交通荷载下台阶式加筋土挡墙动力响应的试验研究

Dynamic response of tiered geogrid-reinforced soil retaining walls under traffic loading

台阶式加筋土挡墙在山区道路边坡支挡结构中应用广泛,针对总高相同的二级台阶式加筋土挡墙开展1∶3大型缩尺模型试验,首先分析交通循环荷载作用下台阶宽度D对加筋土挡墙顶部基础沉降比的影响,进而选取D=0.4H2(H2为下级挡墙高度)的台阶式加筋土挡墙,研究交通荷载幅值及频率变化时,挡墙位移、土压力、筋材应变和潜在滑动面的动力响应规律。结果表明:加载初期挡墙顶部沉降和面板水平位移增加明显,但随循环次数增加呈收敛趋势;面板最大水平位移出现在上级墙高约0.85H(H为总墙高)处,且分布模式几乎不受幅值及频率变化影响;荷载幅值和频率对上级挡墙筋材应变的影响明显,下级挡墙筋材在上级墙趾下方处应变较大;二级挡墙水平土压力值沿墙高均呈顶部与底部小而中部较大的分布形式;上级挡墙潜在破裂面随荷载幅值增大而下移,由局部破坏逐渐向深层整体破坏演变;填筑过程将使下墙近面板处垂直应力增至约为1.5倍自重。研究结果将为台阶式加筋土挡墙设计与施工提供有益指导。

The multi-tiered geogrid-reinforced retaining wall(GRSRW)has been widely used in road retaining projects in mountainous areas.A 1∶3 large-scaled model test is carried out to investigate the performance of a two-tiered GRSRW with the same total height.The influences of offset distance D on its foundation settlement ratio is analyzed firstly,and then under the specified offset D=0.4 H2(H2,the height of the lower wall),the effects of variation of amplitude and frequency of the traffic loading on the panel horizontal displacement,earth pressure,reinforcement strains,strain distribution and potential failure surface are studied comprehensively.The test results show that the settlement ratio of loading plate at the top of retaining wall and the horizontal displacement ratio of panels increase significantly at the very beginning with the increase of the number of the traffic loading,and the displacement increment gradually tends to be convergent with the further increase of cycle times.The maximum displacement occurs at the upper wall height of about 0.85 H(H is the total wall height),and the distribution mode of the horizontal displacement is not affected obviously by the traffic loading.To increase the amplitude and frequency of the traffic loading can remarkably affect the strains of geogrid layers of the upper wall,and the strains of geogrid,below the toe of upper wall,of the lower wall are relatively greater.The horizontal earth pressure of the upper and lower walls is small at the top and bottom of the retaining wall,but large in the middle.The potential failure surface of the upper wall moves downward with the increase of the loading amplitude,and the failure mode of the upper wall gradually changes from local failure to deep global one.The filling process will increase the vertical stress of the lower wall near the panel to about 1.5 times the self-weight.The conclusion can provide a helpful guidance for the design and construction of tiered GRSRWs.