- Asked 2/16
- 2080 Baisakh · 2+2 marks
- 2078 Bhadra · 2+1 marks
Disturbed vs undisturbed samples
Short answer
Disturbed samples lose natural structure, are obtained with augers or split spoons, and suit classification tests. Undisturbed samples retain structure and moisture, are taken with thin-walled samplers, and allow strength and consolidation tests. Quality depends on sampler design, insertion method, soil sensitivity, stress relief, and handling.
Differentiate between disturbed and undisturbed soil samples. What are the factors affecting the quality (disturbance) of a sample?
| Point | Disturbed sample | Undisturbed sample |
|---|---|---|
| Structure | Natural structure and density destroyed | Natural structure, density and moisture largely retained |
| Representative? | Yes, constituents are present (mixed) | Yes, in structure and content |
| Collection | Auger, split spoon, test pit by hand | Thin-walled Shelby tube, piston sampler, block sampling |
| Tests possible | Grain size, specific gravity, Atterberg limits, compaction | Shear strength, consolidation, permeability, unit weight |
| Cost | Cheap, easy | Costly and needs care |
| Use | Classification and identification | Design parameters |
Factors affecting the quality of a sample
- Sampler design: area ratio, inside and outside clearances, cutting edge sharpness.
- Method of boring and advancing (water jets, disturbed bottom of hole, bottom heave).
- Method of sampling: pushing vs hammering, speed and rate of insertion.
- Type of soil: soft sensitive clays and loose sands are easily disturbed.
- Stress release when the sample is taken out, and possible swelling.
- Handling, transport and storage: vibration, moisture loss, rough handling, time delay, extrusion method.
✓ Answer checked by Claude Sonnet 5.5
Related questions
- Sampler disturbed or undisturbed check · Foundation Engineering, chapter 2
- Why undisturbed samples are required · Foundation Engineering, chapter 2
- Factors affecting bearing capacity; water table · Foundation Engineering, chapter 6 · asked 5×
- Representative vs non-representative samples · Foundation Engineering, chapter 2
- Factors affecting selection of pile type · Foundation Engineering, chapter 8
- Soil moisture forms; factors affecting CWR · Irrigation and Drainage Engineering, chapter 2
- Cost vs value; factors affecting valuation · Construction Management, chapter 13
- Quality; QA vs QC; factors in Nepal · Project Engineering, chapter 4
- Differentiate quality control and assurance · Project Engineering, chapter 4