【作者】 单联君；

【导师】 赵明华；

【作者基本信息】 湖南大学 ， 岩土工程， 2005， 硕士

【摘要】 嵌岩桩是我国桥梁、港口及建筑工程中采用较多的基础型式之一,如何合理确定嵌岩桩的竖向承载力一直是工程界所关注的重要问题之一。本文考虑三维应力状态下岩石的强度特性,对嵌岩桩的承载机理及竖向承载力的确定方法进行深入系统地研究,具有重要的理论与工程实际意义。 本文首先深入探讨了嵌岩桩的承载机理,通过对桩侧阻力和桩端阻力的各种计算模式及其影响因素的分析,对现行各种确定嵌岩桩竖向承载力的方法进行了深入分析,在此基础上,针对现行各方法不计桩端岩层应力分布或岩层厚度的缺陷,采用铁摩辛柯弹性理论导得了岩层顶板应力分布,再结合源于岩石三维应力本构模型的修正Drucker-Prager强度准则,提出一种确定嵌岩桩竖向承载力的新方法,其能考虑第二主应力和第三主应力对岩石强度的影响,并采用MATLAB编制出相应的计算程序,将其应用于潭邵高速公路某跨渠桥基嵌岩桩工程实例,计算结果表明,该方法切实可行,且能清楚地反映岩层顶板随荷载增大而逐步破坏的全过程。最后本文将桩端以下岩层划分为3种岩性、4种跨度、6种厚度共72种情况,用Marc有限元程序对每一种情况进行了弹塑性分析,采用岩层塑性区分布情况和桩端位移的双重标准来确定嵌岩桩竖向承载力,根据计算结果提出将岩层的破坏形态可划分为三类,和通常所定义的冲切破坏、剪切破坏和弯拉破坏相比更能反映岩层的破坏特征和过程。此外,对岩性、岩层跨度、岩层厚度三种因素对嵌岩桩竖向承载力的影响以及与岩层三类破坏之间的关系进行了一定的探讨,获得了一些定性的结论和规律。更多还原

【Abstract】 The rock-socketed piles are one of the most used foundations in constructions of bridges, ports and buildings in our country. How to rationally determine the vertical load-bearing capacity of rock-socketed piles is one of the most important questions in engineering. Considering the characters of the rock strength in three-dimension stress state, the load-bearing mechanics and the methods of determining the vertical load-bearing capacity of rock-socketed piles have been deeply system studied, that has important signification in theory and engineering.Firstly, through deeply discussing of the load-bearing mechanics of rock-socketed piles and every calculating mode and effecting factors of the side friction resistance and the end resistance of piles, the actual methods of determination the vertical load-bearing capacity of rock-socketed piles were analyzed. Aimed at the defect of the actual methods which do not consider the stress distributing in the rock mass at the end of rock-socketed pile or the thickness of the terrance, using Timoshenko elastic theory deduces the stress distributing in the rock mass. Combining with the modified Drucker-Prager failure criterion which derived from three-dimension stress rock constitutive model, a new method for determining the vertical load-bearing capacity of rock-socketed piles was put forward, which can consider the effect on the rock strength by the second principle stress and the third principle stress. Corresponding calculating program was compiled using MATLAB and applied to an engineering example of rock-socketed piles bridge foundation in Tan-Shao expressway. The result shows that this method was feasible and correct and can explicitly show the whole terrance failure process as the load added. Finally, the terrance at the end of the pile was sorted 72 classes including different three kind of rocks, different four kind of spans and different six kind of thicknesses. Every instance was elastic-plastic analyzed by Marc software, the vertical load-bearing capacity of rock-socketed piles was determined by double standards of the plastic area distribution and the displacement of the pile bottom. Base on calculating results, three terrance failure modes are put forward. Compared with the usual punching shear failure, shear failure and flexural failure, that can more clearly reflect the terrance failure characters and process. Furthermore, investigated the affections of the vertical load-bearing capacity of rock-socketed pile effected by the three factors of rock更多还原