kaynakve
Civil/Environmental
- Oct 26, 2004
- 3
Hi,
I`m in charge of a dock construction which is just beside sea. It`s length is 100m, parallel to sea, and depth is 8m. I designed the walls as 800mm bored piles, constructed capping beam on them and installed ground anchors from the capping beam towards sea with 40degs, total 21m anchor length (10m root). The horizontal distance from piles (anchor head) to sea is 10m, and sea depth around root is 5m (approx.7-8m soil above root).
The sub-contractor first drilled the hole towards sea by using down the hole machine, applying 10atm air pressure. During drilling at around 15-20meters, big bubbles started to come from the sea bed in two points: 1- just at coast line 2- approx 20m from the root in horizontal in the sea.
After drilling, sub-con injected grout to the hole with a grout pressure of 20-30 bars. And they injected approx. 20tons of cement (W/C:1/2)! (yes, 20tons., not 200 liters or something). And after injection, still grout does not come up from the hole(seems there are caves around root area).
I told sub-con to do two thing:
1- Use Auger but not air-pressurised down the hole machine, as high pressure air damages the soil, and bubbles find ways to go up somewhere.
2- Grout injection pressure should be 1-3bars but not 20-30bars. By this way, even there are some empty spaces around root area, it will not flow too deep or long.
My question is (I will appreciate if you have any idea):
1- Have you ever met a similar problem, anchoring near sea or lake, etc with a cover of 5-10m over root? What method did you apply for drilling and grout injection? What were the speeds?
2- Do you think that it would be better to use admixtures which will fasten curing under water and make grout swell?
Thanks for any idea or advice.
Regards,
Kaynak
I`m in charge of a dock construction which is just beside sea. It`s length is 100m, parallel to sea, and depth is 8m. I designed the walls as 800mm bored piles, constructed capping beam on them and installed ground anchors from the capping beam towards sea with 40degs, total 21m anchor length (10m root). The horizontal distance from piles (anchor head) to sea is 10m, and sea depth around root is 5m (approx.7-8m soil above root).
The sub-contractor first drilled the hole towards sea by using down the hole machine, applying 10atm air pressure. During drilling at around 15-20meters, big bubbles started to come from the sea bed in two points: 1- just at coast line 2- approx 20m from the root in horizontal in the sea.
After drilling, sub-con injected grout to the hole with a grout pressure of 20-30 bars. And they injected approx. 20tons of cement (W/C:1/2)! (yes, 20tons., not 200 liters or something). And after injection, still grout does not come up from the hole(seems there are caves around root area).
I told sub-con to do two thing:
1- Use Auger but not air-pressurised down the hole machine, as high pressure air damages the soil, and bubbles find ways to go up somewhere.
2- Grout injection pressure should be 1-3bars but not 20-30bars. By this way, even there are some empty spaces around root area, it will not flow too deep or long.
My question is (I will appreciate if you have any idea):
1- Have you ever met a similar problem, anchoring near sea or lake, etc with a cover of 5-10m over root? What method did you apply for drilling and grout injection? What were the speeds?
2- Do you think that it would be better to use admixtures which will fasten curing under water and make grout swell?
Thanks for any idea or advice.
Regards,
Kaynak
