Study On Working Mechanism Of Prestressed Cables And Long-term Effectiveness Evaluation

With the speedly development of economy, the investment in the construction of variousWater conservancy and hydropower engineering, Anchor rope (rod) is one of the main measuresof geotechnical reinforcement,the stability problem of geotechnical engineering has been paidmore and more attention. Water conservancy and hydropower engineering which will behundreds of years or even more ancient in the designed and serviced life generally belong tolarge engineering,Whether anchorage structure can be normally used in designed life or not inwater conservancy and hydropower engineering, what is currently the engineeringproblems.Anchorage structure design calculation theory has been relatively mature, but in termsof its long-term effectiveness and stability safety evaluation of research work is relatively rare.Therefore, strengthen anchorage structure of long-term effectiveness studies is a very urgenttask.this paper is based on the mechanism of the prestressed anchor cable,studied ongeotechnical engineering(slope and underground caverns etc.) as research object, researched onthe long-term effectiveness of anchorage structure, in order to obtain more realistic calculationanalysis and the theory of safety evaluation, meet the needs of engineering practice, betterservice for the engineering construction.the main results and conclusions gained can beexpressed as follows.(1) The ideal elastic-plastic model of the anchoring bond shear stress non-uniform distribution isproposed the anchoring bond anchorage structure stress non-uniform distributioncharacteristics in the engineering practice. The general situations of prestressed anchor cableprestress loss includes two parts, one is caused by the springback deformation of anchorsystem, man-made factors such as construction and design after the anchor cable tensionlocked in a relatively short period of time; Another part is caused by the corrosive medium,the creep of grouting materials, rock mass around the anchorage segment and the cyclicloading in long-term loading. At the same time, the influence mechanism of the loss ofprestress is studied on the different influence factors.(2) Through monitoring analysis of the characteristics of the change on actual prestressedanchorage engineering of the anchor cable tension, long-term change rule of prestressedanchor cable anchorage engineering is revealed, periodic combination of the circulation oflarge amplitude, low frequency and tiny loop small amplitude, high frequency is verified, main characteristics on the tension of prestressed anchorage structure runtime changes isconstituted.(3) Anchoring structure durability are studied on the increase of load amplitude is verified, thefinal form of exponential decay cycles in cyclic loading test.(4) Through the indoor accelerating corrosion test and tensile test, the durability problem isstudied on specimens of the durability of prestressed anchorage structures of problemsubjected to corrosion medium.anchor bar was studied on time-varying of pH value, effectsof factors force level of prestressed reinforcement corrosion appearance, corrosion weightper unit length and mechanical performance losschanging with time. The relationshipbetween the unit length of corrosion and other factors is established and verified.(5) Finite element program for calculating the credible degree is compiled which is based on theimproved monte carlo method--joint realization of ABAQUS—MATLAB，and reliabilityof the circular tunnel of high strength prestressed anchor is calculated, analyzed andevaluated: Anchor solid failure probability is gradually increase with the growth of thesurrounding rock mass rheological time, decrease rapidly with the increase of prestresschange, and the value in failure of the anchoring body under different time is probabilityanalyzedon trend.