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.
Tunnelling Methods in Rock Masses -- Guidelines
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
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.