Analyzing the Impact of Large Dams on Seismicity Patterns around Their Locations

Dam construction is one of the most popular solutions for managing water resources. In recent years, changes in patterns of regional seismicity associated with large impoundment dams have raised concerns among environmentalists. In this study, five large dams located in Iran were studied from this perspective. The Gutenberg-Richter, linear regression and T-test were used to examine the seismic changes in the radius of 100 km of each of the dams during a twenty-five-year period before and after the construction of the dams. The results revealed that the seismicity level and relative density of large and small earthquakes in three of these dams have increased after dam construction. A significant difference between the magnitude of earthquakes, as well as the number of earthquakes before and after the construction of dams in the region, was recognized. However, the results of the T-test statistical analysis indicated that the mean depth of the earthquakes and their distance from the dams before and after construction have not changed significantly. Overall, these results indicated that the construction of large impoundment dams has been associated with some changes in patterns of regional seismicity. The findings would guide researchers to further investigate the type of impacts that dam construction may have on seismicity patterns.

Discharge of a Triangular Orifice under Free Flow Conditions

In this paper, flow through a free triangular orifice is considered. The comparison of two formulas was conducted for discharge calculations: a large orifice formula and a small orifice formula. The results show that, above a certain value of upstream head to orifice height ratio there is no need for small-large formula discrimination. The differences in the outcomes for the two formulas are negligible for upstream head to orifice height ratios greater than 3. This means that a small orifice formula can be used instead of a large orifice formula. Calculations were performed for different variants of triangle orientation (with tip downwards, sidewards and upwards) as well as for different dimensions of orifice (equilateral and isosceles). The calculations also included different submergence levels of the upper edge of the orifice and variable dimensions of the orifice with constant upstream head. Neither of these conditions affect the relative deviation values for small and large orifice formulas.

Improving Water Supply Capacity of Drainage Systems at Humid Areas in the Changing Climate

The paper focuses on research on improving the water supply of drainage systems of humid areas in the context of climate change. The aim of the research is to elaborate on the ways for increasing the available water supply of drainage systems and restoring active water regulation on reclaimed lands in a changing climate. The paper presents the results of the research on improving the available water supply of drainage systems in the humid zone of Ukraine in a changing climate. It was specified in the face of increasing water scarcity providing the optimal water regime regulation on drained lands is possible due to the increase in the available water supply of drainage systems. It can be achieved thanks to the accumulating capacity of reclaimed areas, namely usage of free soil capacity of the aeration zone and open canals, accumulation of water reserve volumes in storage tanks due to the accumulation of surface and drainage runoff. Taking into account the design features of different types of drainage systems, existing water management technologies, characteristics of water sources and their close proximity to the drainage systems, the technological schemes of water intake from rivers and reservoirs, and its supply to the drained areas for irrigation needs were developed. In a face of increasing water scarcity, it is also expedient to apply resource-saving technologies to control the available water supply for crops.

The Lower Vistula and Its Ice Problems

In many countries of the northern hemisphere during winter period ice forms appear on various water bodies, which results in significant changes of physical, chemical and ecological conditions. These changes are different in rivers, channels, lakes or once-through reservoirs. On the terrain of Poland ice always caused considerable problems affecting intensive inland navigation and other river use. These problems appeared especially on the Vistula River, which in 17th and 18th century was one of the most navigable rivers in Europe. The Vistula is the largest Polish river, which flows from the south in the Carpathian Mountains to the Baltic Sea in the north. It is the second largest river, after Neva, of the Baltic Sea catchment. The length of the Vistula is 1047 km and its catchment amounts to 194 thousand km2. The predominant part of the Vistula river basin (87%) is now on Polish territory and the remaining (13%) catchment is in Belarus, Ukraine and Slovakia. The course of the Vistula can be divided into three distinctly different sections: upper, middle and lower. These river sections have appropriate catchments with their tributaries. There are hydraulic structures on the main river course and on its tributaries which serve navigation, hydroenergy, flood protection, water supply and recreation. All over the Vistula catchment there are frequent floods during spring and summer time resulting from excessive precipitation but in winter caused by ice phenomena. Numerous flow problems appear especially along the lower Vistula course because of ice phenomena and they result very often in severe flood problems. The Vistula has a very variable time and spatial discharge, because of existing climate conditions over its catchment. The aim of the paper is to present hydraulic and hydrologic characteristics of the Lower Vistula river with special emphasis on the management of this river section for navigation, hydroenergy, flood protection and water supply in view of ice phenomena appearing there. Information concerning changes of water characteristics due to various water temperatures are presented as well as on the formation of various forms of ice in flowing water. Numerous ice studies were carried out in Poland and especially on the Lower Vistula section as it was very ice prone and where many ice jams and ice-jam floods occurred. A special hydraulic situation existed at the mouth of the Vistula, which caused important floods in the 18th century and resulted in the construction of a special direct channel to the sea (Przekop Wisły) solving flood problems in this area. Information is presented on changes in open channel flow due to the appearance of ice cover and other ice forms. The paper includes ample information on the run, consequences and studies connected with a very important ice-jam-flood on the upper part of Włocławek reservoir in 1982.

Compound Channel’s Cross-section Shape Effects on the Kinetic Energy and Momentum Correction Coefficients

Since accurate estimation of the flow kinetic energy (α) and momentum (β) is not easily possible in compound channels, determining their accurate correction coefficients is an important task. This paper has used the “flood channel facility (FCF)” data and the “conveyance estimate system (CES)” model (which is 1D, but considers a term related to the secondary flow) to study how the floodplain width and the main channel wall slope and asymmetry affect the values of α and β. Results have shown that their maximum values at the highest floodplain width are, respectively, 1.36 and 1.13 times of those at the lowest case; an increase in the slope increased their maximum values by 1.05 and 1.01 times, respectively. The mean of error values showed that the CES model estimated the values α and β more accurately than the flow discharge. The maximum differences between the estimated and experimental values were 12.14% for α and 4.3% for β; for the flow discharge, it was 24.4%.

