5 Test procedures
5.1 Selection of cone penetrometer
Select a cone penetrometer to fulfil the requirements of the penetration test according to Table 1.
| Type | Measured parameter |
| ТЕ1 | Cone resistance and sleeve friction |
| ТЕ2 | Cone resistance, sleeve friction and pore pressure |
| NOTE Cone penetration tests with measurements of pore pressures at more than one location are variants оf type TE2. | |
Inclination measurement should be included depending on application class; see Table 2.
5.2 Selection of equipment and procedures
The required accuracy is meant to be a function of what the results are to be used for. Application classes have been developed to give guidance on selecting type of CPT, required accuracy and logging frequency. For given soil profiles and use of CPT results, the application class specifies the needed minimum accuracy and the maximum length between measurements, with an associated degree of uncertainty. The use of CPT results is stated in terms of profiling, material identification and definition of soil parameters.
Equipment and procedures shall be selected according to the required application class given in Table 2. Application classes are defined as follows:
- Application class 1 is intended for soft to very soft soil deposits. Class 1 penetration tests are normally not apt for mixed bedded soil profiles with soft to dense layers (although pre-drilling through stiff layers can overcome the problem). Tests can only be performed with use of the CPTU.
- Application class 2 is intended for precise evaluation for mixed bedded soil profiles (see note 1) with soft to dense layers, in terms of profiling and material identification. Interpretation in terms of engineering properties is also possible, with restriction to indicative use for the soft layers. Penetrometer type to be used depends on project requirements.
- Application class 3 is intended for evaluation of mixed bedded soil profiles (see Note 1) with soft to dense soils, in terms of profiling and material identification. Interpretation in terms of engineering properties is achievable for very stiff to hard and dense to very dense layers. For stiff clays or silts and loose sands, only an indicative interpretation can be given. Penetrometer type to be used depends on project requirements.
- Application class 4 is only intended for indicative profiling and material identification for mixed bedded soil profiles with soft to very stiff or loose to dense layers. No appreciation in terms of engineering parameters can be given. Tests are to be performed with an electrical cone penetrometer (type TE1) and inclination measurement may be omitted.
If all possible sources of errors are added, the accuracy of the recorded measurements shall be better than the largest of the values given in Table 2. The inaccuracy analyses shall include internal friction, errors in the data acquisition, eccentric loading, temperature (ambient and transient) effects and dimensional errors.
Metrological confirmation applicable to a cone penetration test shall be according to ISO 10012.
The actual cross-sectional area of the base of the cone and the actual external cylindrical surface area of the friction sleeve shall be determined and recorded for application class 1.
NOTE 1 Mixed bedded soil profiles refer to soil conditions containing typically dense and compact soils, but possibly also including soft layers.
NOTE 2 The achievable penetration length or penetration depth depends on the soil conditions, the allowable penetration force, the allowable forces on the push rods and push rod connectors and the application of a friction reducer and/or push rod casing and the measuring range of the cone penetrometer.
If dissipation tests are required (see 5.9), equipment of TE2 type tests shall be selected depending on the project requirements.
NOTE 3 For uncertainties in cone penetration testing, see Annex E.
| Application class | Test type | Measured parameter | Allowable minimum accuracya | between measurements | Use | |
| Soilb | Interpretation / evaluationc | |||||
| 1 | TE2 | Cone resistance | 35 kPa or 5 % | 20 mm | A | G, H |
| Sleeve friction | 5 kPa or 10% | |||||
| Pore pressure | 10 kPa or 2 % | |||||
| Inclination | 2° | |||||
| Penetration length | 0,1 m or 1 % | |||||
| 2 | TE1 TE2 |
Cone resistance | 100 kPa or 5 % | 20 mm | A В С D |
G, H* G, H G, H G, H |
| Sleeve friction | 15 kPa or 15 % | |||||
| Pore pressured | 25 kPa or 3 % | |||||
| Inclination | 2° | |||||
| Penetration length | 0,1 m or 1 % | |||||
| 3 | TE1 TE2 |
Cone resistance | 200 kPa or 5 % | 50 mm | A В С D |
G G, H* G, H G, H |
| Sleeve friction | 25 kPa or 15 % | |||||
| Pore pressured | 50 kPa or 5 % | |||||
| Inclination | 5º | |||||
| Penetration length | 0,2 m or 2 % | |||||
| 4 | TE1 | Cone resistance | 500 kPa or 5 % | 50 mm | A В С D |
G* G* G* G* |
| Sleeve friction | 50 kPa or 20 % | |||||
| Penetration length | 0,2 m or 2 % | |||||
| NOTE For extremely soft soils, even higher demands on the accuracy can be needed. | ||||||
| a The aIIowable minimum accuracy of the measured parameter is the larger value of the two quoted. The relative accuracy applies to the measured value and not the measuring range. b According tо ISO 14688-2 [1]: A homogeneously bedded soils with very soft to stiff clays and silts (typically qc < 3 MPa) В mixed bedded soils with soft to stiff clays (typically qc ≤ 3 MPa) and medium dense sands (typically 5 MPa ≤ qc ≤ 10 MPa) С mixed bedded soils with stiff clays (typically 1,5 MPa ≤ qc < 3 MPa) and very dense sands (typically qc > 20 MPa) D very stiff to hard clays (typically qc ≥ 3 MPa) and very dense coarse soils (qc ≥ 20 MPa) cG profiling and material identification with low associated uncertainty level G* indicative profiling and material identification with high associated uncertainty level H interpretation in terms of design with low associated uncertainty level H* indicative interpretation in terms of design with high associated uncertainty level d Pore pressure can be measured if TE2 is used. |
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5.3 Position and level of thrust machine
The distance between the test location and the location of previous investigation points should be sufficient to prevent interaction effects.
Between cone penetration tests, a distance of 2 m is normally sufficient. The distance to a previous borehole should be at least 20 times the borehole diameter. Some borehole techniques, such as air drilling, can require larger distances. Nearby excavations should be avoided.
The thrust machine shall push the push rods so that the axis of the pushing force is as close to vertical as possible. The deviation from the intended axis should be less than 2°. The axis of the penetrometer shall correspond to the loading axis at the start of the penetration.
