Cone Penetration Test
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A method of testing soils by pressing a cone of standard dimensions into the soil under a known load and measuring the penetration. (extensive investigation and research in construction site).
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Cone Penetration Test
- 1. Prepared By : Mohd. Ikhwan Bin Abdullah Matric No. : 2006121149
- 2. ContentContent Background information Use of Cone Penetration Test (CPT) Equipment used in CPT Process of CPT Advantage & Disadvantage Conclusion
- 3. CPT nowadays is the most used and accepted in- situ test methods for soil investigation world wide. It is to determine the GEOtechnical engineering properties of soils. It was initially used in 1950s at the Dutch Lab for soil Mechanics so that it has also been called the “Ducth cone test”.
- 4. CPT are conducted to measure and evaluate characteristics of certain soils (soft sensitive silts and clays and some coarse cohesionless soils) such as: i) Stratification ii) Soil type iii) Relative soil density and in-situ stress conditions iv) Shear strength parameters
- 5. After analysing the results obtained from the test, we can determine the soil type and design of shallow foundations through the estimation of stiffness and shear strength of cohesive soils. The results from CPT may also be used, directly, for design of piled foundations in sand and gravel. Indirectly, it can be used (shear strength) for piles in clay.
- 6. CPT device consists in: - a cylindrical probe with a cone-shaped tip (having a cross-sectional area of either 10 or 15cm², corresponding to diameters of 3.6 and 4.4 cm). - The cone, which has an apex angle of 60º is attached to a rod, this latter being protected by an outer sleave. - Some of them are equipped with a geophone in order to be able to perform shear wave velocity measurements.
- 7. - The data is normally read by a field computer that displays it real-time and stores it at regular depth intervals.
- 8. A 60º cone with face area 10cm² and 150cm² friction sleeve is hydraulically pushed into the ground (the device is pushed, rather than being driven by blows, into the soil). By applying a measure force to the rod, the cone is pushed into the soil at a constant speed of penetration (ranging form 1.5 to 2.5cm/s). Figure 2.0 : Cone Penetration Test
- 9. Advantage Disadvantage Rapid and inexpensive Reproducible result Real time measurement Accurate, detailed subsurface stratigraphy / identification of problem soils No sample recovered Penetration depth limited to 150 – 200 feet Normally cannot push through gravel Requires special equipment and skilled operator
- 10. Save money for the owner by more accurately identifying the geological strata. Seismic evaluations can be done to satisfy the new building code requirements by measuring the low strain shear wave velocity. Can be used to predict vertical pile capacity. In normally consolidated or recently aged cohesionless soils, provides good estimates of settlement for shallow foundations.