Modelling of Quadratic-Surface Sludge Digesters by Smoothed Particle Hydrodynamics (SPH) – Finite Element (FE) Methods

The quadric-surfaced sludge digester (QSD), also known as the egg-shaped sludge digester, has proven its advantages over traditional cylindrical digesters recently. A reduction in operational cost is the dominant factor. Its shell can be described as a revolution of a parabola with the apex and base being either tapered or spherical. This shape provides a surface free of discontinuities, which is advantageous regarding the efficiency during mixing. Since the shape does not produce areas of inactive fluid motion within the tank, sludge settlement and an eventual grit build-up are avoided. The stresses developed in the shell of the sludge digester, vary along the meridian and equatorial diameters. A non-dimensional parameter, ξ, defines the height-to-diameter aspect ratio which is used to delineate the parametric boundary conditions of the shell’s surface. Three groups of analyses were conducted to determine the orthogonal stresses in the shell of the QSD. The first-principles numerical models ran reasonably quickly, and many simulations were made during the study. The results showed that they were in within the range 5.34% to 7.2% to 2D FEA results. The 3D FEA simulation results were within the range of 8.3% to 9.2% to those from the MATLAB time-history models. This is a good indicator that the first principles numerical models are an excellent time-saving method to predict the behaviour of the QSD under seismic excitation. Upon examining the criteria for the design, analysing the results for the 2D FEA simulations showed that the fill height is not a significant variable with sloshing however the 3D FEA showed that the hydrostatic pressure is a significant variable. With the maximum tensile stress of the 3D-printed Acrylonitrile Butadiene Styrene (ABS)-a common thermoplastic polymer typically used for injection molding applications, being 24.4 MPa, the overall maximum stress of 5.45 MPa, the material can be a viable option for the use of QSD construction in small island developing states (SIDS).

Experimental Investigation of Skirted Foundation in Sand Subjected to Rapid Uplift

This paper reports results from 1g model tests carried out under single gravity on a skirted foundation installed in sand and subjected to a rapid uplifting force. The effects of displacement rates ranging from 5 mm/s to 450 mm/s on the ultimate capacity, suction pressure inside the skirt compartment, and time of extraction were investigated. Test results indicate that the displacement rate significantly affected the magnitude of uplift resistance, as well as the magnitude of suction under the foundation lid, but had little effect on the relationship between stress and the displacement of the foundation. The shapes of the uplift capacity-displacement curve and the suction-displacement curve were similar for all experimental displacement rates.

Distinct Element Simulation of a Landslide Process

The paper presents a numerical simulation of the development of a catastrophic landslide in a sandstone quarry and methods of reconstructing the quarry to its previous condition from before the landslide. The important objective of the paper is to present the capabilities of the numerical method used in the analysis of the landslide process, namely the Distinct Element Method (DEM). This method is poorly known, though it is capable of solving important geotechnical problems in which massive displacements are modelled. The features of the method are presented on the basis of a case study. Therefore a numerical analysis is carried out to show the performance of DEM in generating a displacement of several dozen meters in the example of a catastrophic landslide that occurred some years ago in a sandstone quarry. This engineering problem makes it possible to describe and analyse the mechanisms, causes and consequences of the landslide.

Modeling the Impact of Riparian Vegetation on Flow Structure and Bed Sediment Distribution in Rivers

The effect of instream vegetation growth has largely been ignored by hydrological and geomorphological research in river environments, which focused instead on the function of riparian vegetation as a regulator of bank stability or as a buffer for dissolved and particulate matter entering the channel from the hillside. However, in many lowland streams, instream vegetation can be very intensive, resulting in high biomass levels during the growing season. Instream plants have a significant influence on the dynamics of flow, sediment, and nutrients. Plant growth can cause increased frictional resistance to flow and can have a short-to medium-term effects on the geomorphology of the channel. Additionally, plant development influences the velocity of river flow, affects sedimentation dynamics and increases flood risk. To achieve a balance between flooding and ecological management of rivers in the presence of vegetation, a reliable method is required to predict the resistance of channels. In the current study, a two-dimensional hydrodynamic and morphodynamic model is developed and applied using a new scaling expression of shear stress based on vegetation characteristics. These first attempts at field simulations showed qualitatively acceptable results and demonstrated the effectiveness of the model in predicting hydraulic parameters in the presence of vegetation. This model is useful in predicting the effect of vegetation on stream flow and river morphology, as well as in managing flood hazards and stream ecology.

Construction of Pressure Tunnels

The paper focuses on two pressure tunnels in the design of “Kąty-Myscowa” water reservoir. One of them serves as a discharge conduit, whereas the other plays an energetic role. Their depths range between 0 and 75 metres and their diameters equal 5 m. Tunnels are located in the rock mass of Carpathian flysch which is anisotropic and heterogeneous, composed of layers of sandstone and clay shales and intersected with interbedding fissures and numerous joints. The paper is divided in two parts. The first part focuses on methods of excavating and supporting, as well as injecting and sealing (i.e. waterproofing) the tunnel. In the second part, a numerical analysis using the FLAC2D code based on the finite difference method was carried for calculating displacements and internal forces in the preliminary support and in permanent lining. Results of the analysis allow for the assessment of conditions in the tunnel during its excavation and exploitation stages.