A method of reducing the swell potential of an expansive clayey soil comprising expansive clay mineral(s) at a proportion of the total weight of the expansive clayey soil (PECM). The method includes (a) calculating a first amount of a swelling reduction agent to be incorporated into the expansive clayey soil to form a first swelling reduction agent incorporated expansive clayey soil with a reduced swell potential no greater than a pre-set level T with a nano-level constitutive modeling based on the water content and the CEC of the expansive clayey soil and PECM. The swelling reduction agent is at least one selected from calcite, gypsum, potassium chloride, a composition comprising exchangeable K+, a composition comprising exchangeable Ca2−, and/or a composition comprising exchangeable Mg2+, and (b) incorporating the first amount of the swelling reduction agent into the expansive clayey soil to form the first swelling reduction agent incorporated expansive clayey soil.