Microfabric, chemical and mineralogical study of Indian marine clays

Marine clay deposits are encountered in the coastal regions of the world. They are soft in consistency with low shear strength and are highly compressible. The properties of these deposits are complex and diverse, and they mainly depend on the minerals present and microstructural arrangement of constituent particles. In the present investigation, the physico-chemical properties of the sediment samples obtained from marine deposits of east and west metropolitan coastal cities of India are discussed, and the test results obtained are compared with the synthetic samples such as bentonite and kaolinite. Mineralogical and fabric studies were carried out using scanning electron microscopy and x-ray diffraction techniques. Several consolidation and strength tests were carried out to study the engineering behaviour of these deposits. The strength and compressibility (Cc) values of these deposits varies from 27 to 45 kN/m² and 0.37 to 0.81 respectively. XRD studies confirm the presence of highly compressible clay minerals such as smectite, vermiculite, chlorite and traces of the low swelling mineral, kaolinite. The fabric studies indicate that the constituent particles were arranged in an open network, or flocculated structure resulting in a high void ratio.     

Electro-osmotic stabilization of marine clay with chemical piles

Weak marine clay deposits exist all along the seacost of many parts of the world. Due to the poor engineering characteristics of these deposits, they pose several foundation problems to various coastal structures. Because of the high salt content in these deposits, the electro-osmotic technique has been effectively adopted to stabilize these deposits with some inorganic additives. In this investigation, the physico-chemical changes that occurred in a marine clay with various inorganic additives are presented and discussed. The improvement in the strength and plasticity characteristics of the soil have also been studied and reported. The newly formed reaction products arising out of the diffusion of lime are identified using X-ray diffraction technique (XRD). The present study indicates great promise regarding the use of electro-osmotic technique with inorganic additives as a quick remedial measure for the in-situ stabilization of coastal marine clay deposits.     

Fabric and mineralogical studies on lime treated marine clays

The use of lime to improve the engineering properties of weak marine clays is a common method from the past. Recent studies indicate that the various foundation problems occurred with passage of time for offshore structures due to hostile wave conditions and adverse climatic conditions. Hence, there is an urgent need to improve the engineering properties of these soft deposits using well established ground improvement techniques. In the present investigation, an attempt has been made on two marine clays to investigate the microchanges that occurred at particulate level due to the addition of lime and sodium hydroxide chemicals. The influence of sodium hydroxide additive on the fabric of lime treated marine clays has also been studied using scanning electron microscopy (SEM) technique. The formation of various new reaction products due to soil-lime reactions and their stability in marine environment were also studied and reported using x-ray diffraction (XRD) technique. The test results indicate that lime stabilization is effective for improving the properties of marine clays and the presence of sea water increases the efficiency of lime stabilization.