SAMPLED BY GP-R (300mm dia.) SAMPLED BY GP-R (300mm dia.) SAMPLED BY GP-R (300mm dia.)
FILL MATERIAL FOR A ROAD
VERY HARD GRAVELSGRAVELS AND FINESWITH LOOSE SANDSSAMPLED BY GP-R (200mm dia.)
LOOSE GRAVEL LAYERSAMPLED BY GP-D (200mm dia.) GL-16.10 - 17.15m
SANDY MATERIAL LAYERSAMPLED BY GP-D (200mm dia.) GL-18.05 - 19.08m"SHELL BED" , SANDY MATERIAL WITH SHELLSSAMPLED BY GP-D (200mm dia.)
GRAVELS WITH SANDSAMPLED BY GP-R (150mm dia.)
LOOSE SAND OF FILL MATERIALFOR PUSHING THE SAMPLING ASSEMBLY
FOR PUSHING THE SAMPLING ASSEMBLY

The GP-S was improved from one piece to a two pieces configuration.

"GP" means "Gel - Push".
All GP Samplers have a structure to enclose highdensity polymer solution inside.
The sample which is taken into the sample tube
push away the polymer solution to the tip of theGP Sampler.
The polymer solution act as a lubricant or drillingmud.

: Sample pushes the piston.

: Rotation or pushing.
: The piston stations on a sample as thesampler is penetrating.
: The polymer solution is pushed away as thesample comes into the sample tube.
: The polymer solution flows to a space between
sample tube and sample.
: The polymer solution cools down the drill bit
and washes away cuttings.

GP-Tr ,GP-S and GP-D are the same as conventional sampling methods in borehole. However, GP-R isdifferent from conventional methods. It is the method of sampling from ground surface.

A sampling process by GP-R sampler.

The sample disturbance is significant
not only by bit rotation but also by
friction between sample and sampletube.
Polymer solution reduces this friction.

A smaller friction due to polymer
gel makes sample extrusion
easier.

Figure 1. Results of the laboratory
experiments to measure piston pressureand displacement during sample
extrusion. ample can be extruded easierin a thin-wall tube with polymer than athin-wall tube without polymer.

A loose sample sometimes
collapses after extrusion from thesample tube. However a loose
sample coated by polymer gel iseasily self standing.
The polymer will be removed bytrimming just before laboratory
testing.

Figure 1: Relations of Piston Thrust Pressure andDisplacement of Piston.

Photo 2 : Self-standing sand samples after extrusionfrom the sample tubes. They are sampled by GP-S.

Polymer solution prevents the soil and rocksamples from slaking.

Figure 2. Examples of the slaking tests.
Case 1 : Ten seconds later in fresh water. The sample
started slaking.
Case 2 : Ten seconds later in 0.3% polymer solution. No
slaking even 72 hours elapsed.

Figure 2 : Results of the slaking tests
after ten seconds in fresh water andpolymer solution.

"High Quality Soil Testing"is not realized only by a good sampler.
It is achieved by ensuring all processes from a sampling to a laboratory testing, including sampling,packaging, transportation, extrusion, trimming and testing. Developments of GP Samplers remind us
their importance.

The quality of GP sampling is compared with the frozen method. A sample (300mm) by the freezing
sampling method and a GP sample by GP-D (200mm dia.) ware collected at the same site.
The test results show the quality of the GP sample is as good as Frozen sample.

Photo 3 : Samples by Freezing sampling method (Photo A) and GelPush sampling (Photo B).

Figure 3 : Cyclic resistance ratio obtained on the frozen
sample and Gel-Push sample. The results are comparable.

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