Application
Settlement hooks are used with telescoping inclinometer casing to identify the zones and magnitude of settlement in the ground surrounding the casing. Typical applications include:
- Monitoring settlement in foundations, and embankments.
- Monitoring for settlement caused by construction of tunnels and other underground openings.
- Monitoring settlement to increase the accuracy of inclinometer data.
Operation
The operator connects the hook to a survey tape and lowers the hook into the inclinometer casing. When the hook reaches the approximate depth of the first coupling, the operator pulls up, causing the arm of the hook to catch on the bottom edge of the casing section. The operator notes the depth and then repeats the procedure for the next section of casing. When the hook contacts the bottom of the casing, a mechanical action locks the arm in the closed position so it can be withdrawn. Settlements are calculated by comparing the current depth of each casing section with its initial depth. Note that settlement hooks are used with telescoping casing which provides edges for the hook to grab. The hooks do not work with casing that has flush interior joints.
Simple Hook: This hook has a swing-out contact arm or hook. It works to depths of 30 m (100 ft).
USBR-Type Hook: The USBR-type hook has two spring-loaded arms. Guide wheels keep the arms positioned for easy "hooking."
