palmahouse
Geotechnical
- Jan 15, 2008
- 46
What is your opinion on the most appropriate calculation method for evaluating total settlement for this problem?:
A 115-foot diameter prestressed concrete tank (about 30 feet of liquid) on a 300-foot thick deposit of alluvial silty sand (SM) with interlayers of sand (SP) and sand with silt (SP-SM). These soils are medium dense. I have CPT and boring data down to a depth of 70 feet.
With Schmertman, and using a Es/Qc ratio of 2.5 to 3 (depending on the soil type in this case), I am calculating a total settlement of about 2.5 inches. I calculated only slightly less than this using D'Appolonia.
The thing that is throwing me off: I am calculating only about 3/4 inch using Terzaghi and Peck. I would have figured that their method, which is thought to be more reliable and less accurate, whould have yielded something more conservative than Schmertman. I am very familiar with each method, and made the water table correction using Terzaghi and Peck.
Perhaps Terzaghi and Peck ignores creep (unlike Schmertman). Perhaps it is not appropriate for such large loaded areas.
Any thoughts would be appreciated.
A 115-foot diameter prestressed concrete tank (about 30 feet of liquid) on a 300-foot thick deposit of alluvial silty sand (SM) with interlayers of sand (SP) and sand with silt (SP-SM). These soils are medium dense. I have CPT and boring data down to a depth of 70 feet.
With Schmertman, and using a Es/Qc ratio of 2.5 to 3 (depending on the soil type in this case), I am calculating a total settlement of about 2.5 inches. I calculated only slightly less than this using D'Appolonia.
The thing that is throwing me off: I am calculating only about 3/4 inch using Terzaghi and Peck. I would have figured that their method, which is thought to be more reliable and less accurate, whould have yielded something more conservative than Schmertman. I am very familiar with each method, and made the water table correction using Terzaghi and Peck.
Perhaps Terzaghi and Peck ignores creep (unlike Schmertman). Perhaps it is not appropriate for such large loaded areas.
Any thoughts would be appreciated.
