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IS 15026:2002 is the Indian Standard (BIS) for guidelines for use in prediction of subsidence and associated parameters in coal mines having nearly horizontal single seam workings. This standard provides guidelines for predicting ground subsidence, tilt, and strain caused by underground coal mining in near-horizontal single seams. It outlines empirical methods, including profile function and influence function approaches, to estimate the magnitude and extent of surface movement and classify potential damage to surface structures.
Guidelines for Use in Prediction of Subsidence and Associated Parameters in Coal Mines Having Nearly Horizontal Single Seam Workings
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! The prediction methods are empirical and highly dependent on geo-mining parameters specific to Indian coalfields; site-specific calibration is crucial.
! The code's applicability is primarily for sub-critical to critical width single-seam extractions; multi-seam or supercritical scenarios require significant expert judgment.
! Predictions should be accompanied by a robust monitoring plan using instruments like total stations and tiltmeters to validate and refine the model.
BS 6164:2019BSI - British Standards Institution, UK
HighCurrent
Code of practice for health and safety in tunnelling in the construction industry
Provides comprehensive guidance on planning, design, construction, and safety for all types of tunnels, closely mirroring the broad scope of IS 15026.
ÖNORM B 2203-1:2020Austrian Standards International, Austria
MediumCurrent
Underground works - Part 1: Contract and construction
Highly influential for conventional tunnelling (NATM/SCL), providing detailed principles that are referenced within IS 15026.
EM 1110-2-2901USACE - US Army Corps of Engineers, USA
HighCurrent
Tunnels and Shafts in Rock
A detailed technical manual covering investigation, design, and construction of rock tunnels, aligning well with the technical guidelines in the IS code.
ITA-AITES GuidelinesInternational Tunnelling and Underground Space Association, International
HighCurrent
Guidelines for the Design of Tunnels (2004) and others
Serves as a global best-practice reference for tunnel design and construction methods, many principles of which are adopted in IS 15026.
Key Differences
≠IS 15026 is a 'guideline' providing recommendations, whereas standards like BS 6164 are 'codes of practice' often carrying greater contractual and regulatory weight in their respective countries.
≠The Indian standard incorporates considerations for specific local geological conditions, such as the high-stress and complex tectonics of the Himalayas, which are not a focus of European or US standards.
≠International standards like BS 6164 are deeply integrated with their national health and safety legal frameworks (e.g., UK HSE regulations), while IS 15026 cross-references Indian regulations like those from the DGMS (Directorate General of Mines Safety).
≠While IS 15026 gives a balanced overview of D&B, TBM, and NATM, standards like Austria's ÖNORM B 2203-1 provide significantly more in-depth, prescriptive detail on the principles and contractual application of the New Austrian Tunnelling Method (NATM).
Key Similarities
≈All standards universally adopt rock mass classification systems, primarily the RMR (Rock Mass Rating) and Q-System, as the fundamental basis for preliminary design and ground support selection.
≈There is a common emphasis across all standards on the critical importance of a comprehensive geotechnical and geological investigation phase as a prerequisite for design and construction.
≈The core principles of the 'Observational Method' are shared, particularly for conventional tunnelling, where designs and support systems are actively monitored and adjusted based on observed ground behaviour.
≈All documents recognize and provide technical guidance for the same primary rock excavation methods: conventional methods (Drill & Blast, Sequential Excavation) and mechanized tunnelling (TBM).
≈The fundamental components of rock support systems—including rock bolts (passive/active), shotcrete (plain/fibre-reinforced), and steel ribs—are common to all the standards, with similar principles guiding their application.
Parameter Comparison
Parameter
IS Value
International
Source
Rock Support for RMR 41-60 (Fair Rock)
Systematic rock bolts (3-4m long @ 1.5-2m spacing) with 50-100mm of shotcrete.
Systematic bolts (3-4m long @ 1.5-2m spacing) and 50-100mm shotcrete.
Bieniawski's RMR System (1989), widely adopted in international guides like USACE EM 1110-2-2901.
Blast Vibration Limit (PPV) for Residential Structures
Typically 5-12 mm/s, as per DGMS circulars referenced by the code.
Guidance values are frequency-dependent, e.g., 15 mm/s at 4 Hz rising to 50 mm/s at 40 Hz.
BS 7385-2:1993
Stand-up Time for 8m Span in 'Good' Rock (RMR ≈ 70)
Approx. 6 months (Based on adapted Bieniawski charts).
Approx. 6 months (Based on original Bieniawski 1989 charts).
ITA Guidelines / Bieniawski's original work
Rock Bolt Spacing in 'Very Good' Rock (RMR 81-100)
Spot bolting as required.
Generally spot bolting.
USACE EM 1110-2-2901
Minimum Shotcrete Thickness (Sealing Layer) in Good Rock
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Typical Angle of Draw15° to 35°
Tensile Strain for 'Severe' Damage1.0 - 2.0 mm/m
Compressive Strain for 'Severe' Damage2.0 - 3.0 mm/m
Tilt/Slope for 'Severe' Damage5.0 - 10.0 mm/m
Maximum Subsidence Factor 'a' (Typical)0.1 to 0.9 depending on caving method
Key Formulas
Smax = a * m * cos(α) — Maximum possible subsidence calculation
S(x) = Smax * (1 - tanh²(c*x/H)) — Budry-Knothe Profile Function for Subsidence Prediction
T(x) = dS(x)/dx — Ground tilt as the first derivative of the subsidence profile
E(x) = dU(x)/dx — Horizontal strain as the derivative of horizontal displacement
Tables & Referenced Sections
Key Tables
Table 1 - Classification of Degree of Damage on the Basis of Horizontal Ground Strain
Table 2 - Classification of Degree of Damage on the Basis of Slope/Tilt
Key Clauses
Clause 4 - Terminology and Definitions
Clause 5 - Prediction of Subsidence and Associated Parameters
Clause 6 - Subsidence and its Effect on Surface Properties
Annex A - Profile and Half-Profile Function Methods
Annex B - Influence Function Methods
Frequently Asked Questions4
What is the 'angle of draw'?+
It is the angle between the vertical line at the edge of the underground working and the line connecting that edge to the limit of surface subsidence (Clause 4.1.8).
How is potential damage to buildings classified?+
Damage is classified from 'negligible' to 'very severe' based on calculated maximum tensile/compressive strains and ground tilt, as per Table 1 and Table 2.
What is the difference between profile and influence function methods?+
Profile function methods (Annex A) predict the subsidence trough using a single mathematical equation, while influence function methods (Annex B) calculate subsidence at a point by summing the effects of small, individual extraction elements.
What is the maximum subsidence factor 'a'?+
It's an empirical factor representing the ratio of maximum possible subsidence to the extraction height, typically ranging from 0.1 (with stowing) to 0.9 (for caving).