Experimental Study on the Modification Mechanisms of Dispersive Soil Treated with Hydroxyl Aluminum

Table 3

Dispersion identification results of the soil before and after hydroxy aluminum modification.

Al/soil ratio/(mmol·g^-1)	Pinhole test				Crumb test	Comprehensive judgment
	Water head/(mm)	Time/(min)	Final aperture/(mm)	Water	Soil sample
0	50	5	≥6	Muddy	Disintegration	Dispersive soil
0.08	50	5	≥3	Muddy	Disintegration	Dispersive soil
0.10	50	5	≥2	Little muddy	Partial disintegration	Dispersive soil
0.20	50	5	≥1.5	Little muddy	Disintegration	Transition soil
0.40	50	5	1	Clear	Disintegration	Nondispersive soil

Criteria for dispersion: Double hydrometer test: nondispersive soil: dispersion <30%; transition soil: 50%~50%; and dispersive soil: the dispersity is greater than 50%. Pinhole test: nondispersive soil: under the water head - 1020 mm, the water is transparent and the final hole diameter is less than 1.5 mm; transition soil: under 50 mm water head, the outlet water is slightly turbid and the final aperture is less than 1.5 mm or under 380 mm water head, the outlet water is more transparent and the final aperture is greater than 1.5 mm; and dispersive soil: under the water head of 50 mm, the outlet water is turbid and the final pore diameter is greater than 1.5 mm. Fragment test: nondispersive soil: there is no reaction of dispersing colloidal particles. After hydrolysis, the soil blocks are stacked horizontally in the form of fine particles at the bottom of the measuring cup. The watercolor is clear or becomes clear soon after being slightly turbid; transition soil: there is a small amount of muddy water around the soil block after hydrolysis, but the diffusion range is small; and dispersive soil: after hydrolysis, the upper block is turbid and the soil quickly diffuses to the bottom of the whole measuring cup. The water is foggy and unclear for a long time.