浸水状态下湿陷性黄土场地螺旋灌注桩负摩阻力与土体湿陷规律试验  

Experimental Analysis on Negative Friction Resistance of Spiral Cast-in-place Piles and Soil Collapse Law in Collapsible Loess Site

作　　者：马天忠[1] 孙晨东 高玉广 苏天涛 高虹[1] MA Tian-zhong;SUN Chen-dong;GAO Yu-guang;SU Tian-tao;GAO Hong(School of Civil Engineering,Lanzhou University of Technology,Lanzhou 730050,Gansu,China;Gansu Civil Engineering Research Institute Co.,Ltd.,Lanzhou 730050,Gansu,China)

机构地区：[1]兰州理工大学土木工程学院,甘肃兰州730050 [2]甘肃土木工程科学研究院有限公司,甘肃兰州730050

出　　处：《中国公路学报》2022年第8期151-161,共11页China Journal of Highway and Transport

基　　金：国家自然科学基金项目(52068048);甘肃省自然科学基金项目(20JR10RA163,1308RJZA140)。

摘　　要：为深入揭示大厚度黄土地区黄土湿陷特征、水分入渗规律、湿陷范围以及黄土湿陷对长螺旋灌注桩与双向螺旋挤土灌注桩负摩阻力变化的影响等问题,在兰州榆中大厚度湿陷性黄土场地进行了4组双向螺旋挤土灌注桩与2组长螺旋灌注桩浸水载荷试验。试验结果表明:浸水试坑内与试坑外浅标点的湿陷沉降量与时间变化规律基本一致;土体湿陷具有明显的阶段性,并非整体一次完成;土体在不同深度处发生湿陷的时间、湿陷总量各不相同,且深标点整体的湿陷沉降较浅标点发生更加充分;径向与竖向水分入渗速率整体呈函数型衰减,竖向入渗速率是径向的1.5~3.0倍,提出了通过水分入渗速率确定湿陷范围的计算方法,并与试验结果进行对比;土体湿陷竖向深度在24 m范围内,径向在10 m范围内,建议湿陷性黄土地基处理时将竖向24 m、径向10 m作为参考范围;同一工况下双向螺旋挤土灌注桩受到的负摩阻力明显大于长螺旋灌注桩,确定双向螺旋挤土灌注桩桩侧负摩阻力大小时,应将距离桩心0.75D为半径的圆周范围内丧失湿陷性的土体考虑进去,且受力面积按1.5倍桩侧表面积等效放大。To solve the problems of loess collapsibility characteristics,water infiltration law,evaluation of collapsibility range and the influence of loess collapsibility on the change of negative friction of continuous flight auger pile and soil displacement screw pile in large thickness loess area,the immersion test of four groups of soil displacement screw pile and two groups of continuous flight auger pile were carried out in Yuzhong,Lanzhou.The test results show that the collapsible settlement of shallow observation points inside and outside the immersed test pit is basically consistent with the variation law of time;Soil collapsibility has obvious stages,which is not completed at one time;The time of soil collapsing at different depths varies with the total amount of collapsing,and the overall collapsing settlement of deep observation points is more sufficient than that of shallow observation points;The radial and vertical water infiltration rates decay as a function,and the vertical infiltration rate is 1.5-3.0 times that of the radial.The calculation method of determining the collapsibility range by water infiltration rate is proposed and verified with the test results;The vertical depth of soil collapsibility is within 24 m and the radial range is 10 m.It is suggested to take the vertical 24 m and radial 10 m as the reference range in the treatment of collapsible loess foundation;Under the same working condition,the negative friction of the soil displacement screw pile is significantly greater than that of continuous flight auger pile.When the negative friction of the side of the soil displacement screw pile is determined,the soil losing collapsibility within the circumference with a radius of 0.75D from the pile Center shall be taken into account,and the stress area shall be equivalent enlarged by 1.5 times the surface area of the pile side.

关 键 词：桥梁工程 湿陷性黄土 浸水试验 螺旋灌注桩 负摩阻力 

分 类 号：U443.15[建筑科学—桥梁与隧道工程]