基于桩土界面摩擦特性和桩周土体应力状态的基桩极限侧阻力分析
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摘要
结合基桩承载过程中的桩周土体应力状态分析和桩土界面摩擦特性分析,推导出基于土体应力状态的沿桩土界面的土体抗剪强度计算模型和基于界面摩擦特性的界面抗剪强度计算模型。通过对比土体抗剪强度和界面抗剪强度,推导出受该两种强度耦合作用影响的极限侧阻力计算模型,并用上海某工程算例验证该模型的合理性和可行性,同时利用该模型分析不同类型的土的极限侧阻力随埋深的分布规律。结果显示:因内摩擦角和侧压力系数之间的不同关系,极限侧阻力随埋深表现出不同的分布特点,在特定关系下,存在一个临界深度,超过该深度极限侧阻力维持在一个稳定值甚至不断减小直至为零。
By analyzing the stress state of soil around a pile and friction characteristic of the pile-soil interface during the load bearing process of the pile foundation, a calculation model of shear strength of soil based on stress state of soil and calculation model of shear strength of interface based on friction characteristic of pile-soil interface is derived. By comparing the shear strength of soil with that of the interface, the calculating model of ultimate shaft resistance under the influence of the coupling of the two kinds of strength is derived, and the rationality and feasibility of the model is verified by an engineering example in Shanghai, and the distribution law of ultimate shaft resistance of different types of soil with buried depth is analyzed by using the model. The results show that, due to the different relations between the internal friction angle and the lateral pressure coefficient, the ultimate shaft resistance shows different distribution characteristics with buried depth, and in a certain relationship, there is a critical depth beyond which the ultimate shaft resistance is maintained at a stable value or even reduced constantly to zero.
By analyzing the stress state of soil around a pile and friction characteristic of the pile-soil interface during the load bearing process of the pile foundation, a calculation model of shear strength of soil based on stress state of soil and calculation model of shear strength of interface based on friction characteristic of pile-soil interface is derived. By comparing the shear strength of soil with that of the interface, the calculating model of ultimate shaft resistance under the influence of the coupling of the two kinds of strength is derived, and the rationality and feasibility of the model is verified by an engineering example in Shanghai, and the distribution law of ultimate shaft resistance of different types of soil with buried depth is analyzed by using the model. The results show that, due to the different relations between the internal friction angle and the lateral pressure coefficient, the ultimate shaft resistance shows different distribution characteristics with buried depth, and in a certain relationship, there is a critical depth beyond which the ultimate shaft resistance is maintained at a stable value or even reduced constantly to zero.
引文
[1] JGJ 94-2008,建筑桩基技术规范[S]. JGJ 94-2008, Technical code for building pile foundation[S].
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[3] 许宏发,吴华杰,郭少平,等.桩土接触面单元参数分析[J].探矿工程,2002,(5):10-12. XU Hongfa, WU Huajie, GUO Shaoping, et al. Study on the parameters of pile soil contact surface element[J]. Exploration Engineering, 2002,(5):10-12.
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[5] 姚文娟,蔡晨雨.一种新的超长桩荷载传递模型[J].岩土力学,2016,37(S2):783-787. YAO Wenjuan, CAI Chenyu. A new load transfer model of super-long pile[J]. Rock and Soil Mechanics, 2016,37(S2):783-787.
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[9] 刘卡伟,刘岳明.桩侧阻力与抗剪强度的关系及其随深度的变化[J].勘察科学技术,2018,(1):5-8. LIU Kawei, LIU Yueming. The relationship between pile lateral friction and shear strength and its variation with depth[J]. Site Investigation Science and Technology, 2018,(1):5-8.
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[12] 洪毓康.土质学与土力学(第二版)[M].北京:人民交通出版社,1995. HONG Yukang. Soil properties and soil mechanies (Second edition)[M]. Beijing: China Communications Press, 1995.
[2] 李永辉,王卫东,黄茂松,等.超长灌注桩桩-土界面剪切试验研究[J].岩土力学,2015,36(7):1981-1988. LI Yonghui, WANG Weidong, HUANG Maosong, et al. Experimental research on pile-soil interface shear behaviors of super-long bored pile[J]. Rock and Soil Mechanics, 2015,36(7):1981-1988.
[3] 许宏发,吴华杰,郭少平,等.桩土接触面单元参数分析[J].探矿工程,2002,(5):10-12. XU Hongfa, WU Huajie, GUO Shaoping, et al. Study on the parameters of pile soil contact surface element[J]. Exploration Engineering, 2002,(5):10-12.
[4] 王卫东,李永辉,吴江斌.超长灌注桩桩-土界面剪切模型及其有限元模拟[J].岩土力学,2012,33(12):3818-3824. WANG Weidong, LI Yonghui, WU Jiangbin. Pile-soil interface shear model of super long bored pile and its FEM simulation[J]. Rock and Soil Mechanics, 2012,33(12):3818-3824.
[5] 姚文娟,蔡晨雨.一种新的超长桩荷载传递模型[J].岩土力学,2016,37(S2):783-787. YAO Wenjuan, CAI Chenyu. A new load transfer model of super-long pile[J]. Rock and Soil Mechanics, 2016,37(S2):783-787.
[6] 编写委员会.桩基工程手册[M].北京:中国建筑工业出版社,1995. Drafting Committee. Pile foundation engineering handbook[M]. Beijing: China Architecture and Building Press, 1995.
[7] 高俊合,于海学,赵维炳.土与混凝土接触面特性的大型单剪试验研究和数值模拟[J].土木工程学报,2000,33(4):42-46. GAO Junhe, YU Haixue, ZHAO Weibing. Characteristics study of interface between soil and concrete by using large size single shear apparatus and numerical analysis[J].China Civil Engineering Journal, 2000,33(4):42-46.
[8] 陈希哲.土力学与地基基础[M].北京:清华大学出版社,2005. CHEN Xizhe. Soil mechanics and geotechnical engineering[M]. Beijing: Tsinghua University Press, 2005.
[9] 刘卡伟,刘岳明.桩侧阻力与抗剪强度的关系及其随深度的变化[J].勘察科学技术,2018,(1):5-8. LIU Kawei, LIU Yueming. The relationship between pile lateral friction and shear strength and its variation with depth[J]. Site Investigation Science and Technology, 2018,(1):5-8.
[10] GB 50007-2011,建筑地基基础设计规范[S]. GB 50007-2011, Code for design of building foundation[S].
[11] 王卫东,李永辉,吴江斌.上海中心大厦大直径超长灌注桩现场试验研究[J].岩土工程学报,2011,33(12):1817-1826. WANG Weidong, LI Yonghui, WU Jiangbin. Field loading tests on large-diameter and super-long bored piles of ShangHai Center Tower[J]. Chinese Journal of Geotechnical Engineering, 2011,33 (12):1817-1826.
[12] 洪毓康.土质学与土力学(第二版)[M].北京:人民交通出版社,1995. HONG Yukang. Soil properties and soil mechanies (Second edition)[M]. Beijing: China Communications Press, 1995.