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CHECK OF •rGEOMEMBRANE LINER <br />AGAINST PUNCTURE FROM DRAINAGE - GRAVEL <br />O. COUNTY RECYCLINGr SANITARY LANDFILL <br />1.0 Introduction <br />The originally designed maximum waste height above Module 4 was 130 feet. The use <br />of rounded gravel was specified in the original design for Module 4. Therefore, a <br />geotextile protection layer was not used in the original design. The final grading plan <br />prepared as part of the expansion of the North County Recycling Center and Sanitary <br />Landfill shows a maximum waste height of approximately 241 feet above the existing <br />Module 4 liner system. Because of the increase in waste height, a puncture resistance <br />calculation has been performed to determine if the geomembrane can withstand the <br />additional loading without puncturing. <br />The gradation (see attached) for the drainage layer used in Module 4 shows maximum <br />grain size of 3/8 inch or 9.5 millimeters (mm). The calculations below show the <br />minimum mass per unit area of the geotextile cushion required. <br />2.0 Calculations <br />According to Koerner (1998), the allowable pressure (Fallow) that can be tolerated by a <br />geotextile layer subject to a protrusion of effective height H is given by, <br />Polmw = <br />where, <br />C50+0.00045 M 1 1 <br />H' J MFS . MFPD <br />1 <br />MFA RFCR . RFCBD <br />(Eq. 1) <br />P'allow = Allowable pressure (in kPa) <br />M = Mass per unit area of the geotextile cushion (in g/mZ) <br />H = Effective protrusion height (in meters) <br />MFs = Modification factor for shape of protrusion <br />MFPD = Modification factor for packing density <br />MFA = Modification factor for arching <br />FCR = Partial factor of safety for creep <br />FCBD = Partial factor of safety for chemical and biological degradation <br />Assuming a maximum waste height of 240 feet and a waste unit weight of 90 pcf, the <br />actual pressure (P.tual) on the geotextile is, <br />Pactual = (241 ft) x (90 lb/ft) = 21,690 lb/ft' = 1,039 kPa <br />Koerner (1998) recommends a minimum factor of safety of 3 against puncture. The <br />factor of safety (FS) against puncture is given by, <br />Page 1 of 3 <br />N.IGEOTECHNICALWCRC&SL-20071Punture-ResistancelModule 4WCRC&SL_M4 Puncture-Protection.doc <br />