Laboratory Investigation of the Effects of Temperature and Moisture on Interface Shear Strength of Textured Geomembrane and Geosynthetic Clay Liner

<p>A laboratory investigation was conducted to determine the effects of temperature and moisture on the shear strength of textured geomembrane (T-GM) and geosynthetic clay liner (GCL) interface. Several landfill slope failures involving geosynthetics have occurred within the past three decades. Interface shear strength of T-GM/GCL is well documented for testing conducted at laboratory temperatures and at moisture contents associated with GCLs in submerged conditions. However, in-service conditions for landfill liner systems include a wide range of temperatures (extending from below 0 °C to above 40 °C) and a wide range of moisture conditions. Large-scale interface direct shear tests were performed at normal stresses of cover liners (10, 20, and 30 kPa) and bottom liners (100, 200, and 300 kPa). Cover liner specimens were subjected to temperatures of 2, 20 and 40 °C; and bottom liner specimens were subjected to temperatures of 20 and 40 °C. Both cover and bottom liner specimens were prepared at moisture contents of as-received (approx. 18-19%), 50%, and 100%.</p> <p>Cover liner specimens exhibited decreased peak interface shear strength (t_p) with increasing temperature. Specimens sheared at 2 °C exhibited greater t_p than those sheared at 20 °C by as much as 27%. Specimens sheared at 20 °C exhibited greater t_p than those sheared at 40 °C by as much as 16%. Large-displacement interface shear strength (t_ld) generally exhibited a bell-shaped relationship with increasing temperature with the greatest t_ld at 20 °C. A bell-shaped relationship was exhibited between temperature and peak and large-displacement interface friction angle (d_p and d_ld). d_p ranged from 17.4 to 26.3°, 23.8 to 29°, and 20.4 to 22.2° for 2, 20, and 40 °C, respectively. d_ld ranged from 12.7 to 18.2°, 18.2 to 20.6°, and 15.9 to 16.7° for 2, 20, and 40 °C, respectively. Decreased d at 2 and 40 °C were largely attributed to increased geosynthetic damage. Bottom liner specimens exhibited decreased t_p and t_ld with increasing temperature by up to 12% and 16%, respectively. Bottom liner specimens exhibited decreased t_p and t_ld with increasing moisture content by up to 14% and 36%, respectively. For bottom liner specimens, a trend of decreased d_pwith increased temperatures was exhibited. d_p ranged from 20 to 24.7° and 19.5 to 22.2° for 20 °C and 40 °C, respectively. d_ld ranged from 10.4 to 15.6° and 8.9 to 13.9° for 20 °C and 40 °C, respectively. Decreased d at 40 °C was largely attributed to increased geosynthetic damage and increased bentonite extrusion. Increased moisture content resulted in decreased d_p and d_ld by up to 4.7 and 5.1°, respectively. Results of this testing program indicated that T-GM/GCL interface shear strengths are influenced by temperature and moisture content within ranges representative of field conditions. Interpolation factors and reduction factors were developed for use to avoid overestimation of d when determined at standard laboratory temperatures. For cover liners, reduction factors of 0.8 and 0.85 are recommended for d_pand d_ld, respectively. For bottom liners, reduction factors of 0.9 and 0.85 are recommended for d_pand d_ld, respectively.</p>

Name thesis:degree_name

MS in Civil and Environmental Engineering

Discipline thesis:degree_discipline

Civil and Environmental Engineering

Year dc:date.available

2012

Author dc:creator

• Chrysovergis, Taki Stavros

Contributors dc:contributor

• James Hanson

• Geosynthetics
• Interface shear strength
• Temperature
• Geomembrane
• Geosynthetic clay liner
• Environmental Engineering
• Geotechnical Engineering
• Other Civil and Environmental Engineering

Identifier

10.15368/theses.2012.220

OAI identifier oai:identifier

oai:digitalcommons.calpoly.edu:theses-1949