5 common quality problems in construction of self-drilling hollow bolt(SDA system)
by Anchor S. Web DesignerAs 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 06:06. Viewed 221 times.