Location
Chicago, Illinois
Date
04 May 2013, 10:30 am - 11:30 am
Abstract
Estimation of static and seismic settlements is critical for the design of a structure to assess whether the structure can tolerate given levels of total and differential settlements and angular distortion. The design of a public school building required the estimation of both liquefaction-induced settlement due to the presence of a potentially liquefiable layer, and settlement from cyclic softening of soft clay layers. Tolerable levels of differential settlements for the proposed school building were not to exceed 2 inches across the building. The soft clay had a plasticity index of 12, a liquid limit of 32, and SPT blow counts of less than 4. Recent publications do not consider this clay potentially liquefiable, but consider it susceptible to cyclic softening. In addition to the borings, in-situ vane shear testing and CPT soundings were conducted at the site to supplement the data for our analysis. Using published methods we conducted an assessment of the soft clay and calculated factors of safety against cyclic softening as low as 0.0. In-situ vane shear testing resulted in soil sensitivities ranging from 1.6 to 3.4. Using CPT data we conducted a cyclic softening analysis of the entire soil column to a depth of about 50 feet. This paper describes the encountered site conditions, methodology for estimating both seismic and static settlements, criteria for acceptable foundation performance, importance of evaluation of cyclic softening of soft clay layers, and the challenges working with the regulatory agency. The results of our analyses indicate differential settlements of about 2 inches.
Department(s)
Civil, Architectural and Environmental Engineering
Meeting Name
7th Conference of the International Conference on Case Histories in Geotechnical Engineering
Publisher
Missouri University of Science and Technology
Document Version
Final Version
Rights
© 2013 Missouri University of Science and Technology, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Document Type
Article - Conference proceedings
File Type
text
Language
English
Recommended Citation
Wetenkamp, James; Meneses, Jorge; and Zafir, Zia, "Estimating Seismic Settlements from Liquefaction and Cyclic Softening and Their Impact to Design of a School Building" (2013). International Conference on Case Histories in Geotechnical Engineering. 17.
https://scholarsmine.mst.edu/icchge/7icchge/session04/17
Estimating Seismic Settlements from Liquefaction and Cyclic Softening and Their Impact to Design of a School Building
Chicago, Illinois
Estimation of static and seismic settlements is critical for the design of a structure to assess whether the structure can tolerate given levels of total and differential settlements and angular distortion. The design of a public school building required the estimation of both liquefaction-induced settlement due to the presence of a potentially liquefiable layer, and settlement from cyclic softening of soft clay layers. Tolerable levels of differential settlements for the proposed school building were not to exceed 2 inches across the building. The soft clay had a plasticity index of 12, a liquid limit of 32, and SPT blow counts of less than 4. Recent publications do not consider this clay potentially liquefiable, but consider it susceptible to cyclic softening. In addition to the borings, in-situ vane shear testing and CPT soundings were conducted at the site to supplement the data for our analysis. Using published methods we conducted an assessment of the soft clay and calculated factors of safety against cyclic softening as low as 0.0. In-situ vane shear testing resulted in soil sensitivities ranging from 1.6 to 3.4. Using CPT data we conducted a cyclic softening analysis of the entire soil column to a depth of about 50 feet. This paper describes the encountered site conditions, methodology for estimating both seismic and static settlements, criteria for acceptable foundation performance, importance of evaluation of cyclic softening of soft clay layers, and the challenges working with the regulatory agency. The results of our analyses indicate differential settlements of about 2 inches.
