Chung R Song, Ph.D., University of Mississippi

1. An Easy Method of Determining Hydraulic Conductivity of Soils using Pore Pressure Response of Piezocone Penetration Test Chung R Song, Ph.D., University of Mississippi Sreekar Pulijala, Graduate Assistant, University of Mississippi

2. Overview • Hydraulic Conductivity and Piezocone • Hydraulic Conductivity by Piezocone Penetration Test • Previous work • Current results • Conclusions

3. Hydraulic Conductivity • Describes the rate at which water can move through a permeable medium. • Why do we need to know hydraulic conductivity of the soil ?? • However, the determination of hydraulic conductivity is time consuming and not easy.

4. Piezocone • Used for • Site exploration • Assessment of ground improvement • Evaluation of contaminant transport • Measures • Frictional resistance • Pore Pressure • End bearing

5. Hydraulic Conductivity by Piezocone Penetration Test (PCPT) • Advance Piezocone to the desired depth and hold it for dissipation test. • Reliable values of Hydraulic Conductivity, compared to other field tests. • This is still time consuming and expensive (half day).

6. Pore pressure response for soil element during PCPT Chung R. Song and George Z. Voyiadjis (2003)

7. “New Method” • To overcome the drawbacks of conventional dissipation test and provide a more realistic theoretical background. • Key idea : Pore Pressure response of saturated soils is not only a function of stress-strain parameters but also of hydraulic conductivity. Song.C.R and Voyiadjis.G.Z (2003) • Pore pressure observed by clayey soils and sandy soils. • Clay : High PWP • Sand : Low or Zero PWP

8. Relations between the dimensionless excess PWP during Piezocone Penetration and dimensionless Hydraulic Conductivity Chung R. Song and George Z. Voyiadjis (2003)

9. Previous work • Correlates the magnitude of pore water pressure to the Hydraulic Conductivity directly. • Potential for real time process. • An axi- symmetric FE program that is capable of simulating behavior of soils with the advancement of the Piezocone tip was developed and used. • Uses the coupled theory of mixtures

10. Finite Element Mesh Chung R. Song and George Z. Voyiadjis (2003)

11. Coupled equations

12. Objective • Use of Song and Voyiadjis (2003)’s method (i.e. New method) • To perform numerical analyses for various soil conditions and provide simple design charts (monogram type) that an engineer can use without great difficulties.

13. Current stage • Setting up penetration depth and number of increments • By changing some material properties like • κ,λ • Permeability, M • Corresponding values of PWP are obtained for each varying properties when others are kept constant.

14. Permeability (k) vs. PWP

15. M vs. PWP

16. vs. PWP κ κ

17. λ vs. PWP λ

18. Conclusions • The trend of PWP observed by the change of different parameters is reasonable. • Easy to use design charts : a handy tool to geotechnical engineers for the determination of hydraulic conductivity • Reduction in the computation time • Can be used in seepage analysis, soil classification, detection of underground aquifers, etc…

19. THANK YOU