A laboratory sample of clay 2 cm thick took 15 min to attain 60 percent consolidation under a double drainage condition. What time (in days) will be required to attain the same degree of consolidation for a clay layer 3 m thick under the foundation of a building for a similar loading and drainage condition? a.17.15 b.119 c.234 d.564.3

A laboratory sample of clay 2 cm thick took 15 min to attain 60 percent consolidation under a double drainage condition. What time (in days) will be required to attain the same degree of consolidation for a clay layer 3 m thick under the foundation of a building for a similar loading and drainage condition? a.17.15 b.119 c.234 d.564.3

Principles of Geotechnical Engineering (MindTap Course List)

9th Edition

ISBN:9781305970939

Author:Braja M. Das, Khaled Sobhan

Publisher:Braja M. Das, Khaled Sobhan

Chapter12: Shear Strength Of Soil

Section: Chapter Questions

Problem 12.20P

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A clay sample underwent a consolidation test in the lab. The clay specimen has drainage on both sides and a height of 25.4 mm. Assume that the clay sample's preconsolidation pressure was less than 150 kPa prior to the consolidation test. The void ratio was 0.96 when the applied effective vertical pressure was 150 kPa. When the vertical effective pressure increased from 150 to 220 kPa, the void ratio at the end of consolidation and compression was 0.88. It was discovered that the sample needed 3 minutes to consolidate by 30%. Following the consolidation test, a swelling/unloading test was conducted, in which the vertical effective stress was lowered from 220 to 150 kPa and the end-of-swelling void ratio was determined to be 0.9. Required a. The compression index of the clay b. The swelling index of the clay C. The height of the clay sample at the end of compression d. The coefficient of consolidation of the clay e. The final height of the clay sample at the end of swelling
2. A layer of compressible clay 6m thick overlies an impervious bedrock and carries an overburden of pervious sand. A large structure founded in the sand causes the stress on every horizontal section of the clay to increase to the same value. In a standard laboratory oedometer consolidation test performed on a 19 mm thick clay specimen, the void ratio changed from 0.765 to 0.750 under a corresponding increase in stress. Consolidation was 70% complete after 30 min. In the field, a) Estimate the settlement of the structure. b) Determine the time taken for one half of the consolidation settlement to take place (Remember the lab test is for a doubly drained specimen.). c) Determine how long it takes for 50% of the settlement to take place at a depth of 0, 2, 3, 5 and 6 m of the clay stratum. d) If the clay were underlain by pervious sand, determine how long it takes for 50% of the settlement to take place at a depth of 0, 2, 3, 5 and 6 m of the clay stratum.
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