The suction caisson foundation has become one of the important forms of offshore wind turbine foundation due to its wide range of application, simple installation and reusability. In this paper, combined with the engineering application of the offshore wind turbine supported by composite caisson foundation（multi-cabin suction caisson） in Rudong, Jiangsu, the finite element software COMSOL Multiphysics was used to establish a suction installation numerical model based on the linear elastic soil model. By studying the characteristics of soil seepage during foundation installation, it is found that the soil inside the composite caisson is greatly affected by suction than that outside the caisson. Most of the water head loss occurs inside the caisson, showing that the seepage gradient inside the caisson is significantly greater than that outside the caisson. Therefore, the skirt wall friction is less than jack installation. The pore water pressure around the skirt wall and the annular partition changes approximately linearly along the depth near the caisson lid. However, it shows obvious nonlinearity near the tip, where the pore water pressure is discontinuous. By comparing with the single caisson foundation of the same main size, it is found that the existence of the annular partition and the rib partition hinders the transmission of negative pressure inside the caisson to the outside. This weakens the effect of negative pressure on the pore water pressure outside the caisson, and inhibits the development of negative pressure to a deeper seabed.
圆形竖井支护结构的受力变形特性与一般基坑支护有着显著的差异.结合珠三角水资源配置工程中一超深圆形竖井支护的计算分析,讨论类似问题的有限元法及增量法计算模型及计算方法,并将计算结果与现场实测进行对比,研究此类问题计算模型构建时需考虑的因素,及圆形竖井的变形特性.计算对比表明,无论采用有限元法还是增量法,适当选取计算模型参数,对此问题均可给出较为符合实际的计算结果.圆形地连墙加逆作内衬的支撑方式,可以有力发挥支护墙体的环向支撑作用,特别是在小径深比情况下.墙体内的环向内力主要是轴压力,而竖向内力主要是在地连墙的嵌岩部位发生外侧受拉的较大弯矩,而在此部位上方一定范围发生内侧受拉的较大弯矩.
地铁是城市公共交通的重要组成部分.随着我国各大城市地铁的快速发展,需要快速准确地对长程隧道结构病害进行检测以确保地铁安全运营.本文介绍了一种基于裂缝综合检测仪和探地雷达系统的无损检测技术,对地铁隧道管片结构的裂缝宽度和深度进行检测,并探测其内部结构损伤情况.实际工程案例分析结果表明,与传统检测方式相比,无损检测技术具有检测速度快、检测准确度高、无需破坏结构本体等优点,能有效保障地铁隧道的结构安全和运营安全.
紧邻既有地铁设施的深基坑工程在基坑开挖过程中,可能由于土体的卸荷作用而引起周边土体位移,进而带动地铁设施产生变形.本文以杭州地铁16号线八百里站C号、D号出入口旁侧某房地产开发项目地下室基坑工程为例,通过有限元数值分析软件建立二维、三维模型,针对基坑开挖对邻近既有地铁天桥及出入口的影响进行数值模拟分析,预测基坑变形,分析基坑开挖过程中邻近既有地铁天桥与出入口的位移响应,重点分析基坑开挖至坑底及拆换撑工况下地铁设施的位移场,并总结主要测项的变化规律,进行变形趋势分析.数值模拟计算结果与地铁变形监测数据表明,基坑施工对地铁设施的影响较小,满足轨道交通结构变形控制值要求.
With the continuous expansion of urban construction in terms of scope and scale,more and more large thickness miscellaneous fill sites are encountered.The treatment of thick and miscellaneous fill soil foundation is pivotal in engineering construction.Neglecting appropriate treatment may result in uneven settlement of the building foundation in later stages,thereby posing a threat to the structural integrity of building.This work takes a project in Xi'an as an example to analyze and evaluate the application of the combination of Super Down Hole Dynamic Consolidation(SDDC)and cast-in-place piles in the construction of high-rise buildings on thick fill sites.The thickness of miscellaneous fill under the studied building foundation is 7.5 m,and the undisturbed loess layer under the miscellaneous fill has collapsibility.In the application of SDDC,the impact drilling process is employed.At the overlapping point with the cast-in-place pile,plain soil serves as the filling material,while miscellaneous soil is used at other locations.Following the implementation of the SDDC and cast-in-place pile combination for foundation treatment and subsequent foundation testing and building settlement observations,the results show that this foundation scheme significantly enhances the compaction of miscellaneous fill soil,eradicates loess collapsibility,meets the bearing capacity requirements of cast-in-place piles,and reduces building settlement.The successful application of the SDDC and cast-in-place pile combination at this site can serve as a valuable reference for similar engineering construction projects.
