Limits of Directional Drilling: Doomed?

[kmer]

Using a Ditchwitch JT2720, several attempts to directional drill beneath a railway have failed. The plan was to install a 9" steel casing for an outfall pipe to the lakeside of the tracks. The drill rig is equipped with a 5" bit.

The minimum depth required is 2.4m. The length of the run is approximately 40m (120').

At this depth, soils vary from mainly sand/silt and clay with cobble inclusions. The cobbles can vary in size from 6" to 24". As we approach the underside of the railbed, we are likely to encounter blast rock fragments.

Are we doomed? There must be a better mousetrap. But where?

 

[cvg]

you can keep trying with the auger and maybe you will get lucky, or try another method such as bore and jack. With 24 inch boulders, you will have trouble unless your pipe is much larger than 9 inch. A better method would be to jack a 30 inch casing and hand tunnel, removing the 24 inch boulders through the casing without breaking them up.

 

[Zambo]

kmer,

If you don't get a response soon I recommend you change forum to either water teratment and distribution or civil/environmental other topics.

I'm not sure you have described the method you are using correctly. Are you sure you are using a 5" bit for directional drilling of a 9" casing. If this is the case then I recommend you install 4 x 5" casings and place several downsized outlet pipes. Alternatively increase the bit size to 9" but then your Dithwich might not be up to the task.

I think directional drilling is a better answer than pipejacking or micro-tunneling but you may have to go for bigger and better equipment.

 

[BigH]

Can you go deeper and get out of the cobbles? It may also let you get beneath the railway's rock embankment penetration into the surface soils.

 

[idrillforu]

i would use a railhead to get to the other side since its a short run and use a twelve inch reamer make sure the mud is thick to keep the ground stable and hook up the pipe and backream with the casing