Numerical Analysis And Model Test Research On The Reinforcement Mechanism Of Underground Opening Supported By Prestressed Anchor Cables

Prestressed anchoring techniques has become a widely used techniques and made great achievements in geotechnical engineering at home and abroad. Except that some special projects need special anchor cables, the two types of non-bonded prestressed anchor cable and fully grouted anchor cable are most widely used in underground opening engineering and slope engineering at present. In spite of being widely used, some problems are urgent to research on the reinforcement mechanism and design method of prestressed anchor cable. There is no uniform view on the reinforcement mechanism and the engineering-analogic design methods is mostly used in many engineerings. Based on the research of predecessors, the reinforcement effect and mechanism of above two types of prestressed anchor cable for underground opening are deeply studied by geomechanical model tests and numerical modelling method and some achievements have been made in this paper.In this paper, the prestessed anchoring theory is deepened and some significative ideas are put forward. The main contents are concretely as follows:(1) The different anchoring schemes (e.g. two anchor cable types: non-bonded prestressed anchor cable and fully grouted anchor cable; pre-tensioning with big or small tension) are studied by geomechanical model tests. The construction method of "anchoring while excavation" for underground opening is simulated and the difficult problems of simulating technology for underground opening excavation and prestressed anchor cable have been overcome in geomechanical model experiments.(2) Based on the experiment results, it is analyzed that the reinforcement effect of underground opening supported by anchor cable have been influenced by anchor cable types, pre-tension magnitude, etc. The macroscopical failure phenomena of underground opening, the fracture shapes of enclosing rock, the displacement characteristics of rock wall, the strain distribution shapes of enclosing rock and the variation of tension in anchor cable during the underground opening excavation and overloading are given. Some results, such as the tension in above two type cables is generally decreased and the average range is about 15-22% during the underground opening excavation, the relative decrease magnitude of tension in anchor cable is nearly inverse proportion to the initial tension magnitude and the variation of the tension decrease in magnitude of each anchor cable in different place obviously showed with randomness, are helpful to understand the reinforcement mechanism of underground opening supported by anchor cable, to put forward and perfect the...