河床式水电站混凝土蜗壳抗裂和限裂研究

结合某河床式水电站工程实际,对混凝土蜗壳结构进行了三维非线性有限元分析,探讨了钢纤维混凝土、环氧砂浆等材料在蜗壳抗裂和限裂方面的作用。研究表明:混凝土蜗壳虽承受水头不高,但孔口尺寸较大,在蜗壳顶板、底板与边墙相交处、机墩等部位易发生开裂;对规模较大的混凝土蜗壳,采用高强混凝土或钢纤维混凝土可减轻混凝土损伤,但抗裂效果并不显著,且带来水化热较大、施工工艺复杂等问题,可根据实际情况选择强度较低的混凝土,限制结构裂缝宽度在允许范围内,并做好防渗措施;在蜗壳混凝土内表面设钢衬或环氧砂浆涂层均是有效的防渗措施,亦可承担部分荷载,有助于控制裂缝宽度,但环氧砂浆存在老化、脱落等问题,耐久性低于钢衬。

Study on crack resistance and crack-width control of concrete spiral case of hydropower station in river channel

Combined with an in-stream hydropower house, cracking characteristics of reinforced concrete spiral case were analyzed by a nonlinear finite element method, and effects of steel fiber-reinforced concrete and epoxy mortar on concrete crack control are discussed. The results indicate that water head endured by this spiral case is not high, but owing to the large size of its orifices, cracks are very likely to appear in the intersections of its roof, floor and sidewall and on the generator pier. For a large-scale concrete spiral case, high strength concrete or steel fiber-reinforced concrete can reduce the extent of its concrete damage, while they have little effects in prevention of its cracking and they will, on the contrary, induce problems of high hydration heat and complicated construction technology. Thus, adoption of concrete with lower strength is more rational if combined with an effective control on crack width within a certain allowable range and a measure of seepage prevention. To reduce seepage, steel liner and epoxy mortar coating on the inner wall of spiral case are effective, and for crack control, a beneficial measure is to allow the steel liner and epoxy mortar to carry a certain part of the load. During practical operation, aging and spalling of the epoxy mortar are the problems unsolved yet, so steel liner is better and reliable in terms of durability.