5 common quality problems in construction of self-drilling hollow bolt (SDA system)
by Anna S. Optimization SpecialistAs a very effective support method, self-drilling
hollow anchors have been widely used in rock and soil anchor support
systems in recent years. Self-drilling hollow anchors not only
maintain 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 unevenly.
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
are 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 is not less than 10% of the number of anchor rods.
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
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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Created on Oct 23rd 2021 06:16. Viewed 204 times.