Calculating And Design Method And Their Applications Of Stabilizing Piles With Pre-stressed Anchor Cables In Landslides Remediation Works

The technique of stabilizing piles with pre-stressed anchor cables is an effective measure in landslides remediation works, which nowadays has a wide applications in the fields of infrastructure such as transportation construction projects and geo-hazard control in the reservoir areas of the Three Gorges Project, China. However, the design and calculating method of it need more attention and urgent research works. Stabilizing piles with pre-stressed anchor cables are the development on the basis of stabilizing piles. Comparing to stabilizing piles, they make the state of the forces on piles more reasonable. In landslides remediation works, the mechanical model of traditional stabilizing piles are more like cantilever beams, which makes the calculated bending moments and shearing forces of piles very high, thus the size of the piles bodies are considerably large. However, the pre-stressed anchor cables on the upper part of the piles make the whole stabilizing system like freely supported beams or some other hyperstatic structures. With the number of restraints increasing, it makes much easier to control the displacement of the piles and to reduce the bending moments and shearing forces along the piles to a certain extent.In this paper, from the basis of the geological and physical model of this landslide stabilizing system, the mechanical and mathematical model of piles with pre-stressed anchor cables have been set up, which establishes the foundation of the calculation for the structure design of the system. The analytical and numerical solutions of the established mathematical model have been achieved. In the whole paper, two-parameter method is employed to calculate the coefficient of subgrade reaction or subgrade modulus. The two models of rigid and elastic piles have been discussed respectively, in which the anchor cable will be regarded as an elastic hinge. Under the consideration of deformation harmony of anchor cable with piles bodies and pile bottom conditions, the solutions of the internal forces distribution along piles bodies are presented. Calculating method of landslides drive force, and determination of the diameters of borehole and anchor cable, the number of the anchor cables, the anchorage length and types of the anchor head as well are also discussed. A case study in the reservoir areas of the Three Gorges Project is presented at the last part of the paper, in which the application of this technique in landslides remediation works is analyzed and discussed in details. Some conclusions are obtained as follows:1. Elastic or rigid pile model of the studied structure is however a relative concept. When elastic pile model is employed, the depth of the piles embedded in the slide bed is relatively large, whereas the dimensions of the pile body are relatively small. Nevertheless, if rigid pile model is employed, the situation is reverse. Which one is better is not easy to determine. In applications, the two models can be employed in the calculations respectively for the same case. Then, the better one will stick up after havingtaken technological and economical factors into sufficient considerations.2. Various distribution models of the coefficient of subgrade reaction can be considered after the two-parameter method is employed. The commonly used "K" method, "m" method, and "c" method can easily be obtained from it. Thus, the solutions of the internal force along the studied stabilizing piles have more ordinary representation by the two-parameter method. However, the situation will become more complex, especially, how to determine the parameters of " m " and " 1 / n " reasonably is absolutely difficult.3. In applications, the structure of stabilizing piles with pre-stressed anchor cables can be associated with retaining wall, combined bolting and shotcrete, precast concrete lagging (plain, troughlike, archlike shapes), and so on, which enlarge the application areas of this structure.4. To prevent anchor cables from erosion is vital to make sure the studied structu...