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The Triaxial Test is one of the most common and accurate geotechnical methods used to determine the shear strength of soil. This test plays a crucial role in the design of foundations, slopes, embankments, and other structures that directly interact with soil conditions.
There are three main types of triaxial tests: UU (Unconsolidated Undrained), CU (Consolidated Undrained), and CD (Consolidated Drained). Each method has its own procedure, duration, and application. Let’s break them down one by one.
1. UU Triaxial Test (Unconsolidated Undrained)
In the UU test, the soil sample is neither consolidated nor allowed to drain. The deviator stress is applied immediately after the specimen is placed in the testing apparatus.
Key Characteristics:
No consolidation, no drainage
Quick testing process
Suitable for emergency conditions such as earthquakes or sudden failures
Pore water pressure is not measured
Results reflect short-term soil strength
When to Use?
The UU test is commonly used for saturated soils under rapid loading, for example, slope stability analysis after heavy rainfall or sudden failure conditions.
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2. CU Triaxial Test (Consolidated Undrained)
In the CU test, the soil sample is first consolidated under a given pressure, but drainage is not allowed during loading. Pore water pressure is usually measured in this test.
Key Characteristics:
Consolidation occurs, but no drainage during loading
Moderate testing time
Measures pore water pressure → provides effective stress strength parameters
Suitable for staged loading conditions
When to Use?
This test is ideal for projects involving gradual loading, such as multi-story buildings, highways, or other infrastructures with staged construction.
3. CD Triaxial Test (Consolidated Drained)
The CD test is the most comprehensive and time-consuming type. The soil sample is fully consolidated, and during the loading stage, pore water is allowed to drain gradually.
Key Characteristics:
Full consolidation with drainage allowed
Longest testing duration
No pore water pressure during shearing
Results represent long-term soil strength
When to Use?
The CD test is typically used for long-term projects such as embankments, dams, and levees where soil is subjected to sustained loads.
| Test Type | Consolidation | Drainage | Test Duration | Suitable For |
|---|---|---|---|---|
| UU | No | No | Fast | Emergency conditions, earthquakes |
| CU | Yes | No | Moderate | Staged loading (buildings, roads) |
| CD | Yes | Yes | Long | Long-term loads (embankments, dams) |
Understanding the differences between UU, CU, and CD triaxial tests is essential in selecting the most appropriate soil testing method. The choice of test directly influences the analysis results and ultimately impacts the safety and efficiency of engineering structures.
✅ Need Professional Triaxial Testing?
PT Geo Sinergi Utama provides international-standard soil laboratory testing services, including UU, CU, and CD triaxial tests. With experienced engineers and complete testing equipment, we deliver accurate, reliable, and timely results to support your project.