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IS 15632 : 2015Criteria for Seismic Design of Hydraulic Structures

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EM 1110-2 · ICOLD Bulletin 148 · FEMA P
CurrentSpecializedCode of PracticeBIMWater Resources · Irrigation and Canal Structures
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Link points to Internet Archive / others. Not hosted by InfraLens. Details
OverviewValues4InternationalTablesFAQ5Related

IS 15632:2015 is the Indian Standard (BIS) for criteria for seismic design of hydraulic structures. This code provides design criteria for hydraulic structures like weirs and barrages founded on permeable soil. It focuses on analyzing and controlling subsurface seepage to ensure safety against uplift pressure and piping failure, primarily using Khosla's theory of seepage flow. Note: This code does NOT cover seismic design.

Lays down criteria for the seismic analysis and design of various hydraulic structures.

Overview

Status
Current
Usage level
Specialized
Domain
Water Resources — Irrigation and Canal Structures
Type
Code of Practice
International equivalents
EM 1110-2-6053 · U.S. Army Corps of Engineers (USACE), USAICOLD Bulletin 148 · International Commission on Large Dams (ICOLD), InternationalFEMA P-1026 (2013) · Federal Emergency Management Agency (FEMA), USAEN 1998-5:2004 · European Committee for Standardization (CEN), Europe
Typically used with
IS 6512IS 7784
Also on InfraLens for IS 15632
4Key values1Tables5FAQs

BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.

Practical Notes
! The user's provided title 'Criteria for Seismic Design of Hydraulic Structures' is incorrect for this code. IS 15632 deals with seepage below hydraulic structures, not seismic design. For seismic design, refer to IS 1893 (Part 5).
! Khosla's theory (Annex A) is the cornerstone of this standard and requires careful application of correction factors for mutual interference of piles, floor thickness, and slope.
! Determining the safe exit gradient (Table 1) is critical, but it relies on accurate soil classification, which is often a major source of uncertainty in design.
Frequently referenced clauses
Cl. 5.2Safety Against Piping or UnderminingCl. 5.3Safety Against Uplift PressureCl. 6Methods of Seepage ControlAnnex A - Khosla's Theory and Method of Independent Variables
Pulled from IS 15632:2015. Browse the full clause & table index below in Tables & Referenced Sections.
concretesoilsteel sheet piles

