高速铁路小变形下陡坡地基路肩桩板墙力学响应

Mechanical response of shoulder sheet-pile wall under strictly restricted deformation condition in steep ground along a high-speed railway

掌握高速铁路陡坡地基条件下路肩桩板墙力学特性是路堤侧向变形控制的关键。以贵广高速铁路某陡坡地基路肩桩板墙为试验工点,对墙背土压力、桩身内力与变形进行了900余天现场长期观测,讨论了墙后路堤分层填筑引起的墙土侧向变形形态差异及机械碾压残余应力对土压力分布的影响。结果表明:适应高速铁路小变形要求的强约束、深锚固路肩桩板墙能有效控制陡坡地基路堤侧向变形,桩体仅呈0.94‰的近似刚性转动,填筑完成后变形约占30%,且1.0~1.5 a趋于稳定;经碾压密实的墙后粗粒土填料,即使在小变形下依然能达到主动土压力状态;分层填筑引起墙后填土侧向变形呈现的"上小下大"分布形态与墙体位移相反,是墙背土压力呈现出中部大、两端小抛物线分布模式的重要因素;基于适筋梁受力状态及平截面假定,分别结合实测钢筋应力与混凝土应变换算得到的桩身弯矩具有良好的一致性,与极限地基反力法的理论计算吻合。

It is key to grasp mechanical response of shoulder sheet-pile wall in steep ground along a high-speed railway for control of lateral deformation of embankment. In this study, the sheet-pile walls in steep ground along Guiyang-Guangzhou high-speed railway were selected as monitored objects. Long-term observations for the earth pressure behind the wall, the internal force and deformation of the pile were made for more than 900 days. The layered filling-induced differential deformation between sheet pile walls was intensively discussed, and the effect of roller compaction-induced residual stress on distribution of earth pressure was discussed as well. The results indicate that the lateral deformation of embankment is effectively limited by sheet-pile walls. The lateral deformation of the pile top is about 0.949/00 height of the wall and tends to be stable in 1-1.5 years later, this is about 30% of the total displacement after embankment is filled. The roller-compacted coarse-granular filler behind the wall can still reach active earth presSUre state even in small lateral deformation. The lateral deformation of fills caused by the layered filling presents a shape of small at top and large at bottom and is opposite with the displacement distribution of sheet-pile wall. The lateral deformation of fills is the main factor for parabolic distribution of earth pressure behind the wall. The recommended bending moment formula about pile according to concrete stress and steel bar strain in field test is consistent with theoretical calculation value.