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http://dx.doi.org/10.9711/KTAJ.2022.24.3.231

Numerical study on basal heave stability of a circular vertical shaft constructed in clay  

Kang, Seok-Jun (Dept. of Civil and Environmental Engineering, KAIST)
Cho, Gye-Chun (Dept. of Civil and Environmental Engineering, KAIST)
Publication Information
Journal of Korean Tunnelling and Underground Space Association / v.24, no.3, 2022 , pp. 231-245 More about this Journal
Abstract
When vertical shafts are constructed in soft clay with low strength, there is a risk of basal heave, which causes the excavation surface to heave due to the low bearing capacity of the ground against the imbalance of earth pressure at the excavation surface. Methods of deriving a safety factor have been proposed to evaluate the stability against the basal heave. However, there are limitations in that it is difficult to accurately evaluate the heave stability because many assumptions are included in the theoretical derivation. In this study, assuming that a circular vertical shaft is constructed in soft clay, the existing safety factor equation proposed through a theoretical approach was supplemented. Bearing capacity according to the shaft geometry, inhomogeneity of the soil, and the effect of soil plug were considered theoretically and applied in a previous safety factor equation. A three-dimensional numerical analysis was conducted to simulate the occurrence of basal heave and review the supplemented equation through various case studies. Several series of case studies were conducted targeting various factors affecting heave stability. It was verified that the additionally considered characteristics were properly reflected in the supplemented equation. Furthermore, the effects of each factor constituting the safety factor equation were examined using the results of the numerical analysis performed by simulating various cases. It was confirmed that considering the undrained shear strength increment according to depth had the most significant effect on the calculation of the safety factor.
Keywords
Vertical shaft; Basal heave; Safety factor; Numerical analysis; Soil plug;
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Times Cited By KSCI : 2  (Citation Analysis)
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