北京地区钻杆直径对标准贯入试验击数的影响研究  

Study on the influence of drill pipe diameter to blow number of SPT in Beijing area

作　　者：刘坦 韩非[1] 王瑞永[1] Liu Tan;Han Fei;Wang Ruiyong(AVIC Institute of Geotechnical Engincering Co.,Ltd.,Beijing 100098,China)

机构地区：[1]中航勘察设计研究院有限公司,北京100098

出　　处：《工程勘察》2023年第4期25-30,共6页Geotechnical Investigation & Surveying

摘　　要：《岩土工程勘察规范》(GB 50021-2001)(2009版)中标准贯入试验设备规格要求钻杆直径为42mm,目前北京地区岩土工程勘察项目中越来越多地使用Φ50型钻杆,得到的标准贯入击数直接进行地基土液化判别、地基土承载力确定和参数选取的真实性无法判断。本文通过在北京地区7个场地进行不同杆径的标准贯入试验对比研究,结果表明:钻杆长度为3.0~20.0m时,砂土中Φ42型钻杆标贯击数与Φ50型钻杆标贯击数比值为0.94~0.99,随着钻杆长度的增加,其比值由较大值向平均值倾斜;粉土中Φ42型钻杆标贯击数与Φ50型钻杆标贯击数比值为0.88~0.93,随着钻杆长度的增加,其比值向较小值倾斜;黏性土中二者之间的关系并不明显。对砂土地基进行液化判别时,当使用Φ50型钻杆得到的标贯击数处于液化边界线附近且判定结果为不液化时,实际上存在液化的可能性,建议使用Φ42型钻杆进行标准贯入试验和液化判定。本研究在北京地区尚属首次,对地区经验积累和指导工程实际具有现实意义。The drill pipe diameter of the equipment of SPT is 42mm in the Code for Investigation of Geotechnical Engineering(GB 50021-2001)(2009 Edition),but the drill pipe withΦ50 is used more and more currently in geotechnical engineering investigation projects in Beijing area.It is impossible to judge the authenticity of the foundation soil liquefaction discrimination,foundation soil bearing capacity determination and parameters selection directly by the blow number of SPT.In this paper,a comparative study on SPT with different drill pipe diameters is carried out at 7 sites in Beijing.The study results show that when the length of drill pipe is 3.0~20.Om,the ratio of the blow number of SPT for theΦ42 and theΦ50 drill pipe in sand is 0.94~0.99,and with the increase of drill pipe length,the ratio can be tilted from the larger value to the average value.The ratio of the blow number said above is 0.88~0.93 in silt,and with the increase of drill pipe length,the ratio tends to a smaller value.The relationship is not obvious in clay soil.When the blow numbers of SPT of sand obtained by using$50 drll pipe are near the liquefaction boundary and the judgment results are not liquefaction,there is a possibility of liquefaction in fact.Therefore,it is suggested to use 42 drill pipe to conduct SPT for liquefaction judgment.This study is the first time in Beijing area,which is of practical significance for accumulating regional experience and guiding engineering practice.

关 键 词：标准贯入试验 钻杆直径 标贯击数 液化判别 

分 类 号：TU413[建筑科学—岩土工程]