Experimental investigation of cast iron corrosion on clay soil and GPR performance

Moghareh Abed, Tara (2016). Experimental investigation of cast iron corrosion on clay soil and GPR performance. University of Birmingham. Ph.D.

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Abstract

Cast iron water distribution pipes exist widely in UK and elsewhere. As these cast iron pipes were traditionally directly buried into local soil, where the soil is chemically aggressive (as in the case of some clays) corrosion of the pipes often occurs due to an electrochemical process, which both changes the pH environment and releases iron ions into the clay. This can cause chemical alteration to clay minerals and ‘corrosion products’, such as iron oxide, hydroxide and aqueous salts, to form in the soil. These chemical interactions are complex and time dependent, and can result in failure, and thus the conditions under which they occur need to be understood. Ground Penetration Radar (GPR) has been proposed for routinely detecting, assessing and monitoring buried cast iron pipes, and thus it is important to know how these chemical changes affect the electromagnetic properties of soil. A bespoke set of laboratory experiments was devised to simulate and accelerate (using electrokinetics) cast iron corrosion and ion migration processes in two types of clay: a relatively inactive Kaolin Clay and Oxford Clay, which has a mixed mineralogy. Tests were conducted for periods of up to 3 months using both inert electrodes and with a cast iron disc as the anode, and changes in the geotechnical (undrained shear strength, moisture content and Atterberg limits), geophysical (permittivity) and geochemical (iron content, pH and conductivity) properties were monitored. The conductivity and permittivity results were used in GPR simulations to investigate reported difficulties in detecting corroded cast iron pipes.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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