广三高速公路扩建工程中桩承式加筋路堤的现场试验

In-situ test of pile-supported reinforced embankment in Guang-San highway expansion project

结合广三高速公路扩建工程,对素混凝土桩和PHC管桩桩承式加筋路堤工作性状开展现场试验调查,在路堤填筑中以及填筑完成后对路基沉降、孔隙水压力以及深部水平位移进行监测和分析,试验结果表明:当软土厚度小于18m时,采用桩径为50cm的C15素混凝土桩,打穿软土层,桩中心间距1.8-2.0m,平面呈三角形布置,桩帽采用C30混凝土浇筑成尺寸为1m×1m×0.4m的面板,拓宽路基孔隙水压力变化与填土高度和桩的龄期有关,路基工后沉降得到了有效控制;当软土厚度超过18m时,采用桩径为30cm,桩壁厚7cm的PHC管桩,按照桩中心间距2.5-3.0m间距呈正方形布置,桩帽采用设置双层钢筋的C30混凝土浇筑成尺寸为1.5m×1.5m×0.4m的面板,路堤填筑完成后预压期内路基孔隙水压力基本未发生变化,路基几乎未发生侧向位移,路基剩余沉降很小,可以节省预压时间,尽早开展路面结构层施工,开放交通。

Taking Guang-San highway widening engineering as background,in-situ monitoring investigation on working performance of concrete pile and prestressed concrete pipe pile（PHC）supported embankment were carried out.The settlement,pore water pressure,and deep lateral displacement of subgrade were tested and analyzed during and after the embankment filling construction.The test results indicated that when the thickness of the soft soil was less than 18 m,the widening subgrade was strengthened by C15 concrete pile with diameter of 50 cm,center distance of 1.8-2.0 m,and C30 concrete pile cap with size of 1m×1m×0.4m,triangularly distributed on plane and vertically penetrating through the whole soft soil layer,the pore water pressure of widening subgrade was influenced by the height of embankment filling and the age of concrete pile;the post-construction settlement has been effectively controlled.And when the thickness of the soft soil was more than 18 m,the widening subgrade was strengthened by prestressed concrete pipe pile with diameter of 30 cm,pipe wall thickness of 7mm,center distance of 2.5-3.0 m,and double-layer steel reinforced C30 concrete pile cap with size of 1.5 m×1.5 m×0.4 m,squarely distributed on plane and vertically penetrating through the whole soft soil layer,little variation of the pore water pressure and deep lateral displacement was observed since the end of embankment filling construction.The residual settlement of subgrade was quite small,and the preloading time could be significantly saved,then the pavement could be constructed immediately,and the traffic could be opened as soon as possible.