潮汕车站超大面积深厚软土桩网复合地基性状数值分析
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摘要
桩-网复合地基处理软土具有施工速度快,对周围环境扰动小,工后不均匀沉降较小,且大部分沉降发生在施工期等特点,是一种有效的深厚软土地基处理形式。因此近年来在国内外获得广泛应用,目前已应用于高速公路基础处理、桥头跳车处理、铁路软基、油罐基础及工民建等。
本文基于潮汕车站地区深厚软土的地基处理,采用统计分析、数值模拟的方法,研究潮汕软土的工程特性以及软土在无加固情况下变形规律、桩网复合地基的作用机理和沉降规律等。主要研究内容和成果如下：
(1)对国内外桩网复合地基理论研究现状进行了总结,分析了桩网复合地基的组成及其机理。
(2)基于潮汕车站地区典型地段软土的工程勘察资料,对其物理力学特性进行了详细的阐述,分析了潮汕地区软土的“三高三低”工程特性。
(3)根据潮汕车站DK205+870断面路堤的特性,运用数值软件FLAC3D进行了不同模型下桩网复合结构荷载传递规律和沉降规律的分析。分析发现：①软土沉降量随填土高度的增加而增大。最大沉降发生在路基中心表层,最大侧向位移发生在坡脚下1Om处。②随着桩间距的增加,桩身轴力、桩侧摩阻力及负摩阻力影响深度都随之增大。桩帽对桩身轴力及桩侧摩阻力影响深度有限,超过一定深度,有无桩帽模型曲线基本重合。桩间距的减小和桩帽的设置能够减小地基面桩间土沉降。
(4)针对国内尚无关于桩网复合地基设计规范,总结了国外关于桩网复合地基设计方法。
Pile-net composite foundation is a method to improve the behavior of deep soft soil, and has been used broadly in highway embankment, railway embankment, and industral and civil construction recently.
In this paper, based on the wide deep soft soil treatment project of the ChaoShan railway station area, statistical analysis and numerical simulation were used to study the engineering properties of soft soil, the deformation rules of non-supporting model, the action mechanism and deformation rules of the pile-net composite foundation, and so on. The main contents and results are as follows:
(1) The previous methods dealing with pile-net composite foundation are outlined. The composition and mechanism of the pile-net composite foundation are summed up.
(2) Base on the analysis of the physical and mechanical parameters of the ChaoShan deep soft soil, the following characteristics have been found:high water content, high void ratio, and high compressiblity, as well as low intensity, low permeability and low bearing capacity.
(3) According to the characteristics of the embankment section DK205+870 of Chaoshan station, the pile-net composite foundation settlement rules and load transfer law of different models were studied using the numerical simulation software FLAC3D. It is concluded that:①the settlement of foundation distributes in bubble shape, and increases with the filling height increasing. The maximum settlement occurs at the center of the roadbed surface, and the maximum lateral displacement occurs at the place which is 10m lower than the toe.②The influence depth of axial force, skin friction, and negative skin friction increase with the pile spacing increasing. The influence of pile cap to axial force and skin friction is limited, presenting the law that, more than a certain depth, whether there is pile cap, the model curves will coincide. Reducing pile spacing and setting pile cap can reduce the settlement of soil among pile foundation.
(4) Finally, the design methods for pile-net composite foundation are summed up.
本文基于潮汕车站地区深厚软土的地基处理,采用统计分析、数值模拟的方法,研究潮汕软土的工程特性以及软土在无加固情况下变形规律、桩网复合地基的作用机理和沉降规律等。主要研究内容和成果如下：
(1)对国内外桩网复合地基理论研究现状进行了总结,分析了桩网复合地基的组成及其机理。
(2)基于潮汕车站地区典型地段软土的工程勘察资料,对其物理力学特性进行了详细的阐述,分析了潮汕地区软土的“三高三低”工程特性。
(3)根据潮汕车站DK205+870断面路堤的特性,运用数值软件FLAC3D进行了不同模型下桩网复合结构荷载传递规律和沉降规律的分析。分析发现：①软土沉降量随填土高度的增加而增大。最大沉降发生在路基中心表层,最大侧向位移发生在坡脚下1Om处。②随着桩间距的增加,桩身轴力、桩侧摩阻力及负摩阻力影响深度都随之增大。桩帽对桩身轴力及桩侧摩阻力影响深度有限,超过一定深度,有无桩帽模型曲线基本重合。桩间距的减小和桩帽的设置能够减小地基面桩间土沉降。
(4)针对国内尚无关于桩网复合地基设计规范,总结了国外关于桩网复合地基设计方法。
Pile-net composite foundation is a method to improve the behavior of deep soft soil, and has been used broadly in highway embankment, railway embankment, and industral and civil construction recently.
In this paper, based on the wide deep soft soil treatment project of the ChaoShan railway station area, statistical analysis and numerical simulation were used to study the engineering properties of soft soil, the deformation rules of non-supporting model, the action mechanism and deformation rules of the pile-net composite foundation, and so on. The main contents and results are as follows:
(1) The previous methods dealing with pile-net composite foundation are outlined. The composition and mechanism of the pile-net composite foundation are summed up.
(2) Base on the analysis of the physical and mechanical parameters of the ChaoShan deep soft soil, the following characteristics have been found:high water content, high void ratio, and high compressiblity, as well as low intensity, low permeability and low bearing capacity.
