Microscopic mechanism analysis of calcareous sand in electrolysis desaturation using [sup.1]H L-F NMR

Electrolysis desaturation is a novel method to improve the liquefaction resistance of liquefiable foundations. The microscopic mechanism of the horizontal-layered electrolysis desaturation of calcareous sand specimens was revealed using a lowfield nuclear magnetic resonance ([sup.1]H L-F NMR) apparatus. The expansion and recovery of sand pores was detected, and variation pattern of saturation distribution was explored, as well as the generation and migration of gas bubbles. The test results show that the electrolysis mainly discharged free water from the specimen, and the content of bound water or mechanical bound water kept basically unchanged. The rapid generation of the bubbles could lead to the expansion of the sand pores. Within 3 h after stopping electrolysis, the macropores in the calcareous sand essentially returned to the initial state, and the expansion of micropores and mesopores also remained basically stable. The construction method of prolonged low-current electrolysis or short-time multiple electrolysis could be applied for on-site desaturated foundation treatment. The shape and size of the bubbles produced by electrolysis were related to the calcareous sand pores. The migration of gas after stopping electrolysis was mainly in the vertically upward direction, resulting in the fusion of bubbles and the formation of larger bubbles.