压力隧洞复合预应力混凝土衬砌修补加固防渗结构计算分析及其施工工艺

Calculation and analysis on anti-seepage structure for repair and strengthening of lining of built-pressure tunnel with composite pre-stressed concrete and its construction technology

复合预应力混凝土衬砌修补、加固防渗方案是在原衬砌混凝土上二次浇筑一高性能纤维混凝土薄层,在新老混凝土中间设置薄钢板,通过在老混凝土表面开槽等手段,在老混凝土与防渗层之间形成一密闭中空的环形空间。利用水泥浆通过有限的径向位移对新浇筑的薄层混凝土根据需要人为地施加某一数值与分布的均布压应力,使二次衬砌混凝土层具有一定数值的环向预压应力。通过对新衬混凝土屈曲破坏和新老混凝土联合受力的分析表明,对于大洞径,选择外加预应力法对新内衬混凝土层施加预应力,理论上是可行的,这样可以分担部分的内水压力,而使该方案具有预应力混凝土补强加固效果及复合防渗功能。其优点是不仅省去预应力筋,达到防渗加固效果,而且施工简便,损失过水断面较小。

The composite pre-stressed concrete lining repair and strengthening anti-seepage scheme is that secondarily placing a thin layer of high-performance fiber concrete on the original concrete with thin steel plate arranged between the new and old concretes,and then forming a closed hollow annular space between the old concrete and the anti-seepage layer by means of making grooves on the surface of the old concrete. In accordance with the relevant demand,the uniformly-distributed compressive stress with a certain numerical value is artificially applied to the newly-placed thin concrete layer with cement grout through limited radial displacement. Through the analysis made on both the buckling failure of the newly-lined concrete and the joint stress of the old and new concretes,it is indicated that it is theoretically feasible for the larger tunnel diameter to select the external prestressing method for applying pre-stress to the new lining concrete layer. In this way,a part of internal water pressure can be shared,thus makes the scheme has the reinforcing and strengthening effect of the pre-stressed concrete as well as the composite anti-seepage function. The merit of this method is that not only the pre-stressing bar is omitted and the anti-seepage strengthening effect is obtained,but also the construction is simple and the loss of the flow cross-section is small.