Cone penetrometer test is also referred to as cone penetration test, often abbreviated as CPT. This is a method that is used in the determination of geotechnical engineering properties of soils and the delineation of soil stratigraphy. The invention of CPT happened in the 1950s in Delft. The invention happened in the Dutch Lab for Soil Mechanics when scientists were investigating soft soils. Here are facts regarding cone penetrometer test for soil.
Sometimes, the process is referred to as Dutch cone test because it originated from the Netherlands. This process has been accepted all over the world despite it having been invented and developed in Europe. It is among the best methods of investigating soils. Projects that deal with ground compaction mostly apply this method. Currently, various types of mechanical and electrical cone penetrometers are available. However, the electric cone is the most common.
CPT utilizes a conical tip that is normally pushed into the earth at a rate of 2 cm per minute. This conical tip has a diameter of 35.7 millimeter and an apex angle of 60 degrees. A steel rod connects to the conical tip and has a similar diameter as the conical tip. The pinecone is normally pushed into the earth at a rate that varies between 1.5 and 2.5 centimeters per second.
The penetration resistance at the tip and along the shaft of the pinecone is measured as the pinecone is pushed deeper into the ground. Friction is experienced where the shaft connects to the pinecone. This area is known as the friction sleeve. Normally, the friction sleeve has a surface area of 15,000 square millimeters.
The recording of the friction is done using transducers that make part of the electric CPT. If the CPT probe is incorporated with a pore-water pressure sensor, it is referred to as a CPTU. It is vital that the filter ring of the pore-water element is completely saturated with water. Failing to saturate the element with water will cause erroneous results to be recorded by the piezo-transducer.
One can include other types of sensors in the CPT in order to measure other elements of the ground that is being worked on. For example, one can include vibration sensors that will help determine acceleration and vibration velocity. CPT is a standardized operation whose results are not dependent on the operator like is the case with SPT. Since CPT results are independent of the operator, it implies that they are reproducible.
Sleeve friction and pinecone resistance which are measured by CPT are used to gauge the friction ratio (FR). Difference in lateral earth pressure in the ground is indicated by the sleeve friction. Therefore, the state of stress in relation to ground compaction can be determined using the sleeve friction. Overburdened pressure interferes with the measurement of sleeve and pinecone friction to a greater extent.
The purpose of CPT is to gather information about soil variation and stratification in both horizontal and vertical directions. Friction ratio is used in identifying the type of soil and is used in providing information on alternative compaction techniques. On the other hand, measuring excess pore-water pressure is used in ascertaining layers and seams in fine-grained materials.
Sometimes, the process is referred to as Dutch cone test because it originated from the Netherlands. This process has been accepted all over the world despite it having been invented and developed in Europe. It is among the best methods of investigating soils. Projects that deal with ground compaction mostly apply this method. Currently, various types of mechanical and electrical cone penetrometers are available. However, the electric cone is the most common.
CPT utilizes a conical tip that is normally pushed into the earth at a rate of 2 cm per minute. This conical tip has a diameter of 35.7 millimeter and an apex angle of 60 degrees. A steel rod connects to the conical tip and has a similar diameter as the conical tip. The pinecone is normally pushed into the earth at a rate that varies between 1.5 and 2.5 centimeters per second.
The penetration resistance at the tip and along the shaft of the pinecone is measured as the pinecone is pushed deeper into the ground. Friction is experienced where the shaft connects to the pinecone. This area is known as the friction sleeve. Normally, the friction sleeve has a surface area of 15,000 square millimeters.
The recording of the friction is done using transducers that make part of the electric CPT. If the CPT probe is incorporated with a pore-water pressure sensor, it is referred to as a CPTU. It is vital that the filter ring of the pore-water element is completely saturated with water. Failing to saturate the element with water will cause erroneous results to be recorded by the piezo-transducer.
One can include other types of sensors in the CPT in order to measure other elements of the ground that is being worked on. For example, one can include vibration sensors that will help determine acceleration and vibration velocity. CPT is a standardized operation whose results are not dependent on the operator like is the case with SPT. Since CPT results are independent of the operator, it implies that they are reproducible.
Sleeve friction and pinecone resistance which are measured by CPT are used to gauge the friction ratio (FR). Difference in lateral earth pressure in the ground is indicated by the sleeve friction. Therefore, the state of stress in relation to ground compaction can be determined using the sleeve friction. Overburdened pressure interferes with the measurement of sleeve and pinecone friction to a greater extent.
The purpose of CPT is to gather information about soil variation and stratification in both horizontal and vertical directions. Friction ratio is used in identifying the type of soil and is used in providing information on alternative compaction techniques. On the other hand, measuring excess pore-water pressure is used in ascertaining layers and seams in fine-grained materials.
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