Study On Supporting Mechanism Of Prestressed Cable With Beam And Its Design & Calculation In High Slope Construction

Study on supporting mechanism of pre-stressed cable with beam frame and its design&calculation method are delayed greatly than their applications, and is being in urgent need of further improvement. Aiming to solve the problem, several aspects such as load transfer mechanism,design parameter and method,computation method of internal force for beam frame and prediction of pre-stress loss, are comprehensively studied by means of numerical simulation and theoretical analysis, combining with some in-situ testing and indoor testing data. The main research content and results are as follows:1) Through theoretical and numerical analysis, rules for prestress's transverse attenuation and interaction of anchorage part, are gotten. These rules can provide theoretical base for stipulation of anchorage spacing;2) There are two simulated mechanisms for cable with free part: one is that the grouted cable slip along the interface after the progressive failure of ambient rock because of the action of pull press, the other is that the rock fail under the anchor pier and lose bearing capacity;3) Based on load transfer principle,hypothesis upon interfacial constitutive law and different boundary condition, the P-S relationship of cable, which is well accordant with that gotten from numerical simulation,indoor or on-site pull-out test, is derived and analyzed. P-S curve from pull-out test is still approximately linear while part of the interface is in plastic state, and linear at the initial stage;4) To the shortcomings of present cable design methods, a new design method and its realization procedure are put forward after load transfer mechanism and computation method of design parameters are ascertained. In this method, the simple design parameter with better reliability can be obtained from on-site P-S curve and embody the syntheticalengineering condition, plastic-zone length near the interface can also be designated;5) As for disintegrated or loose slope, it may collapse if the anchorage spacing is excessively big even with shallow anchors in it. So, in this thesis, some control conditions are provided to calculate the "biggest critical anchorage spacing" between parallel and adjacent beams according to soil arch theory and the formula is got; 6) Through computational examples and comparative analyses based on theoretical analysis, several traditional methods for assessing the internal force of beam frame, are respectively examined and their suitability discussed. For the Winkle elastic foundation beam method, finite element computation model, which can consider the seperation and nonlinearity of p-y relationship between beam and slope by MARC's secondary development, are put up and utilized to analyze the influence factors of internal force. To study the effect of slope construction and beam position on internal force, Winkle beams were embedded into FEM model of a practical slope for numerical analysis and the gained result is that-internal force of beam may augment greatly with the proceeding of construction and be obviously affected by beam position;7) By referring to large amount of field test data and pertinent literatures, the general law of prestress loss after lock-off and its affecting factors are extensively analysed. Coupled by prestress change, a general Kelvin rheological model is established and incorporated into MARC to analyse the effect of rock rheology on prestress loss. Meanwhile, two forecast model named equal interval GM(1,1) model and non-equal interval GM(1,1) model, are presented and programmed according to grey system theory respectively. Suitability and reliability of the two models are explicitly demonstrated by computational examples.