Module 1 : Site Exploration and Geotechnical Investigation
Lecture 3 : Soil samplings and samplers [ Section 3.1 : Soil sampling, Disturbed samples, Undisturbed samples ]
   


The penetration resistance of the sampler, the possibility of entrance of excess soil and danger of disturbance of sample all increase with increase in area ratio. The allowable area ratio intended for obtaining undisturbed samples depends on diameter, design and method of operation of the sampler. The area ratio should be preferably be less than 10 %, but it is possible that the greater area ratio can be tolerated when the sampler is provided with a stationary piston and / or the cutting edge having very small angle of taper .

Outside clearance ratio
For good sampling process, the ratio should be within 0-2 %.
Minimum inside diameter = = 75mm.
The length (L) should be at least equal to (the intended length + 100mm) for residual soils.
For soft soils depending upon the sensitivity, ( L / ) ratios are given in table 1.1
The cutting edge angle ( – refer fig. 1.6 ) should be within .
The tube should be uniform and should not have any protrusions or irregularities. The inside of the tube should beclean and smooth.
 
 
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