Experimental and DEM simulation on engineering properties of soft soil stabilized by industrial solid waste-cement synergy

The industrial solid wastes (slag powder, fly ash and gypsum powder) were used to stabilize the soft soil to reduce cement consumption in soft soil improvement engineering projects. Unconfined compressive strength (UCS) and direct shear (DS) tests were conducted to explore the impact of solidified soil ratio and curing time on the engineering properties of solidified soil. Moreover, the software PFC 2D was adopted to simulate the axial stress - strain response and crack development of solidified soils in UCS tests. The test results showed that: the UC strength of A13 solidified soil reached the maximum value, and the UC strength and cohesion of A13 solidified soil were 1004.3 kPa and 206.5 kPa, respectively after being cured for 28 d. While the UC strength and cohesion of A0 cemented soil were 370.1 kPa and 75.4 kPa, respectively after being cured for 28 d. The ratio of cement: slag powder: fly ash: gypsum powder of A13 solidified soil was 43.5 %: 29 %: 7.5 %: 20 %, which indicated that the addition of industrial solid wastes could increase solidified soil strength as well as decrease cement consumption. The UC strength of solidified soil also increased logarithmically with the curing time, and the UC strength of A13 solidified soil increased from 676.5 kPa to 1428.7 kPa as the curing time increased from 7 d to 28 d. The PFC 2D simulation results indicated that the failure mode of solidified soil in UCS tests changed from shear failure to tensile failure with the increase of UC strength. The research results can be used for the design of industrial solid wastes in engineering practice.