Principle and application
The crosshole test measures the velocity of seismic waves propagated between boreholes, obtaining the small-strain shear modulus of the soil (G0). This is the dynamic stiffness parameter required by seismic design and the foundations of vibrating machinery, with accuracy higher than that of surface methods.
The test in stages
Aligned boreholes
Boreholes are drilled and cased at a known spacing.
Source and receivers
A wave is generated in one borehole and its arrival is measured in the others.
Velocity calculation
From the distance and the travel time, Vs and Vp are obtained by depth.
Dynamic moduli
The shear modulus G0 and the dynamic modulus are derived.
As Vs between boreholes
| Vs | Shear wave velocity |
|---|---|
| Vp | Compression wave velocity |
| G0 | Small-strain shear modulus |
| Profile | Variation with depth |
Quality and field operation
Data quality
- Cased and verticalised boreholes for a reliable geometry.
- Synchronised source and receivers.
- Control of the spacing between boreholes.
- Interpretation by a geophysics specialist.
Safety and operation
- Qualified for high-compliance areas: mining, industry and ports.
- Organised, signed work front with an HSE procedure in place.
- Own crews and fleet, including night shifts.
The deliverable
| Vs/Vp profile | Velocities by depth |
|---|---|
| Dynamic moduli | G0 and dynamic modulus |
| Report | Methodology and results |
| Typical lead time | According to the number of boreholes and depth |
Sectors and project types
Frequently asked questions about the Crosshole Test
What is the Crosshole test used for?
The crosshole test measures the velocity of seismic waves propagated between boreholes, obtaining the small-strain shear modulus of the soil (G0). This is the dynamic stiffness parameter required by seismic design and the foundations of vibrating machinery, with accuracy higher than that of surface methods.
Crosshole, downhole and MASW, what is the difference?
All of them measure wave velocity. Crosshole measures between boreholes (most accurate); downhole measures along a single borehole; MASW measures from the surface (no borehole). The choice balances accuracy, cost and access.
What is the G0 modulus used for?
It is the small-strain stiffness of the soil, the basis for dynamic analysis: seismic response of the ground and foundations for vibrating equipment.
S-waves: measuring the dynamic stiffness of the soil
Technical bulletin on shear wave velocity tests.
Crosshole test for your project
Tell us about your project and we will prepare the investigation plan and the quote.