支盘桩加固既有填砂路基深层软土的模型试验研究  

Model tests on deep soft ground improvement of existing sand-filled subgrade with squeezed branch piles

作　　者：李国维[1,2] 赵星宇 张黎明 周洋 熊力 赫新荣 LI Guowei;ZHAO Xingyu;ZHANG Liming;ZHOU Yang;XIONG Li;HE Xinrong(Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,Hohai University,Nanjing 210024,China;Highway and Railway Research Institute,Hohai University,Nanjing 210024,China;Guangdong Road and Bridge Construction Development Co.,Ltd.,Guangzhou 510660,China;Henan University of Technology,Zhengzhou 450001,China)

机构地区：[1]河海大学岩土力学与堤坝工程教育部重点实验室,江苏南京210024 [2]河海大学道路与铁道工程研究所,江苏南京210024 [3]广东省路桥建设发展有限公司,广东广州510660 [4]河南工业大学土木工程学院,河南郑州450001

出　　处：《岩土工程学报》2024年第8期1768-1775,共8页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(42177126)。

摘　　要：高速公路改扩建中既有填砂路基深层软土加固时存在路面结构层和施工场地空间限制的问题。首先,提出使用单盘挤扩支盘桩方案进行地基处理,通过挤扩法成盘于桩顶,以期实现不破除路面结构层的情况下达到设置桩顶承台或托板的效果。其次,利用群桩地基物理模型试验模拟一个桩土单元体研究加固方案的承载过程,通过分析桩体、盘体和土体的力学及变形指标研究支盘桩加固既有填砂路堤的承载表现和土体变形特征,最后,考虑土体参数和桩体尺寸推导了既有填砂路基深层软土支盘桩加固方法的二维简化模型。研究结果表明,软土在恒载下桩体轴力和土压力随时间变化调整,原因在于软土的压缩性和砂土的散粒体属性;桩顶轴力总和与恒载大小近似线性正相关,同时支盘直径越大桩顶轴力总和越大、桩承荷载占比越高,试验发现支盘桩加固法的桩承荷载占比约70%。另外,利用所建二维简化模型进行参数分析发现填砂路基中的最小盘间净距与上覆荷载、填砂内摩擦角、深层软土强度指标和支盘桩几何参数相关。There are limitations from the pavement structure layer and construction site space during the deep soft soil reinforcement of the existing sand-filled subgrade in expansion of expressways.Firstly,a new method using the squeezed branch pile(SBP)with one single plate for treatment of the existing soft foundation is proposed.In this method,a plate is set on the top of the piler to achieve the effects similar to a pile cap or support plate without breaking the road structure layer.Secondly,a physical model test on the pile group foundation is performed,and a pile-soil unit is simulated to study the bearing behavior of the SBP.By analyzing the mechanical and deformation indices of the pile,plate and soil,the bearing performance and soil-deformation characteristics of the new reinforcement method are studied.Finally,a simplified two-dimensional model for the reinforcement method with SBPs for the existing sand-filled embankment is derived by considering the soil parameters and pile sizes.The results indicate that the axial force of piles and soil pressure vary with time under constant loads due to the compressibility of soft soil and the properties of loose sand.The total axial force at the top of the pile is approximately positively correlated with the magnitude of the constant loads linearly.At the same time,the larger the diameter of the support plate,the greater the total axial force at the top of the pile and the higher the proportion of pile-bearing loads.It is found that the pile-bearing ratio of the reinforcement method with SBPs is about 70%.In addition,the proposed two-dimensional simplified model for parameter analysis shows that the minimum pile spacing in the sand-filled subgrade is related to the overlying load,internal friction angle of sand-filled soil,strength index of deep soft soil and geometric parameters of support piles.

关 键 词：高速公路 改扩建 既有填砂路基 支盘桩 模型试验 

分 类 号：TU431[建筑科学—岩土工程]