Influences of rigid and flexible normal contacts on stress of concrete cut-off walls
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摘要: 为在深厚覆盖层上高土质心墙堆石坝的设计中准确预测混凝土防渗墙的应力,开展了防渗墙刺入黏土的模型试验,利用CT断层扫描获得了防渗墙顶端土体的变形性状;提出在防渗墙顶端与土体的法向接触模拟中,应采用柔性法向接触本构模型;建立了有限元模型,研究了刚柔性法向接触对混凝土防渗墙应力的影响。结果表明：防渗墙顶端切削周边土体,发生了明显的刺入位移;刚性法向接触本构模型不允许接触面发生嵌入,因而防渗墙顶端周边土体对防渗墙的约束效应过于强烈,导致防渗墙顶端较高的压应力;柔性法向接触本构模型允许一定程度的接触面嵌入,接触面嵌入位移可理解为实际刺入位移,可较好地模拟实际工程中防渗墙刺入黏土的冲切破坏现象。Abstract: In the design of high rockfill dams with clay core wall on deep overburden, how to accurately predict the stress of concrete cut-off walls is the key scientific problem to be solved. An experimental study on the penetration of a cut-off wall into clay is carried out, and the deformation behavior of the clay at the top of the cut-off wall is obtained by means of the computed tomography. It is proposed that the flexible normal contact constitutive model should be adopted in the simulation of the normal contact between the top of the cut-off wall and the clay, and the finite element model is established to study the stress of the concrete cut-off wall under the rigid and flexible normal contacts. The results show that the top of the cut-off wall cuts the surrounding soil, and obvious penetration into soil displacement occurs. The normal hard contact constitutive model does not allow the contact surface to be embedded, so the restriction effect of the clay around the top of the cut-off wall is too strong, which leads to the high compressive stress at the top of the cut-off wall. The flexible normal contact constitutive model allows a certain degree of contact surface to be embedded and the embedding displacement of the contact surface can be interpreted as the actual penetration displacement. It can well simulate the punching failure phenomenon of cut-off walls penetrating into clay in practical engineering.
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