MEASUREMENT OF SOIL SUCTION FOR REMOULDED CHENGDU CLAY WITH CHILLED-MIRROR DEW-POINT TECHNOLOGY

The aim of this study is to assess the method for measuring the total suction of compacted soil samples of Chengdu Clay with Chilled-mirror dew-point technology, an indirect measurement method for soil suction. The total suction of compacted soil samples of Chengdu Clay is measured with a WP4-C dew point potentiometer. Soil samples are taken from the depths of a foundation pit in the eastern suburbs of Chengdu. After grinding to pass 0.075mm sieve, configured into 10 different initial moisture content, the remoulded soil is then statically compacted into a fixed volume with a custom mold of diameter 3.5cm and thickness 0.5cm. A total of 40 soil samples are prepared. The average dry density is 1.7g ·cm^-3.Based on the Van Genuchten model and the Origin software, we obtain the SWCC curve of the Chengdu Clay, and the reference value of the fitting parameter. The conductivity of the soil sample is measured by the CT-3031 conductivity meter. It is calculated with the conversion formula to obtain the osmotic suction. For the matrix suction is equal to the total suction minus the osmotic suction, the relationship between the matrix suction and the water content is indirectly obtained. It is pointed out that there is a certain deviation between the design moisture content and the actual moisture content of the soil sample, because the size of the soil sample is too small to maintain a constant water content when it is transferred from the sealed bag to the chilled-mirror dew-point meter. After the end of the test, it is necessary to recalculate the moisture content of soil samples. Next, another SWCC curve is obtained using the filter paper method to test the same soil samples. The test results obtained by the two test methods are compared. It is concluded that the suction values measured by the chilled-mirror dew-point technology is lower than that measured by the filter paper method, when the soil samples are at the same water content. This conclusion is in accordance with that of S.S.Agus, which proves that the chilled-mirror dew-point technology has the characteristics of fastness, convenience and accuracy. As a fast method of measuring the suction, the chilled-mirror dew-point technology has a wide range of suction measurement, which can reduce more testing time than the filter paper method. The SWCC curves in this study show that the chilled-mirror dew-point technology is feasible in suction test of the unsaturated Chengdu Clay, and can be extended to the suction test in geotechnical engineering fields in China.