预应力锚杆柔性支护方法的数值分析

【作者】 朱亚林；

【导师】 孔宪京；

【作者基本信息】 大连理工大学 ， 防灾减灾及防护工程， 2004， 硕士

【摘要】 预应力锚杆柔性支护方法作为支护深基坑的一种新型支护形式，与其它支护方法相比，该方法由于其经济、可靠、施工便捷、变形小、支护深度大等显著优点，在我国岩土工程领域中已得到广泛的应用。本文使用非线性有限元方法对预应力锚杆支护进行数值分析研究，以期该技术得到更广泛的应用提供较为科学的依据。 首先，采用有限元方法，对预应力锚杆柔性支护进行数值模拟。通过研究基坑的变形，锚杆的受力状态和轴力的分布规律，来分析预应力锚杆柔性支护的力学性能。其次，通过与土钉支护进行数值分析比较，对基坑的控制变形的影响以及本身的受力情况的分析，进一步了解预应力锚杆柔性支护的作用机理。第三，通过对预应力锚杆柔性支护进行结构变参数分析，研究了锚杆长度、锚杆支护倾角、锚杆布置间距、锚杆长度布置方式以及面层厚度的变化对基坑变形和锚杆轴力的影响。最后，对工程实例进行有限元数值分析，与实测结果进行比较。主要研究结论如下： (1) 预应力锚杆支护下基坑的水平位移和地表沉降均呈曲线分布，与土钉支护相似。水平位移最大值发生在基坑顶面，随深度的增加逐渐减小；地表沉降最大值发生在坑壁处，随离坑壁距离的增大而减小。 (2) 锚杆在自由段范围内轴力相同，随开挖深度加深，自由段轴力增加；锚杆锚固段的轴力与自由段相连处轴力最大，其后轴力逐渐减小，末端为零。 (3) 锚杆所施加的预应力大小对基坑位移影响很大。随着锚杆预应力的增加，基坑位移大幅度减小，但当预应力施加到一定大值之后，对基坑位移的影响幅度较小。 (4) 在相同条件下，即使土钉间距变小，土钉支护下的基坑位移比预应力锚杆支护下的位移都大，可见对于变形要求严格的基坑，预应力锚杆支护由于施加了预应力比土钉支护能更有效控制基坑位移。 (5) 通过对预应力锚杆支护的结构参数进行变化研究，建议锚杆的布置方式将上下各排锚杆取成等长，或将顶部锚杆做的长些等一些定性规律。 (6) 通过对工程实例的计算分析，验证了模型建立的合理性以及采用预应力锚杆支护深基坑的可行性。更多还原

【Abstract】 The prestressed anchor flexible retaining method is a new kind of excavation support technology. It has been widely applied in the practical engineering of China because of their advantages, such as less investment, safety, convenient in construction, small displacement and applicable to super-deep excavation compared with other retaining methods. In this paper, the prestressed anchor flexible retaining method is numerically analyzed using nonlinear finite element to provide some scientific basis for its broad application.At first, a finite element method is used for the numerically analysis of prestressed anchor flexible retaining. The mechanics of its performance are studied by researching the deformation of excavation, the force of anchor and the distribution of axial force. Secondly, the effects of deformation of excavation and the internal force are analyzed through the comparison with soil nailing, which indicates the mechanics of the support more deeply. Thirdly, by studying the effects of the structural parameter of the prestressed anchor flexible retaining, attentions are paid to the problems, such as different anchor length, anchor space, shoring obliquity and surface thickness. The effects of these factors on the deflection of excavation and internal force of anchor are considered. Finally, the project is studied by the finite element analysis method and the calculated results are compared with the measured results. Some significant conclusions are remarked as follows:(l)The horizontal displacement and vertical displacement of excavation show curve distribution under retaining of the system, which is conform to the soil nailing. The maximum horizontal displacement occurs on the top of excavation and horizontal displacement decreases along the depth. The maximum vertical displacement occurs in the side of excavation and vertical displacement decreases with departing the side of excavation.(2)The axial forces of anchor are same in the free part. The axial force of the free part in anchor is increased with the along depth. The maximum anchor axial force occurs in coterminous with the free part and at fixed part of anchor. Then, the axial force is gradually decreases and the end becomes zero.(3)The anchor prestress influences displacement of excavation greatly. The displacement of excavation decreases with the increasing of anchor prestress. However, when the anchor prestress reach a big value, its influences is small.(4)At the same condition, even if the space of soil nailing decreases, the displacement is bigger than the anchor retaining. So the prestressed anchor flexible retaining method can control deformation more effectively at the strict deformation requisition.(5)By studying the effects of the structural parameters of the prestressed anchor flexible retaining, it is proposed that the anchor should be the same length, or in the upper should be longer.(6)By calculating and analyzing the engineering project, the correctness of model and the feasibility of retaining method using the prestressed anchor in the depth excavation are verified.更多还原