55surface and subˉsurface samples of expansive soils were collected in the HandanYongnian area

Nanyang district

Pingdingshan area along the middle line of the NorthSouth Diversion Water Project and in Xiangfan area and Zhongxiang districts in Jingmeng city.Clay mineral composition and smectite contents were measured using XRD and dye absorption methods.The effective smectite contents were calculated.Meanwhile the visibleshort wave infrared spectra of the swelling soils was collected

the spectral absorption indices

such as:wavelength position

depth

width

asymmetry

area

were calculated automatically.Then the correlation relationships between the spectral indices and the smectite contents and the colloid contents and clay contents of the swelling soils were statistically analyzed.The results showthat the very high

high

medium

weak potential soils can be identified according to the relative strengths of the2200nm

1900nm

1400nm absorptions in the spectral features of the swelling soils;the smectite contents and the colloid contents and the clay contents of the swelling soils can be estimated with the1400nm and1900nm absorption;the absorption widths of the1900nm and1400nm absorptions can be used to estimate the smectite contents;the absorption area and asymmetry cannot be used to estimate the contents of smectite and colloid and clay;the laboratory spectral measurement and analysis techniques to the dried and homogenous swelling soils can be productively used for quickly

economically

and conveniently identifying swelling soils

and estimating the contents of smectite

colloid

and clay in the engineering sites.