Link points to Internet Archive / others. Not hosted by InfraLens. Details
IS 11629:1986 is the Indian Standard (BIS) for installation and operation of the single-point hydraulic over-flow setting gauge. 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
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
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.
EM 1110-2-1908US Army Corps of Engineers (USACE), USA
HighCurrent
Instrumentation of Embankment Dams and Levees
Provides comprehensive guidance on all dam instrumentation, including hydraulic settlement systems similar to IS 11629.
ASTM D6598 - 18American Society for Testing and Materials (ASTM International), USA
MediumCurrent
Standard Guide for Installing and Operating Settlement Platforms for Monitoring Vertical Deformations
Covers monitoring of vertical settlement, but focuses on settlement plates rather than hydraulic gauges.
BS EN ISO 18674-4:2019International Organization for Standardization (ISO)
MediumCurrent
Geotechnical investigation and testing — Geotechnical monitoring by field instrumentation — Part 4: Measurement of pore water pressure
Details installation of piezometers, which share the same hydraulic principles and installation challenges as the IS 11629 gauge.
Key Differences
≠The IS code is highly specific to a single instrument type (single-point hydraulic overflow gauge), whereas modern standards like USACE EM 1110-2-1908 cover a wide array of instruments including vibrating wire, electrical resistance, and GPS-based systems.
≠IS 11629 describes a completely manual reading process. International standards extensively discuss and provide guidance for automated data acquisition systems (dataloggers), remote telemetry, and data management software.
≠Modern standards like the USACE manual specify more advanced procedures, such as the use of de-aired water (prepared with a vacuum) for the hydraulic fluid to significantly improve measurement accuracy and stability, a step not detailed in the IS code.
≠Material specifications in IS 11629 are based on 1980s availability (e.g., GI pipes, generic polythene). International standards are more performance-oriented, recommending modern materials like armored nylon or HDPE tubing for better durability and lower gas permeability.
Key Similarities
≈The fundamental measurement principle—communicating vessels where fluid in connected tubes seeks the same level—is identical across the IS code and international manuals describing hydraulic settlement systems.
≈All standards emphasize the critical importance of a stable reference datum. The requirement in IS 11629 to place the gauge house on firm ground away from settlement influence is a core principle in all geotechnical monitoring.
≈Meticulous installation procedures, such as protecting tubing from kinking or damage, ensuring a continuous gradient, and careful backfilling, are common requirements in both IS 11629 and modern guides like ASTM D6598.
≈The need for system maintenance, specifically the procedure of flushing or purging the hydraulic lines to remove air bubbles and ensure clear passage, is a shared operational requirement.
Parameter Comparison
Parameter
IS Value
International
Source
Tubing Gradient
Continuous rising gradient not flatter than 1 in 100
Minimum continuous gradient of 1% (1 in 100) is recommended to promote air bubble migration.
USACE EM 1110-2-1908
Hydraulic Fluid
Clean water, with optional non-corrosive disinfectant or antifreeze.
De-aired water is standard; a 50/50 ethylene glycol/water mixture for antifreeze is common.
USACE EM 1110-2-1908
Tubing Internal Diameter
Not less than 10 mm
Typically smaller, e.g., 4 to 6 mm (1/4 inch), is common for modern twin-tube systems to reduce fluid volume.
USACE EM 1110-2-1908
System Reading Accuracy
±1 to ±2 mm (inferred from manual hook/staff gauge method)
System precision should be ±3 mm or better for hydraulic systems.
Locate on stable ground and verify terminal stability with periodic, high-precision surveys against a remote benchmark.
ASTM D6598 - 18
⚠ Verify details from original standards before use
Key Values4
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
Tables & Referenced Sections
Key Tables
No tables data
Key Clauses
Clause 2 - Principle
Clause 4 - Installation
Clause 5 - Operation and Observation
Clause 6 - Maintenance
Frequently Asked Questions3
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).