5 common quality problems in construction of self-drilling hollow bolt (SDA system)

 As a very effective support method, self-drilling hollow anchors have been widely used in rock and soil anchor support system in recent years. Self-drilling hollow anchors not only maintains the stability of soil and rock mass during construction, but also plays an important role as a part of permanent support structure after construction, so it is very important to ensure the construction quality of self-drilling hollow bolt.
However, from the construction situation in recent years, there are the following quality problems in the construction of self-drilling hollow anchor rods:
1. The water cement ratio is not correct, the cement dosage is insufficient. Field testers and supervisors should always measure the consistency of cement slurry to ensure that it is within the designed range before grouting. Otherwise, the reason should be found out. The general reason is less cement, or cement caking, mixing uneven.
2. The angle of the anchor rod is horizontal. At present, because most of the anchor rod is drilled by a digging and drilling trolley, the hole is formed by a Jackhammer (air gun) . And the height direction of the trolley can not be adjusted. The general rock drill is on the long side and not vertical, and it often tops the platform on the roof of the trolley. In this way, the anchor rod above the spandrel can easily be made at a horizontal angle, and can not be made perpendicular to the excavation contour line, it is very common for the top of the arch to leak.
3. The deviation of bolt positioning is large, and the depth of hole forming is insufficient. Some construction workers greedy for easy, not in accordance with the provisions of the hands-line, marking, fixed point, but by the workers intuitive drilling, resulting in hole position deviation. The hole depth is insufficient, is the technical information is not clear or lazy workers lead to. Spot-check should be random, frequency not less than 10% of the number of anchor rod.
4. The anchor rod root number is insufficient, many are intentionally jerry-built. Should be in the bolt before grouting an inventory, after all the completion of grouting again inventory. Finally, it should be counted again before the initial spray.
5. No grouting, false grouting or insufficient grouting. Not grouting, false grouting is a serious intentional jerry-building behavior. It is mainly shown that the anchoring agent is used to plug the grouted opening of the anchor rod intentionally, which results in the false grouting. Check the hole to see whether there is slurry overflow around the stop plug, you can also use the method of tapping anchor to listen to the sound to determine whether the grouting has been.
The above quality problems seriously affect the safety of the project, must be put an end to it, the constructors must carry out the construction in strict accordance with the standard operating procedures, the site management staff must also do a good job of supervision and inspection. Only in this way can the construction of the self-drilling hollow bolt really become an effective form of support.

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