Prestressed Anchor Flexible Methods Of Numerical Analysis

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.