This standard details the procedure for cross-hole seismic testing to determine the in-situ dynamic properties of rock masses. It covers the required equipment, test execution, and the computation of P-wave and S-wave velocities, Dynamic Young's Modulus, and Poisson's Ratio from the collected data.
Code of practice for seismic testing of rock mass, Part 2: Between the borehole
Quick Reference Values
Typical P-wave velocity in competent rock3000-6000 m/s
Typical S-wave velocity in competent rock1500-3500 m/s
Typical Dynamic Poisson's Ratio in rock0.15 - 0.35
Key Formulas
Vp = L/t_p — P-wave velocity from travel time
μd = [ (Vp/Vs)^2 - 2 ] / [ 2 * ( (Vp/Vs)^2 - 1 ) ] — Dynamic Poisson's Ratio
Ed = ρ * Vs^2 * (3*Vp^2 - 4*Vs^2) / (Vp^2 - Vs^2) — Dynamic Young's Modulus
Practical Notes
Proper coupling of geophones to the borehole wall is critical for good signal quality.
Accurate surveying of borehole deviation is essential, as velocity calculations depend on the precise source-to-receiver distance.
The energy source (e.g., sparker, mechanical hammer) should be chosen based on rock conditions and required penetration depth.