Analysis And Design Practice Of Hydraulic Concrete Structures.epub

Abstract:The worldwide current practice of the structural design of sewers is based on procedures which usually include the effects caused by chemical and biological deterioration. However, in the last few decades, many sewer pipes have been designed using reinforced concrete which have succinctly considered such deterioration promoters. Indeed, knowledge related to reinforced concrete deterioration processes has become an important issue when forecasting the expected or remaining lifespan of sewers. Within these processes, thickness and strength losses and porosity augments have been found to be the result of the vital activity of sulfur-oxidizing bacteria and some types of fungus. This paper presents a rational methodology that uses biodeterioration measurements to describe how biodeterioration effects can affect the probability of failure during the lifetime of sewers. The probability of failure was obtained using Monte Carlo simulations based on numerical sampling from lognormal and uniform distributions. The concrete and reinforcement strength, geometric properties, H2S concentration in the headspace, and load values were considered as the main sources of uncertainty. The results indicate that the expected service lifespan can vary between 55 and 37 years for low and high H2S concentrations, respectively.Keywords: biodeterioration; buried sewers; bending strength; probability of failure

There are many criteria in the design of hydraulic structures that must be optimized at the same time. Construction, operating and maintenance costs, construction reliability, environmental impact, social disruption and potential loss of life can be identified as one of the most noticeable of a large number of criteria (Rasekh, Afshar & Afshar, 2010). Therefore, a comprehensive research on the environmental risk of hydrotechnical structures failure is necessary. One aspect of this type of research is a proper recognition of hydraulic and morphodynamic processes that accompany the construction of water structures using physical and mathematical models (Lopardo & Seoane, 2004; Syvitski et al., 2010).

Local scouring in the aquatic environment may be particularly desirable during the season of low dischagres. It can then serve as a reservoir in which particular species that require a certain water depth, can survive. Lowering of the river bed may also be beneficial in the construction of a fish pass. The inlet and outlet of fishponds must be submerged deep enough under the water surface level, and this could be difficult in the structure stand downstream, where the depth of the stream is normally lower than in upstream stand area (Siwicki & Urbański, 2004). At the design stage, it is important to develop a reliable forecast of a size, shape and position of the local scour, both in dams and small hydraulic structures, such as gated checks, weirs or sluices.

In spite of many experimental works carried out under various constructional conditions and high variability of hydraulic conditions, the universal principles of calculating the local scour dimensions and transferring it to field conditions are still unknown. Solutions are sought, involving different coefficients, which characterize a given construction, based on identified factors that influence scour size and position (Franke, 1960; Straube, 1963; Tarajmovič, 1966; Rossinski & Kuzmin, 1969). The formation and expansion of local scouring that results from time-varying, two-phase movement of water and sediment is one of the most undiscovered processes in hydrotechnical engineering (Graf, 1998; Nouri Imamzadehei et al., 2016). Despite numerous studies carried out since the first decades of last century (for example Lacey, 1946; Ahmad, 1953; Breusers & Raudkivi, 1991; Lenzi, Marion & Comiti, 2003; Ślizowski & Radecki-Pawlik, 2003; Ben Meftah & Mossa, 2006; Kiraga & Popek, 2016; Pagliara et al., 2016; Kiraga & Popek, 2018; Al-Husseini, Al-Madhhachi & Naser, 2019), there is no sufficient and unquestionable basis for the mathematical description of the process of local erosion, and thus for a development of forecasts of scour holes that will occur during the design of structures. Also, it is not always possible to predict fully reliable estimation based on the results of laboratory tests, because in laboratories the researchers are usually unable to lead to the occurrence of the so-called final scour, i.e., to a state in which the extension of the duration of the experiment does not cause changes in the dimensions and location of sandy bottom and banks (Chabert & Engeldinger, 1956; Barbhuiya & Dey, 2004). Moreover, designers find it difficult to choose those that give reliable results. Due to the diversity of applied constructions of structures and the variability of hydraulic conditions, it is difficult to generalize the derived formulas ((Graf, 1998; Barbhuiya & Dey, 2004; Ben Meftah & Mossa 2006).

The estimation of the maximal scour hole depth and the channel reach infested by extensive erosion allows for a proper design of the downstream of hydraulic structure, ensuring safety and stability, as well as reducing the construction and subsequent operation cost. Therefore, the estimation of the geometry of forecasted scour should be an integral part of the design stage of hydrotechnical structures (Brandimarte, Paron & Di Baldasarre, 2012; Prendergast & Gavin, 2014).

This work was supported by the Department of Hydrotechnics and Technology and the Department of Water Engineering and Applied Geology of Warsaw University of Life Sciences. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. 2b1af7f3a8