CIVIL ENGINEERING 365 ALL ABOUT CIVIL ENGINEERING



AbstractDeep mixing method (DMM) has been widely used in geotechnical and highway engineering to stabilize soft soil foundations. The emerging material, one-part geopolymer (OPG), is environmentally friendly, which is promising to be used as an alternative binder to replace ordinary portland cement (OPC) partially or even completely for stabilizing the soft clay. In this paper, the dynamic shear modulus and damping ratio of the OPG-stabilized soft clay are investigated through the dynamic triaxial test. X-ray computed tomography (X-ray CT) is adopted to analyze the evolution of microstructure, especially the porosity distribution in OPG-stabilized soil samples. Factors affecting the dynamic behaviors of the OPG-stabilized soil, including the mass ratio of fly ash (FA) to ground granulated blast furnace slag (GGBFS), curing stress, curing time, confining pressure, cyclic-stress frequency, and cyclic-stress ratio (CSR) are studied. Results show that among all the mixing proportions, the sample with FA/GGBFS mass ratio of 0.1 could get the highest dynamic shear modulus and lowest damping ratio. With the curing stress increasing and curing time elapsing, dynamic shear modulus increases and the damping ratio decreases significantly. Furthermore, the higher the confining pressure is, the higher the dynamic shear modulus achieves. However, the higher confining pressure, such as 300 kPa, might disturb the original structure of the OPG-stabilized soil sample and then induce the breakage of bonding between hydration gels and soil particles, further causing the substantial loss of transmission energy. Finally, the higher cyclic-stress frequency would induce the larger shear strain of the sample under the given CSR, resulting in the lower dynamic shear modulus and higher damping ratio. The outcome of this study could provide guidance for the application of OPG binder in the ground improvement.



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