地基水荷载对混凝土坝位移影响研究

Study of concrete dam displacement with foundation water load

分析了地基变形模量随深度逐渐增加、渗透系数随深度逐渐减小、坝基渗透系数各向异性、坝踵设置帷幕排水,以及考虑渗流场和应力场耦合等对混凝土坝位移分量的影响,得出如下结论:作用在地基上的水荷载,使混凝土坝坝顶相对参考基点(倒垂锚固点或坝踵正下方1倍坝高处)的水平位移指向上游,而参考基点的水平位移随地基截取范围的增大而增大.由于大坝工程上常将倒垂线锚固在岩基深处,并认为该倒垂线测值为绝对位移.当考虑作用在地基上的水荷载时,将倒垂线测值作为绝对位移的认识存在局限性.为了获得精度良好的参数反演值,必须考虑参考基点的位移,应采用大坝有限元数值计算的坝体位移和基点位移的相对值,联合实测位移分离出的水压分量进行参数反分析.

The concrete dam displacement is studied considering the factors such as foundation modulus increasing with depth, seepage coefficient reducing as depth, seepage coefficient anisotropic, curtain and drainage in the dam heel and seepage field and stress field coupling. Some conclusions are obtained： if the foundation is considered only with the seepage volume load, the dam top horizontal displacement of the reference base point develops upstream. When the foundation size increases, the reference base point＇s horizontal displacement increases. However, the value measured by the reversed pendulum anchored to the rock foundation is often regarded to be absolute displacement. The above practice is estimated to be limited when the water load on the dam foundation is taken into account. It is proposed that the displacement of the reference base point should be considered, in order to obtain accurate inversion value of parameters. The parameter back analysis needs to adapt to the relative displacement value of dam crest and base point calculated by the infinite element numerical computation, together with the measured component of water pressure from displacement.