Abstract: Grouting in soft clay for ground improvement is subjected to significant excess pore water pressure and structure destruction, leading to slight improvement of soil strength and appreciable settlement after grouting. A new method, named capsule expansion combined with electro-osmosis, for soft clayey ground improvement is proposed. The capsule expansion aims at the avoidance of uncontrollable flow of grout, and synchronous electro-osmosis mitigates the generated excess pore water pressure. Two small-scale model tests are carried out to figure out the behavior of mud with sand due to capsule expansion combined with electro-osmosis. The difference between the two tests is the content of sand within the mud of the model ground. Excess pore water pressure, ground vertical displacement, and compression modulus are monitored during the tests. It is found that electro-osmosis can effectively dissipate the excess pore water pressure caused by capsule grouting. The soil structure significantly affects the evolution of the excess pore water pressure. The lower the sand content in the soil, the greater the excess pore water pressure generated by grouting, and the more significant the dissipation effect of electro-osmosis. The ground vertical displacement of the ground surface shows a small and uniform characteristic under the synergistic action of capsule grouting and electro-osmosis. Moreover, the combined action can significantly enhance the soil stiffness, with the compression modulus of the soil increasing up to 2.3 times the initial value. The reinforcement effect is more pronounced in closer proximity to the grouting area.