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GG <br /> IM E am Pore Pressure Dissipation Tests <br /> sus <br /> (PPDT) <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 piezometric pressure <br /> • Phreatic Surface <br /> • In situ horizontal coefficient of consolidation-(Ch) <br /> k <br /> • In situ horizontal coefficient of permability (kh) <br /> In order to correctly interpret the equilibrium piezometric pressure and/or tie <br /> phreatic surface, the pore pressure must be monitored until such time as there is <br /> no variation in pore pressure with time, Figure PPDT. This time is commonly <br /> referred to as t,00, the point at which 100% of the excess pore pressure has <br /> �- dissipated. <br /> A complete reference <br /> on pore pressure �- <br /> dissipation tests is [� 0 '>] -�•=-•r <br /> presented by <br /> cr,�rrt:J <br /> Robertson et al. 1991. <br /> 14 <br /> A summary of the pore <br /> pressure dissipation wr,:Pr TO], � w'u•l•.i wr4i_a.. <br /> r;�•„ft .ene <br /> tests is summarized in N�tr <br /> Table 1. Pore pressure -•a�u=;:_,cA .�4.... <br /> dissipation data is Pore Pressure(U) <br /> presented in graphical "Eiasuredher <br /> V.nrn rrarltt.F Core <br /> form in Appendix rr lkph r:,A::_T;,:-r,_ <br /> PPDT. <br /> VYalr�r Tatils Calsxr a�or • <br /> Dwate r = D Co <br /> where Hwalef= Ue(depth units) <br /> Usarul Carwcmior 1 WLOM: 1psi=U,FC4rr =2.51 fccr (water; <br /> 1isr -o.968 bar-1j.9 psi <br /> 1m -3.18 foot <br /> Figure PPDT <br />