Back Issues 11-20

EFFECT OF DISSOLVED AIR IN WATER ON CONSOLIDATION TEST RESULTS

Tse-Shan Hsu

President, Institute of Mitigation for Earthquake Shear Banding Disasters

Chair Professor, College of Construction and Development, 

Feng-Chia University, Taiwan R.O.C., ">

Lin-Yao Wang

Student, Ph.D. Program for Civil Engineering, Water Resources Engineering, and

Infrastructure Planning, Feng-Chia University, Taiwan, R.O.C.

Da-Jie Lin, Tsai-Fu Chuang

Associate Professors, Feng-Chia University, Taiwan R.O.C.

Abstract

Although the total settlement of saturated clay specimens under the action of vertical pressure increment includes the immediate settlement, primary consolidation settlement, and secondary compression settlement, the traditional consolidation test results only show the primary consolidation settlement and secondary compression settlement. Therefore, in the case where the primary consolidation settlement contains immediate settlement, the line type of the fitting curve of consolidation test deviates from the theoretical one. In view of this, the authors of this paper redefine saturation and immediate settlement for the first time and provide a trial-and-error procedure to separate the immediate settlement and primary consolidation settlement. Further, through two case studies, the following are determined: (1) When the pore space of the clay specimen is filled with water containing highly compressible dissolved air, and the dissolved air in water is compressed instantaneously after the vertical pressure increment is applied, the sum of the settlements that occur directly or indirectly after the dissolved air in water is compressed is defined as immediate settlement. (2) The proposed trial-and-error procedure can clearly distinguish the immediate settlement of the seemingly saturated clay specimen from the primary consolidation settlement. (3) The immediate settlement of the seemingly saturated clay specimen is a highly complex nonlinear problem, and its magnitude may exceed half of that of the primary consolidation settlement; therefore, it cannot be calculated by the elastic theory formula, because such kind of calculation will give an incorrect result that the immediate settlement is only a small part of the total settlement. (4) When the primary consolidation settlement does not contain the immediate settlement, the line type of the fitting curve of consolidation test will be consistent with that of the theoretical one; therefore, the difference between the coefficients of consolidation obtained by the square root of time fitting method and the logarithm of time fitting method will be greatly reduced. Based on the above four conclusions, the authors suggest to incorporate the definition of immediate settlement and the trial-and-error procedure proposed in this paper into traditional soil mechanics. This would ensure that the consolidation test results including the immediate settlement, primary consolidation settlement, and coefficient of consolidation meet practical needs.

Keywords: dissolved air in water, seemingly saturated clay, consolidation test, immediate settlement, primary consolidation settlement.

Attachments:

1203 Final.pdf

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