Academic literature on the topic 'Clay mineralogy'

Currently, there is very little research available on nonpoint source pollution from rural watersheds. Government regulatory agencies are desperate for information regarding the causes of nonpoint source pollution, which includes the relationship between suspended soil particles and dispersion. Since soil dispersion is dependent on clay mineralogy, knowing the clay mineralogy of the soil in an area can help predict sediment loads entering the surrounding surface waters. This information is necessary to protect the resource value of our rivers, lakes, and estuaries, as well as to protect recreational activities such as fishing or hunting; but most importantly, this information is necessary to ensure the safety of our drinking water supply. Clay mineralogy and its influence on dispersion, as well as dispersion and its relation to water quality are the focus of this study. Soil mineralogy affects water quality in several ways: soil mineralogy determines the dispersivity of the clay portion of the soil and dispersive clays are likely to end up as suspended sediment in surface waters; weathering reactions contribute elements to water as dissolved load, and the sorption properties of clay minerals contribute to soils' ability to filter and carry pollutants. Through the use of X-ray diffraction, dispersivity, atomic absorption spectrometry, cation exchange capacity, and petrographic microscopy, this study shows that the clay mineral fraction of a soil determines the dispersivity, and that dispersed clay minerals contribute excess nutrients and metals as nonpoint source pollutants to surface waters.

The clay mineral composition of sediments deposited in the last six oxygen isotope stages in the Gulf of Mexico continental slope was characterized. Smectite and illite were found to be the two major clay minerals of the clay fraction while kaolinite, chlorite and quartz were present in the clay fraction but in less proportions. Variations in clay mineral abundances, especially in the relative abundances of smectite and illite, were identified in relation to climate changes. Smectite was the most abundant mineral in sediments of the current (stage 1) and last interglacial maxima (stage 5) while illite dominates the clay min-eralogy of sediments from the last glacial maximum (stage 2). Relationships between clay mineralogy and physical properties were investigated as well. Significant positive correla-tions were found between Atterberg limits with the smectite content of the bulk sediment and with clay content. However, the relationship with smectite yielded a significantly higher correlation coefficient. Smectite and clay content also affect the natural water con-tent of sediments and its changes with depth.

This research has evaluated the engineering behaviour of the tropical clay soils of Dhaka, Bangladesh. Attempts have been made to show the relationship of mineralogy and fabric with engineering properties. The engineering behaviour has been investigated by comparing the soil properties in a natural and destructured state at the same void ratio. Consolidation behaviour of the soils are discussed, based on oedometer and triaxial tests. Undrained and drained mechanical behaviour have been evaluated from triaxial tests in terms of stress-strain curves, stress paths, bonding effects, critical state conditions, stiffness and yielding behaviour. A framework for the tropical clay soils of Dhaka is presented. The tropical clay soils of Dhaka are intermediate to high plasticity inorganic clay. These soils are mainly composed of illite,. kaolinite, chlorite and some non clay minerals mainly quartz and feldspar. It was observed that these sods showed a random open microfabric of silt and clay. There was also some evidence that aluminosilicates, iron compounds and silica formed bonds between and within the grains. An apparent preconsolidation pressure of 170 kPa to 250 kPa was estimated for the natural soils, which is likely to be due to the bonded structure of the soils. The compressibility of the soil is very low to medium. The consolidation results are consistent with the mineralogy of the soils. It is established that the tropical clay soils of Dhaka are bonded. Bonding has an influence on the development of stress-strain and stiffness of these soils. Under undrained shearing, samples initially showed peak positive values of excess pore water pressure followed by negative values at higher strains due to the tendency of the samples to dilate. No negative pore water pressures were observed at high confining pressures. Only a few samples at low confining pressures reach the critical state at very large strains approximately in excess of 20%. High confining pressure samples may not have reached the critical state due to the formation of distinct shear surfaces. A significant difference between the natural and destructured failure surfaces was observed due to the presence of bonds in the natural soils. Differences in failure type were observed between the natural and destructured soils of three boreholes. It was observed that stiffness values gradually decreased with increasing strain. For the natural soils, two yield points could be identified at low confining pressures below the final yield. It was also observed that bond breakdown would occur in isotropic compression for tests at high confining pressures. At the final yield, the soil looses almost all of its stiffness due to bonding. After final yield, a soil’s behaviour is controlled only by friction. It was observed that three zones of behaviour could be identified for these soils in the stress space.

Yes<br>This paper examines the impacts of clay mineralogy on the effectiveness of lime stabilisation at different temperatures. A comprehensive experimental programme was conducted to track down the evolution of lime-clay reactions and their durations through monitoring the evolution of strength gain at predetermined times using the Unconfined Compressive Strength (UCS) test. The study examined clays with different mineralogy compositions comprising Na+ Bentonite and Ball (Kaolinite) clay. Four different clays were tested including 100% bentonite, 100% Ball clay and two clay mixtures with ratios of 1:1 and 1:3 by mass of bentonite to Ball clay. All clays were treated using a range of lime content up to 25% and cured for a period of time up to 672 h at two different temperatures of 20 and 40 °C. The results showed that the continuity of the fast phase (stage 1) of strength gain was dependent on the availability of lime in particular at the higher temperature. Whereas, for the same lime content, the duration of the fast phase and the kinetic of strength gain were significantly related to the clay mineralogy and curing temperature. Except for the initial strength gain at 0 h curing time, the lime-treated Ball clay specimens at 20 °C appeared to show no strength gain throughout the curing period that extended up to 672 h. However, when curing occurred at 40 °C, the no strength gain stage only lasted for 72 h after which a gradual increase in the strength was observed over the remaining curing period of time. The addition of Bentonite to Ball clay succeeded in kicking off the strength gain after a short period of curing time at both curing temperatures.

The Yazoo Clay is a calcareous fossiliferous mudrock that outcrops in a northwest-southeast belt across much of Mississippi and in adjacent states. Based on over 240 X-ray diffraction analyses, the average composition of the Yazoo Clay is 28% smectite, 24% kaolinite, 22% quartz, 15% calcite, 8% illite, 2% feldspar, and 1% gypsum. Exposed Yazoo clay is weathered to a depth of 30-40 ft. and has a distinctive yellow/brown color; unweathered Yazoo is blue/gray. In most wells, smectite is more abundant in weathered clay than in unweathered clay. Mineralogic changes correlate well with engineering properties of the samples, which in general show a decrease in plasticity indices with depth. Weathered Yazoo clay exhibits greater mineralogic variability than unweathered clay. Mineralogical content also varies laterally. Lateral variation, along with correlative smectite content and engineering properties, is the reason for ?roller coaster? roadways and structural damage caused by the swelling Yazoo Clay.