– The cone penetration or cone penetrometer test (CPT) is a method used to determine the geotechnical engineering properties of soils (especially in soft soil layer) and delineating soil stratigraphy. CPT is one of the most used and accepted soil methods for soil investigation worldwide.
– The test method consists of pushing an instrumented cone, with the tip facing down, into the ground at a controlled rate (controlled between 1.5 -2.5 cm/s accepted). The resolution of the CPT in delineating stratigraphic layers is related to the size of the cone tip, with typical cone tips having a cross-sectional area of either 10 or 15 cm², corresponding to diameters of 3.6 and 4.4 cm.
– For geotechnical soil investigations, CPT is more popular compared to SPT as a method of geotechnical soil investigation. Its increased accuracy, speed of deployment, more continuous soil profile and reduced cost over other soil testing methods.
– In GOSCO, CPT equipment is used with drilling jackup flatform for offshore projects especially for offshore wind farm projects with competitive price. Our capable engineers have carried out several offshore CP tests with high quality and meet the progress schedule of the projects.
Steps to perform the SPT test:
– Step 1: Drill to the test depth, cleaning & dredged muck from bottom of the borehole, and install equipment according to standards.
– Step 2: Mark 3 equal intervals (15cm) on the drliing rod.
– Step 3: Release the donut hammer in free fall and count the total number of hammers through the marked segments.
– Step 4: Take the hammer number of the last 2 segments as SPT index
– Step 5: Uninstaling SPT inquipment and remove SPT sample, repeat the steps when performing the experiment at the next times.
Figure 1:Standard Penetration Test
|Figure 1:Standard Penetration Test||Tools for Standard Penetration Test:|
1. Standard Split Spoon Sampler
2. Drop Hammer weighing 63.5kg
3. Guiding rod
4. Drilling Rig.
5. Driving head (anvil).
The main purpose of the test is to provide an indication of the relative density of granular deposits, such as sands and gravels from which it is virtually impossible to obtain undisturbed samples. The great merit of the test, and the main reason for its widespread use is that it is simple and inexpensive.