【作者】 周磊；

【导师】 赵明华；

【作者基本信息】 湖南大学 ， 岩土工程， 2010， 硕士

【摘要】 随着我国交通事业的迅猛发展,桩基础在公路桥梁中应用日益广泛。较多的桩基使用在岩溶区地基,我国岩溶分布广泛,当桩基础穿越该类地区时,由于存在下伏溶洞等工程隐患,使得桩基对竖向变形极为敏感,一旦出现过量变形,将直接影响桩端岩溶顶板厚度的稳定性,情况严重则可能导致溶洞塌陷,对整个桥梁工程产生致命危害。为此,本文采用理论分析与数值模拟方法,对岩溶区嵌岩桩承载机理及设计方法进行探讨,主要研究工作如下：首先,针对岩溶区嵌岩桩承载力和设计方法的特殊性,深入分析了岩溶区嵌岩桩在水平荷载和竖向荷载作用下的受力特性和承载机理,对嵌岩桩的荷载传递过程、桩侧阻力和桩端阻力的各种计算模式、破坏性状；同时探讨了岩溶区嵌岩桩桩端岩层的受力特性与破坏机理,为岩溶区嵌岩桩的合理设计与计算提供了基础。其次,引进Hoek-Brown强度理论,通过变换推导出能考虑岩体质量的岩体抗拉强度,同时考虑竖向应力的岩体抗剪强度公式,将其应用于基桩桩端下伏溶洞的岩层顶板的安全厚度确定中,得到了岩溶区嵌岩桩桩端溶洞顶板安全厚度确定新方法。再之,分析了岩溶区嵌岩桩的承载机理及侧阻端阻的传递规律,建立了桩侧桩周的荷载传递模型,在荷载传递理论的基础上,根据桩侧土(岩)与桩端岩层阻力的发挥程度,导得了桩顶沉降量与桩顶荷载之间的关系式,提出了按桩顶沉降控制岩溶区嵌岩桩竖向承载力计算方法。然后,应用数值模拟方法,深入分析影响岩溶区桩基下溶洞顶板稳定性的因素,对不同洞径条件下溶洞变形力学特性及顶板安全厚度的影响因素进行探讨,获得了场地溶洞顶板位移变化规律溶、洞洞周各点主应力变化规律、溶洞上覆岩层中沿竖向各点主应力变化规律。最后,结合实际工程,对岩溶区嵌岩桩的设计与计算进行了验证分析,结果表明了本文方法的合理性。更多还原

【Abstract】 Along with the transportation enterprise’s rapid development in our country, the pile foundation is applied in the highway bridge day by day widely. many pile foundations are used in the karst area region, our country karst are widely distribution, when the pile foundation passes through this kind of local zone, because has project hidden dangers and so on last ten days of the dog-day period limestone cave, causes the pile foundation to be extremely sensitive to the vertical distortion, once presents the excessive distortion, the immediate influence tip of pile karst roof thickness’s stability, the situation serious possibly causes the limestone cave collapse, which has tfatal harmed to the entire bridge building. Therefore, this article uses the theoretical analysis and numerical simulation method, pile load bearing mechanism and the design method to the karst area were carriedon the discussion, the main research work as follows:Firstly, inlaying the crag pile supporting capacity and the design method particularity in view of the karst area, analyzed the karst area to inlay the crag pile thoroughly in the horizontal load and under the vertical load function stress characteristic and the load bearing mechanism, to inlaid the crag pile the load transmission process, the pile side resistance and the tip of pile resistance each kind of computation pattern, the destruction character; Simultaneously discussed the karst area to inlay the crag pile tip of pile rock layer the stress characteristic and the failure mechanism, inlaid the crag pile for the karst area the reasonable design and the computation has provided the foundation.Nextly, introduced the Hoek-Brown theory of strength, infers through the transformation can consider that the rock mass quality the rock mass tensile strength, simultaneously considered the vertical stress the rock mass shearing strength formula, applies it in the foundation pile tip of pile last ten days of the dog-day period limestone cave rock layer roof security thickness determination, obtained the karst area to inlay the crag pile tip of pile limestone cave roof security thickness to determine the new method. it, analyzed the karst area to inlay the crag pile again the load bearing mechanism and the side anti- end anti- transmission rule, has established the pile side pile week load transmission model, in the load transmission theory’s foundation, according to the pile side earth (crag) with the tip of pile rock layer resistance’s display degree, led between the head of pile subsidence quantity and the head of pile load relationship, proposed inlaid the crag pile vertical supporting capacity computational method according to the head of pile subsidence control karst area.Then, the application numerical simulation method, analyzes under thoroughly the influence karst area pile foundation the limestone cave roof stable factor, the limestone cave distortion mechanics characteristic and the roof security thickness’s influencing factor carries on the discussion to the different hole diameter condition, obtained the location limestone cave roof displacement change rule to dissolve, hole hole the principal stress change rule, in the limestone cave overburden along the vertical each principal stress change rule.Finally, the union actual project, inlaid the crag pile to the karst area the design and the computation has carried on the confirmation analysis, which has indicated the method rationality更多还原