Prediction of unsaturated shear strength of an adobe soil from the soil–water characteristic curve

Abstract This paper studied the unsaturated shear strength properties of a soil with the gradation characteristics of the material typically used in adobe construction. The main goal was to predict the unsaturated shear strength of the adobe soil using the soil–water characteristic curve (SWCC) and the effective cohesion and friction angle of the material. Specimens were trimmed from adobe bricks made according to the traditional technique of the southwestern region of the United States. The SWCC of the adobe soil was constructed using data obtained with the filter paper test. The effective cohesion and friction angle were found to be 11.7 kPa and 31.4°, respectively, from the results of consolidated drained direct shear tests. In addition, unconsolidated undrained direct shear tests were done on specimens at different water contents to determine the apparent shear strength parameters. The predicted shear strength was found to increase significantly with decreasing water content, and the strength increase was approximately 350 kPa between near saturation condition and water content of 6.01%. The predicted failure envelopes in the shear strength–matric suction plane were nonlinear; their initial slope was close to the (saturated) effective friction angle, and the slope decreased as the suction increased.

[1]  C. Ng,et al.  The axis-translation and osmotic techniques in shear testing of unsaturated soils : A comparison , 2007 .

[2]  Delwyn G. Fredlund,et al.  The relationship of the unsaturated soil shear strength to the soil-water characteristic curve , 1996 .

[3]  Anthony Crosby.  Monitoring Moisture at Tumacacori , 1987 .

[4]  Van Genuchten,et al.  A closed-form equation for predicting the hydraulic conductivity of unsaturated soils , 1980 .

[5]  D. Fredlund,et al.  The shear strength of unsaturated soils , 1978 .

[6]  Ning Lu,et al.  Unsaturated Soil Mechanics , 2004 .

[7]  S. Houston.  Characterization of Unsaturated Soils: The Importance of Response to Wetting , 2014 .

[8]  Anthony Crosby.  A Preservation Monitoring System at Tumacacori National Monument , 1978 .

[9]  D. Fredlund,et al.  Equations for the soil-water characteristic curve , 1994 .

[10]  William N. Houston,et al.  Laboratory Filter Paper Suction Measurements , 1994 .

[11]  Si-hong Liu,et al.  Measurement of the Shear Strength of an Expansive Soil by Combining a Filter Paper Method and Direct Shear Tests , 2012 .

[12]  R. H. Brooks,et al.  Hydraulic properties of porous media , 1963 .

[13]  E. Leroy Tolles.  Survey of damage to historic adobe buildings after the January 1994 Northridge earthquake , 1996 .

[14]  E. Çokça,et al.  Shear strength-suction relationship of compacted Ankara clay , 2010 .

[15]  Harianto Rahardjo,et al.  Factors affecting the filter paper method for total and matric suction measurements , 2002 .

[16]  D. E. Pufahl,et al.  Model for the prediction of shear strength with respect to soil suction , 1996 .

[17]  Nasser Khalili,et al.  Effective Stress in Unsaturated Soils: Review with New Evidence , 2004 .