Scour Mitigation Research Articles

Prediction of Scour Depth for Diverse Pier Shapes Utilizing Two-Dimensional Hydraulic Engineering Center’s River Analysis System Sediment Model

Examining scouring around bridge piers is crucial for ensuring water-related infrastructure’s long-term safety and stability. Accurate forecasting models are essential for addressing scour, especially in complex water systems where traditional methods fall short. This study investigates the application of the HEC-RAS 2D sedimentation model, which has recently become available for detailed sediment analysis, to evaluate its effectiveness in predicting scoring around various pier shapes and under different water conditions. This study offers a comprehensive assessment of the model’s predictive capabilities by focusing on variables such as water velocity, shear stress, and riverbed changes. Particular attention was paid to the influence of factors like floating debris and different pier geometries on scour predictions. The results demonstrate that while the HEC-RAS 2D model generally provides accurate predictions for simpler pier shapes—achieving up to 85% precision—it shows varied performance for more complex designs and debris-influenced scenarios. Specifically, the model overpredicted scouring depths by approximately 20% for diamond-shaped piers and underpredicted by 15% for square piers in debris conditions. Elliptical piers, in contrast, experienced significantly less erosion, with scour depths up to 30% shallower compared to other shapes. This study highlights the novel application of the HEC-RAS 2D model in this context and underscores its strengths and limitations. Identified issues include difficulties in modeling water flow and debris-induced bottlenecks. This research points to the improved calibration of sediment movement parameters and the development of advanced computational techniques to enhance scour prediction accuracy in complex environments. This work contributes valuable insights for future research and practical applications in civil engineering, especially where traditional scour mitigation methods, such as apron coverings, are not feasible.

Optimizing Trapezoidal Labyrinth Weir Design for Enhanced Scour Mitigation in Straight Channels

Designing hydraulic structures requires careful consideration of local scouring downstream. This study investigated the performance of trapezoidal labyrinth weirs in controlling flow and mitigating scour in straight channels through physical model experiments. Sixty configurations were examined, using weir apex angles of 20°, 45°, 60°, and 80°, heights of 30 cm, 35 cm, and 40 cm, and flow rates of 50–200 L/s. A linear weir served as a reference. The results showed that the 60° apex angle consistently outperformed other configurations, reducing scour depth by up to 41% and scour length by up to 50% compared to the linear weir. It also decreased deposition depth by 40% and length by 50%. Lowering weir height from 40 cm to 30 cm led to reductions of 35% in scour depth and 40% in scour length at low discharges. These improvements remained significant even at higher flow rates, with a 29% reduction in scour depth and 25% in scour length at 200 L/s. This study provides evidence-based recommendations for optimizing labyrinth weir designs to define the relationship between hydraulic efficiency and erosion control. It offers valuable insights into weir geometry, flow conditions, and the resulting scour and deposition patterns. These findings contribute to the optimization of labyrinth weir designs to minimize downstream bed configurations. The tests were conducted under limited flow conditions.

Optimal spur dike orientation for scour mitigation under downward seepage conditions

Optimal spur dike orientation for scour mitigation under downward seepage conditions

Baffle-Enhanced Scour Mitigation in Rectangular and Trapezoidal Piano Key Weirs: An Experimental and Machine Learning Investigation

The assessment of scour depth downstream of weirs holds paramount importance in ensuring the structural stability of these hydraulic structures. This study presents groundbreaking experimental investigations highlighting the innovative use of baffles to enhance energy dissipation and mitigate scour in the downstream beds of rectangular piano key weirs (RPKWs) and trapezoidal piano key weirs (TPKWs). By leveraging three state-of-the-art supervised machine learning algorithms—multi-layer perceptron (MLP), extreme gradient boosting (XGBoost), and support vector regression (SVR)—to estimate scour hole parameters, this research showcases significant advancements in predictive modeling for scour analysis. Experimental results reveal that the incorporation of baffles leads to a remarkable 18–22% increase in energy dissipation and an 11–14% reduction in scour depth for both RPKWs and TPKWs. Specifically, introducing baffles in RPKWs resulted in a noteworthy 26.7% reduction in scour hole area and a 30.3% decrease in scour volume compared to RPKWs without baffles. Moreover, novel empirical equations were developed to estimate scour parameters, achieving impressive performance metrics with an average R2 = 0.951, RMSE = 0.145, and MRPE = 4.429%. The MLP models demonstrate superior performance in predicting maximum scour depth across all scenarios with an average R2 = 0.988, RMSE = 0.035, and MRPE = 1.036%. However, the predictive capabilities varied when estimating weir toe scour depth under diverse circumstances, with the XGBoost model proving more accurate in scenarios involving baffled TPKWs with R2 = 0.965, RMSE = 0.048, and MRPE = 2.798% than the MLP and SVR models. This research underscores the significant role of baffles in minimizing scouring effects in TPKWs compared to RPKWs, showcasing the potential for improved design and efficiency in water-management systems.

