桩锚结构加固边坡的作用机制研究
文献类型：学位论文
| 作者 | 李新坡
|
| 学位类别 | 博士 |
| 答辩日期 | 2006-06-06 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 王成华 |
| 关键词 | 边坡 极限分析 数值模拟 桩 预应力锚索 高切坡超前支护 |
| 其他题名 | Reinforcement mechanisms of piles and anchors in slope stabilization |
| 学位专业 | 自然地理学 |
| 中文摘要 | 桩锚结构用于边坡加固防护得到了广泛的应用，在很多国家和地区都有成功的经验，同时桩锚结构加固边坡的分析计算方法也得到了很大发展，提出了多种设计理论。但是，由于岩土体自身结构的复杂以及岩土体和加固结构之间的相互作用的不确定性，这些计算理论仍存在很多不合理之处。为提高桩锚结构的设计理论，有必要对桩锚结构加固边坡的作用机制进行深入研究。论文采用极限分析理论和数值分析技术，对边坡开挖及桩锚结构加固作用机制问题进行深入研究，内容包括确定开挖边坡临界高度的极限分析方法、基于FLAC3D的边坡稳定性分析方法、桩加固边坡的极限解耦分析、桩加固边坡的耦合分析、预应力锚索（杆）的荷载传递机制及极限抗拔力计算、预应力锚索加固边坡的稳定性极限分析以及边坡超前支护的概念及分析理论。在以下几个方面进行了深入研究，得出了一些成果和结论：（1）把层状岩体视为横观各向同性材料，采用抗剪强度随滑面与层面之间的夹角线性变化的关系，导出了利用极限分析上限定理计算层状岩体临界高度的方法，分析认为该方法可以用于指导层状岩体边坡开挖；基于“切线法”的思想和分段积分的方法，推导了基于土体非线性破坏准则的极限分析上限法求解碎石土边坡临界开挖高度的计算公式。（2）对采用强度折减法和有限差分软件FLAC3D计算边坡的安全系数时，边坡破坏的判断标准、边坡滑面位置的确定及计算参数对计算结果的影响进行了研究。分析认为：边坡发生破坏可以通过节点最大不平衡力的突变、特定点的位移是否收敛、节点最大速度突变和剪应变增量等值线图等特征进行判断。另外，土体的弹性参数和土的剪胀对安全系数的计算结果影响都很小。（3）把桩的作用考虑为施加在滑面上的剪力和弯矩，其大小采用Ito理论计算，从而得出了一种基于极限分析的桩加固边坡稳定性分析方法。桩的作用不但改变边坡的安全系数，而且改变了边坡的临界滑面位置和形状，如果仍按照没有桩时的临界滑面计算，得到的边坡安全性结果偏于危险（安全系数较大）。对桩的位置的分析结果认为，当桩位于边坡的中上部时加固效果最为显著。（4）对水平荷载桩的计算，考虑上部土体发生屈服的情况，结合土体弹塑性模型和弹性地基梁计算理论，推导了桩的内力计算公式。通过计算发现如果不考虑土体的屈服，得到的桩的位移和弯矩计算结果偏于危险。（5）桩-边坡系统的耦合分析中，把桩和边坡土体作为整体，采用有限差分数值分析软件FLAC3D，对二者的相互作用进行分析，计算系统的安全系数，分析桩的位置对安全系数的影响。桩的刚度对位移有明显的影响，但对作用在桩上的土压力分布影响不明显。 （6）把预应力锚杆看成空间轴对称的弹性力学问题，推导了完全粘结和部分脱粘时的界面剪应力分布计算公式。对其荷载传递机制进行分析。根据注浆锚杆（索）的粘结和脱粘机制，提出了一种剪应力分布模式，推导了极限抗拔力的计算公式。提出了一种基于极限分析上限定理的锚索加固边坡的稳定性计算方法，建立计算模型，并编制程序，计算结果经比较合理。锚索可以有效地提高边坡的稳定性，锚索作用的最有效位置是在边坡的中部到坡脚附近。（7）对高切坡超前支护理论进行了研究，内容包括：超前支护的概念、高切坡稳定性的超前判别、高切坡超前支护桩开挖段上的土压力分布形式研究、超前支护锚杆与变形岩体之间的相互作用机制，为超前支护桩锚结构的设计和施工提供了理论依据。 |
| 英文摘要 | The use of piles and anchors are well recognized in slope stabilization. Many successful practices have been achieved in many situations, and numerous methods have been developed for the analysis and design of slopes reinforced by piles or anchors. However, all of these analysis theories have some degree of weakless in representing the real mechanism of reinforcement because it is difficult to clearly consider the soil-structures interaction due to the implication of the soil and rocks mechanics. In order to improve piles and anchors design, it is necessary to have a good understanding of the behavior of piles and anchors in slopes. Plastic limit analysis and 3D numerical analysis have been used to study the problems involving slope excavation and reinforcement in this paper. It includes determining of the limit excavation height of slopes using limit analysis method; slope stability analysis using the finite difference code, FLAC3D; the limit decoupled analysis of piled slopes; the coupled analysis of piled slopes; the load transfer mechanism of prestressed anchors and calculation of pull-out load; stability analysis of slopes reinforced with anchor cables; and pre-reinforcement theory using in slope stabilization. The most important contents of this study are as follows: 1) Linear equations were introduced to express the shear strength of laminated rocks, which was treated as a transverse isotropy material. Then, an equation was derived to calculate the critical height of the slope using the kinematic approach of limit analysis. In the same chapter, an improved method using a ‘‘generalized tangential’’ technique to approximate a nonlinear failure criterion was proposed to estimate the stability factor of a slope on the basis of the upper bound theorem of plasticity. Integration method was used to estimate the rate of energy dissipation on the critical slip surface. 