Rare Alkali Metals in the Waters of Lithium-containing Deposits in Eastern Transbaikalia

The results of hydrogeochemical studies on the content of rare alkaline elements in man-made waters of mining facilities at Zavitinskoye, Orlovskoye, and Etykinskoye rare metal deposits of Eastern Transbaikalia are presented. Concentrations of these elements are determined both by the content in the ores and rocks of deposits and by their water-migration properties. It was found that the acidic sub-basement waters of the Orlovskoye and the quarry waters of the Zavitinskoye deposits contain abnormally high concentrations of lithium, up to 3.74 and 3.88 mg / L, respectively. The high content of lithium (Li) in the waters of these deposits was determined relative to the average values for the waters of the hypergenesis zone, as well as the standards of maximum permissible concentrations (MPC) of chemicals for water bodies used for fisheries, drinking water, and other activities.

The Temperature Field Evolution and Water Migration Law of Coal under Low-Temperature Freezing Conditions

This study examines the evolution law of the coal temperature field under low-temperature freezing conditions. The temperature inside coal samples with different water contents was measured in real-time at several measurement points in different locations inside the sample under the condition of low-temperature medium (liquid nitrogen) freezing. The temperature change curve was then used to analyse the laws of temperature propagation and the movement of the freezing front of the coal, which revealed the mechanism of internal water migration in the coal under low-temperature freezing conditions. The results indicate that the greater the water content of the coal sample, the greater the temperature propagation rate. The reasons for this are the phase change of ice and water inside the coal during the freezing process; the increase in the contact area of the ice and coal matrix caused by the volume expansion; and the joint action of the two. The process of the movement of the freezing front is due to the greater adsorption force of the ice lens than that of the coal matrix. Thus, the water molecules adsorbed in the unfrozen area of the coal matrix migrate towards the freezing front and form a new ice lens. Considering the temperature gradient and water content of the coal samples, Darcy’s permeation equation and water migration equation for the inside of the coal under freezing conditions were derived, and the segregation potential and matrix potential were analysed. The obtained theoretical and experimental results were found to be consistent. The higher the water content of the coal samples, the smaller the matrix potential for the hindrance of water migration. Furthermore, the larger the temperature gradient, the larger the segregation potential, and the faster the water migration rate.

Rapid freezing of saturated clays under large thermal gradients

This study investigates the rapid freezing behavior of saturated clays under large thermal gradients. Although the freezing characteristics of soils under natural/low thermal gradients such as ice lens formation and water migration have been extensively studied, the freezing of a saturated soil under a large thermal gradient is not understood. This study presents rapid freezing tests to examine the freezing behavior of saturated fine-grained soils in a closed system under large thermal gradients using liquid nitrogen (LN). Temperatures are measured inside specimens during freezing and micro-CT visualized internally after freezing. Results show that large thermal gradients develop near the surfaces of specimens upon their submersion in LN. The specimens freeze homogeneously, and no visible ice lenses form, owing to the insufficient time for water migration and ice segregation under rapid freezing. The specimens fracture and split into major pieces, under no confining stresses in this study; freezing first occurs near the boundaries, and the freezing front propagates inward, creating temporal, differential volume changes between the outer and inner parts of the specimens, which leads to fractures in the unconfined state. The fractures affect subsequent temperature propagation and thermal gradients.