Get Bore Log Sheet

Except in the case of very dense materials or bedrock, the minimum depth of borehole is 6m. Drill a borehole at least 3m into bedrock. For dense, coarse-grained soil and very stiff clays, extend boring depth up to a range of 5-6m to corroborate that soil layer thickness is sufficient.

Deep boring means an exploratory boring or excavation performed to provide additional information including soil type, moisture, depth to the water table, perched or otherwise, rock or an impervious strata.

All information should be provided on the first sheet of each boring log. The boring location (coordinates and/or station and offset) and ground surface elevation (with datum) must be recorded on each boring log. Procedures discussed in Section 2.5.

Looking at the bore log shown in Figure 1, the Blow Counts (Field Value) is shown in the fifth column from the left.. This is a strict reading of the number of drops. The readings, such as (5-5-6) are how many drops it takes for each successive 6” depth increment. The first 6” is ignored and the blows per foot are 11.

The boring log is the basic record of almost every geotechnical exploration and provides a detailed record of the work performed and the findings of the investigation. The field log should be written or printed legibly, and should be kept as clean as is practical.

Geotechnical investigation depth would be four times the diameter of the pile in hard rock but a minimum of 3m in such rock (Ref: Clause No. 1102.1 of Section 1100 for “Pile Foundation” and Clause No. 1202.3 of section 1200 for “Well Foundation”).

Borings should penetrate at least 3 m into rock. Borings must penetrate below any fills or very soft deposits below the proposed structure. The minimum depth of boreholes should be 6 m unless bedrock or very dense material is encountered.