The Study of Scale Effect and Loading Mechanism on the Friction Behavior at the Interface of Sand/Geomembrane Systems

• Main Authors: Ming-Wen Hsieh, 謝明紋
• Other Authors: Chiwan Hsieh
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/25899339187163467647

碩士 === 國立屏東科技大學 === 土木工程系碩士班 === 89 === The scale effect of shear box and loading mechanism on the frictional behavior at the interface of a quartz sand and HDPE geomembranes was analyzed in the study. At present, ASTM D5321 standard specification is the primarily test method for measuring the shear strength at the interface of soil and geosynthetic or geosynthetic and geosynthetic. ASTM D5321 standard test method states that both square and rectangular containers can be used in the test; the containers should have a minimum dimension that is greater of 300 mm, 15 times the d85 of the coarser soil used in the test, or a minimum of five times the maximum opening size of the geosynthetic tested. Smaller containers can be used if it can be shown that data generated by the smaller devices contain no scale or edge effects bias when compared to the minimum size device specified in the standard. Four different dimensions of direct shear boxes were used to study the scale effect on the shear behavior at the soil/geomembrane interface. The dimensions of the shear boxes are 100 x 100 mm, 200 x 200 mm, 300 x 300 mm, and 400 x 400 mm. Besides to use the conventional rigid bearing plate to transfer applied load to the test sample, a flexible silicon water bag was also designed attaching to the bottom of rigid bearing plate to establish a flexible loading mechanism. Moreover, load cells were placed at the base of the bottom shear box to measure the variation of reaction pressure. The test materials included a quartz sand, and smooth and rough surface HDPE geomembranes. The results of the study indicated that a minimum of 50 mm in thickness of soil should be used in upper shear box in order to provide repeatable loading condition when rigid bearing plate is used. Higher stress concentration at the center of shear box was measured under rigid loading mechanism. However, the reaction pressure at the bottom of shear box is approximately uniform distributed under flexible loading mechanism. Thus, a flexible loading plate is strongly suggested should be used in large-scale direct shear test. Based upon the results obtained from the direct shear tests using varies sizes direct shear boxes, dimension of shear box has some effect on the shear behavior at the interface of Geomembrane/soil. It is recommended that a minimum 300 x 300 mm direct shear box should be used in Geomembrane/soil direct shear test.