• Examining the Terzaghi Filter Pack-Aquifer Formation Relationship in Sustainable Groundwater Development in Malawi

    Thenford M. Kachulu, Petros N. Zuzani, Dr. G Chavula

    University of Malawi, The Polytechnic/Bag 303, Chichiri, Blantyre 3, Malawi.


    Examining the Terzaghi Filter Pack-Aquifer (P-A) Formation Relationship Theory in Sustainable Groundwater Development in Malawi.

    In Malawi, boreholes have a non-functionality rate of about 30%. Non-functionality due to incongruent properties of filter pack and aquifer formation, according to the theory developed by Terzaghi which states

    d15(filter)/d85(formation)<4< d15(filter)/d15(formation)

    has not been explored. This study examined the extent to which the Terzaghi P-A Relationship Theory is applied in sustainable groundwater development in Malawi.

    Fifty three aquifers were sampled. Filter pack samples were collected from Mangochi and Karonga. Grading and analyses to BS 1377 Part 2: 1990 were done.  Terzaghi Migration (Tm), Terzaghi Permeability, (Tp) factors and filter pack Uniformity Coefficient, CuF, were deduced. Tm and Tp were checked against Terzaghi theory. CuF was checked against The Code of Practice (CoP) for Borehole Drilling in Malawi which limits   CuF ≤ 2 and D50F ≤ 1.  Borehole drilling, design and construction were observed to relate theory to practice.

    There was 100% compliance on Tp and 87% on Tm . Nineteen percent of the samples had P-A ratios between 4 and 10,  CuF > 2, and D50F > 1. Malawi’s filter pack, from source, is not compatible with the aquifer formation properties. Consistency with either the Terzaghi criteria or CoP for borehole drilling is not clear. No filter park selection is done.

    Keywords: Aquifer Formation, Boreholes, Filter Pack, Non-functionality, Terzaghi Theory.

    Pages: 61 – 78 | Full PDF Paper