Soil investigation – tube boring method: Which of the following features are essential to the traditional tube-boring setup?

Introduction / Context:
For shallow geotechnical investigations in soft soils, simple tube-boring (also called shell and auger variants) provides disturbed samples and stratification indications. Knowing the basic components and sequence of operation helps plan low-cost site explorations where rotary rigs are unnecessary.

Given Data / Assumptions:

• A cylindrical tube sampler with cutting edge is used.
• A check (flap) valve at the bottom retains soil during withdrawal.
• The setup uses a tripod, pulley, and rope for handling.
• A casing is advanced to stabilize the bore as depth increases.

Concept / Approach:
The cutting shoe at the tube tip shears soil; the flap valve prevents loss of material as the tube is hoisted. The tripod-and-pulley arrangement allows repeated drops under gravity to penetrate further. A surrounding casing prevents collapse of the borehole walls and reduces contamination. Together, these elements constitute the essential features of the classic tube-boring method for near-surface profiling and sampling.

Step-by-Step Solution:
Confirm each listed item is part of the standard setup: cutting-edge tube, flap valve, tripod-and-pulley handling, and gravity drop inside a driven casing.Recognize that all are complementary and collectively necessary for efficient operation.Therefore the comprehensive choice is “All of the above.”

Verification / Alternative check:
Geotechnical field manuals illustrate similar assemblies for wash/auger/tube boring with casing advancement and simple lifting gear.

Why Other Options Are Wrong:
Any single item alone cannot ensure successful boring and sample retrieval; the method relies on the combined system.

Common Pitfalls:
Operating without casing in loose soils (leads to collapse); omitting the flap valve (sample loss); using inadequate lifting gear (safety hazard).

Final Answer:
All of the above.