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Ltb <br />The CSE Drainage Design Manual <br />JiSo: overall factor of safety for drainage (dimensionlebs), <br />,RF'sp: reduction factor for long-term creep (dimensionfess), <br />RF6g: reduotion facfor for chemical clogging (dimensilnless), <br />J?Fgc = reduction factor for biological ctogging (dimendiontess). <br />in a "go no-go" determination, in which the designer deci{es that the <br />Chapter 4 - Design Methods And Cerncepts <br />with the 100-hour <br />value shorrld be <br />hour transmissivity <br />manufacturers <br />compatibility <br />to, shou:ld be <br />where <br />iew should result <br />is acceptable for <br />the perfornirance <br />propose alralue <br />The allowable tmnsmissiviw @au") in Equation 4.24 should be comp <br />transmissivity value obtained from a test. The specified 1O0-hour transmi <br />equal to or higher than the allowable value of uansmissifity. Typical I <br />data for some products is presented in Appendix A. The dpsignei should <br />for the most up-to-date information on theii produots. <br />In addition to the reduction faotors in Equation 4.24, areview of theof the resin used in the geonet to rhe lluid JltT Jh* sNonet will be <br />performed. Most geonets are made of HDpE, which is very resistant to mo$t <br />they are used; therefore, this is selclom an issue. ultimateln the engineer,s <br />performed bslween steel plates for 15 minutes at a <br />completely unsuitable for the purpose of design. <br />performance and index hansmissivity requirements <br />between them. <br />4.3.1 Drainage Faetor of Safety, FSp <br />use or not. If it is deemed acceptable, no reduction in the reduired transmissi is applied due to <br />the chemicaldegradation associated with chemical com lity issues. <br />The allowable transmissivity discussed here should not be with the index <br />transmissivity used fbr purposes of quality control or con rce testing. <br />of 10,000 <br />latter is typically <br />15,000 psf a,nd is <br />can include both <br />that a clear is made <br />The overall drainage.factor of safety should be appliecl to tai ible uncedainties <br />in the selection and determination of the design parameters, when selectin5;appropriate thctor <br />considering suchfaotors as: (i) the cost of repair; (ii) the potential for loss of lilb; (iii) th;a6s^.*^4^--" ^.^l /:--\ r{^ - c I .rc.inty of the designparameters; and (iv) the probability of failure. Reoomniended-values <br />ka*."^^- /) n +^ t n fali-^"--J -r -t <br />FrSlr are typically <br />between 2"0 to 3.0 [Giroud, et al." 2000aJ, with a largor value resultingg a larger requiredgeocomposite transrnissivity, and therefore, higher coit. rrhe authors ol design manualbelieve that lower-end values (i.e., 2.0) are aeceptable for rnost proiects, <br />of geosynthetie materials is,fairly well establishei. Narejo & Riclardson <br />of 2"0 as an overall factor of safety for drainage <br />4,3.2 Chemical tllogging Reduction "Factor, RFsg <br />clogging of' the <br />the drainage system. GRr-GCg recommends using values in ihe <br />ly calcium and <br />being place,d on <br />I.2 for chenricalclogging in the final cover sysrem (see Table +.+i trtne degigner finds that alkalinity soilsor other precipitants are not present, use of the lower value 1i.J., r "01 should <br />Page 4-14 <br />acceptable.