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�! EGG Pore Pressure Dissipation Tests <br /> � P <br /> (PPDT) <br /> I1 <br /> i <br /> Pore Pressure Dissipation Tests (PPDT's) conducted at various intervals <br /> measured hydrostatic water pressures and determined the approximate depth of <br /> the ground water table A PPDT is conducted when the cone is halted at specific <br /> intervals determined by the field representative. The variation of the penetration <br /> pore pressure (u) with time is measured behind the tip of the cone and recorded <br /> by a computer system <br /> Pore pressure dissipation data can be interpreted to provide estimates of <br /> • Equilibrium piezometnc pressure <br /> • Phreatic Surface <br /> • In situ horizontal coefficient of consolidation (ch) <br /> • In situ horizontal coefficient of permability (kh) <br /> In order to correctly interpret the equilibrium piezometric pressure and/or the <br /> phreatic surface, the pore pressure must be monitored until such time as there is <br /> no variation in pore pressure with tame, Figure PPDT This time is commonly <br /> referred to as troo, the point at which 100% of the excess pore pressure has <br /> dissipated <br /> A complete reference <br /> on pore pressure w <br /> dissipation tests is Cp @ a w .►�a—. <br /> presented by GMUW 0- <br /> Robertson et al. 1991d� � � <br /> L <br /> A summary of the pore w <br /> pressure dissipation <br /> Wsoer ra <br /> tests is summarized in °°°`� ak <br /> Table 1. Pore pressure <br /> dissipation data is Pore Fissure(U) "w <br /> presented in graphical Com �umd t� <br /> �, <br /> form in Appendix Dimmr_umWater reMa ° �. ,. <br /> PPDT. I Hvwo,r-How of Ulhber aro <br /> WaterraWsC*uis w <br /> Dwater = Dcone - Hwater <br /> WhM fhvaw=Ue(deM mft) <br /> Uasful Carrverslm Famm 1pai-0 704m =2-31 feat (wamr) <br /> itsf-0 958 bar-13R psi <br /> 1m =328 teat <br /> )79u/L-PPDT <br /> 1 <br />