Experimental analysis of scour around an offshore wind gravity base foundation

Scour processes and corresponding scour protection measures have been extensively studied for vertical cylinders. Several formulations for estimating scour and determining the optimum size of rocks for scour protection are widely available in the literature. However, when studying other types of structures, the geometric variability of the structures, limits the application of available semiempirical formulations. Scour phenomena around complex structures have been investigated experimentally in reduced-scale wave-current basins. However, the number of tests focused on support typologies different from monopile structures is still limited, restricting the availability of semiempirical formulations focused on conceptual design of scour protection solutions or in the estimation of the free scour development.In this work, a better understanding of the scour processes around gravity-based foundations (GBFs) and the performance of different scour protection solutions is gained via experimental results obtained from a large-scale test programme (1:35 test scale), including combined wave and current tests. The experimental tests were divided into two main types: (1) free scour and (2) scour protection tests. The main conclusion was that the triggering of a horseshoe vortex is the main driver of scour processes together with the contraction of flow lines at the foundation contours. Since monopile semiempirical formulations are not suitable for scour prediction, a new semiempirical approach was obtained from the test results. Moreover, two distinct scour mitigation methods were analysed (rock protection and concrete mattresses). Based on the undisturbed mobility parameter, statistical and dynamic limits were defined considering the rock grading tested. Finally, for concrete mattresses, the design driver was identified, and the adaptability of these types of solutions to seabed changes was verified.

Methodology to assess scour development around complex structures

Accurate prediction of scour evolution around fixed offshore foundations is a key parameter for selecting the most appropriate scour mitigation strategy. Various formulations can be used to estimate scour around monopiles. However, non-specific formulations have been developed for more complex foundations. In the case of jacketed offshore substations (OSS), the geometry can be one of the most complex. This paper describes a hybrid methodology (numerical model simulations, semi-empirical approaches and physical experiments) to estimate the scour evolution around OSS. The application of this methodology allows the selection of the most appropriate mitigation strategy from an early stage of the project to the final decision. The methodology is accompanied by some examples. In general, the results obtained from the semi-empirical approaches show quite good agreement with the measurements from the physical experiments. Nevertheless, considering the complex geometry of the OSS and the potential non-linearities associated with the platform geometry, physical experiments are required to ensure the correct estimation of the maximum scour (local and global).

Investigation of Bridge Scour Mitigation with Nature Binding Materials: Biopolymers

The use of biopolymers to tackle geotechnical problems is an essential step toward the development of sustainable geotechnical systems. The strength and erosion resistance of biopolymer-treated Hot Coffee soil sampled from the bridge site in Jackson, Mississippi were examined in this research. The optimum biopolymer concentration and moisture content were tested for Agar Gum, Xanthan Gum, and Guar Gum treatment of Hot Coffee soil, respectively. The mechanical behavior and erosion resistance of biopolymer-treated soil samples were evaluated through the unconfined compressive strength test, splitting tensile test, triaxial test, and pocket erodometer test. The results indicated that all three biopolymers improved Hot Coffee soil strength, but Guar Gum improved soil unconfined compressive and tensile strength greatly. The addition of 1% Guar Gum can improve the unconfined compression stress (UCS) and split the tensile strength of Hot Coffee soil to roughly 4,000 kPa and 600 kPa, respectively. At the same time, the cohesion of Hot Coffee soil treated with biopolymer was enhanced. The cohesion of the soil treated with 1.5% Xanthan Gum increased from 0 to 41.5 kPa. In addition, the erosion resistance of biopolymer-treated soil was also increased. With a 1.5% Xanthan Gum addition, the erosion resistance level of Hot Coffee soil reduced from very high erodibility to medium erodibility. Therefore, biopolymers have great potential for bridge scour mitigation.

