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@REGG Pore Pressure Dissipation Tests (PPDT) <br />Porn Pressure Dissipation Tests (PPDT's) conducted at various intervals measured <br />hydrostatic water pressures and determined the approximate depth of the ground water <br />table. A PPDT is conducted when the cone is halted at specific intervals determined by <br />the field representative. The variation of the penetration pore pressure (u) with time is <br />measured behind the tip of the cone and recorded by a computer system. <br />Pore pressure dissipation data can be interpreted to provide estimates of: <br />• Equilibrium piezometric pressure <br />• Phreatic Surface <br />• In situ horizontal coefficient of consolidation (ct,) <br />• In situ horizontal coefficient of permeability (4) <br />In order to correctly interpret ..In.......0*.llc.v <br />the equilibrium plezometric C-- <br />pressure and/or the phreatic <br />surface, the pore pressure *............... <br />must be monitored until such <br />time as there is no variation in <br />pore pressure with time, <br />Figure PPDT.This time is <br />commonly referred to as boo,fim,; <br />the point at which 100% of the . <br />I./-10*•-4€*Ca•!,Uexcess pore pressure has -----pore pressure (u) <br />dissipated.measured here <br />U <br />0 <br />Gound <br />surloce <br />U <br />- Water Table 0 <br />Dcone - Depth or Cone <br />Dwater - Depth to Water T*bio 0 ttrne <br />A complete reference on pore Hwater - Head of Water <br />pressure dissipation tests is Water Table Calculation <br />presented by Robertson et al. <br />1992.Dwater = D cone - Hwater <br />where Hwater = Ue (depth units) <br />A summary of the pore <br />pressure dissipation tests is <br />summarized in Table 1. <br />Useful Conversion Factors:1031 = 0.704m = 2.31 feet (water) <br />1tsf = 0.958 bar = 13.9 psi <br />im = 3.28 feet <br />Figure PPDT <br />SL Rvcd 2019.01.21