温降和水库蓄水引起的碾压混凝土拱坝裂缝分析

施工温降是引起碾压混凝土拱坝裂缝的主要荷载。均匀温降作用下拱坝在裂缝前整个断面处于受拉状态，最大拉应力出现在拱端上游面和拱冠下游面。均匀温降使碾压混凝土拱坝全断面受拉，坝体形成深层的或贯穿性的裂缝对拱坝的危害较大。施工温降在水库放空时所产生的裂缝深度一般比水库蓄满时大。水荷载所产生的压应力可以部分或全部抵销温降所产生的拉应力。一般来说，上游水荷载对拱坝的作用更大，它在拱圈大部分区域产生很大的压力，因而使裂缝的扩展受到抑制。用水平拱作为计算图形进行结构分析，能较好地反映出碾压混凝土拱坝的应力和裂缝状况；混凝土的钝裂缝带模型用于有限元断裂分析和确定裂缝扩展深度比较方便。

Analysis on RCC arch dam cracks caused by temperature drop and reservoir filling

Temperature drop in the construction is a main factor which causes the cracks of RCC arch dam. Acted by uniform temperature drop, the whole section arch dam is in the state of tension before the crack happens. The maximum tensile stress is in the upstream section of arch abutment and the downstream section of crown. The uniform temperature drop causes the whole section of RCC arch dam to be in tension. The deep of cracks through arch dam body will endanger greatly the arch dam. The crack depth caused by temperature drop during the reservoir empty is larger than that during the reservoir fill. Because the compressive stress caused by water load could counteract partly or wholly the tensile sir*ess caused by temperature drop. Generally, the upstream water load would creategreater acting force on arch dam and greater compressive force on most of arch ring so that the crack extension could be restrained. Adopting horizontal arch as calculating chart for structural analysis could express well the stress and cracks of RCC arch dam. It is very convenient to use the model of blunt crack zone in concrete for finite element fracture analysis and the determination of the depth of crack developing.