●Read the SPT drive record

For a completed standard penetration test, the technician drives a split-barrel sampler in three nominal 150 mm increments. The first increment seats the sampler. Add the blows from the next two increments to get the field N-value for the final 300 mm. If the test stops early, read the actual blows and distance advanced. Keep a partial drive separate from a completed N-value. Look at the borehole log and any disturbed sample from the test interval.

A high count or refusal may come from dense soil, a coarse particle, an obstruction or other site or test conditions. Use the samples, drilling notes and nearby investigation points to assess the cause and the layer’s extent. One refusal entry cannot confirm continuous rock or establish a pile-driving refusal limit.

●Check the correction basis

The hammer’s delivered energy affects the blow count. N60 puts the count on a reference energy ratio of 60 percent. Depending on the adopted correlation, the procedure may also account for rod length, borehole diameter and sampler configuration. Keep the field count, the correction method and its inputs in the record so another engineer can trace the value.

Where the selected method calls for effective overburden normalization, it uses (N1)60. Check which quantity the correlation requires before comparing values. A correction cannot remove local geology or sampling limits.

●Read CPT and CPTu channels by depth

A cone penetration test pushes an instrumented probe at a controlled rate. The probe records cone resistance qc and sleeve friction fs. A piezocone test, or CPTu, also measures pore pressure. u2 denotes a measurement at the cone shoulder, just behind the tip. Check the reported filter location and saturation record when interpreting the pressure channel. Where the unequal-area correction applies, qt denotes cone resistance corrected for pore pressure acting on the cone’s unequal end areas. Keep qc and qt distinct.

Use sleeve friction and any friction ratio or normalized index with the calculation convention in the report. Dissipation data, where available, can help assess pore pressure response and drainage. The near-continuous profile can flag changes between spaced SPT intervals. Cone response can blur thin layers, and gravel, cobbles, obstructions or hard ground can stop a push. CPT yields no soil sample. Compare the interpreted soil behavior with borehole samples, laboratory classification and groundwater observations.

●Compare the logs on the same datum

Check the test locations, depth references and ground elevations before lining up profiles. Compare a rise in resistance with the soil description, sample recovery and any drilling or push termination notes. If the logs conflict or coverage is thin, flag the interval for geotechnical review. The responsible engineer can specify more investigation or an approved contingency before production driving.

●Check driveability and field acceptance

Combine the interpreted profile with the pile type, toe, length, target depth, groundwater and site restrictions. No single N-value, cone resistance or pore pressure reading sizes a hammer or establishes pile capacity. For impact driving, a wave equation analysis can estimate blow count and driving stresses for the assumed hammer, pile, cushion and soil resistance. Review vibration limits, access and the full equipment package with the project team.

Compare installation records with the approved procedure as work proceeds. Record depth, operating settings, penetration or blow counts, pile condition and any required monitoring. The responsible engineer specifies any trial, restrike, dynamic or static testing and the applicable acceptance criteria. Stop and obtain review if driving or monitoring reaches a project limit.