软土地基加筋土挡墙数值模拟及稳定性探讨

NUMERICAL SIMULATION AND STABILITY DISCUSSION OF A REINFORCED SOIL RETAINING WALL ON SOFT SOIL FOUNDATION

对一软土地基加筋土挡墙建立二维数值模型,模拟其在分级堆载情况下挡墙和地基内的沉降、水平位移、土压力,以及土工格栅轴向应变的变化规律,模拟结果与现场实测结果基本吻合。采用有限元强度折减法计算的挡墙稳定性和滑裂面位置与实测情况一致,表现为深层滑动失稳。模拟和实测的各层筋材最大应变出现在距墙面4～6 m的位置,与目前土工合成材料加筋挡墙设计理论的朗肯破坏面位置不同,其原因是目前的挡墙设计理论基于刚性地基假定,未考虑地基变形对筋材应变分布及稳定性的影响。采用该数值模型探讨加长挡墙底部筋材对其稳定性的影响,得出挡墙稳定性与底部筋材加长长度和层数关系密切。得到的挡墙稳定性与筋材加长长度和层数的关系曲线,对于软土地基加筋土挡墙设计有指导意义。

A two-dimensional numerical model was established for a reinforced soil retaining wall on soft soil foundation. The settlements, horizontal displacements, earth pressures of retaining wall and axial strains of geogrid were simulated under the condition of step loading. The computed results were found to basically agree with the measurements. The stability and location of slip surface of the reinforced soil retaining wall computed by the finite element strength reduction method coincide with the observed results, indicating a deep-seated failure. The maximum computed and measured strains of each geogrid layer appear at the position 4 to 6 m away from the wall, which is very different from the Rankine failure surface stated by current design theory for reinforced soil retaining walls. The reason is that the current design theory for reinforced soil retaining wails is based on the hypothesis of rigidity foundation and does not consider the effect of foundation deformation on the strain distributions and stability of reinforced soil retaining walls. The effect of lengthening the bottom reinforcements on the stability of the reinforced soil retaining wall was further analyzed using the numerical model. It is indicated that the lengthening values and reinforcement-lengthening numbers apparently affect the stability of the reinforced soil retaining wall on soft soil foundation. The obtained curves of factor of safety versus reinforcement-lengthening number for various lengthening values were considered to be significant for design of reinforced soil retaining walls on soft soil foundation.