This is useful to decide no of boring

1. 1
Depth of Boring
For hospitals and office buildings, the following rule
could be use to determine boring depth

2. NUMBER OF TEST BORES
As per IS:1892,Clause 2.3.1 “For a compact building site covering
an area of 0.4 hectare (4000m2), one borehole or trial pit in each
corner and one in center should be adequate. For smaller and
less important buildings even one borehole or trial pit in the
centre will sufficient”.
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3. 3
If soil is highly heterogeneous, some reference
books suggests as under:

4. • However, for ordinary buildings, investigation can be limited
to economize and time and two test bores may be taken
across the site. If highly variable strata are encountered
additional test bores may be taken.
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5. • When area to be
investigated is large and
plant layout is not finalized,
the area may be divided into
grid of suitable size and test
points taken on grid corners.
• Where structural layout has
been finalized, test points
may be taken to correspond
with all the important
building units.
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6. • For various structures the number of test points may be considered as under:
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7. DEPTH OF TEST BORES
The depth of test bores should extend up to the point at which
the vertical stress due to proposed structure is equal to or less
than 10% of original effective stress at the point before the
structure is constructed. Normally, it should be one and half
times the width of footing below the foundation level.
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