路涵过渡段膨胀土地基沉降特性现场试验研究

为研究斜交涵洞路涵过渡段膨胀土地基沉降特性,依托云桂铁路建设,开展了路涵过渡段桩网复合地基现场试验研究,监测了桩顶与桩间土土压力、孔隙水压力、地基面沉降和地基分层沉降的时程变化。研究结果表明:对与斜交涵洞平行的过渡段路基横断面而言,膨胀土地基的沉降分布规律与正交的普通路基横断面沉降规律类似;受过渡段路基填筑影响,涵洞产生了明显的附加沉降;沿线路纵向,过渡段沉降随着距涵背距离的增加而逐渐增大,之后沉降趋于稳定,吻合于普通路基的沉降;过渡段首部、中部和尾部工后沉降分别为3.0、6.3、6.7mm,路涵工后差异沉降为3.8mm,折角为0.3‰,满足高速铁路无砟轨道路基沉降控制要求。基于考虑附加应力转正效应的沉降计算方法,对斜交涵洞过渡段膨胀土地基开展了沉降计算,得到了过渡段首部、中部和尾部沉降计算修正系数分别为0.53、0.64、0.74。研究成果可为高速铁路路涵过渡段设计提供参考。

To study the settlement characteristics of expansive soil foundation at roadbed-culvert transition section near to oblique culvert,combined with the construction of Yun-Gui railway,pile-net composite foundation is employed to treating expansive soil foundation at roadbed-culvert transition section. Field test results,including,soil pressure on both the pile and soil surface,pore-water pressure,total settlement and layered settlement are presented. The study results indicate that the distribution of settlement at oblique section which is parallel and near to oblique culvert is similar to the normal cross section. The construction of transition section has significant effect on the settlement of culvert,however,the distribution of culvert settlement is well,the maximum value is 16.2 mm. The settlement increases gradually with the distance from the culvert at transition section,but it is tended to be stable when the distance is longer than 19 m. The post-construction settlement at head,middle and tail part of transition section are 3.0 mm,6.3 mm and 6.7 mm respectively. The differential post-construction settlement is 3.8 mm and the deflection angle is 0.3‰. Both of them are lesser than the limit values of high speed railway. The settlement of transition section nearly oblique culvert can be calculated by the method considering the normalization of additional stress. The correction coefficient of settlement at head,middle and tail part of transition section are 0.53,0.64 and 0.74 respectively. Research results can be used as a reference for the design of roadbed-culvert transition section in high-speed railway.