曲面滑坡条件下h型抗滑桩受力性状模型试验研究

MODEL TEST ON MECHANICAL BEHAVIOR OF H-TYPE ANTI-SLIDE PILE UNDER CURVED LANDSLIDE

依托公路大型滑坡治理工程,设计物理模型试验装置,设置同一滑面和桩体锚固深度,进行6组h型抗滑桩室内模型试验,分析不同连梁长度及后排桩悬臂段高度(连梁高度)时桩顶位移变化规律、桩身弯矩和桩后土压力分布特征,研究曲面滑坡条件下h型抗滑桩受力性状及其内在机制,并给出桩后滑坡推力抛物线型分布的一般函数表达式。试验结果表明:h型抗滑桩受力过程桩顶水平位移变化表现出较为明显的三阶段特征,桩身弯矩分布呈现正、负交变现象,后排桩桩顶水平位移及桩身弯矩明显大于前排桩;降低后排桩悬臂段高度不影响桩身弯矩分布特征,但对于桩顶水平位移及桩身弯矩量值,后排桩明显减小,前排桩有所增大;增减连梁长度对前、后排桩之间荷载传递与协同受力特性影响显著,使得前、后排桩水平变形及桩身弯矩随之产生变化;连梁正、负弯矩极值均处于连梁端部,相比于连梁长度,连梁弯矩的大小及分布形态受后排桩悬臂段长度的影响更为明显;随着连梁长度的减小或后排桩悬臂段长度的增加,后排桩桩后土压力表现出抛物线型、重心偏下的抛物线型及近似梯形的分布形态。此外,给出的滑坡推力函数表达式能较好的表征其抛物线型分布特征,通过调整合力作用点参数,亦可对滑坡推力近似梯形的分布类型进行描述。

Based on a large highway landslide management project,six groups of model tests were performed using a newly designed device.In these tests,same slip surface and pile anchorage depth but different coupling beam length and back pile cantilever length(coupling beam height)were set.Pile mechanical behaviors(including the pile top displacement,pile bending moment and soil pressure distribution)changing disciplines and mechanisms were studied.Furthermore,the general expression capable of describing the parabolic distribution of post-pile landslide thrust was proposed.The experimental results indicate that the horizontal displacement of the h-type pile top could be divided into three stages.The positive and negative distribution of pile bending moment alternatively appears.The pile top horizontal displacement and the bending moment of the back pile are significantly larger than those of the front pile.With a reduction in the back pile cantilever height,the pile moment distribution shows minor changes.However,in this process the front pile gains a significant increment in pile top horizontal displacement and pile moment while the back pile suffers a dramatic reduction.The length variation of the coupling beam significantly affects the load transfer and synergistic force characteristics between the front and back piles,resulting in changes in the horizontal deformation and bending moment.The extreme values of both positive and negative bending moments are located at the end of the coupling beam.Compared with the length of the coupling beam,the size and distribution of the bending moments of the coupling beam are more obviously influenced by the cantilever length of the back pile.With the decrease of the coupling beam length or the increase of the back pile cantilever length,the soil pressure behind the back pile shows a parabolic type,a parabolic type with a lower gravity center,or an approximate trapezoid type distribution.In addition,the proposed expression could well characterize the parabolic distribution of the landslide thrust.By adjusting the parameters describing the position of the joint force action point,the approximate trapezoidal type distribution of the landslide thrust could be described as well.