基于颗粒形状参数的火山渣桩侧摩阻特性研究
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摘要
由于形状参数较一般土体差异较大,已有桩基工程中的传统经验难以适用于火山渣地层。为分析东非裂谷区火山渣地层内灌注桩桩侧摩阻,利用四根钻孔灌注桩的现场静载试验测试火山渣地层的桩侧摩阻值,并对火山渣级配、颗粒形状(棱角度和表面粗糙度)、抗剪强度等物理力学性质进行试验。通过与一般角砾土进行对比,分析二者在颗粒棱角度和表面粗糙度上的区别及其对内摩擦角和桩侧摩阻的影响。结果表明:颗粒形状影响颗粒的内摩擦角和桩侧摩阻;火山渣虽属于角砾范畴,但因其棱角度和表面粗糙度远大于一般角砾,导致该土体在稍密状态下,不仅内摩擦角(42°)与一般角砾土的中密程度上限值(36°～42°)相当,桩侧摩阻极限值(124 kPa)也不低于规范中中密角砾土(90～150 kPa)。研究成果可为火山渣地层桩基工程设计施工提供一定的参考依据。
Due to the larger difference of the shape parameter from the normal soil mass, the existing conventional pile foundation engineering experiences are difficult to be applied to volcanic scoria stratum. In order to analyze the lateral friction characteristics of cast-in-place pile in the scoria stratum within the region of East African Great Rift Valley, the lateral friction value of the pile in the scoria stratum is tested through the static load test made with four bored cast-in-place piles, while the physical and mechanical properties, i.e. scoria gradation, particle shape(angularity and surface roughness) and shear strength are tested as well. Through comparing with the general breccia soil, the difference between them in grain angularity and surface roughness as well as their influences on the internal friction angle and pile lateral friction are analyzed. The result shows that both the internal friction angle and the lateral friction resistance of pile are affected by the particle shape. Though volcanic scoria belongs to the category of breccia, its angularity and surface roughness are far greater than those of general breccia, which leads to that the internal friction angle(42°) of the scoria soil mass is not only equivalent to the upper limit of the mid-density of the general breccia soil(36～42°), but the ultimate value of pile lateral friction(124 kPa) is also not lower than that of the mid-density breccia soil(90～150 kPa) specified in the relevant specification. The study result can provide a certaon reference for both the design and construction of the project of pile foundation in volcanic scoria stratum.
Due to the larger difference of the shape parameter from the normal soil mass, the existing conventional pile foundation engineering experiences are difficult to be applied to volcanic scoria stratum. In order to analyze the lateral friction characteristics of cast-in-place pile in the scoria stratum within the region of East African Great Rift Valley, the lateral friction value of the pile in the scoria stratum is tested through the static load test made with four bored cast-in-place piles, while the physical and mechanical properties, i.e. scoria gradation, particle shape(angularity and surface roughness) and shear strength are tested as well. Through comparing with the general breccia soil, the difference between them in grain angularity and surface roughness as well as their influences on the internal friction angle and pile lateral friction are analyzed. The result shows that both the internal friction angle and the lateral friction resistance of pile are affected by the particle shape. Though volcanic scoria belongs to the category of breccia, its angularity and surface roughness are far greater than those of general breccia, which leads to that the internal friction angle(42°) of the scoria soil mass is not only equivalent to the upper limit of the mid-density of the general breccia soil(36～42°), but the ultimate value of pile lateral friction(124 kPa) is also not lower than that of the mid-density breccia soil(90～150 kPa) specified in the relevant specification. The study result can provide a certaon reference for both the design and construction of the project of pile foundation in volcanic scoria stratum.
引文
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[3] 杨福珍,黄清友,张建栋.火山渣在路基工程中的应用[J].内蒙古公路与运输,2006(4):24- 27.
[4] 李利,吕奋.火山熔岩地区公路路基设计研究[J].公路,2014,59(7):99- 102.
[5] ORENSE R,ZAPANTA A,HATA A,et al..Geotechnical characteristics of volcanic soils taken from recent eruptions[J].Geotechnical and Geological Engineering,2006,24:129- 161.
[6] 唐林,徐正宣,赵平.埃塞铁路的火山系列工程地质问题及对策探讨[J].四川建筑,2015,35(1):91- 94.
[7] 杨超,江浩,岳健,等.钙质砂中桩基承载性状的模型试验研究[J].长江科学院院报,2017,34(1):87- 90.
[8] 陈旻.深厚软土地区大直径钻孔桩荷载传递试验研究[J].地下空间与工程学报,2016,12(5):1205- 1210.
[9] 李国旗.关中黄土地层公路桥梁钻孔灌注桩侧摩阻力研究[D].西安:长安大学,2013.
[10] 杨宇,马晔,宋春霞.中风化花岗岩层与基桩侧摩阻性能现场试验研究[J].岩石力学与工程学报,2013,32(1):97- 106.
[11] 梁多伟,罗强,刘钢,等.埃塞俄比亚铁路火山渣填料颗粒形状特征分析[J].铁道科学与工程学报,2018,15(1):52- 63.
[12] MARIA A,CAREY S.Quantitative discrimination of magma fragmentation and pyroclastic transport processes using the fractal spectrum technique[J].Journal of Volcanology and Geothermal Research,2007,161(3):234- 246.
[13] RAUSCH J,GROBéTY B,VONLANTHEN P.Eifel maars:Quantitative shape characterization of juvenile ash particles(Eifel Volcanic Field,Germany)[J].Journal of Volcanology and Geothermal Research,2015,291(1):86- 100.
[14] 梁多伟,罗强,刘孟适.火山渣掺配土质砾砂改良填料剪切特性试验研究[J].武汉理工大学学报,2017,39(3):71- 77.
[15] 中国铁道科学研究院.铁路工程基桩检测技术规程:TB 10218—2008[S].北京:中国铁道出版社,2008.
[16] 中华人民共和国住房和城乡建设部.建筑基桩检测技术规范:JGJ 106—2014[S].北京:中国建筑工业出版社,2014.
[17] 中华人民共和国住房和城乡建设部.建筑地基基础设计规范:GB 50007—2011[S].北京:中国建筑工业出版社,2011.
[18] 中华人民共和国建设部.岩土工程勘察规范:GB 50021—2001[S].北京:中国建筑工业出版社,2009.
[19] 铁道第三勘察设计院集团有限责任公司.铁路桥涵地基和基础设计规范:TB 10002.5—2005[S].北京:中国铁道出版社,2017.
[20] 铁道部第一勘测设计院.铁路工程地质手册[M].北京:中国铁道出版社,1999.
[21] 戴金林.钻孔灌注桩侧壁摩阻力极限值计算[J].建筑结构,2007,37(8):85- 87.
[22] 林宗元.岩土工程勘察设计手册[M].沈阳:辽宁科学技术出版社,1996.