flexible formula; when prestress is greater than the largest prestress, the interface is in three stages, and bonding length is determined through the same area integral approach.5、Based on the anchor properties of soft rock, combined key strata theory for control of strata movement with the ideas of the deformation on compound beams, anchored-wall theory is brought out on describing the soft rock anchoring mechanism. the taper structure in structural engineering is introducted in the rock anchoring engieering, and the taper bolt is designed.6、Through the similarity experiment of soft rock, pull-out tests and numerical simulation, the displacements of both tension-type bolt and pressure-type bolt are transfered gradually from the buttom of the hole. Howerver, tension-type anchor is not. Compared the chart of stress vector and the chart of displacement vector, This taper structure of cone-shaped bolt has the effect on the scattering of the direction of stress, but the role of decentralization is very limited. Optimizing its structure is the further need.更多还原