What is bore hole and What are the table for minimum spacing of bore hole?
During advancing the bore hole, it must be made as close as possible to the proposed location of the foundation. This is particularly important where soil strata are erratic or irregular. Figure 1 shows typical layouts for multistory building, factory building and the site where the layout of the structure has not been decided. Whereas tabl2 show table for minimum spacing of bore hole. For extensive areas, it is possible to adopt a widely spaced grid of bore holes with some form of in-situ probes, such as dynamic or static cone penetration tests or wash borings.
Number of Boreholes | Bore Hole
With the greater number of boreholes in particular layouts, wide range of information about the location can be collected. As more boreholes sunk, we get additional knowledge of site condition and greater economy is achieved in foundation design. However, the decision with regard to numbers of borehole to be sunk is a difficult task. This is tied up with the cost of investigation and cost of the project as with the increase in number of boreholes, the project cost rises in the same proportion.
Usually for small structures, the minimum number of borehole to be sunk must be two or three so that the true dip of the strata could be established. Even doing so, the false interpretation about soil stratification could still be persistent.
Checkout the article on Depth of boring
Spacing of Bore Holes
Table for minimum spacing of bore hole
| S.N |
Types of job |
Types of soil in horizontal extent |
Minimum no. of boring |
||
|
Uniform |
Average |
Erratic |
|||
|
Spacing, m |
|||||
|
1 |
1 or 2 storied structure |
60 |
30 |
15 |
3 |
|
2 |
Multi-storied structure |
45 |
30 |
15 |
4 |
|
3 |
Bridge piers, abutments |
– |
30 |
15 |
1-2 per foundation |
|
4 |
Transmission tower |
– |
30 |
15 |
1-2 per foundation |
|
5 |
Highway and airports |
300 |
150 |
100 |
– |
|
6 |
Borrow pits |
300-150 |
150-100 |
30-15 |
– |