International Equivalents

Similar International Standards
EM 1110-2-6053U.S. Army Corps of Engineers (USACE), USA
HighCurrent
Earthquake Design and Evaluation for Civil Works Projects
Covers comprehensive seismic design and evaluation for hydraulic structures like dams, levees, and floodwalls.
ICOLD Bulletin 148International Commission on Large Dams (ICOLD), International
HighCurrent
Selecting seismic parameters for large dams - Guideline
Focuses specifically on the selection of seismic parameters, a core component of IS 15632's scope.
FEMA P-1026 (2013)Federal Emergency Management Agency (FEMA), USA
HighCurrent
Seismic Design of Dams
Provides guidelines for the seismic design, evaluation, and analysis of various types of dams.
EN 1998-5:2004European Committee for Standardization (CEN), Europe
MediumCurrent
Eurocode 8: Design of structures for earthquake resistance - Part 5: Foundations, retaining structures and geotechnical aspects
Overlaps on geotechnical aspects, slope stability, and foundations for dams and retaining structures.
Key Differences
≠IS 15632 bases its seismic hazard on the zonal map from IS 1893 (Part 1), which assigns a single Zone Factor (Z) to large regions. Most international standards (e.g., USACE, ICOLD) mandate or strongly prefer site-specific Probabilistic (PSHA) or Deterministic (DSHA) Seismic Hazard Analysis.
≠IS 15632 uses a prescriptive Importance Factor (I=1.5 for most dams) to scale the design forces. In contrast, USACE and ICOLD use a risk-based or performance-based approach, defining performance goals for different earthquake levels (e.g., MCE, OBE) without using a single scaling factor.
≠While IS 15632 allows for FEM, it primarily references the simplified Westergaard or Zangar methods for hydrodynamic pressure. Modern international standards like USACE EM 1110-2-6053 provide more detailed guidance on using advanced numerical methods (FEM/BEM) for complex dam-reservoir-foundation interaction.
≠For embankment dam stability, IS 15632 provides simplified criteria for using the pseudo-static method based on dam height and seismic zone. International practice (e.g., FEMA P-1026) places greater emphasis on deformation analysis (Newmark's sliding block method) as a standard procedure even for initial screening.
Key Similarities
≈Both IS 15632 and major international codes advocate a two-level seismic design philosophy: ensuring no-damage or repairable damage under a Design Basis Earthquake (DBE)/Operating Basis Earthquake (OBE) and preventing catastrophic collapse under a Maximum Credible Earthquake (MCE)/Safety Evaluation Earthquake (SEE).
≈A similar hierarchy of analysis methods is recognized, progressing from the Seismic Coefficient (pseudo-static) method for simple structures to Response Spectrum Analysis and ultimately non-linear Time History Analysis for critical and complex dams.
≈All standards, including IS 15632, mandate the consideration of the vertical component of seismic ground motion, recognizing its importance for the stability of gravity dams, cantilever components, and soil liquefaction potential.
≈The fundamental principle of accounting for hydrodynamic pressure on the upstream face of dams, based on Westergaard's added mass concept, is a common cornerstone of seismic analysis in both IS 15632 and its international counterparts.
Parameter Comparison
ParameterIS ValueInternationalSource
Seismic Hazard DefinitionBased on Seismic Zone Factor 'Z' (0.10 to 0.36) from IS 1893 map.Based on site-specific PSHA, providing spectral accelerations (Ss, S1) at various return periods.USACE EM 1110-2-6053
Importance FactorTypically 1.5 for dams.Not used directly. Risk-based performance goals are defined for specific earthquake levels (e.g., MCE, OBE).ICOLD Bulletin 148
Vertical/Horizontal Spectral RatioGenerally taken as 2/3 of the horizontal spectral value, unless site-specific data is available.Recommends site-specific V/H ratios. In absence, provides default ratios that vary with spectral period.USACE EM 1110-2-6053
Damping for Concrete Dams (Response Spectrum)5% of critical for Design Basis Earthquake (DBE).5-7% for concrete dams at DBE/SEE stress levels.ICOLD Bulletin 148
Liquefaction Analysis TriggeringRecommends detailed investigation for dams in Zones IV and V founded on liquefiable soils.Requires evaluation for any site with potentially liquefiable soils and a design PGA > 0.1g, using methods like SPT/CPT correlations.FEMA P-1026
Required Seismic FreeboardSpecifies minimum seismic freeboard as 75% of the computed maximum wave height due to earthquake.Requires calculation of total loss of freeboard from sloshing, settlement, and fault displacement, with no prescriptive reduction factor.FEMA P-1026
⚠ Verify details from original standards before use

Key Values4

Quick Reference Values
Safe exit gradient for fine sand/silt1/7 to 1/6
Safe exit gradient for coarse sand1/6 to 1/5
Safe exit gradient for shingle1/5 to 1/4
Recommended factor of safety for floor thickness against uplift1.33 (or 4/3)
Key Formulas
Exit Gradient GE = (H/d) * (1 / (π * sqrt(λ))) — Khosla's formula for exit gradient at the downstream end of a simple floor.
Floor Thickness t = h / (G-1) — Basic formula to calculate floor thickness required to balance uplift pressure 'h' by its submerged weight (G=sp. gravity of material).

Tables & Referenced Sections

Key Tables
Table 1 - Safe Exit Gradient for Different Types of Soils
Key Clauses
Clause 5.2 - Safety Against Piping or Undermining
Clause 5.3 - Safety Against Uplift Pressure
Clause 6 - Methods of Seepage Control
Annex A - Khosla's Theory and Method of Independent Variables

Related Resources on InfraLens

Cross-Referenced Codes
IS 6512:2018Criteria for Design of Cross-Section for Cana...
→
IS 7784:2010Code of Practice for Design of Parallel Runwa...
→

Frequently Asked Questions5

What is this code's primary purpose?+
To design hydraulic structures (weirs, barrages) on sandy foundations to be safe against failure from subsurface water flow (seepage).
What is the most critical check in this code?+
Ensuring the exit gradient at the downstream end is less than the safe exit gradient for the foundation soil to prevent piping failure (Clause 5.2).
What theory is this code based on?+
It is primarily based on Khosla's theory of subsurface flow, which calculates uplift pressures under the structure (Annex A).
What is a safe exit gradient for fine sand?+
Between 1/7 and 1/6, as per Table 1.
Does this code cover dam design?+
No, this code is for weirs and barrages on permeable foundations. For dam design, refer to codes like IS 6512 (Gravity Dams) or IS 1893 Part 5 (Seismic Design of Dams).

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