Down-hole/cross-hole tests
• Down-hole/cross hole tests are in-situ test methods
- to measure dynamic soil/rock properties
- to determine P-wave and S-wave velocities
- to identify soil stratification
- to determine shear modulus, G =r.vs
Down-hole/cross-hole/krishna Aryal 1
Down-hole Seismic test
Surface source S-wave arrival time, t
vs = dz/dt
Layer 1
Transd. 1
Layer 2
Transd. 2
Depth, z
Down-hole/cross-hole/krishna Aryal 2
Down-hole test
Source of impulse Receiver
Receiver Source of impulse
a) Down-hole test b) Up-hole test
Down-hole/cross-hole/krishna Aryal 3
Cross-hole test
Source Receiver
L
2 boreholes arrangement
Down-hole/cross-hole/krishna Aryal 4
Cross-hole test
Source
Receivers
L
3 boreholes arrangement
Down-hole/cross-hole/krishna Aryal 5
Down-hole testing
Oscilloscope Downhole
Pump
Testing Plank
Horizontal
with normal load
x
t Hammer
z1
z2 packer
Horizontal
Test
Depth
Velocity
Interval Transducers
(Geophone
Receivers)
Shear Wave Velocity: R12 = z12 + x2
R22 = z22 + x2
Vs = R/t Cased
Borehole
x
Down-hole/cross-hole/krishna Aryal 6
Results
P and S-waves are determined from the t-z plot
Down-hole/cross-hole/krishna Aryal 7