6.4 Sampling using samplers
6.4.1 General
6.4.1.1 Sampling using samplers can be used in combination with many drilling methods. The drilling diameter shall be chosen so that the sampler can be lowered to the borehole bottom without hindrances.
6.4.1.2 Depending on the soil conditions, different samplers can be used (see Table 3). Usually sampling with samplers is used in combination with any drilling methods using drilling mud or a casing to support the borehole. The drilling method and technique shall be chosen in such a way that unacceptable disturbance of the soil samples is prevented.
6.4.1.3 The inside of the sampling tube or the liner shall be clean and smooth without any protruding edges or irregularities, which can cause disturbance of the sample.
6.4.1.4 Drilling of the casing with percussion is not allowed to the full depth in case of category A sampling. The percussion process shall be halted at least 0,25 m or 5 times the diameter of the borehole before reaching the sampling depth.
6.4.1.5 If a casing is used in sensitive clays, it shall not be brought closer than 2,5 times the outside diameter of the casing to the sampling depth to minimise disturbance. In other soils, the casing can be lowered to the borehole bottom. Samples shall be taken from the undisturbed soil below the casing in a pre- cased or slurry-supported borehole, slightly larger than the diameter of the sampler.
6.4.1.6 When drilling mud is used, its characteristics shall be chosen with respect to the drilling method, the soil and groundwater conditions to obtain a stable borehole.
6.4.1.7 Before taking undisturbed samples from borehole bottom, any loose or disturbed material shall be removed. In the case of cleaning the borehole bottom by circulating flushing medium, the rotary drill bit shall be advanced with utmost caution, and the fluid circulation reduced until the bit reaches the sampling depth. Remaining loose material shall be removed in a controlled manner.
| Column | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| Line | Type of sampler b | Preferred sample dimensions | Technique used | Applications and limitations | Sampling category for soils as in column 6 a | Achievable quality class a | ||
| Diameter mm | Length mm | Unsuitable for | Recommended for use in | |||||
| 1 | thin-walled (OS-T/W) | 70 to 120 | 250 to 1 000 | static or dynamic driving | gravel, loose sand below water surface, firm cohesive soils, soils including coarse particles | cohesive or organic soils of soft or stiff consistency | A | 1 |
| (medium) dense sand below water surface | B (A) | 3 (2) | ||||||
| cohesive or organic soils of stiff consistency | A | 2 (1) | ||||||
| 2 | thick-walled (OS-TK/W) | >100 | 250 to 1 000 | dynamic driving | gravel, sand below water surface, pasty and firm cohesive or organic soils, soils including coarse particles | cohesive or organic soils of soft to stiff consistency, and including coarse particles | B (A) | 3 (2) |
| 3 | thin-walled (PS-T/W) | 50 to 100 | 600 to 800 | static driving | gravel, very loose and dense sands, semi-firm and firm cohesive or organic soils, soils including coarse particles | cohesive or organic soils of pasty or stiff consistency, and sensitive soils | A | 1 |
| sand above ground water | B | 3 | ||||||
| 4 | thick-walled (PS-TK/W) | 50 to 100 | 600 to 1 000 | static driving | gravel, sand below water surface, pasty and firm cohesive or organic soils, soils including coarse particles | cohesive or organic soils of soft to stiff consistency, and sensitive soils | B (A) | 2 (1) |
| 5 | cylinder (LS) |
250 | 350 | static rotating | sand | clay, silt | A | 1 |
| 6 | cylinder (S-SPT) |
35 | 450 | dynamic driving | coarse gravel, blocks | sand, silt, clays | B | 4 |
| 7 | window | 44 to 98 | 1 500 or 3 000 | static or dynamic driving | sand, gravel | silt, clay | C | 5 |
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a The sampling categories and achievable quality classes given in parentheses can only be achieved in particularly favourable soil conditions, which shall be explained in such cases. b OS-T/W open-tube samplers, thin-walled PS-TK/W piston samplers, thick-walled OS-TK/W open-tube samplers, thick-walled LS large sampler PS-T/W piston samplers, thin-walled S-SPT SPT (standard penetration test) sampler |
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