岩溶区桥梁桩基承载机理及试验研究
发布时间：2019-03-23 17:07
【摘要】：随着我国西部建设的高速发展，公路、桥梁、港口码头等实际工程建设中会更多地遇到岩溶地质条件。因此岩溶区基桩与溶洞相互作用关系、基桩嵌入溶洞顶板的深度、溶洞顶板的稳定性以及最小安全厚度等问题成为岩溶区桥梁桩基研究的热点。由于岩溶地质条件的复杂性与不确定性使得岩溶区桩基的研究尤为困难。本文在已有研究的基础之上，结合国家自然科学基金项目“岩溶区基桩竖向承载机理及其设计计算方法研究”（项目编号：51278187）对岩溶区桩基及溶洞顶板做了如下研究工作： 本文首先对岩溶区桩基已有的研究做了简要的概括，继而基于普通嵌岩桩的桩端荷载传递机理，结合岩溶区基桩与溶洞顶板相互作用的特点，假定出不同顶板厚度情况下桩端荷载传递方程，并通过室内大比例尺模型试验进行验证。考虑基桩嵌岩段岩石性质的差异性，分别提出了软岩与硬岩条件下嵌岩深度计算模型并推导出了最小嵌岩深度解析解。通过某室内试验以及某现场工程实例对本文方法进行对比验证，并对影响嵌岩深度的计算参数进行了参数分析。 为深入研究岩溶区桥梁桩基竖向承载机理与溶洞顶板破坏模式，基于相似定理设计出岩溶区基桩与顶板作用大比例尺室内模型试验，通过多组配合比试验确定顶板模拟材料，根据溶洞顶板厚度的不同分别设计了四组大比例尺室内模型试验。对厚度分别为0.5d、1d、2d以及3d的溶洞顶板进行竖向加载，获得了不同顶板厚度条件下基桩荷载传递规律、溶洞顶板荷载位移曲线以及顶板的破坏形式，最后对试验现象以及试验数据进行了理论分析。采用FLAC3D有限差分软件模拟室内模型试验，并将桩顶位移以及实际顶板破坏形式与有限差分模拟结果进行对比分析，，从而进行相互验证。针对室内模型试验没有考虑溶洞顶板厚跨比变化对于顶板竖向承载影响的不足，最后利用FLAC3D数值模拟软件对于不同厚跨比的溶洞顶板进行数值模拟分析，以期获得厚跨比变化对于溶洞顶板竖向承载影响的变化规律，从而对室内模型试验做进一步的补充。
[Abstract]:With the rapid development of the construction of the western part of China, more karst geological conditions will be encountered in the construction of highway, bridge, port and wharf. Therefore, the interaction between pile and karst cave in karst area, the depth of pile embedding into karst cave roof, the stability of karst cave roof and the minimum safety thickness have become the hot spots in the research of bridge pile foundation in karst area. Because of the complexity and uncertainty of karst geological conditions, the study of pile foundation in karst area is especially difficult. On the basis of the existing research, Combined with the project of National Natural Science Foundation of China, "Research on Vertical bearing Mechanism and Design calculation method of pile Foundation in Karst area" (Project No.: 51278187), the research work on pile foundation and karst cave roof in karst area has been done as follows: first of all, this paper has done the following research work: The existing research on pile foundation in karst area is briefly summarized. Then, based on the load transfer mechanism of common rock socketed pile, combined with the characteristics of interaction between pile and karst cave roof in karst area, the load transfer equation of pile tip under different roof thickness is assumed. And through the indoor large-scale model test to verify. Considering the difference of rock properties of rock-socketed section of pile, the calculation models of rock-socketed depth in soft rock and hard rock are put forward, and the analytical solution of minimum rock-socketed depth is deduced. Through a laboratory test and a field engineering example, the method is compared and verified, and the parameters affecting the depth of rock socketed are analyzed. In order to deeply study the vertical bearing mechanism of bridge pile foundation in karst area and the failure mode of karst cave roof, a large scale indoor model test of the interaction between pile and roof in karst area was designed based on the similarity theorem, and the roof simulation material was determined by multi-group mix ratio test. Four groups of large scale indoor model tests were designed according to the different thickness of cave roof. When the roof thickness is 0.5 d, 1 d, 2 d and 3 d respectively, the load transfer law of foundation pile, the load displacement curve of karst cave roof and the failure form of roof are obtained under the condition of different roof thickness, and the vertical loading is carried out on the roof of karst cave under the condition of different roof thickness. Finally, the experimental phenomena and experimental data are analyzed theoretically. The FLAC3D finite difference software is used to simulate the indoor model test, and the pile top displacement and the actual roof failure form are compared and analyzed with the finite difference simulation results, so as to verify each other. In view of the inadequacy of indoor model test which does not consider the influence of roof thickness-span ratio change on the vertical bearing capacity of the roof, the numerical simulation analysis of the karst cave roof with different thickness-span ratio is carried out by using FLAC3D numerical simulation software. In order to obtain the variation rule of the influence of the ratio of thickness to span on the vertical bearing capacity of the roof of the karst cave, further supplement to the indoor model test is made.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U443.15
