Design And Program Development Of Anti-slide Pile With Pre-stressed Anchored Cables Based On Pile-anchor's Cooperation

Anti-slide pile with pre-stressed anchor cables is a new pattern of structure to controllinglandslide, which has widely used in many fields of engineering practice. However, the study onaction mechanism of anti-slide pile with pre-stressed anchor cables is still in the stage of exploration,for the complexity of the interaction of pile-anchor system and landslide body. It still exist someproblems in mechanical calculated model and design method of anti-slide pile with pre-stressedanchor cables, and the correlative design code is faultiness now.Firstly, the paper analyzed and summarized the research results of the interaction among piles,anchor cables and landslide, and gave a deep research and discussion aimed at the existing mainproblems: coordinated deformation and stress between piles and cables, in mechanical calculatedmodel of anti-slide pile with pre-stressed anchor cables, which's reasonable mechanical calculatedmodel has been established here. Secondly, the design and calculation theory of anti-slide pile withpre-stressed anchor cables have been studied, and the relatively mature research results of thedesign and calculation theory of anti-slide pile were referenced, to solve the new mechanicalcalculated model of anti-slide pile with pre-stressed anchor cables which added the coordinatedconditions about deformation and stress, especially the calculation of pre-stressed force value orforce value of anchor cables. Thirdly, a computer program about the design and calculation ofanti-slide pile with pre-stressed anchor cables is developed by language Visual B, which realizedthe ordinary methods for design and calculating anti-slide pile or anti-slide pile with pre-stressedanchor cables, and the graph about pile's internal forces and deformation are obtained automatic atthe same time. Finally, for the change of pile-cables' work condition, the design idea of takenmulti-engineering processes into account is necessary and rational, which is explained in specificengineering example, and the problem of optimal design for pile-anchor composite structure wasdiscussed: what is the pre-stressed force value or force value of anchor cables, while the pile-anchorcomposite structure obtained the best effect?On the basis of summarizing and analyzing the predecessor's achievements, this paper did some exploring study on pile-anchor's co-operation, and developed a program to design andcalculating anti-slide pile with pre-stressed anchor cables in different boundary conditions withsome ordinary methods. The conclusion can be described as followers:1. Pile-anchor's coordinate deformation conditions were studied and three of that conditionsproposed in some literatures were analyzed, and some problems existed in which were pointed out,based on the interaction analysis theory between pile and anchors. An improved pile-anchor'scoordinate deformation condition was put forward, taken the pile-anchor's practical working statusinto account: the pile body's deformation occurred already in the phase of pre-stress applied. Theimproved pile-anchor's coordinate deformation condition can obtain satisfying cable stress value,which is proper and safe, and accorded to pile-anchor's practical stress status.2. In the phase of cables' pre-stress applied, it must be give a extrusion action on the soilbehind pile through the pile, and change the distribution rule of the soil stress on the pile. By theanalysis of the influence of pre-reinforce effect to mechanical calculated model of anti-slide pilewith pre-stressed anchor cables, and on the basis of physical content of landslide thrust, twoconclusions proposed as follows:â‘ . The soil behind the pile is effect by pre-reinforce indeed, but the value of landslide thrustbehind the pile isn't decreased yet. The action of pre-reinforce, is only limiting the deformation ofpile body while pre-stress applied, and it has little influence on mechanical calculated model whilethe pile body's deformation stabilization, so the landslide thrust could not decreased.â‘¡. The problem ofpre-reinforce power's solution is actually the problem of interaction modelbetween pile and soil behind the pile, is also the problem of cables' pre-stress bear both by pile andsoil, and has direct relation to the solution of pile body's deformation in the phase of pre-stressapplied. It must satisfy the assumption that the pile's deformation is minus in this working phase,when calculating pre-reinforce power by the foundation coefficient method of whole pile, that is toassume the pile moves direct to the soil body behind the pile.3. Aiming at the existing problems in mechanical calculated model of anti-slide pile withpre-stressed anchor cables, an improved mechanical calculated model for landslide controlling wasproposed on the basis of pile-anchor's cooperation. This model adopt not only the improvedpile-anchor's coordinate deformation condition, but also the pile-anchor's coordinate stresscondition which was put forward by this paper. In the improved mechanical calculated model, pileand anchored cables assume the design value of landslide thrust together, its physical meaning isclear. The cables exert sliding resistance immediately, as well as throw pull on pile in order torestrict the pile's deformation.4. This paper gave the solution of mechanical calculated model of cantilever beam separately,including elastic pile and rigid pile, on the basis of traditional method for anti-slide pile' design andcomputing, aimed at the improved mechanical calculated model of anti-slide pile with pre-stressedanchor cables. The calculation expressions of cable force or cable pre-stressed force were deducedthrough two ways: cable force determined by cable pre-stressed force, cable pre-stressed force determined by cable force.5. The design and calculation of anti-slide pile with pre-stressed anchor cables related to largenumbers of formula, it's very complex by look-up table or handwork, so it will be an inevitabletendency. For the study's needs, the author developed a program for the design and calculation ofanti-slide pile with pre-stressed anchor cables. The program contains some related ordinarycalculating methods and the solution of the new improved mechanical calculated model, in which,the pile's internal force and deformation are computed by two methods: finite difference and matrixanalysis. The program can also make the graphs of pile's internal force and deformation automatic,and make the distributed steel calculation of pile body and the structure design of anchored cables,and estimate the cost of single anti-slide pile with pre-stressed anchor cables, which can be aneconomic index used convenient in the optimal design of anti-slide pile with pre-stressed anchorcables. The program includes three independent modules, which suited some boundary conditionsas follows: the load acted on pile presented as triangular, rectangular or trapezoidal distributing style;the top of the pile has bending moment and shear or none; the bottom of the pile is free, twist or fix;the foundation coefficient distributed as rectangular or trapezoidal ("m", "k" method); the pile'ssection is the same with multi-anchored cables while the pile model is cantilever beam. Theprogram is trustiness through validation by some calculating examples.6. By designing and calculating the anti-slide pile with pre-stressed anchor cables in a detailengineering example, using the program described above, the improved mechanical calculatedmodel is applied and analyzed, and proved to be validated. It also explained the necessity andrationality taking multi-engineering processes into account while designing the anti-slide pile withpre-stressed anchor cables. In order to illuminate the differences between this improved model andothers, three calculating models are employed in this engineering example, and the results showthat the improved model reduced the design value of pile and cables' beating capacity greatly,because of considering the pile-anchor's coordinate stress condition, thus deduced the costeffectively, and advanced the design level.7. A discussion about the optimal design of pile-anchor composite structure carried, from theaspect of the determination of cable pre-stressed value and cable stress value, and a conclusion wasobtained: the engineering of piles with anchored cables is mainly engineering of piles, while themaximum positive and negative bending moment are equal, the pile bears proper force, and it costthe least, at the same time the piles with anchored cables' engineering cost is the least.