Changes In Hydrogeological Conditions Research Articles

Vulnerability Assessment of Groundwater Inrush from Underlying Aquifers Based on Variable Weight Model and its Application

Groundwater inrush from aquifers underlying coal seams is a serious geohazard during coal mining in China. Its occurrence is affected by multiple factors, while the importance of these factors may change over the entire mining area. Traditional model with constant weight cannot reflect the influence of index value mutates with changes in hydrogeological conditions on the comprehensive evaluation value. The theory of variable weight model is thus proposed to evaluate the dynamic processes involved in groundwater inrushes. The model is applied to the Yuzhou coalfield in north China to demonstrate the construction process of the variable weight model and to verify its improvement over the traditional constant weight model in assessing the vulnerability of groundwater inrushes from the underlying aquifers. This innovative method offers not only another tool on assessment of groundwater bursting but also has practical significance in reducing water geohazards in mines.

EXPERIENCE OF STRENGTHENING BASES OF EMERGENCY BRIDGE

The creation of the cascade of hydroelectric power stations in Dnepr-river channel was accompanied by creation of artificial water basins. Change of hydro-geological conditions has resulted in flooding of adjoining territories and necessity of maintenance of the operational suitability of buildings and constructions located on them. The results of works on restoration of automobile overbridge above railroad tracks with intensive movement of trains in the city of Nikopollocated on the coast ofKakhovskoewater basin are presented. During operation more than 40 years, the inadmissible deformations in the above-ground overbridge constructions, caused by non-uniform settlements of foundations of supports, have taken place. The non-uniformity of foundations settlements has achieved600 mm.The foundations settlements were due to the changes of physical-and-mechanical characteristics of loessial soil of foundation owing to heaving of the underground water level.

A new tracer technique for monitoring groundwater fluxes: The Finite Volume Point Dilution Method

Quantification of pollutant mass fluxes is essential for assessing the impact of contaminated sites on their surrounding environment, particularly on adjacent surface water bodies. In this context, it is essential to quantify but also to be able to monitor the variations with time of Darcy fluxes in relation with changes in hydrogeological conditions and groundwater — surface water interactions. A new tracer technique is proposed that generalizes the single-well point dilution method to the case of finite volumes of tracer fluid and water flush. It is called the Finite Volume Point Dilution Method (FVPDM). It is based on an analytical solution derived from a mathematical model proposed recently to accurately model tracer injection into a well. Using a non-dimensional formulation of the analytical solution, a sensitivity analysis is performed on the concentration evolution in the injection well, according to tracer injection conditions and well-aquifer interactions. Based on this analysis, optimised field techniques and interpretation methods are proposed. The new tracer technique is easier to implement in the field than the classical point dilution method while it further allows monitoring temporal changes of the magnitude of estimated Darcy fluxes, which is not the case for the former technique. The new technique was applied to two experimental sites with contrasting objectives, geological and hydrogeological conditions, and field equipment facilities. In both cases, field tracer concentrations monitored in the injection wells were used to fit the calculated modelled concentrations by adjusting the apparent Darcy flux crossing the well screens. Modelling results are very satisfactory and indicate that the methodology is efficient and accurate, with a wide range of potential applications in different environments and experimental conditions, including the monitoring with time of changes in Darcy fluxes.

Effect of climate changes on groundwater

Predictive estimates of anticipated changes in groundwater resources in the territory of Russia as applied to global climate warming by 1, 2, and 3–4°C at different scenarios of changes in the regional distribution of atmospheric precipitation are given. Potential environmental and socio-economic consequences of changes in hydrogeological conditions are considered.

Some problems of further development of engineering geology for hydrotechnical construction

Comparison of scales and degree of detailing by geological and engineering geological mapping shows higher requirements in the latter case. New trends of science should be developed for the solution of engineering geological problems for hydrotechnical construction in young folded regions. Methods of large-scale investigations aimed at establishing the mechanism of engineering geological processes and determining the history of relief evolution should be elaborated. This is necessary for forecasting the behaviour of hydraulic structures after the change of hydrogeological conditions and for taking the correct engineering decisions. Results of engineering geological exploration at the site of an hydroelectric plant are given as an example of the application of these propositions.