永临结合U形槽在黏土地基中的承载特性

Bearing Characteristics of Permanent and Temporary Combined U⁃shaped Groove in Clay Foundation

以常用于铁路隧道与传统路堤过渡段的U形槽结构为研究对象,基于有限元方法,对不同长宽比条件下永临结合U形槽的竖向、水平和抗弯承载力进行计算,分析其破坏模式,并提出无量纲承载力系数计算方法。结果表明:永临结合U形槽结构的竖向破坏模式仍类似于Prandtl破坏模式;黏土强度梯度和接触面摩擦因数的降低将减小土体的激发范围,相比于传统U形槽,竖向承载力最大增幅可达到51%。在水平极限荷载作用下,底部弧形区域与两侧的楔形剪切区域共同组成了W形的破坏模式;随着长宽比的增加,永临结合U形槽水平承载力提高幅度从1.0倍增长至2.3倍;当长宽比较小时,弯矩极限承载力只存在底部勺形破坏模式;随着长宽比的增加,楔形破坏模式得到一定的发展;在均质黏土地基中,楔形破坏模式并不明显,主要以边墙底部土体和侧壁土体组成的勺形破坏区域为主;随着长宽比增加,永临结合U形槽抗弯承载力提高幅度从1.4倍增长至3.6倍。

The U-shaped groove structure commonly used in the transition section between railway tunnels and traditional embankments was taken as the research object.Based on the finite element method,the vertical,horizontal,and bending bearing capacity of the permanent and temporary combined U-shaped groove under different aspect ratios were calculated.The failure mode was analyzed,and a dimensionless bearing capacity coefficient calculation method was proposed.The results show that the vertical failure mode of the permanent and temporary combined U-shaped groove structure is still similar to the Prandtl failure mode.The decrease in clay strength gradient and contact surface friction coefficient will reduce the excitation range of the soil,and compared to traditional U-shaped grooves,the maximum increase in vertical bearing capacity can reach 51%.Under the action of horizontal ultimate load,the bottom arc-shaped area and the wedge-shaped shear areas on both sides jointly form a W-shaped failure mode.As the aspect ratio increases,the increase in horizontal bearing capacity of the permanent and temporary combined U-shaped groove increases from 1.0 times to 2.3 times.When the aspect ratio is small,the ultimate bending moment bearing capacity only exists in the bottom spoon shaped failure mode.As the aspect ratio increases,the wedge-shaped failure mode develops to a certain extent.In homogeneous clay foundation,the wedge-shaped failure mode is not obvious,and the spoon shaped failure area mainly consists of the soil at the bottom of the side wall and the soil on the side wall.As the aspect ratio increases,the increase in the bending bearing capacity of the permanent and temporary combined U-shaped groove increases from 1.4 times to 3.6 times.