Common Operating Abnormalities of Prestressed Anchorage
Prestressed anchorages are one of the common accessories in bridge engineering. When there is no problem with the quality of the anchorages, the subsequent construction site loss is also small, and abnormalities will inevitably occur during the construction process. Below, I will summarize the common abnormal problems and treatment methods of the prestressed anchorage in the construction process.
- The grout inlet pipe of the anchorage is blocked. For the anchor cable that has been blocked in the grouting pipe, the methods of supplementing the grouting pipe, grouting with the original grouting pipe, and increasing the grouting pressure are adopted. Anchorage tension and extension value overrun (exceeding the calculated value -5%, +10%). The reasons for the abnormal elongation value include: the cracks in the anchoring section shortening the tension section, and the rock cracks are closed under pressure. If it is believed that the elongation value is abnormal due to geological reasons, it can be saved and used, otherwise, the entire anchor cable should be reworked.
- The anchorage wedge slides or the amount of retraction is overrun. The reasons for the abnormality include shortcomings in the processing of some wedges, and the steel strands being infected by dust. Treatment methods include: replacing the wedge after unloading and re-tensioning and compensating for the tensioning of a single steel strand.
- The grouting condition of the anchorage tension section is abnormal. In the grouting process, abnormal conditions such as crack leakage and pipe blockage are often encountered. Measures such as plugging the cracks and extending the grouting time can be adapted to deal with it. Grouting the surrounding rock of the anchor hole is generally only applied once. Repeated irrigating frequently and briefly, often delays the construction period, constitutes a waste, and the benefit is not much improved. If the effect of one-time grouting cannot meet the planning requirements, the fineness of cement can be improved, the grout can be improved, or chemical grouting can be used. When the grouting of the surrounding rock of the anchor hole causes serious stringing due to poor geological conditions, it will form a dangerous situation of bearing the grouting pressure on a large area, which is extremely unfavorable for anti-sliding and anti-overturning stability. Therefore, the grouting should be given single by single, that is, after filling a hole, drill the adjacent hole.
After summarizing the above several common situations, I believe we have an understanding of the common problems and solutions of prestressed anchorage, which will be helpful for future operations.