- 2078 Poush · 3 marks
Cylindrical specimen, 95% compaction
Short answer
Assuming the printed wet weight is 30 N, volume is 1.571×10⁻³ m³. Dry unit weight γ_d = 19.10/1.15 = 16.61 kN/m³; void ratio e = 0.565; saturation S = 70.3%. For 95% relative compaction, field dry unit weight must be at least 15.78 kN/m³.
A cylindrical specimen of a cohesive soil of 10 cm diameter and 20 cm height was prepared by compaction in a mold. Taking the specific gravity of soil solid as 2.65 and the wet weight of this specimen as 30 kN [as printed] and water content as 15%, find the following: (i) dry unit weight, void ratio and degree of saturation of this cylindrical specimen; (ii) if 95% of relative compaction is to be achieved in the field, what should be the dry unit weight of compacted soil of the same soil specimen in the field.
Given
cm, cm, , , kN/m³.
Assumption: the weight "30 kN" is a misprint for 30 N, since 30 kN in this small mould would give an impossible unit weight of about 19,000 kN/m³.
Volume and unit weights
Void ratio
Degree of saturation
(ii) Field requirement
Taking the specimen's dry unit weight as the maximum (laboratory) dry unit weight:
Answer: (i) kN/m³, , ; (ii) field kN/m³.
✓ Answer checked by Claude Opus 5.5 (high effort)
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