岩溶区穿越溶洞桩基极限承载力及破坏模式试验研究  

Experimental study on ultimate bearing capacity and failure mode of pile foundation crossing karst cave in karst areas

作　　者：雷勇[1] 李鹏甲 刘泽宇[1] 李金朝 胡伟[1] 陈俐光 刘运思[1] LEI Yong;LI Pengjia;LIU Zeyu;LI Jinzhao;HU Wei;CHEN Liguang;LIU Yunsi(Hunan Provincial Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring,Hunan University of Science and Technology,411201 Xiangtan,China;China Construction Municipal Engineering Corporation Limited,100071 Beijing,China)

机构地区：[1]湖南科技大学岩土工程稳定控制与健康监测湖南省重点实验室,湘潭411201 [2]中建市政工程有限公司,北京100071

出　　处：《应用力学学报》2023年第6期1343-1353,共11页Chinese Journal of Applied Mechanics

基　　金：国家自然科学基金资助项目(No.51878270,52178332);湖南省自然科学基金资助项目(No.2022JJ30253)。

摘　　要：针对岩溶区穿越溶洞桩基承载机理及破坏模式相关问题,开展了穿越溶洞桩基极限承载力及破坏模式室内模型试验,揭示了桩基极限承载力随溶洞高度变化的规律,并将不同高度溶洞下桩基和溶洞顶板的破坏模式进行了分类。根据试验结果给出了穿越不同洞高溶洞桩基的桩身稳定系数Φ。最后对穿越不同洞高溶洞桩基极限状态下端阻分担比及穿越洞高为10d时桩基承载过程中侧阻及端阻分担比的变化曲线进行了分析,结果表明:1)溶洞顶板抗弯能力不足时,若桩-岩界面侧摩阻力较大,且顶板与周围岩体整体性好时发生固支板受弯破坏,整体性差时发生简支板受弯破坏,桩-岩界面侧摩阻力小时,发生剪切破坏或剪切与冲切的组合破坏。2)穿越溶洞桩基发生屈曲的最小洞高为6d,穿越小洞高溶洞桩基在单轴抗压强度小于桩端及桩侧极限阻力时发生桩身材料受压破坏,反之发生桩端基岩破坏。穿越大洞高溶洞桩基在屈曲失稳承载力小于桩端及桩侧极限阻力时发生桩身屈曲失稳破坏,反之发生桩端基岩破坏,且随着洞高增加,桩基屈曲失稳承载力大致呈线性降低。3)穿越溶洞桩基极限承载力取决于桩身材料强度、溶洞高度、桩周岩体强度等多种因素,桩身材料受压破坏、桩基屈曲破坏、桩端基岩破坏3者极限承载力中的最小值即为穿越溶洞桩基极限承载力。4)极限状态下,穿越溶洞桩基端阻分担比随洞高增大而减小,但减小幅度较小;穿越溶洞桩基桩顶荷载越大,端阻分担比越大,侧阻分担比越小。Aiming at the bearing mechanism and failure mode of the pile foundation passing through karst caves,laboratory model tests of ultimate bearing capacity and failure mode of pile foundation passing through karst caves were carried out to reveal the law of ultimate bearing capacity of pile foundation varying with the height of karst caves,and the failure modes of pile foundation and cave roof were classified when pile foundation passing through different cavern heights.According to the test results,the stability coefficient Φ of pile foundations passing through different high karst caves was given.Finally,the pile tip resistance ratio of pile foundation passing through cavern of different heights in the limit state was analyzed,and the ratios of pile side resistance and pile tip resistance in the bearing process of 10d cavern height test were analyzed.The results show that:1)When the bending resistance of the cave roof is insufficient,the lateral friction resistance of the pile-rock interface is large,and the integrity of the roof and surrounding rock mass is good,the flexural failure of fixed plate occurs;when the integrity is poor,the flexural failure of the simple-supported plate occurs;when the lateral friction resistance of the pile-rock interface is small,the shear failure or the combined failure of shear and punching occurs.2)The minimum cave height of pile foundation buckling is 6d.When the uniaxial compressive strength of pile foundation is less than the ultimate resistance of pile tip and pile side,the pile material compression failure occurs in the pile foundation passing through small cavern;otherwise,the bedrock of pile tip will be damaged.When the buckling bearing capacity of pile foundation is less than the ultimate resistance of pile tip and pile side,the pile body buckling failure occurs in the pile foundation passing through large cavern,and the bedrock of pile tip will be damaged otherwise,and the buckling bearing capacity of pile foundation decreases linearly with the increase of cavern height.3

关 键 词：试验研究 岩溶桩基 极限承载力 破坏模式 穿越溶洞 

分 类 号：TU473[建筑科学—结构工程]