1. Embedding of anchor rods
First, drill a hole in the bedrock (diameter ≥ 90mm) where the bedrock displacement meter is installed, and the depth of the hole is according to the design requirements.
Prepare an anchor rod whose length is slightly less than the drilling depth, and weld the displacement gauge adapter to the end of the anchor rod.
Put the anchor rod welded with the adapter into the hole, the elevation is slightly lower than the hole, and after positioning, pour cement mortar into the bottom of the hole. The pouring depth of the mortar is less than 1/2 of the drilling depth, and the upper part is filled with yellow sand to the hole. mouth (exposing the connector).
When burying the bolt, block the threaded hole of the adapter with something to prevent the blockage of the threaded hole from affecting the connection with the bedrock displacement gauge.
2. Installation
First connect the displacement meter to the reading instrument, and pull the displacement meter rod by hand to check whether the reading is normal. After confirming that the displacement gauge is in good condition, it can be installed. Assemble the bedrock displacement meter according to the structure shown in (Figure 3.1).
Connect the measuring rod of the displacement meter to the connector, connect the measuring rod protective tube to the protective tube seat, fix it at the bedrock hole, adjust the measuring range of the displacement meter, and seal the surroundings of the base with mortar to prevent the mortar from flowing into the bottom plate when pouring concrete in bedrock holes. Connect long cables according to the design requirements, and pay attention to protecting the cables during laying.
3. Adjust the measurement range
After the bedrock displacement gauge is installed in place, the measurement range should be adjusted in time.
Method 1: Push the displacement gauge into the protective tube until it can’t be pushed, draw a marking line on the outer circle of the displacement gauge at the port of the protective tube, and then pull the displacement gauge so that the distance between the marking line and the port of the protective tube is the measured pressure range required by the design .
Method 2: Connect the reading instrument to the bedrock displacement meter, push the displacement meter into the casing until it stops, read the zero reading, determine the reading at the initial position according to the calculation formula, and then pull the displacement meter to the set reading value .
Finally, use a reading instrument to check whether the displacement gauge is intact, and solve the problem in time if any problem is found. In order to prevent disturbance during pouring of the bedrock displacement meter, the bedrock displacement meter can be piled and buried manually with concrete, and the floor concrete can be poured after it is consolidated.
After the installation is completed, the instrument number and design number should be recorded and archived in time, and the lead-out cables of the instrument should be strictly protected.
4. Select the benchmark value
The measurement value of the bedrock displacement meter is the change of the real-time measurement value relative to the reference value, so the accuracy of the reference value selection will directly affect the accuracy of the measurement value.
When the external load does not change much, select 3 similar readings at the same time and stable temperature, and use them as the reference value after averaging. When the bedrock displacement meter is installed in the concrete, the measured value after the heat of hydration should be selected. After the benchmark value is selected, it should be recorded well as the benchmark value for calculation.
In order to make the reference value more accurate, the above operation can be repeated twice, if the two measured values are basically the same (error ≤ 0.5% FS), it proves that the reference value is correct.
When the measured value of the bedrock displacement meter deviates, the above method can be used to recalibrate the reference value.
The above is the embedding and installation content of the displacement meter. For more information, please continue to pay attention.