SPT borehole for line transmission

[halc]

In brazilian line transmission 238 or 500kV foundation design, we do not make one SPT borehole per tower but one per 500m moreless.
Is the same in your countries?
Tell me something of your experiences about, please.

 

[BigH]

In my view, geotechnical programmes need to be tailored to the job and tailored to the geotechnical conditions at the site. If my experience is that the site stratigraphy is relatively uniform across the area, I might use the 500m spacing but only after being sure - you might do some very shallow holes (perhaps 1/2 depth) to confirm the upper zone which is typically the problematic one - because of topsoil thickness, undulations in lower strata that have been infilled with alluvium, etc. If I had a quite variable subsurface conditions (based on the widely spaced borings revealing such), then you would need to put your borings down at much closer spacing and, in fact, may very well need to be at each tower. You might also use agriculture mapping (at least in US and Canada) to identify variations in the surface layers. You might also do a air photo interpretation to assist in getting a handle on whether you are likely needing to closely spaced borings. So, in summary, the requirements for the borings are based on your site conditions and you should be flexible enough to adjust as necessary.

 

[cbosy]

How far are the towers apart?

 

[halc]

Wow...
I'm new here and I don't know how to answer the question of eng cbosy (private or public)...well...Let's go...

The distance between two support towers is 300m in my case today and I'm thinking to consider 600m max (each 2) maybe 900m (each 3). What do you think about?