Behaviors of Soft Bangkok Clay behind Diaphragm Wall Under Unloading Compression Triaxial Test

서지정보

· 발행기관 : 한국지반공학회
· 수록지 정보 : 한국지반공학회논문집 / 23권 / 9호 / 5 ~ 16페이지
· 저자명 : Nghia Trong Le, Wanchai Teparaksa, Toshiyuki Mitachi, Takayuki Kawaguchi

초록

The simple linear elastic-perfectly plastic model with soil parameters su, Eu and n of undrained condition is usually applied to predict the displacement of a constructed diaphragm wall (DW) on soft soils during excavation. However, the application of this soil model for finite element analysis could not interpret the continued increment of the lateral displacement of the DW for the large and deep excavation area both during the elapsed time without activity of excavation and after finishing excavation. To study the characteristic behaviors of soil behind the DW during the periods without excavation, a series of tests on soft Bangkok clay samples are simulated in the same manner as stress condition of soil elements happening behind diaphragm wall by triaxial tests. Three kinds of triaxial tests are carried out in this research: K0 consolidated undrained compression (CK0UC) and K0 consolidated drained/ undrained unloading compression with periodic decrement of horizontal pressure (CK0DUC and CK0UUC). The study shows that the shear strength of series CK0DUC tests is equal to the residual strength of CK0UC tests. The Young’s modulus determined at each decrement step of the horizontal pressure of soil specimen on CK0DUC tests decreases with increase in the deviator stress. In addition, the slope of Critical State Line of both CK0UC and CK0DUC tests is equal. Moreover, the axial and radial strain rates of each decrement of horizontal pressure step of CK0DUC tests are established with the function of time, a slope of critical state line and a ratio of deviator and mean effective stress. This study shows that the results of the unloading compression triaxial tests can be used to predict the diaphragm wall deflection during excavation.

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