超厚细砂地层大直径后压浆桩荷载传递计算与分析  

Calculation and analysis of load transfer in large-diameter grouted pile in extra-thick fine sand layers

作　　者：万志辉[1,2] 戴国亮[1,2] 龚维明[1,2] WAN Zhi-hui;DAI Guo-liang;GONG Wei-ming(Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, Southeast University, Nanjing, Jiangsu 210096, China;School of Civil Engineering, Southeast University, Nanjing, Jiangsu 210096, China)

机构地区：[1]东南大学混凝土及预应力混凝土结构教育部重点实验室,江苏南京210096 [2]东南大学土木工程学院,江苏南京210096

出　　处：《岩土力学》2018年第4期1386-1394,共9页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.51478109;No.51678145);浙江省交通运输厅科研计划项目(No.2014H10);江苏高校优势学科建设工程资助项目(No.1105007002)~~

摘　　要：为了研究超厚细砂地层大直径后压浆桩的荷载变形特性,基于石首长江公路大桥8根大直径钻孔灌注桩现场静载荷试验结果,分析大直径后压浆桩的荷载传递特性,采用BoxLucas1函数的荷载传递模型,在考虑浆泡半径和桩身水泥结石体厚度的基础上建立了后压浆桩荷载-沉降关系的计算方法,并给出了不同土层桩侧、桩端增强因子经验取值范围,通过工程实例验证了方法的合理性;基于实际工程通过改变桩长及桩径,进一步计算分析超厚细砂地层大直径桩承载特性的变化规律。结果表明,该方法能较好地给出后压浆桩荷载-沉降关系的范围,可采用计算结果的下限作为工程设计使用;大直径桩承载性能随着桩长或桩径增加逐渐提高,桩径一定时,大直径桩的承载性能提高幅度随着桩长增加而逐渐趋于缓慢,且桩长达到一定值时,端阻所占比例几乎为0,表明通过增加桩长来提升大直径桩的承载性能受到有效桩长的影响;而桩端、桩侧组合后压浆技术能改善大直径桩的有效桩长问题,并能显著地提高大直径桩的极限承载力和端阻力所占比例。To study the deformation behavior of large-diameter grouted pile in extra-thick fine sand layer, load transfer of large-diameter grouted pile was analyzed in a case study of eight in-situ pile load tests of Shishou Yangtze River Highway Bridge. The BoxLucas1 load transfer function was used to calculate the relationship between load and settlement of the grouted pile considering the radius of the grout bulb and the thickness of cement grouting along the pile. The empirical range of enhancement factors for side friction and tip resistance in different soil deposits was also given. Then, case history was cited to demonstrate the validity of the method. Finally, according to the engineering example and calculation method of this paper, the bearing capacities of the large-diameter pile under extra-thick fine sand layer were further analyzed. The results show that the presented method can well determine the range of settlement of the grouted pile. It is suggested that the calculated lower bound can be used as an engineering design. The bearing capacity of the large-diameter pile is gradually increasing with the increase of pile diameter or pile length. When the pile diameter is constant, the increased range of bearing capacity of the large-diameter pile is decreased with the increase of pile length. The pile length reaches a certain value, the ratio of the mobilized base resistance to the total capacity is almost zero. This indicates an effective pile length problem by increasing the pile length to improve the bearing capacity of large diameter pile. Effective pile length, bearing capacity and percentage of load carried by pile tip of the large-diameter pile can be significantly improved by combined grouting of pile tip and side.

关 键 词：超厚细砂地层 大直径后压浆桩 荷载传递法 Box Lucas1模型 增强因子 荷载-沉降关系 

分 类 号：TU473[建筑科学—结构工程]