本文编号：2446056
[Abstract]:With the rapid development of the construction of the western part of China, more karst geological conditions will be encountered in the construction of highway, bridge, port and wharf. Therefore, the interaction between pile and karst cave in karst area, the depth of pile embedding into karst cave roof, the stability of karst cave roof and the minimum safety thickness have become the hot spots in the research of bridge pile foundation in karst area. Because of the complexity and uncertainty of karst geological conditions, the study of pile foundation in karst area is especially difficult. On the basis of the existing research, Combined with the project of National Natural Science Foundation of China, "Research on Vertical bearing Mechanism and Design calculation method of pile Foundation in Karst area" (Project No.: 51278187), the research work on pile foundation and karst cave roof in karst area has been done as follows: first of all, this paper has done the following research work: The existing research on pile foundation in karst area is briefly summarized. Then, based on the load transfer mechanism of common rock socketed pile, combined with the characteristics of interaction between pile and karst cave roof in karst area, the load transfer equation of pile tip under different roof thickness is assumed. And through the indoor large-scale model test to verify. Considering the difference of rock properties of rock-socketed section of pile, the calculation models of rock-socketed depth in soft rock and hard rock are put forward, and the analytical solution of minimum rock-socketed depth is deduced. Through a laboratory test and a field engineering example, the method is compared and verified, and the parameters affecting the depth of rock socketed are analyzed. In order to deeply study the vertical bearing mechanism of bridge pile foundation in karst area and the failure mode of karst cave roof, a large scale indoor model test of the interaction between pile and roof in karst area was designed based on the similarity theorem, and the roof simulation material was determined by multi-group mix ratio test. Four groups of large scale indoor model tests were designed according to the different thickness of cave roof. When the roof thickness is 0.5 d, 1 d, 2 d and 3 d respectively, the load transfer law of foundation pile, the load displacement curve of karst cave roof and the failure form of roof are obtained under the condition of different roof thickness, and the vertical loading is carried out on the roof of karst cave under the condition of different roof thickness. Finally, the experimental phenomena and experimental data are analyzed theoretically. The FLAC3D finite difference software is used to simulate the indoor model test, and the pile top displacement and the actual roof failure form are compared and analyzed with the finite difference simulation results, so as to verify each other. In view of the inadequacy of indoor model test which does not consider the influence of roof thickness-span ratio change on the vertical bearing capacity of the roof, the numerical simulation analysis of the karst cave roof with different thickness-span ratio is carried out by using FLAC3D numerical simulation software. In order to obtain the variation rule of the influence of the ratio of thickness to span on the vertical bearing capacity of the roof of the karst cave, further supplement to the indoor model test is made.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U443.15
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