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At present many new housing projects are being realized in Poland. They are often built in areas characterized by complex hydrogeological and geotechnical conditions. In such cases, the need to build deep excavations is complicated, especially when there is a high water table. The paper presents analysis of dewatering process of deep excavation of residential building. The excavation was carried out to the depth of 10 m below the ground surface. Due to the location of the investment near the river the water table was changing dynamically. To determine dewatering process of deep excavation numerical calculations using finite element method (FEM) were performed. On the basis of numerical calculations the pore water pressure in the subsoil and deformations at the bottom of the excavation were determined. The calculations were performed for different water levels in the river, observed during the research. The numerical calculation results were compared with field research and measurements. The comparison of numerical calculations with field studies allowed for a detailed analysis of the dewatering process of deep excavation and many practical conclusions. [ABSTRACT FROM AUTHOR]

Foundation construction issues have emerged from ancient times, since antiquity, along with the constructions of dams, canals, ports and buildings with different destinations. On the occasion of these constructions, practice has shown that are obtained a low strain and a high stability if are included in their composition a distinct part that is lowered below the natural ground. The construction of foundations by ordinary methods becomes even more difficult if is made under the underground water level. Also when the constructions are carried out in winter, the cost and execution time are increasing. Therefore, is necessary to search for new technological processes of a high technical and economic efficiency. One of the most difficult problems to be solved by the civil engineer on the foundations execution is linked to the presence of surface water and underground water. Current technology offers a whole range of methods to solve these problems, but the use of these methods must be made discerning, depending on the specific condition of the site and the work. Working methodologies adopted to achieve excavations in the presence of groundwater depend on a number of factors that are including the construction size, the foundation level, foundation soil, etc. The authors propose to carry out a description of the solutions adopted for the implementation of deep excavations, theirs environmental impact and also which will be the influence of these solutions for deep underground foundations on hydrogeological conditions. This paperwork addresses a number of issues related to the choice of solutions for achieve deep excavations, as well as a number of issues regarding the dewatering and drainage works. These aspects take into account the problems that may occur in dewatering works or drainage works may be classified as: • Risks related to mechanical effects (for example: hydrodynamic entrainment); • Hydraulic breaking of the excavation base; • Differential settlement. [ABSTRACT FROM AUTHOR]

The paper provides data on the Bílina opencast brown coal mine, namely the geography, environmental situation, climatic, hydrologic, geological and hydro-geological conditions of the relevant area. The existing basic water management system of the Bílina Mine is described as well as the proposal of the technical approach concerning disposal of sediments, which pose major effects not only on the chemistry of mine water, but, in particular, on the dump site stability. On the basis of the information learned and on the basis of facts verified through long-term experience, the paper describes and proposes optimum methodology of disposal of the muddy sediments in the coming years. The purpose of the proposal of the optimum disposal of the sediments is minimisation of the costs spent on extracting or pumping out these sediments in the classic manner, nevertheless what is of greater importance is improvement of the stability of overburden dumps. The final part of the paper includes evaluation of the proposed changes in terms of the economic and environmental effects on operation of the mine. [ABSTRACT FROM AUTHOR]

Printed-circuit boards are widely used for miniaturizing electronic equipment. According to the demand, diameter of holes in the boards is decreasing. There is a problem in their fabrication processes, in which they should be cleaned in water. After the cleaning process, water remains in the small holes. The remained water contains chemical material and/or dusts and might cause damage of the boards in the future. Conventionally, air pressure has been used to remove the water in the boards. But the method is not valid for holes that have bottoms inside neither for much smaller holes. Heating could be an alternative method, but this method might leave chemical material in the water and cause deflection of the board. In this research, a new dewatering method has been proposed. The method utilizes standing wave of ultrasonic wave in air. An experimental apparatus was organized to observe the ultrasonic dewatering and consisted of a Langevin type ultrasonic transducer and a reflector. Proposed dewatering was observed successfully and recorded by a high speed camera. The sound pressure in the standing wave was measured by a microphone. [ABSTRACT FROM PUBLISHER]