What is the primary purpose of an IS 11629 gauge?

To monitor vertical settlement or heave at a specific, inaccessible point within a soil or rock mass, such as inside an earth dam or under a large foundation (Clause 1.1).

How does this settlement gauge work?

It works on the principle of communicating vessels where water finds its own level. The settlement of an embedded gauge unit is measured by comparing its elevation with a fixed overflow point in a control unit via a water-filled tube (Clause 2).

What is the most common cause of inaccurate readings?

Entrapped air in the hydraulic lines is the most common issue, which prevents the water from freely communicating between the gauge and control unit. Regular de-airing is a key maintenance task (Clause 6.1).

IS 11629

: 1986

Code of practice for installation and operation of the single-point hydraulic over-flow setting gauge

CurrentSpecializedCode of PracticeBIMGeotechnical · Soil and Foundation Engineering

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This standard provides a code of practice for the installation and operation of single-point hydraulic overflow settlement gauges. It details the principles of operation, equipment required, installation procedures in various ground conditions, and the method for taking observations to monitor settlement or heave.

Code of practice for installation and operation of the single-point hydraulic over-flow setting gauge

Quick Reference Values

Typical measurement accuracy± 1.0 mm

Recommended internal diameter of tubing4 to 6 mm

Recommended de-airing pressure for wateraround 7 kg/cm²

Minimum bend radius for tubing300 mm

Practical Notes

The complete removal of air from the hydraulic system is the most critical factor for obtaining accurate readings. Repeated de-airing cycles are often necessary.

Protecting the hydraulic tubing from damage (kinking, crushing) during construction activities is essential for the long-term functionality of the gauge.

Temperature fluctuations can affect the density of the water and the length of the tubing, potentially introducing errors. These effects should be considered, especially for long tubing runs.