Deterioration of concrete sewers

The corrosion and maintenance of concrete sewers have always been an area of social as well as financial priority. The corrosion of the concrete sewer system is related to biodegradation of concrete which led to formation of sulphuric acid. The sulphuric acid so produced affects the life span of structure by causing expansion which eventually led to collapse of structure as a whole. The damage is further amplified in case of splashing of waste waters in the sewer network as compared to stagnant waters. In order to access the degree of damage an experimental program was carried out. This paper presents the results of degradation depth of concrete subjected to stagnant and flowing condition of sulphuric acid solution (H2SO4) made with different the water-cement ratio and concentration of sulphuric acid. For this purpose, concrete cubes with various water-cement ratios were made. These cubes were exposed to sulphuric acid solution of pH 1,2,3 and 4. The results revealed that surrounding conditions play one the important role in deciding the erosion depth in addition to water cement ratio. From the experiment it was also affirmed that erosion depth depends on the concentration of the acidic solution.

DEM- and GIS-Based Analysis of Soil Erosion Depth Using Machine Learning

Soil erosion is a form of land degradation. It is the process of moving surface soil with the action of external forces such as wind or water. Tillage also causes soil erosion. As outlined by the United Nations Sustainable Development Goal (UN SDG) #15, it is a global challenge to “combat desertification, and halt and reverse land degradation and halt biodiversity loss.” In order to advance this goal, we studied and modeled the soil erosion depth of a typical watershed in Taiwan using 26 morphometric factors derived from a digital elevation model (DEM) and 10 environmental factors. Feature selection was performed using the Boruta algorithm to determine 15 factors with confirmed importance and one tentative factor. Then, machine learning models, including the random forest (RF) and gradient boosting machine (GBM), were used to create prediction models validated by erosion pin measurements. The results show that GBM, coupled with 15 important factors (confirmed), achieved the best result in the context of root mean square error (RMSE) and Nash–Sutcliffe efficiency (NSE). Finally, we present the maps of soil erosion depth using the two machine learning models. The maps are useful for conservation planning and mitigating future soil erosion.

The Cross-Dike Failure Probability by Wave Overtopping over Grass-Covered and Damaged Dikes

A probabilistic framework is developed to calculate the cross-dike failure probability by overtopping waves on grass-covered dikes. The cross-dike failure probability of dike profiles including transitions and damages can be computed to find the most likely location of failure and quantify the decrease in the failure probability when this location is strengthened. The erosion depth along the dike profile is calculated using probability distributions for the water level, wind speed and dike cover strength. Failure is defined as the exceedance of 20 cm erosion depth when the topsoil of the grass cover is eroded. The cross-dike failure probability shows that the landward toe is the most vulnerable location for wave overtopping. Herein, the quality of the grass cover significantly affects the failure probability up to a factor 1000. Next, the failure probability for different types of damages on the landward slope are calculated. In case of a damage where the grass cover is still intact and strong, the dike is most likely to fail at the landward toe due to high flow velocity and additional load due to the slope change. However, when the grass cover is also damaged, the probability of failure at the damage is between 4 and 125 times higher than for a regular dike profile.

SLURRY EROSION BEHAVIORS OF COPPER ALLOY BARREL OF MEASURE-MENT WHILE DRILLING

Measurement while drilling (MWD) has been widely used in petroleum drilling engineering because it can realize borehole trajectory monitoring and improve the drilling speed. However, the slurry erosion will deteriorate and shorten the life of MWD. A user-defined function (UDF) code was developed to calculate the particle properties (particle impact velocity, particle impact angle and particle impact number) and erosion depth to understand the erosion process. The results show that the Realizable κ-ε model can accurately predict the erosion profile and the erosion depth is consistent with the experiment results. Furthermore, high pressure will aggravate surface damage and expand the area of slurry erosion. It has been demonstrated that computational fluid dynamics (CFD) and experimental approach can be used to identify and explain the erosion mechanisms in different regions where the surface morphologies reveal four erosion patterns, namely, micro-cutting, cracks, pits and plastic deformation.

MODELLING OF WAVE OVERTOPPING FLOW OVER COMPLEX DIKE GEOMETRIES: CASE STUDY OF THE AFSLUITDIJK

Grass cover erosion by overtopping waves is one of the main failure mechanisms of dikes. Transitions in cover type and geometry can increase the hydraulic load and are therefore identified as vulnerable locations for grass cover erosion. Two models are applied to the inner slope of the Afsluitdijk in the Netherlands to show how transitions can be included in overtopping models. Firstly, the analytical grass-erosion model is used to simulate the erosion depth along the profile for a six-hour storm. The model results show that the erosion depth is maximal at the end of the two slopes in the profile. Secondly, the effect of transitions on the hydraulic load is computed with a detailed hydrodynamic model. The model results show that geometric transitions significantly influence the shear stress, the normal stress and the pressure. Four vulnerable locations for grass cover erosion are identified based on the model results that are related to slope changes along the profile. Furthermore, the model results show that the overtopping flow is mainly affected by geometric transitions, while no effect of roughness transitions on the modelled forces was observed.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/t1cPJwf72nE

Standoff Distance in Ultrasonic Pulsating Water Jet

The water hammer effect is the basis of technologies which is artificially responsible for the decay of continuous jets. A recently developed technique enhances the pressure fluctuations using an acoustic chamber, leading to enhanced erosion effects for various water volume flow rates. The optimum standoff distance for an ultrasonic enhanced water jet is not appropriately estimated using an inclined trajectory. The objective of this study is to comprehend the true nature of the interaction of the standoff distance following the stair trajectory and traverse speed of the nozzle on the erosion depth. Additionally, it also critically compares the new method (staircase trajectory) that obeys the variation in frequency of the impingements for defined volume flow rates with the inclined trajectory. In this study, at constant pressure (p = 70 MPa), the role of impingement distribution with the variation of traverse speed (v = 5–35 mm/s) along the centerline of the footprint was investigated. The maximum erosion depth corresponding to each traverse speed is observed at approximately same standoff distance (65 ± 5 mm) and decreases with the increment in traverse speed (h = 1042 and 47 µm at v = 5 and 35 mm/s, respectively). The results are attributed to the variation in the number of impingements per unit length. The surface and morphology analysis of the cross-section using SEM manifested the presence of erosion characteristics (micro-cracks, cavities, voids, and upheaved surface). By varying the water cluster, different impingement densities can be achieved that are suitable for technological operations such as surface peening, material disintegration, or surface roughening.

Investigation of the Dynamic Performance of a Large-Span Suspension Bridge Influenced by Scouring Based on Vehicle-Bridge Coupled Vibration

To study the damage of bridge pile foundations caused by scouring, two damage mechanisms of scouring are proposed in this paper. Considering the vehicle-bridge coupled vibration in terms of two aspects of the scouring depth and erosion depth, the vertical and transversal dynamic characteristics and dynamic responses of the bridge are studied under different cases for the most sensitive vehicle speed. The dynamic characteristics include the 1st and 2nd vibration modes of the vertical and transversal directions of the bridge. The dynamic responses include the vertical and transversal dynamic load allowances and acceleration of the bridge. The souring depth is more sensitive than the erosion depth, and the 2nd vertical mode is most substantially influenced by scouring and erosion. Because of the small value of the natural frequency of the vertical vibration modes, the transversal vibration modes may be more convenient to obtain. The study of the dynamic responses shows that the scouring depth can be represented by the dynamic load allowance in the middle of the span’s section and the erosion depth can be characterized by the dynamic load allowance at the quarter location of the span’s section.