Dear Paul
Just some ideas from the top of my head.
I am not sure that you can compare the horisontal drilling with ground
movement associated with driving of displacement piles due to following
reasons:
1. When drilling horisontal you "cut" the soil. - When driving you "move"
the soil
2. Driving is almost an axialsymmetric "case - Horisontal drilling is
3-dimensional
3. In clay you drill during undrained conditions and install a type of pipe
in the hole. The deformation depends very much on how the pipe "fits" the
drilled hole - Whwen driving you always have "a perfect fit" between the
hole and the pile.
4. When drilling You activ try to reduce the deformations by slurry under
some kind of pressure.
When you make horisontal drilling without during anything and just let
collaps an arch will form around the hole. In practice this will give an
area around the collapsed hole where the void ratio (In sand) will be higher
than the rest of the soil in the area (assuming homogenious soil In situ ).
In a project in Denmark I have seen some FEM calculations of the magnitude
of surface settlements due to total collaps of holes drilled for ground
anchors in approximately 2 to 3 m depth (In sand). The calculated
deformations where very small.
Regards
Morten S Rasmussen
> -----Oprindelig meddelelse-----
> Fra: Ng, Paul [SMTP:[log in to unmask]]
> Sendt: 6. juni 2001 16:45
> Til: [log in to unmask]
> Emne: Soil movement of displacement pile
>
> Dear list members,
>
> I am doing some preliminary study on the soil movement
> associated with horizontal directional drilling. One way to
> look at the problem is to compare it with the horizontal
> ground movement associated with driving displacement pile
> into the ground. Could anyone give me an indication of the
> size of the "influence zone", i.e. approximately how many
> pile diameter away from the pile, the soil displacement will
> become "insignificant"? The soil conditions I am looking at
> are soft to firm clay and medium dense sand.
>
> Thank you in advance.
>
> Paul
>
> ----------------------------------
> Dr Paul C. F. Ng
> Senior Geotechnical Engineer
> Advantica Technologies Ltd
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