- 2073 Bhadra · 3 marks
Compaction curves of sand and clay
Short answer
Sand shows a flat curve with a dip due to bulking; highest density occurs dry or saturated, and vibration is effective. Clay has a distinct peak at high OMC and lower MDD; kneading compaction gives the best results.
Compare the compaction characteristic curve for sand and clay.
| Basis | Sand (cohesionless) | Clay (cohesive) |
|---|---|---|
| Shape of curve | Flat, with a "dip" at low to intermediate water content and higher values when dry or saturated | Distinct peak at OMC |
| Sensitivity to water | Very low | High |
| Maximum dry density | High (about 18 - 21 kN/m³) | Low (about 14 - 19 kN/m³) |
| OMC | Low (about 6 - 10%) | High (about 12 - 30%) |
| Reason | Moisture is not essential; bulking at low water content due to capillary tension; at saturation the water drains out | Water lubricates the particles; excess water reduces density |
| Best method | Vibration | Kneading (sheep-foot) |
gd
| Sand ___.-~~~~~-.___
| (flat, dips)
|
| Clay .-"-.
| / \
+-------------------- w
In sand, the highest density is obtained when it is either completely dry or fully saturated; the minimum occurs at about 4 - 8% water content because of bulking (capillary tension holds the particles apart). In clay the density follows the typical bell-shaped curve with a clear optimum.
✓ Answer checked by Claude Opus 5.5 (high effort)
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