The Cone Penetration Test (CPT)

The Cone Penetration Test (CPT) is a geotechnical test that involves driving a conical-tipped probe into the ground using hydraulic force. The cone has a diameter of 35 mm, an angle of 60°, and a projected area of 10 cm². The penetration is performed at a rate of 2 cm/s with a hydraulic force of up to 20 tons.

During the penetration, resistance values are measured at two-centimeter intervals, including the tip resistance (qc) at the cone’s tip, frictional resistance (qs) along the cone jacket, and pore pressure (u). These values are recorded and plotted on a graph.

**Cost of CPT Test:**
The cost of the CPT test is relatively low as it doesn’t require drilling. The transportation of the CPT test machine involves a carrier, an operator for the carrier, one engineer, and two workers. Depending on the soil and terrain type, 2-5 tests can be conducted per day. If soil samples are required, it may slightly increase the cost.

**Advantages and Limitations of CPT:**

1. No need for drilling boreholes for the test.
2. Cost-effective.
3. Continuous data can be obtained from the ground (up to 40 meters).
4. Multiple parameters like groundwater level, pore pressure, soil density, SPT value, internal friction angle, etc., can be determined with a single CPT test.
5. It helps in determining foundation bearing capacities, settlement amounts, liquefaction potential, and pile bearing capacities.

1. The main limitation is the inability to collect soil samples during the test, preventing laboratory experiments.
2. CPT is suitable for soft clay, silt, sand, and fine gravel but may not be appropriate for heavily gravelly or blocky soils or very dense soils.
3. CPT tests are not typically performed in boreholes, except in special circumstances. However, if a blocky layer is present above the level of testing, the test can be conducted after drilling through this layer.
4. CPT penetration depth is limited.

This information provides an overview of the CPT test, its cost considerations, and its advantages and limitations. If you have any specific questions or need further clarification, feel free to ask.

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