Research On Loading Characteristics Of Large Cross Section Pile Foundation In Soft Rock

In the characteristics of the modern pile foundation, there is a trend that the pile length is getting deeper and deeper and that the diameter is getting longer and longer. With the acceleration of Western Development, the mountain railways, highways and other infrastructure facilities are pushed forward. But with their linear limit, the mountain railways and highways inevitably meet with many obstacles, and mostly pass them through the large bridges or long tunnels. For bridges, the safety and reliability of the foundation are particular important. The load-bearing features of big cross-section pile foundation are different from those of general small pile foundation. There is also a disagreement between completely rock-socketed pile and general rock-socketed pile Therefore, the analysis based on conventional theory of big cross-section pile and completely rock-socketed pile will probably lead to different results. For example, it could be hard to be premised on the assumption of big cross-section pile, m method used for calculating the lateral bearing is likely to make errors. The major task of this research is to make clear how to analyze big cross-section pile foundation, to find out and make good use of its advantageous side, then to find its downside on which we can take effective measures.Due to the underestimation of the load-bearing features that big cross-section pile foundation has in soft rock foundation, the designer can’t determine whether or not its design basis is safe and reliable. With regard to such an engineering problem, the author of this paper takes the giant arch foundation of Yelang River Bridge for example. On the basis of site investigation, the author analyzes the load-bearing features of individual big cross-section pile foundation by integrating its geological environment and rock mass structure. The analysis will be applied to the real project in the hope of solving the existing problems. In this paper, the FLAC3D software simulation is implemented and on the whole, the results show the agreement between simulation and the research findings. In the final section of the paper, the author puts forward some improvement measures and suggestions in view of the problem.From this study the author found that when the rock-socketed pile foundation bears load in weathered soft rock foundation, its side resistance still functions very well. The exertion level is closely related to the pile lateral lithological conditions. The main area of internal force and pile deformation is more concentrated than that of small pile foundations. It focuses mainly on the small upper part of pile foundation, while at the bottom end, the build-in effect is more apparent. This results in not only greater deformation but also higher stress level of the upper foundation and subgrade. In this way, rational improvement in the upper area of foundation becomes the key to the problem-solving. This foundation belongs to completely rock-socketed piles. In terms of load bearing, due to the better stimulation of lateral resistance, it seems uneconomic to rely too much on the end resistance. However, since the effect of lateral resistance is impacted by various factors, it is one of the major research points in this paper to reasonably determine socketed depth and to bring side resistance and end resistance into full play in load bearing. The core issue of this work is to control the deformation and internal force within safe scope by means of load analysis of the big cross-section pile, to optimize the design, and to maximize the bearing capacity of the pile foundation so as to satisfy the engineering requirement. The solution to this issue acts as a practical reference to similar load-bearing features of big individual cross-section pile or soft rock subgrade.