geotech888
Geotechnical
A chemical storage terminal is in operation since last 25 years. The subsoil for the terminal is as below
0-2.0m filled up soil - sandy clay (SC)
2.0-20.0 soft greyish/blackish marine clay (CL,CI) with SPT ranging from 2 to 10 improving with depth.
20.0m to 30.0m is Hard reddish clay SPT > 50.
Gound Water level about 0.8m below ground.
The tank of dia 30.0m and height of 10.0m was serving since past 25 years on earthen pad without any ground improvment or deep foundation in place. Now as tank steel is corroded, client need to rebuild the same of the same diameter, height and loads at same location. This tank has two tanks of the same capacity on either side at a distance of about 5.0m and 7.0m.
The site informed that the settlement has happened over a period of time, however no records have been maintained for the same. Also they have a procedure of lifting the tanks when the tank bottom settles the desired level. No rigid pipe connections are provided to tank.
The long term settlment predicted is 1000mm over a period of more than 100 years with the given tank loading of 100 kN/sqm. However the tank life is considered to be 25 years, for which the settlement predicted is 450mm.
Can the hydrotest period extension help in reducing the long term settlement. at present it is kept 45 days.
Now foundation systems options can be,
1) To go with ground improvement by Sotne columns or PVD, how to ascertain its affect on adjacent operational tanks w.r.t tilt or uneven settlement.
2) To provide earthen pad by excavating 1.0m filled up soil and replacing with 230mm thk rubble soling at bottom and filled up soil with geotextiles/geogrids. (same as it was done in past)
3)To provide pile foundation but time period and cost is constraint.
Please guide what can be the right choice for foundation system?
0-2.0m filled up soil - sandy clay (SC)
2.0-20.0 soft greyish/blackish marine clay (CL,CI) with SPT ranging from 2 to 10 improving with depth.
20.0m to 30.0m is Hard reddish clay SPT > 50.
Gound Water level about 0.8m below ground.
The tank of dia 30.0m and height of 10.0m was serving since past 25 years on earthen pad without any ground improvment or deep foundation in place. Now as tank steel is corroded, client need to rebuild the same of the same diameter, height and loads at same location. This tank has two tanks of the same capacity on either side at a distance of about 5.0m and 7.0m.
The site informed that the settlement has happened over a period of time, however no records have been maintained for the same. Also they have a procedure of lifting the tanks when the tank bottom settles the desired level. No rigid pipe connections are provided to tank.
The long term settlment predicted is 1000mm over a period of more than 100 years with the given tank loading of 100 kN/sqm. However the tank life is considered to be 25 years, for which the settlement predicted is 450mm.
Can the hydrotest period extension help in reducing the long term settlement. at present it is kept 45 days.
Now foundation systems options can be,
1) To go with ground improvement by Sotne columns or PVD, how to ascertain its affect on adjacent operational tanks w.r.t tilt or uneven settlement.
2) To provide earthen pad by excavating 1.0m filled up soil and replacing with 230mm thk rubble soling at bottom and filled up soil with geotextiles/geogrids. (same as it was done in past)
3)To provide pile foundation but time period and cost is constraint.
Please guide what can be the right choice for foundation system?
