Research On Calculation Method Of Elongation For Pre-stress Anchor

Prestressed anchor cable is a kind of driving rod inside the rock and soil body structure, through active prestressing, the stress transfer to the surrounding rock and soil reinforcement, to strengthen and limit deformation of rock and soil mass. Due to the characteristics of reinforcement, convenient and economic efficiency, anchor cable has been widely used in slope engineering, underground engineering, water conservancy project, the structure of anti floating engineering and municipal engineering etc..For the prestressing technology, effective prestress is the most important parameter, which has a direct impact on the safe and stable of reinforced structure, is the key of the prestressed concrete engineering. At present The double control method widely used in projects to monitor prestress, by means of measuring dynamometer or other ways in which the magnitude of the stress, the elongation of tensile stress in matrix, comparing the two in order to achieve the purpose of verification. Unfortunately, the calculation method of elongation has been rarely studied, the calculation formula providing by all kinds of specification is too simple, which is different from the actual situation. In this paper, the calculation method of prestressed anchor cable tensioning elongation is the research subject, the main work includes:①Taking the Mindlin problem as a model, analyze the tensile type anchor cable force characteristics, point out that the two interface bond stress distribution is not uniformity, and deduce the calculating formula of elongation and the anchoring and freedom junction of debonding length. Then analyze the mechanical characteristics of pressure type, point out that the bearing displacement effect on the elongation measurement, and its calculation formula is deduced.② According to the characteristics of distribution of prestressed anchor cable drilling hole trajectory is analyzed, discussed and compared centralized borehole said calculation method and drilling quality, selected projection graph representation and corrected average angle method as the representation method and the corresponding calculation method, laying a foundation for the research on the effect of the friction.③By the foundation of the work of the formers, I investigated the distribution of the stress on the interface of the anchor and the wall of the passage.④ Introduce the widely used tension technology at present, analyze the measurement error caused by the elongation step, point out some deficiencies of them, and put forward the intelligent tensioning technology to replace the traditional tensioning technology. Then according to the intelligent tensioning process realization, including intelligent tensioning process intelligent and tensioning process control is studied and designed.⑤Two slope anchorage engineering in fifth contract section of the Mengxin high way in Yunnan field test was conducted, to obtain some valuable data.