JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI ›› 2014, Vol. 31 ›› Issue (10): 128-133.DOI: 10.3969/j.issn.1001-5485.2014.10.020

• ROCK-SOIL ENGINEERING • Previous Articles     Next Articles

Experimental Research on Three-dimensional Swelling Characteristics of Expansive Soil Improved with Straw Ash

ZHANG De-heng1,2,SUN Shu-lin3,4,XU Fen-qiang1   

  1. 1.Department of Architecture Civil Engineering, Nanjing Institute of Technology, Nanjing 211167, China;
    2.College of Civil and Transportation Engineering, Hohai University, Nanjing 210098, China;
    3.State Key Laboratory of Hydrology, Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China;
    4.College of Earth Sciences and Engineering, Hohai University, Nanjing 210098, China
  • Received:2013-09-05 Revised:2014-10-17 Online:2014-10-01 Published:2014-10-20

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Abstract: Laboratory tests were carried out on expansive soil improved with straw ash as additive to research the 3-D free volume change and unconfined compressive strength (UCS) characteristics of expansive soil improved with straw ash. Straw ash content (weight of straw ash/weight of dry soil) at 0%, 10%, 15% and 20% were mixed with expansive soil and then compacted. Tests on the 3-D free volumetric swell strain, vertical swell pressure and unconfined compressive strength were conducted in the presence of maximum dry density and optimum moisture content, and also tests on the volumetric shrinkage strain was conducted in liquid limit state. The linear equation of the optimum content of straw ash was fitted based on the 3-D free volumetric strain and swelling pressure properties of expansive soil, and the optimum content of straw ash was 17%. The test results show that with the increasing of straw ash, the volume strain, plasticity index and swell pressure decreased whereas the UCS increased. There is no remarkable change in the UCS of the samples immediately tested with straw ash, however, curing of 7 days could bring a remarkable increase in the UCS.

Key words: expansive soil, straw ash, three-dimensional free volume strain, swelling pressure, UCS

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