The cone penetration test is used to investigate the geotechnical engineering properties of the soil. The cone test is performed by two methods the first method is Static Cone Penetration Test and the second one is Dynamic Cone Penetration Test.
The cone penetration test was developed in Dutch Government Laboratory so it is also called the “Dutch Cone Test” or “Dutch Cone Penetrometers”.
Let’s dive into the cone penetration test for the soil-
Static Cone Penetration Test | Dutch Cone Penetrometer Test
The static cone penetration test or Dutch Cone Penetrometer Test or Dutch Cone Penetration Test provides a very accurate value below the water table where the standard penetration test (SPT test) fails.
Basically, this test provides a continuous record of the soil resistance by the cone when the cone is pushed into the soil at the rate of 10 mm/sec up to a depth of 100mm the resistance offered by the soil is recorded as a cone penetration resistance.
Static Cone Penetration Test Apparatus
- Standard Cone ( having a weight of 1.1 Kg )
- Sounding Rod (having a 1.5 kg )
Static Cone Penetration Test Procedure
1- In the Dutch Cone Penetrometer Test, for obtaining the cone resistance, the standard cone is pushed into the soil by applying thrust at the rate of 10 mm/sec.
2- When the cone resistance (qc) has been determined, the cone is withdrawn and the sleeve is pushed onto the cone.
3- Now both cone and sleeve are pushed into the soil and combined resistance is determined.
4- For the resistance of the sleeve we have to subtract the cone resistance from the combined resistance.
Note– In the Dutch cone penetrometers a modification is done and after modification, it is called “Refined Dutch Cone” and it has got a Friction Sleeve above the cone point.
5- The use of the friction sleeve is basically for obtaining the point resistance of the cone and frictional resistance (qf) of the soil above the cone point.
Normalization of CPT values–
Similar to the correction in SPT N value the CPT value ( qc that is cone resistance) also required some correction to the overburden pressure of 100 kN/m2, using the formula qcn= Cn. qc
Here, qcn= normalized value, qc = cone resistance
Advantages Of Static Cone Penetration Test
Here are the following advantages of the static cone penetration test-
1- The Dutch Cone Penetrometer Test ( static cone penetration test ) is most useful where the soil properties get disturbed by the boring or due to blows.
2- It is useful in bearing capacity determination at different depths below the foundation level.
3- Dutch cone penetration test plays an important role on very soft and loose soil where heavy types of equipment may not be transported.
4- We can determine the length of piles by using the skin friction value.
Limitations Of Static Cone Penetration Test | Disadvantages Of Static Cone Penetration Test
1-The first limitation or disadvantage of static cone penetration is it is unsuitable for field test operation because of the incorrect value obtained due to the presence of brickbats, stones, etc.
2-The cone penetration test is not suitable for gravelly soils.
3- This test is not applicable when the SPT value or SPT number obtained from the standard penetration test is greater than 50.
4-In this test, we can not obtain any soil sample for further testing because there is not any space on the cone sampler for the collection of soil.
Static Cone Penetration Test VS Standard Penetration Test
|Static Cone Penetration Test||Standard Penetration Test|
|Not required heavy instrument.||Required heavy instruments.|
|We can not collect a soil sample.||We can collect a soil sample.|
|A Cone sampler is used.||A Split-spoon sampler is used.|
|Suitable below the water table.||Not suitable below the water table.|
|Less time-consuming than the SPT test.||More time-consuming.|
Frequently Asked Questions (FAQ)
When would you use a cone penetration test?
The cone penetration test is used for very soft and loose soils where the transportation of heavy types of equipment required for the DCPT and SPT test may not be possible.
What is the importance of the cone penetration test?
The importance of the cone penetration test are as follow-
1- Most useful where the soil properties get disturbed by boring or blows.
2-Determination of bearing capacity.
3- Determination of the length of the piles.
4- Suitable for very soft and loose soils.
What is the IS code for a static cone penetration test?
The IS 4968 ( Part 3) code is the IS code for a static cone penetration test.
What is the difference between SPT and CPT?
The main difference between the SPT and CPT is the SPT test is time-consuming and not suitable below the water table whereas the CPT test is less time-consuming and suitable below the water table.
What is the commonly used penetration test in civil engineering?
The commonly used penetration test is a standard penetration test, cone penetration test, and plate load test.