Directional drilling 5

[pelelo]

Engineers,

From the geotechnical point of view, what are the soil parameters i need to consider for directional drilling works?.

My project consist of a 6 in diameter pipe that will be installed (directional drilling), about 10 ft below surface. Water table is about 4 feet, below ground surface.

Please let me know,

Thanks

 

[Mad Mike]

Pelelo,

Watch out for potential obstructions in the soil - those holes deflect very easily- even relatively small hard cobbles can have you coming out at the wrong point!

I once had a job where the holes deflected hugely on hard cobbles in a stiff soil matrix- the contractor managed to put in 3 cock-eyed holes before reverting to jacked pipes.

All the best,
Mike

 

[oldestguy]

On a city near me the location of a buried utility was not known correctly and a major fire developed when a gas line was hit. Beware.

 

[EireChch]

Direction drilling can generally penetrate all soil (clay, sand, silt and gravel) no matter what strength.

Its when you get into rock that strength becomes much more important. There can be huge variation of rock strength (UCS) depending on the degree of weathering. Definitely have at least one borehole along the alignment if you know the ground conditions are consistent. If they are likely variable and rock can be encountered then do more than one....

 

[pelelo]

Gents,

Thanks a lot for your replies.

In this case, the soils are SP/SM/SP-SM, so luckily no rock is present.

Does anyone know if there is any specific parameter I need to provide in the report that would be critical for the directional drilling contractor.

Water table I know is going to be a problem as it is very shallow and drilling depth will be under the Water level.

 

[jake_1]

Typically I only provided boring profiles for directional drilling. Unconfined compressive strengths in rock can be useful for drill bit selection but in generally sandy granular bit selection is not an issue for the contractor. The presence of any oversized cobbles as mentioned by Mad mike is also important to the driller.