黄明, 张冰淇, 陈福全, 黄治璟, 张旭东. 2017: 串珠状溶洞地层中桩基荷载传递特征的数值计算. 工程地质学报, 25(6): 1574-1582. DOI: 10.13544/j.cnki.jeg.2017.06.021
    引用本文: 黄明, 张冰淇, 陈福全, 黄治璟, 张旭东. 2017: 串珠状溶洞地层中桩基荷载传递特征的数值计算. 工程地质学报, 25(6): 1574-1582. DOI: 10.13544/j.cnki.jeg.2017.06.021
    HUANG Ming, ZHANG Bingqi, CHEN Fuquan, HUANG Zhijing, ZHANG Xudong. 2017: NUMERICAL CALCULATION ON LOAD TRANSFER PROGRESS OF PILE FOUNDATION IN BEADED KARST CAVE STRATUM. JOURNAL OF ENGINEERING GEOLOGY, 25(6): 1574-1582. DOI: 10.13544/j.cnki.jeg.2017.06.021
    Citation: HUANG Ming, ZHANG Bingqi, CHEN Fuquan, HUANG Zhijing, ZHANG Xudong. 2017: NUMERICAL CALCULATION ON LOAD TRANSFER PROGRESS OF PILE FOUNDATION IN BEADED KARST CAVE STRATUM. JOURNAL OF ENGINEERING GEOLOGY, 25(6): 1574-1582. DOI: 10.13544/j.cnki.jeg.2017.06.021

    串珠状溶洞地层中桩基荷载传递特征的数值计算

    NUMERICAL CALCULATION ON LOAD TRANSFER PROGRESS OF PILE FOUNDATION IN BEADED KARST CAVE STRATUM

    • 摘要: 桩基下穿串珠状溶洞时的承载性状极其复杂,分析桩基荷载传递与溶洞稳定性的耦合响应特征具有重要意义。建立地质模型上述问题进行数值计算,主要得到以下结论:受桩侧荷载传递作用,顶板厚度与溶洞跨度之比小于某一数值时岩层将产生冲切破坏,比例相对较大时剪应力将集中分布并发生冲剪破坏;溶洞的存在使桩侧阻力分布存在多个极值点,其数量与上覆岩层厚度、溶洞数量及底板岩层厚度等相关;溶洞顶板临空面处侧阻力存在迅速衰减段,其范围受卸荷岩层厚度及岩层竖向位移影响较大,当外荷载增大到一定数值以后该区域侧阻力变化较小;中夹岩层处侧阻力极大值位于岩层中部,且随层厚的增大而减小,厚度较小时侧阻力呈等腰三角形对称分布,厚度较大时呈阶梯型分布,厚度越大阶梯跨度越大,分布越均匀;中夹岩层侧阻力分布受桩长变化影响较小,但下部底板侧阻力分布受桩长及外荷载影响较大;中夹岩层的荷载-位移曲线(Q-S')呈抛物线型变化,存在明显的屈服拐点,层厚越大竖向位移越小,相同外荷载作用下桩越长其位移越大;桩径越大,Q-S'曲线拐点对应外荷载越大,对应中夹岩层位移越大,但桩径超过某一值后影响程度逐渐变小。

       

      Abstract: Bearing behaviour of the pile in the beaded karst cave is very complex. It is of great significant to study the response characteristics coupling the load transfer of the pile and the stability of karst cave. Calculation on the bearing characteristics of the pile and the stability of beaded karst cave is made with the Plaxis 2D and Abaqus 3D.The numerical results show that the punching failure happens in the top rock when the ratio of the top rock thickness vs the cave span is small, while punching shear failure happens at larger ratio. There are multiple maxima of the side resistance around the pile because of the existence of the beaded karst carve. The number of the points is related to the top rock thickness, number of the karst carves and the floor rock thickness. The side resistance will fall down quickly around the free face of the top rock. The area size is related to the thickness of the surrounding rock and its displacement. The difference will become small under larger load. The maximum of the side resistance around the middle rock layer locates at the middle, and the maximum value declines with the increase of the middle rock layer thickness. Besides, the side resistance distributes as the isosceles triangle with the thin middle rock layer, while it distributes as ladder shape with thick middle rock layer. The thicker the middle rock layer, the greater the ladder span, and the more uniform distribution of the side resistance. However, the side resistance distribution around the middle rock layer is not related to the length of the pile. Only the side resistance around the floor rock layer is related to the length of the pile and the load value. The curve of load vs displacement of the middle rock layer is parabolic shape, and there is an obvious inflection point in the load-displacement curve. The vertical displacement of the middle rock layer grows with the increase of the length of the pile and the decrease of the thickness of middle rock layer. The greater the diameter of the pile, the greater the external load corresponding to the inflection point of the load-displacement curve, and the greater the vertical displacement of the middle rock layer. However, the influence of the pile diameter changing to the curve will become smaller when the pile diameter is large enough.

       

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