Cone Penetration Test

 Cone penetration test (CPT) can be used to identify the soil strata underneath. This test is governed by EN ISO 22476 part 1 for United Kingdom and European region, and ASTM D5778 for the United States.

The penetrometer consists of a cone with a cross sectional area of 1000mm2 and apex angle of 60 degree. Above the cone, friction sleeve with surface area of 15000mm2 is prepared. During the test, the penetrometer is driven into the ground at a rate of 20mm/s. When it is necessary to determine the pore pressure, filters are provided to measure it. Such instrument is known as piezocone (CPTU). The cone measures the resistance during the driving process, while friction sleeve measures the sleeve friction along the path.

The test may be terminated once the desired penetration length is achieved. Other than that, we can terminate the test as soon as the agreed maximum thrust, or maximum capacity of the penetrometer or measuring system is reached.

Data from CPT can be used to estimate the bearing capacity of shallow foundation. For deep foundation, especially the driven pile, its result can produce reliable estimation for its capacity.