Scour Mitigation at Bridge Abutments Using Spur Dikes

Scour Mitigation at Bridge Abutments Using Spur Dikes

Development of a reactive transport model for microbial induced calcium carbonate precipitation in unsaturated conditions

Microbial induced calcium carbonate precipitation (MICP) offers a sustainable technique to improve geologic properties of soils in engineering structures. The applications encompass improved soil strength, scour mitigation, fracture sealing, and in situ contaminant immobilization. Previous studies have presented fundamental processes and implementation in lab- and field-scale. Most of these studies were examined in saturated conditions despite many MICP applications including those in coastal and riverside areas which will likely take place under unsaturated conditions. The study herein investigated the effect of soil water retention curve (SWRC) parameters and attachment coefficient ( Kat ) on CaCO3 precipitation in sand. Using numerical analyses, a continuum model was developed in which unsaturated flow and transport were coupled with biological and chemical reactions in variably saturated conditions. Predictive modeling results compare mass percentage of calcium carbonate resulting from MICP at degrees of soil water saturations of 20%, 40%, 80%, and 100% in sandy soil media. The results indicate the bacteria attachment coefficient increases by a factor of 3 as the degree of saturation is decreased from 100% to 20%, as the higher suctions at lower saturation levels improve bacteria fixation. The drying branch of SWRC versus wetting front yields higher CaCO3 for identical MICP treatment. Numerical results show the trend in hydraulic conductivity with increasing cementation level.

Investigation of using mangrove-inspired skirt pile group as a scour countermeasure

Mangrove forests are able to protect the coastline because their dense prop root system reduces the flow velocity and stabilizes sediments against erosion. Inspired by this unique character of the mangrove root structure, a ring of skirt piles is proposed as a measure to mitigate local scour around monopile foundations. Numerical simulations using computational fluid dynamics (CFD) modeling as well as laboratory flume experiments were conducted to evaluate the scour mitigation effect in clear water current. The simulation results reveal that the presence of skirt piles reduces the near-bed tangential velocity and affects the vertical flow field around the monopile. The experimental results indicate that if all other parameters are held constant, the scour depth and volume increase with skirt pile spacing, decreases with the number of skirt pile rings. With a single ring of skirt piles, the scour potential reaches the lowest with an intermediate critical submerged height of the skirt piles; the scour depth and volume increase when the submerged height deviates from the critical value. The comparison between the numerical and experimental results implies that the installation of the skirt piles has not only hydraulic but also geotechnical benefits for scour mitigation.

A monitoring-based classification system for risk management of bridge scour

Flood-induced scour is the principal cause of bridge failure worldwide. Nevertheless, bridge scour risk assessment is still based on visual inspections, which may be affected by human errors and cannot be performed during flood peaks. This problem, together with the simplifications in scour estimation, might cause misclassification of the bridge scour risk, unnecessary bridge closures or recourse to avoidable scour mitigation measures. Structural-health-monitoring (SHM) systems allow overcoming these issues, providing bridge managers with more accurate information about scour, thus supporting them in taking optimal management decisions. This paper illustrates the development of an SHM- and event-based classification system for bridge scour management, which extends and complements current risk-rating procedures by incorporating the various sources of uncertainty characterising the scour estimation and information from different sensors. The proposed system is based on a probabilistic framework for scour risk estimation and can be used to provide transport agencies with real-time scour risk classification of bridges under a heavy-flood event. The system is applied to a bridge network located in south-west Scotland in a heavy-flood scenario, and information from heterogeneous sources is considered for updating the knowledge of scour. It is shown that integrating scour-monitoring data leads to an overall uncertainty reduction that is reflected in more accurate scour risk classification, thus helping transport agencies in prioritising bridge inspections and risk mitigation actions.

Erodibility improvement and scour mitigation of beach sand by enzymatic induced carbonate precipitation

