Studies on the Development and Control of Desiccation cracks in compacted clay liner soils

The present study aimed at critically looking at the current practice of the installation of compacted clay liner using bentonite enhanced sand (BES). The application of bentonite is currently the most accepted practice for lining purposes. The ideal bentonite sand combination, which satisfies the liner requirements is 20% bentonite and 80% sand, was selected as one of the liner materials for the investigation of development of desiccation cracks. Locally available sundried marine clay and its combination with bentonite were also included in the study. The desiccation tests on liner materials were conducted for wet/dry cycles to simulate the seasonal variations. Digital image processing techniques were used to measure the crack intensity factor (CIF), a useful and effective parameter for quantification of desiccation cracking. The repeatability of the tests could be well established, as the variation in CIF values of identical samples had a very narrow range of 0 to 2%. The studies on the development of desiccation cracks showed that the CIF of bentonite enhanced sand mixture (BES) was 18.09%, 39.75% and 21.22% for the first, second and third cycles respectively, while it was only 9.83%, 7.52% and 4.58% respectively for sun dried marine clay (SMC). Thus the locally available, alternate liner material suggested, viz SMC, is far superior to BES, when subjected to alternate wet/dry cycles. Further, the improvement of these liner materials when amended with randomly distributed fibre reinforcements was also investigated. Three types of fibres ,namely nylon fibre, polypropylene monofilament and polypropylene fibre mesh were used for the study of fibre amended BES and SMC.The influence of these amendments on the properties of the above liner materials is also studied. The results showed that there is definite improvement in the properties of the liner materials when it is reinforced with discrete random fibres. The study also proved that the desiccation cracks could be controlled with the help of fibre reinforcement.

Studies on a sea anemone ,anthopleura nicrescens(verrill) from the south west coast of India

The present study was undertaken with a view to understanding some aspects of the morphology, bionomics and physiology of the sea anemone A.nigrescens. This species was selected for the study since it is abundantly available along the coast throughout the year and can successfully reared in the laboratory without much effort. The present study deals with the following aspects of A.nigrescens. description of the species, habitat, food and feeding, digestion, studies on salinity tolerance, studies on oxygen consumption, studies on tolerance to desiccation, asexual reproduction and regeneration.

Studies on sporulation and propagation in selected agarophytes

Studies on sporulation of four commercially important red (sea-weeds) algae ^(agarophytes) namely Gelidiella acerosa, Gracilaria corticata, G edulis and Hypnea musciformis growing in the vicinity of’ Mandapam coast were carried out from October 1981 to September 1983. During the two years of study; fruiting behavior in the natural population of these species was also investigated. Laboratory experiments were carried out with the four algae sea weeds to collect information on seasonal aspects of spore production and diurnal variation of spore shedding. Detailed studies were made under laboratory conditions to know the effects of some selected environmental factors such as desiccation, salinity, temperature, light intensity and photoperiod on spore output in Gelidiella acerosa, Gracilaria edulis and kypnea musciformis hydrological data were also collected from the inter-tial region around mandapam area. The result obtained on all the above aspects are presented in this thesis