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Taj Bahadori <br />July 13, 2015 <br />Page 2 of 6 <br />• Test Series 3 - HDPE geomembrane vs. geocomposite 0 <br />In addition to Series 1 through 3 for single interfaces called for in the specifications two <br />additional multi -layer (sandwich) test series, Series 4 and 5 representing the composite liner <br />section for the base liner and the side slope liner respectively, were performed at the direction <br />of the County. The sandwich test configurations for these test series included all of the soil and <br />geosynthetics materials of the composite liner as follows: <br />Test Series 4 - Base Liner (bottom to top as set up in shear box) <br />Foundation layer soil <br />GCL <br />HDPE Geomembrane <br />LCRS gravel <br />Test Series 5 - Side Slope Liner top to bottom as set up in shear box) <br />Operations layer soil <br />Geocomposite <br />HDPE geomembrane <br />GCL <br />Side slope subgrade soil <br />The sample set up and testing procedures, including GCL hydration and consolidation time and <br />pressures and rate of shear for all of the test series were as specified in Section 02800 of the <br />specifications except that rate of shear for Test Series 5 (side slope liner sandwich test) was <br />revised to 0.04 inch/min from 0.2 inch/min specified for Test Series 3 - HDPE <br />geomembrane/geocomposite interface. This is because the side slope liner sandwich test <br />configuration includes soil materials and GCL, in addition to HDPE geomembrane and <br />geocomposite materials for Test Series 3. The test configurations for Test Series 1 through 3 are <br />listed on Table 1 and for Test Series 4 and'S are listed in Table 2 attached. <br />3.0 Geosynthetic Materials Index Properties <br />The key index properties of geosynthetics materials that would significantly influence the <br />interface shear strengths include peel strength of GCL and asperity height of 60 -mil DST HDPE <br />v t \ v, v�V AAAV vY ,���A�v0l\Vv\�A�� A�AVVAA�AAVAvvlV1vv \vvv oey V A wv c v v v A AAv vO®�� <br />geomembrane. <br />�� wv A .y. � .... Av\_�y�� .y A ,��0 ,�� ..AVO\\\\\\��AVV�\"\O�w A\\\\Vyov cz �a�AyvvV AV�.�� \vv �yyv°vVvywa�•��yV yy . yv� y <br />PA14 Projects\14-101 ( SJCDPW North County and Foothill)\Correspondence\Memo - Foothill Interface Shear Strength Test Results.docx <br />