Our experience is not advisable. This is not preloading but creating a "water bomb" that may explode at any time.

Because the height of ordinary water bags is not enough, when using water bags, many manufacturers or construction units first think of multi-layer stacking like stacking sandbags. According to the product pictures of some manufacturers on the current network, there are two layers, with a height of about 2 meters, and each layer is about 1 meter. Moreover, the area of water bags on the upper side is much smaller than that on the lower side, which can not really meet the preloading requirements.

At present, the pre pressed water bags in the market are welded and heat sealed with PVC layer cloth, and the heat sealed welding seam becomes the weakest link. The water bag at the bottom may burst at any time under the pressure of the upper layer, which is a major hazard source; At the same time, water is a fluid liquid, which flows wherever it is low. The box girder floor itself has a slope. It is difficult and time-consuming to manually level again. In this way, the upper layer will not slide well, and the lower layer will not bear the risk of pressure burst. Therefore, this method is not advisable.

The water level of the preloaded water bag of Wuhan suanda company can be directly loaded to 2.5-3.5 meters high. There are also safety measures, which can meet the preloading requirements of the cast-in-situ supports of most bridges.