- Asked 2/16
- 2080 Baisakh · 4 marks
- 2075 Asoj · 3 marks
Borehole log format
Short answer
A borehole log has a header with project, boring method, and groundwater level, plus columns for depth, soil description and graphic symbol, sample type, SPT N-values, and remarks. It records the vertical succession of strata, water table, and in-situ test results for foundation design.
Describe briefly the borehole log format with a suitable example.
A borehole log is a graphical and written record of the soil encountered in one borehole against depth. It is prepared from field notes and laboratory results.
Information in the header
- Project name, location, client, borehole number and coordinates/reference level.
- Method of boring, diameter, date started and completed, driller/engineer.
- Groundwater level (date of observation).
Columns of the log
| Depth (m) | Soil description / symbol | Sample type and depth | SPT N | Remarks |
|---|
- Depth/RL scale and thickness of each layer.
- Graphic legend (hatch symbols) and soil description with IS classification (colour, consistency/density, grain size).
- Sample type (disturbed D, undisturbed U, SPT) and depths.
- SPT N-value (and optionally core recovery, RQD for rock).
- Water table and any seepage, loss of drilling water, cavity or boulders.
- Remarks such as refusal and end of hole.
Example (BH-1, RL 100.00 m, GWT 2.0 m)
| Depth (m) | Description | Sample | N |
|---|---|---|---|
| 0.0-1.5 | Brown silty clay (CI), soft | D | - |
| 1.5-4.5 | Grey sandy silt (ML), medium | U, SPT | 8 |
| 4.5-9.0 | Brown medium sand (SP), dense | SPT | 28 |
| 9.0-12.0 | Gravelly sand (GW), very dense | SPT | 50+ |
Boring terminated at 12.0 m. The log is used to draw soil profiles and to choose foundation type and depth.
✓ Answer checked by Claude Sonnet 5.5