(3) According to the characteristics of the embankment section DK205+870 of Chaoshan station, the pile-net composite foundation settlement rules and load transfer law of different models were studied using the numerical simulation software FLAC3D. It is concluded that:①the settlement of foundation distributes in bubble shape, and increases with the filling height increasing. The maximum settlement occurs at the center of the roadbed surface, and the maximum lateral displacement occurs at the place which is 10m lower than the toe.②The influence depth of axial force, skin friction, and negative skin friction increase with the pile spacing increasing. The influence of pile cap to axial force and skin friction is limited, presenting the law that, more than a certain depth, whether there is pile cap, the model curves will coincide. Reducing pile spacing and setting pile cap can reduce the settlement of soil among pile foundation.
(4) Finally, the design methods for pile-net composite foundation are summed up.
引文
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[4]Jones C J, Lawson C R, Ayres D J. Geotextile reinforced piled embankment. In Geotextile Gemembranes and Related Products. Balkema, Rotterdam,1990, Pages 155-159
[5]Low B K, Tang S K, and Choa V. Arching in piled embankment. Journal of Geotechnical Engineering[J].1994,120(11):1917-1938
[6]Russell D. and Pierpoint N. An assessment of design methods for piled embankments. Ground Engineering[J].1997, (11):39-44
[7]Hewlett W J, Randolphm F. Analysis of piled embankments [J]. Ground Engineering, 1988,21(3):12-18
[8]Han J. Design and construction of embankments on geosynthetic reinforced platforms supported by piles. In ASCE J P A DOT Geotechnicai Seminar, Hershey, PA, Invited Speaker 1999, April 14-16
[9]Han J. Development of design charts for geosynthetically reinforced embankments on deep mixed columns. Technical report, Widener University, Chester, PA,2002-2003
[10]饶为国,江辉煌,尤昌龙.桩-网复合地基工后沉降量的三点推算法[J].岩土工程界,2001,4(8)：55-57
[11]饶为国,江辉煌,邓安雄.桩-网复合路基工后沉降的实时预测[J].应用力学学报,2002,19(2)：133-136
[12]饶为国,赵成刚.复合地基工后沉降的薄板变形模拟[J].水利学报,2002,(4)：24-27
[13]于延寿,张卉,饶为国.土工合成材料加固软土路堤的力学分析[J].铁道标准设计,2002,(8)：45-46
[14]陈凯杰,雷学文.桩-网复合地基桩土应力比的影响因素分析[J].土工基础,2006,20(1)：57-59
[15]鲁长亮,黄生文,朱树彬.桩承土工加筋地基桩土应力比计算及其优化设计[J].西部探矿工程,2005,(5)：43-45
[16]孙宏林,王祥,李丹.土工材料与高速铁路路基工后沉降控制[J].铁道勘察,2005,(1)：36-41
[17]李昌宁,王炳龙,周顺华.CFG桩-网复合结构软基加固技术及其实际应用[J].铁道工程学报,2006,(1)：27-31
[18]曹新文,卿三惠,周立新.桩网结构路基土工格栅加筋效应的试验研究[J].岩石 力学与工程学报,2006,25(增1)：3162-3167
[19]徐世强,折学森,李培林.桩-网复合基础在公路盐渍土地基处理中的应用[J].西安工程科技学院学报,2006,20(5)：587-589
[20]张建勋,陈福全,简洪钰.桩承土工织物加筋地基的研究与工程应用综述[J].福建工程学院学报,2003,1(3)：10-15
[21]晏莉.桩承土工合成材料加筋垫层复合地基作用机理数值分析[D].长沙：长沙理工大学硕士学位论文,2004
[22]陈凯杰.桩-网复合地基工作性状的研究.武汉：武汉科技大学硕士学位论文,2005
[23]闫澍旺,周宏杰.水泥土桩与土工格栅联合加固沟谷软基机理研究[J].岩土力学,2005,26(4)：633-637
[24]陈福全,李大勇.桩承加筋路堤性状的有限元分析[J].山东科技大学学报(自然科学版),2006.25(2)：50-53
[25]强小俊.桩-网复合地基的性状分析研究[D].南昌：南昌大学硕士学位论文,2006
[26]连峰,龚晓南,崔诗才,刘吉福.桩-网复合地基承载性状现场试验研究[J].岩土力学.2009,30(4)：1057-1062
[27]芮瑞,夏元友.桩-网复合地基与桩承式路堤的对比数值模拟[J].岩土工程学报.2007,29(5)：769-772
[28]张栋,臧延伟.桩网复合结构桩间土应力计算方法研究[J].铁道工程学报.2009,(7)：25-28
[29]肖宏,蒋关鲁,魏永幸.桩网结构模型试验柔性拱研究[J].岩土力学.2008,29(11)：3031-3036
[30]程栋栋,闫澍旺,侯晋芳,杨昌民.桩与土工格栅联合作用对高速公路路堤地基承载力影响的有限元分析[J].岩土力学.2007,10(28)：886-890
[31]饶为国著.桩-网复合地基原理及实践[M].北京：中国水利水电出版社,2004
[32]龚晓南编著.复合地基理论及工程应用(第二版)[M].北京：中国建筑工业出版社,2007
[33]孔宪立编著.工程地质学[M].北京：中国建筑工业出版社,1997
[34]折学森编著.软土地基沉降计算[M].北京：人民交通出版社,1998
[35]刘波,韩彦辉编著.FLAC原理、实例与应用指南[M].北京：人民交通出版社,2005
[36]陈育民,徐鼎平编著.FLAC/FLAC3D基础与工程实例[M].北京：中国水利水电出版社,2008
[37]Marston A and Anderson A O. The theory of loads on pipe in ditches and tests of cement and clay drain tile and sewer pipe. Technical Report Bulletin 31, Engineering Experiment Station, Ames, Iowa,1913
[38]Terzaghi K. Theoretical soil mechanics. John Wiley&Son, New York,1943
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