Investigation of Frozen Soil Behavior under Unconfined Compression Test

Document Type : Research Article

Authors

1 Associate Professor Department of Civil Engineering

2 Department of Civil Engineering, University of Mohaghegh Ardabili, Iran

3 Assistant Professor, Department of Civil Engineering, University of Mohaghegh Ardabili,

Abstract

Frozen sand soils are often observed in underground urban and engineering constructions in cold climates. Artificial ground freezing is a soil improvement technique, and soils in coastal areas are mostly comprised of poorly-graded sand with low moisture and temperature. Thus, it is required to explore the effects of different factors on the strength of frozen soils in such areas. In addition, the freezing age required to obtain sufficient strength is studied. The present study investigates sand from the Shorabil Lake shore in Ardabil, Iran, frozen in cold seasons. To evaluate the effects of the soil grain size, sands with gran sizes of 0.15 and 0.25 mm mixed with clay in different ratios were employed. Uniaxial compressive testing was implemented to measure the unconfined compressive strength of ten soil mixtures with four moisture contents. Thus, a total of 40 mixtures were studied at three freezing ages. The stress-strain curves showed strain softening. The specimens had almost the same strength at shorter freezing ages. As the freezing age increased, different stresses were observed due to the clay content; the strength of a specimen with a low clay content remained almost unchanged as the freezing age increased. The specimen with a clay content of 50% and a moisture content of 15% had a strength of 205.5 kPa at a freezing age of 24 h and 283.8 kPa at a freezing age of 72 h. Also, the specimen with a clay content of 10% and a moisture of 15% was found to have strengths of 265.4 and 283.8 kPa at the freezing ages of 24 and 72 h, respectively. Several specimens underwent an up to 36% decline in strength as the sand grain size decreased; however, the trend was still the case, and the specimen with 30% clay showed the highest strength in most cases.

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Main Subjects


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