The main objective of this study was to evaluate the use of enzymatic induced carbonate precipitation (EICP) treatment for erodibility improvement, scour mitigation, and water infiltration capacity of beach sand at one, two, and three cycles of treatment. EICP is a biochemical process that produces calcium carbonate precipitation within a soil matrix to improve the geotechnical properties of the soil. Direct shear test (DST) was used to examine the shear behavior of bio-cemented beach sand after one and two cycle treatment, the results of which showed that the cohesion was increased substantially, especially after the second cycle; conversely, the friction angle was decreased. The mineralogy of treated soil was also assessed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mini-jet test has been used to adequately measure the soil erosion characteristics of the biotreated sand (1–3 treatment cycles) in the laboratory, the results of which indicated a significant improvement compared to the control specimen after the third cycle of EICP treatment, with reduced erosion rate and scour depth in the order of approximately 88-fold and 23-fold respectively. After three treatment cycles, the seepage rate was decreased to 71 times lower than the untreated specimens. Strong positive correlations were found between CaCO3, seepage rate, erosion rate, and soil cohesion. The results of this study have confirmed that there is strong evidence for improving erodibility behavior and shear strength of beach sand via EICP treatment. The results of this study would be beneficial to engineers in better understanding bio-cementation techniques and their implementations.

Apron and Cutoff Wall Scour Protection for Piano Key Weirs

Piano key (PK) weirs are used in a variety of flow control structure applications, including spillway crests and open channel diversion structures. However, to the best of authors’ knowledge, structure-specific design guidance for scour mitigation is still needed. To fill this gap of knowledge, a systematic experimental campaign was conducted by testing different configurations of horizontal aprons with a cutoff wall. Protection structures were located at the toe of the PK weir. Namely, experiments were performed at large-scale to assess the effect of three apron lengths on downstream scour hole geometry under different hydraulic conditions. It was observed that a horizontal apron deflects the plunging jets originating from the PK weir, thus significantly reducing scour. Experimental evidence allowed corroboration that significant scour depth reduction occurs for an apron length 1.5 times the weir height, with longer aprons found to provide marginal benefits. Finally, also provided herein are tools to estimate the main scour characteristics and help practitioners in optimizing apron design.

A feasibility study of reducing scour around monopile foundation using a tidal current turbine

The monopile foundations of offshore wind turbines in shallow waters are susceptible to be affected by tidal scour, which takes away the sand and soil around the monopiles and poses a serious threat to the safety of the turbines. To mitigate this issue, much effort has been made previously. However, all of the existing protective measures do not have added value other than scouring mitigation. In view of this, a new scour mitigation measure that utilizes tidal current turbine (TCT) is investigated in this study, which can not only reduce the scour around the wind turbine foundation but can also generate clean power simultaneously. In the research, the proposed method is studied by using a combined numerical simulation and laboratory testing approach. Both numerical calculation and experimental results have shown that a TCT installed in front of the monopile foundation of an offshore wind turbine does have a positive role in reducing the scour around the foundation when it generates electricity in the meantime. Moreover, the contribution of the TCT to scour reduction can be further improved through optimizing its installation position in front of the wind turbine.

Reducing Bridge Pier Scour Using Gabion Mattresses Filled with Recycled and Alternative Materials

Scour is caused by the erosive action of flowing water, which causes materials from the bed and the banks of a river to be moved or unsettled. Hydraulic structures can be drastically impacted as a result of scour, which is why it is one of the most common causes of bridge failure around the world. With a predicted increase in climate conditions, the subsequent failure of hydraulic structures due to scour is likely to proliferate as the flooding of waterways is projected to rise. This study aims to determine the viability of introducing alternative materials to a scour countermeasure used in construction—gabion models—in a bid to improve the sustainability of a project whilst providing suitable scour mitigation measures. Existing literature was examined to comprehend the different scour countermeasures used, as well as the use of alternative materials that can be used as a scour countermeasure. A laboratory experiment was then carried out using a bridge pier embedded in a flume channel protected by gabion mattresses filled with alternative materials—stone, clothing and plastic—to analyse their effectiveness. The results demonstrate that stone filled gabions are most effective at reducing bridge pier scour. However, recycled clothing as a gabion fill could prove to be a viable alternative in construction projects, potentially leading to reduced construction costs and greater sustainability. However, more research on a greater scale is required to test this thesis.

Scour Mitigation and Erodibility Improvement Using Microbially Induced Carbonate Precipitation

Enhancing the scour resistance of foundation systems supporting superstructures over waterways is required for the sustainable functionality of the structure. In this article, the use of microbially induced carbonate precipitation (MICP) was investigated for the potential of its use in scour mitigation and erodibility improvement of sand. Testing was performed in a 0.91 by 1.22 by 1.22-m model box, and a double wall delivery system was developed and used to target cementation near the surface. A comparative study was performed on the scour behavior of untreated and treated samples using data from a series of flow tests. Impinging jet testing was used to evaluate the erodibility parameters of treated sand. The results from flow testing indicated that untreated and lightly cemented zones showed similar scour depth, whereas indiscernible scour was observed for the heavily cemented zone. The improvement distribution pattern throughout the media showed an ellipsoidal shape with respect to the injection source. The scour behavior and the cementation pattern indicated less cementation was achieved at the zone near the injection source because of high induced seepage velocity. Based on the impinging jet testing results, an empirical erosion model for MICP-treated sand is proposed as a function of the level of cementation.

