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.
Given the history of CPT, it is sometimes referred to as Dutch cone test. Although this method was invented and developed in Europe, it is now recognized worldwide as one of the best methods used in investigation of soils. The method is used mostly in ground compaction projects. There are several types of electric and mechanical cone penetrometers in existence today, but the most commonly used is electric cone.
The process of CPT involves the use of a pinecone-tipped shaft. The conical tip is pushed into the ground at a rate of 2 centimeters per second. The tip has a diameter of 35.7 millimeters and an angle of 60 degrees at the apex. A rod of the same diameter as the pinecone is connected to the pinecone. As said earlier, the pinecone is pushed into the soil at a rate of 2 centimeters per minute. However, the speed is generally varied between 1.5 and 2.5 centimeters per second.
When the pinecone is being pushed deeper into the soil, there is resistance at its tip and also along its shaft. This friction is measured. Friction sleeve is the portion that is located just after the pinecone, and it is subjected to friction. In most cases, the friction sleeve is 15,000 millimeters in diameter.
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.
CPTs can also be used to determine other elements of the soil by having different types of sensors incorporated. It is possible for CPTs to measure the velocity and acceleration of vibration when they have vibration sensors. Results from an SPT usually depend on the operator. This is not the case with CPT since the process is highly standardized. As such, CPTs are reproducible because the results from them are independent of the operator.
CPT works by measuring pinecone resistance and sleeve friction to determine the friction ratio, denoted as FR. Sleeve friction usually reflects the variation of lateral earth pressure within the ground. As such, it can be used in the investigation of the effect of ground compaction on the state of stress. Sleeve and pinecone friction measurements also get affected strongly by effective overburden pressure.
CPT aims to obtain information concerning ground stratification and variation in soil properties both in vertical and horizontal directions. The friction ratio is an indicator of soil type and provides useful information in the evaluation of alternative compaction methods. Measurements of excess pore water pressure are used in detecting seams and layers of fine-grained materials.
Given the history of CPT, it is sometimes referred to as Dutch cone test. Although this method was invented and developed in Europe, it is now recognized worldwide as one of the best methods used in investigation of soils. The method is used mostly in ground compaction projects. There are several types of electric and mechanical cone penetrometers in existence today, but the most commonly used is electric cone.
The process of CPT involves the use of a pinecone-tipped shaft. The conical tip is pushed into the ground at a rate of 2 centimeters per second. The tip has a diameter of 35.7 millimeters and an angle of 60 degrees at the apex. A rod of the same diameter as the pinecone is connected to the pinecone. As said earlier, the pinecone is pushed into the soil at a rate of 2 centimeters per minute. However, the speed is generally varied between 1.5 and 2.5 centimeters per second.
When the pinecone is being pushed deeper into the soil, there is resistance at its tip and also along its shaft. This friction is measured. Friction sleeve is the portion that is located just after the pinecone, and it is subjected to friction. In most cases, the friction sleeve is 15,000 millimeters in diameter.
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.
CPTs can also be used to determine other elements of the soil by having different types of sensors incorporated. It is possible for CPTs to measure the velocity and acceleration of vibration when they have vibration sensors. Results from an SPT usually depend on the operator. This is not the case with CPT since the process is highly standardized. As such, CPTs are reproducible because the results from them are independent of the operator.
CPT works by measuring pinecone resistance and sleeve friction to determine the friction ratio, denoted as FR. Sleeve friction usually reflects the variation of lateral earth pressure within the ground. As such, it can be used in the investigation of the effect of ground compaction on the state of stress. Sleeve and pinecone friction measurements also get affected strongly by effective overburden pressure.
CPT aims to obtain information concerning ground stratification and variation in soil properties both in vertical and horizontal directions. The friction ratio is an indicator of soil type and provides useful information in the evaluation of alternative compaction methods. Measurements of excess pore water pressure are used in detecting seams and layers of fine-grained materials.
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