To support foundations on expansive black cotton soils, the preferred ground-improvement technique is_________________?
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Answer: D. replace the poor soil
Explanation
Expansive black cotton soils undergo severe volume changes with moisture, making soil replacement the best remedy. Excavating poor expansive clay and backfilling with stable granular material creates a reliable foundation platform. Option D is correct as replacing poor soil eliminates the shrinking and swelling hazards beneath shallow foundations. Black cotton soils contain montmorillonite clay minerals that swell extensively when wet and shrink when dry. Fluctuating moisture levels generate immense uplift pressures that crack foundations, floors, and walls. Ground improvement techniques are essential for constructing safe structures on problematic geotechnical formations.
Civil engineers conduct thorough soil investigations before designing foundations in regions with black cotton deposits. Alternative stabilization methods include lime treatment or deep pile foundations reaching down to stable strata. Ignoring expansive soil properties leads to severe structural distress and expensive building remediation projects. Option A suggests increasing foundation depth, which alone does not prevent uplift pressures from swelling soils. Option B proposes draining the soil, which is practically impossible to maintain consistently in expansive clay strata. Option C recommends compaction, which fails because compacted expansive clay will still swell when moisture enters.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
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