Swelling Characteristics of Bentonite Clay Mats

Bentonite absorbs water to a greater extent than any other ordinary plastic clay and as a
consequence it swells depending on the change in its moisture content. This paper aims to give an
overview of the swelling characteristic of bentonites with particular observations from that of
prehydrated clay mats. How the swelling characteristics vary with the type of clay, water, and the
encompassing boundary materials is presented. Accordingly, it examines the swelling response of the
clay mat and the pressure exerted when the swelling is both fully and partially restrained. The
development of a new apparatus to measure pressures exerted by the clay as a result of the swelling
process is also described. A theoretical study is made to postulate how these pressures can be
evaluated for field situations. Though bentonites are known to have very high swelling pressures, how
this is negated by the compressibility of the composite behaviour with the necessary backfill is
demonstrated. Tests show significant differences in swelling behaviour and pressure development
when the GCL is in deionized water and sea water environments. Free swell characteristics were
similarly affected.. Unique variation of pressure exerted due to swelling in partially restrained
conditions was established with experimental observations made during the study.