Automatic Unconfined Compression Apparatus
1. Description
This equipment is a Fully Automatic Unconfined Compression Apparatus (BTU-WXY series), including models WXY-1F, WXY-3F, and WXY-6F. It is mainly used
for unconfined compressive strength testing in geotechnical
engineering (i.e., uniaxial compression test without confining
pressure). The apparatus enables fully automatic control, data
acquisition, and processing throughout the test, real-time display
of various curves, and automatic generation of standard-compliant
test tables and curves.
2. Test Standards
- ASTM D2166(Unconfined Compressive Strength Test)
- BS 1377: Part 7(British Standard)
- ISO 17892-2(Geotechnical laboratory testing)
- SL 237-1999(Chinese specification for soil testing)
- JGS 0523(Japanese soil testing method)
3. Specification (Parameter)
| Model | Max. specimen size (mm) | Max. axial force (kN) | Shearing speed (mm/min) |
| BTU-WXY-1F | Ø101 × H200 | 10 | 0.00001 ~ 6 |
| BTU-WXY-3F | Ø101 × H200 | 30 | 0.00001 ~ 6 |
| BTU-WXY-6F | Ø101 × H200 | 60 | 0.00001 ~ 6 |
4. Detail (technical details)
l Specimen size: Max. Ø101 mm × H200 mm, a standard size for unconfined tests.
l Axial force ranges: Three optional capacities – 10kN, 30kN, 60kN – allowing selection
of an appropriate load range based on soil strength to improve
measurement accuracy.
l Shearing speed: 0.00001 ~ 6 mm/min, wide adjustable range, supporting both
ultra-slow creep-type failure tests and conventional speeds (e.g.,
1–2 mm/min) for standard tests.
l Software functions:
u Fully automatic control of shearing speed and loading process
u Real-time acquisition and display of displacement, stress,
strain, and other curves
u Automatic generation of standard-compliant tables and curves
after the test
u Supports data export and printing
5. Application
l Road and subgrade engineering: Determine unconfined compressive strength of soils to evaluate
bearing capacity
l Slope and excavation engineering: Obtain undrained shear strength 
l Soft soil evaluation: Quality control of soft clays, compacted fills
l Material comparison: Strength comparison tests of different stabilized soils
(cement/lime treated soils)
l Teaching laboratories: Basic soil mechanics experimental instruction
6. Advantages
l Fully automatic operation: No manual intervention required for shearing speed or data
recording, improving test efficiency and repeatability
l Selectable load ranges(10/30/60kN): Different models cover different strength ranges;
alternatively, a single unit may accommodate multiple ranges by
changing sensors (depending on configuration)
l Ultra-low speed capability: 0.00001 mm/min for studying failure processes or creep
characteristics
l Highly integrated software: From control and acquisition to report generation – all in one,
lowering operational barriers
l Compact design: Simpler than triaxial apparatus, suitable for field laboratories
or rapid testing
7. What To Choose (selection guide)
| Specimen type / strength range | Recommended model | Reason |
| Soft clay, clay (qu < 200 kPa) | WXY-1F (10kN) | Range matches, better sensor accuracy |
| Ordinary cohesive soil, silt (qu ~ 200–600 kPa) | WXY-3F (30kN) | Common range, with margin |
| Stiff clay, cement-stabilized soil, treated soil | WXY-6F (60kN) | Suitable for high-strength materials, avoids overloading |
| Teaching lab (various soil types) | WXY-3F or WXY-6F | Broader coverage, suits both soft and hard soils |
| Ultra-slow failure process study | Any model | All models support 0.00001 mm/min |
8. Process Flow
1. Specimen preparation→ Prepare a cylindrical soil specimen of Ø101×H200 mm (undisturbed
or remoulded)
2. Mount specimen→ Place the specimen centered on the lower platen; adjust the upper
platen to contact the specimen surface (apply a minimal initial
seating load)
3. Parameter setting→ Set shearing speed 
and data acquisition frequency in the software
4. Start test→ The system automatically applies axial load at the set speed,
acquiring axial force and displacement in real time
5. Data monitoring→ Software plots stress-strain curve, axial force vs. time curve,
etc., in real time
6. Failure determination→ Stop when a peak stress is followed by continued loading to
15–20% axial strain, or when the specimen shows obvious failure
7. Result processing→ Calculate unconfined compressive strength qu; if needed,
calculate undrained shear strength Su = qu/2
8. Report output→ Software automatically generates standard-compliant tables and
stress-strain curves; supports printing or export