2) In slope stability analysis using shear strength reduction technique and finite ifference code, FLAC3D, some difficulties including the failure criterion of slopes, determining of the critical slip surface and effects of material properties on safety factor were discussed. As the results, the failure of a slope can be determined by observation of unbalanced force, maximum velocity, and maximum displacement. And the results also showed that there is no significant effect of elastic modulus and dilatancy on the factor of safety of the slope. 3) A coupled pile force determination and limit analysis stability method was proposed for determining stability of slopes reinforced with piles. To account for the presence of the piles, a lateral force and a moment were assumed to be applied at the depth of the potentially sliding surface. And the magnitude of the forces was determined by Ito’s equation. It was found that the pile changes not only the safety factor of the slope but also the critical slip surface. The assumption that the critical surface does not change with the addition of the piles would lead to non-conservative answers for the factor of safety. Furthermore, the results also indicated that the optimal location of the piles within the slope is near the middle part of the slope. 4) A theoretical elastic-plastic solution for laterally loaded piles was proposed to consider the yielding of the soil. The calculated results of an example pile indicated that the elastic model of soil can lead to non-conservation results. 5) Coupled analyses were performed for stabilizing piles in a slope, in which the pile response and slope stability are considered simultaneously and subsequently the soil pressure acting on the piles are examined. Effects of pile position on the factor of safety were discussed. Analysis on the pile bending stiffness on pile displacement and soil pressure was performed too. 6) Based on the assumption of spatial axial symmetry problem, the distribution equation of shear stress along a fully coupled and partially decoupled rock bolts were derived. Based on the mechanism of coupling and decoupling of grouted bolts, a distribution model of shear stress along grouted bolts was proposed, and equation for pull out load calculation was derived. A stability analysis method for slopes reinforced with anchor cables was proposed bases on the upper bound method of limit analysis. A computer program was developed to calculate the safety factor of the slope. The results showed that anchor cables are useful to improve slope stability, and the most effective location of a cable is in the toe-middle part of the slope. 7) Studies were curried out on the theory of pre-reinforcement of high cut slopes ncluding: conception of pre-reinforcement, pre-determining of the stability of cut slopes, and mechanisms of pre-piles and pre-bolts. It can be guidances for the design of slopes pre-reinforcement. |
| 语种 | 中文 |
| 公开日期 | 2013-06-27 |
| 分类号 | TU457 |
| 源URL | [http://ir.imde.ac.cn/handle/131551/5543]  |
| 专题 | 成都山地灾害与环境研究所_成都山地所知识仓储（2009年以前） 成都山地灾害与环境研究所_山地灾害与地表过程重点实验室 |
| 推荐引用方式 GB/T 7714 | 李新坡. 桩锚结构加固边坡的作用机制研究[D]. 北京. 中国科学院研究生院. 2006. |
入库方式： OAI收割
来源：成都山地灾害与环境研究所
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