Triaxial shear testing modes (concept check): If drainage is permitted continuously during the application of both the normal stress (cell pressure) and the shear (deviator) stress so that full consolidation occurs and no excess pore-water pressure develops at any stage, the test is called:

Introduction / Context:
Understanding the drainage and consolidation conditions in laboratory shear tests is fundamental for interpreting soil strength parameters. The three classical triaxial modes are UU (quick), CU, and CD, each producing different pore pressure responses and effective stresses.

Given Data / Assumptions:

• Drainage is allowed at all stages: during application of cell pressure and during shearing.
• No excess pore-water pressure builds up at any time.
• Full consolidation is achieved before and maintained during shear.

Concept / Approach:
In a consolidated–drained (CD) test, the specimen first consolidates under the applied all-round pressure with drainage open. During subsequent shearing, drainage remains open and the piston is advanced slowly so pore pressures do not develop. Shear strength is evaluated directly in terms of effective stresses; c′ and φ′ are obtained for design under long-term drained conditions.

Step-by-Step Solution:

Verification / Alternative check:
In UU, drainage is closed at all times → excess pore pressure develops. In CU, drainage is open during consolidation but closed during shear → excess pore pressure develops only during shearing. Only CD has no excess pore pressure at any stage.

Why Other Options Are Wrong:

• UU (quick): always undrained, hence excess pore pressure occurs.
• CU: undrained during shear; pore pressures are generated.
• “None of these” and “partially drained direct shear”: do not match the fully drained definition.

Common Pitfalls:
Confusing CU with CD because both consolidate under open drainage; the key difference is drainage during shearing.

Final Answer:
Drained test (CD: consolidated–drained)