Control of River Bend Migration Using Permeable Rectangular Vane Made by Six-Pillar Concrete Elements

Controlling the bends migration in the large meandering rivers using common groins is too costly, time consuming and needs some types of river by passing. Developing deep scour around nose of groins can lead to failure of the structure. However, it is necessary to investigate the new measures and materials to have less scour and to easily be installed, respectively. The six-pillar concrete (SPC) element is one of the materials which have been used successfully in bridge scour control. By constructing rectangular vane with SPC elements (RV-SPC) can take advantage of both economy and scour mitigation. In the present experimental study, the application of new technique has been studied. Tests were carried out at 180° flume bend for high flow condition (Froude number = 0.263). Two series of tests were carried out: (1) the base line tests without installing RV-SPC and (2) with RV-SPC at various intervals (5L, 6L, 7L, 8L) with the effective length equal to 20% of flume width (L = 12 cm). By comparing the results of two series of tests, it was determined that by installing RV-SPC at interval of 6L from each other, the maximum scour depth around the structure is reduced up to 70.0%.

Influence of collars on reduction in scour depth at two piers in a tandem configuration

Bridge failure, due to local scour at bridge pier foundations, has become a critical issue in river and bridge engineering, which might lead to transportation disruption, loss of lives and economic problems. A practical solution to prevent bridge collapses is the implementation of scour mitigation methods around bridge foundations. Based on an experimental perspective, this study is focused on the influence of the size and position of circular collars from the sediment bed on scour depth at two tandem piers. To meet this end, long-lasting experiments are performed under clear-water conditions using uniform sand for bed materials. Compared to the adjacent position of the collar on the bed, placing the collars below the bed would increase the delay time of scour at the piers up to four times. However, regardless of the delay time, the observations indicate that locating the collars on the initial bed surface results in maximum reduction in scour depths around the piers. It was found that diminishing the flow intensity has a dramatic impact on the scour reduction at the piers, so that maximum reduction in scour depths at piers increased on average from 20 to 70% with the reduction in the flow intensity from 0.95 to 0.9.

RESONANT OSCILLATIONS IN SMALL CRAFT HARBOURS: OBSERVATIONS AND MITIGATION MODELING EXAMPLES FROM ATLANTIC CANADA

Agitation from swells and long waves can pose serious challenges for harbours, in terms of both infrastructure design and operations. Wave gauge observations from Atlantic Canadian harbours of varying sizes were used to assess how combinations of basin dimensions and external wave forcing may lead to swell agitation, resonance, and scour problems. This paper summarizes how basin resonances were investigated with field observations, analytical methods, and then phase-resolving numerical models. The case studies illustrate how resonance mitigation may require substantial (and sometimes impractical) changes in harbour layout. Swell and scour mitigation may be more readily achieved by modifications or additions to existing structures.

A framework for probabilistic assessment of clear-water scour around bridge piers

Scouring at the base of bridge piers is the major cause of bridge collapses worldwide. Computing the scour risk of bridge foundations is therefore key for a correct management and allocation of resources for maintenance and scour mitigation works. Existing risk-assessment models compute the vulnerability of bridge foundations to scour by comparing the equilibrium scour depth associated with peak-flow discharges characterized by a given return period (usually of 100–200years) with the critical foundation depth of the bridge. This approach neglects completely the history-dependent and time-dependent nature of scour. Yet, it is well known that bridge collapses can often be induced by the accumulation of scour during multiple flood events.This study aims at developing a novel probabilistic framework for the computation of bridge-pier vulnerability to scour using a Markovian approach to account for memory effects in scour development. The paper focuses on the case of local pier scour occurring in clear-water conditions whereby cumulative effects are significant, well understood and known to be the cause of recent reported bridge collapses.A simplified numerical example consisting of an idealised bridge pier in a canal is considered to clarify the application of the proposed framework and to shed light on the effects of some assumptions introduced to simplify the probabilistic scour assessment.