Study On Underreamed Ground Prestressed Bolt With Fabric Bag In Soft Clay Excavation Supporting

Different number of soft soil is distributed all over the country. Owing to soft soil has low intensity, high compression, high sensitivity, long period of consolidation and other characteristics, the ordinary anchor conducting retaining and protection of excavation does not achieve the uplift bearing capacity of design requirements, because of the hole wall collapsing easily, grouting poor controllability. Although there are already underreamed anchor appling to excavation of soft soil, but in terms of using and operation, or the economy, there are still many problems. There is practical significance to research and develop a simple, inexpensive underreamed anchor, suitable for excavation of soft soil. Therefore, in this paper fiber bag grouting underreamed prestressed anchor is studied using to excavation of soft soil, combined with the project research of retaining and protection of excavation of soft soil of my company. The following aspects are included for the main study contents:1) For the existing deficiency of underreamed anchor, considered from two respects of practicality and economy, fiber bag grouting anchor with the air permeability, water permeability is used in excavation of soft soil, underreamed anchor suitable for excavation of soft soil is developed. The structure and using method of fiber bag grouting underreamed anchor are introduced.2) Numerical simulation analysis is made on the fiber bag grouting underreamed anchor using FLAC3D software, in order to understand deformation distribution for fiber bag grouting underreamed anchor when be stressed, influence range and maximum bearing capacity that can be reached. Displacement distribution of surrounding soil is understanded when underreamed anchor is stressed, stress influence range of expansion body section of anchor is at about 5 times the diameter of the hole, stress influence range of non expansion body section of anchor is at about 10 times the diameter of the hole. The influence area expands unceasingly in expansion body section stress concentration zone, and the shape eventually develops into a "pear shaped" when the stress of anchor chieving limit. The advantages of high bearing capacity can be fully played for underreamed anchor, and the maximum capacity can be achieved to the ultimate bearing capacity of rod body of anchor.3)The construction process for fiber bag grouting underreamed anchor is sdudied in excavation of soft soil,and the "construction method of fiber bag grouting underreamed anchor" is compiled, the scene test of the project of Ji’nan riverside business center retaining and protection of excavation and Ji’nan third grain anti-floating anchor are made, the anchoring limit capacity of 11 fiber bag grouting underreamed anchor can be reached to 800～1000kN in the project of Ji’nan riverside business center retaining and protection of excavation, basically according to the simulation results. The pulling resistance limits of 3 high strength anchor are 791.36kN in the Ji’nan third grain, achieving the design requirements.