1. SDMT MULTIPLE CHOICE QUESTIONNAIRE (ANSWERS)!
SDMT MULTIPLE CHOICE QUESTIONNAIRE (ANSWERS)      ! 

2. Recommended SDMT Test Sequence
1) When performing both DMT and seismic measurements at the same depth, in what order should they be done:
Seismic measurements first
DMT measurements first
In any order 
Recommended SDMT Test Sequence
(DMT tests every 20 cm; Seismic test every 50 cm)
When both tests, DMT first;
If a DMT test has to be interrupted, the recommended moment is after the readings have been taken, just before advancing to the next test depth;
Seismic test useless before 1 m, (first seismic test recommended after 1.50 m)
the center of the 2 sensors is 0.5 m above DMT, so first sensor is at 0.25 m when DMT is at 1.0 m!

3. Shear Wave Source Issues
2) When generating the shear wave with a hammer and beam, at what approximate distance from the rods should the shear beam be placed:
About 5 m
As close as possible, in contact with the rods
As close as possible, but not in contact with the rods (say between m) 
Shear Wave Source Issues
Distance from SWS to rods (closest without touching rods)
SWS Placement and Orientation
SDMT Sensor Orientation

4. Shear Wave Source (hammer)
3) Where should the shear beam be placed if the test site has a pavement:
On the pavement
On natural soil, after pavement removal (adding soil if necessary) 
Shear Wave Source (hammer)
Geometry & weight: influence only on max test depth (not results)
SWS transmits vibration only if good adherence with soil
Apply load on SWS (i.e. truck jacks)
Remove pavement under SWS (if present)
Use rubber for decoupling with load  energy to soil not to load

5. Shear Wave Source (hammer)
4) Why should the operator load the shear beam (ex. with a lift jack of the pushing machine):
In order to minimize the beam’s vibration when the hammer hits it
So that there is a good coupling between the beam and the soil and also so that the shear beam does not advance when the hammer hits it
None of the above 
Shear Wave Source (hammer)
Geometry & weight: influence only on max test depth (not results)
SWS transmits vibration only if good adherence with soil
Apply load on SWS (i.e. truck jacks)
Remove pavement under SWS (if present)
Use rubber for decoupling with load  energy to soil not to load

6. Shear Wave Source (hammer)
5) Why is it recommended to place a rubber sheet between the load and the shear beam:
To avoid scratches on the beam
To avoid scratches on the load
To minimize the energy transmitted to the load on the beam 
Shear Wave Source (hammer)
Geometry & weight: influence only on max test depth (not results)
SWS transmits vibration only if good adherence with soil
Apply load on SWS (i.e. truck jacks)
Remove pavement under SWS (if present)
Use rubber for decoupling with load  energy to soil not to load

7. 6) What is the correct placement of the shear beam with respect to the rods:
The hitting direction of the hammer should be approximately perpendicular to the line between the center of the beam and the rods
The hitting direction of the hammer must be approximately parallel to the line between the center of the beam and the rods
A preferential orientation does not exist 

8. 7) What is the correct orientation of the sensors with respect to the hitting direction of the hammer ?
The hitting direction of the hammer must be perpendicular to the axis of the sensors
The hitting direction of the hammer must be parallel to the axis of the sensors
A preferential direction does not exist 

9. 8) When performing SDMT test in marine sites, where should the shear beam be installed:
Floating on the water
Anywhere on the seafloor
On the seafloor, as close as possible to the rods without contact (say between m) 

10. 9) Is it possible to perform seismic measurements in non-penetrable soils:
Yes, as a standard SDMT test in a borehole filled with water
Yes, as a standard SDMT test in a borehole with casing
Yes, as a standard SDMT test in a uncased borehole backfilled with clay or silt
Yes, as a standard SDMT test in a uncased borehole backfilled with gravel (diameter grain size between 5-15mm)
It is not possible 

11. Seismic dilatometer – SDMT
10) Why are SDMT shear wave velocity measurements performed every 0.50 m:
Because 0.50 m is a standard recommended by the norms
Because the sensors are spaced 0.50 m, to cover all the soil profile
Because the sensors are spaced 1.0 m 
Seismic dilatometer – SDMT
0.5 m
0.5 m

12. 11) In penetrable soils, why are Vs measurements faster with the SDMT compared to the traditional innhole seismic measurements (multiple answers possible):
It is not faster
The downhole method requires to wait for the cementation of the pipe in the borehole
The downhole method requires at each depth to guarantee a good contact between the sensors and the pipe  
SDMT features
SDMT
Vs interpretation
automatic
operator indipendant
real time
Accuracy of delay (Δt) calculation
True-interval (2 receivers instead of 1)
Same wave to both receivers
No Trigger influence on Δt calculation
Signals are amplified and digitized in depth  clean waves  delay Δt very clear
Test execution is rapid
no hole
no cementation (e.g. crosshole)

13. Seismic Test Configuration
12) To perform SDMT tests, in what position must the DMT membrane be:
In the open position (sound off)
In the closed position (sound on)
In any position 
Seismic Test Configuration
DMT membrane must be in A position (check acoustic signal ON when switch is on DMT)
After DMT readings in sand, generally membrane is not pushed back to A position  no contact  no sound (advance a few cm until signal ON)
Switch to ‘Seismic’