Roughness Coefficient Values Research Articles

Experimental investigation of permeability evolution and progressive damage of sandstone in the complete process of direct shear

Permeability evolution and damage behavior under shearing conditions are critical for reliable predictions of rock seepage characteristics during excavation and a correct assessment of their impacts on the occurrence of natural or induced hazards. However, publications concerned with this problem have been poorly issued so far. The primary objective of this study is to innovatively investigate permeability evolution and damage behaviors of sandstone in the complete process of direct shear. Several groups of red sandstone specimens are deformed in direct shearing using a newly modified servo-controlled direct shear apparatus to measure permeability evolution and monitor acoustic emission (AE) activities with damage under various normal stress conditions. The morphology of the rupture surfaces is scanned using a 3D laser scanner after tests. According to our experimental results, the locus of the shear stress-displacement curve is found to be closely associated with microcrack progressivity. The initial permeability in advance of shearing test and the peak permeability appearing after the peak shear stress decrease with the increasing normal stress. The minimal and maximum permeability values exhibit a lag-effect with respect to the turning and the peak points on the shear stress-displacement curve. Furthermore, a palpable surge is found in the interevent time function during shearing, which can be a potential indicator for early warning of catastrophic rupture of brittle rock materials under shearing or compression. The joint roughness coefficient (JRC) values in the direction of shearing deformation for each normal stress case are more significant than those in the direction perpendicular to the shear displacement. The impacts of our obtained results are potential ramifications for permeability control in rock engineering projects.

Acclimatize experimental approach to adjudicate hydraulic coefficients under different bed material configurations and slopes with and without weir

The primary purpose of this study was to evaluate the hydraulic coefficient of coarse aggregate grain size beds and hydraulic parameters under random and perpendicular bed configurations, as well as to explore the discharge coefficient for rectangular weirs. The research objectives were to compare flow resistance coefficients, evaluate the discharge coefficient for rectangular weirs, investigate the relationship between roughness coefficient and hydraulic parameters, and validate the theoretical hydraulic equation for the rectangular weir. This was achieved by analysing different bed configurations, bed slopes, and 20 and 30-mm bed materials. Sieve analysis was conducted on bed materials using American-standard sieves to determine their particle size distribution. The experiment was performed in a rectangular flume measuring 12 m in length, 0.31 m in width, and 0.45 m in depth. In a laboratory experiment, water was pumped into a flume using centrifugal pumps, and a rectangular weir was attached downstream for discharge measurement. The experiment investigated factors such as Manning roughness coefficient, bed material geometry, bed slope, and weir shapes. Approximately 1680 tests were conducted to analysed the impact of these factors on discharge and the coefficient of discharge. The average Manning's roughness coefficients for a grain size of 20 mm were 0.019 (with weir) and 0.019 (without weir) in a random bed configuration, and 0.028 (with weir) and 0.027 (without weir) in a perpendicular flow bed configuration. For a grain size of 30 mm, the coefficients were 0.023 (with weir) and 0.022 (without weir) in a random bed configuration, and 0.033 (with weir) and 0.026 (without weir) in a perpendicular flow bed configuration. The presence of a weir has affected Manning's roughness coefficients and discharge coefficients. With a weir, the roughness coefficients have generally been higher compared to without a weir, indicating increased roughness in the channel. The discharge coefficient for a rectangular weir with a grain size of 20 mm ranged from 0.39 to 0.84 (random bed) and 0.27 to 0.68 (perpendicular flow bed), while for a grain size of 30 mm it ranged from 0.31 to 0.81 (random bed) and 0.23 to 0.48 (perpendicular flow bed). The discharge coefficients have varied depending on the grain size and bed configuration, reflecting different flow efficiencies over the weir. Rough particles influenced flow and Manning's roughness coefficient value, then reduced discharge and velocity values. Under two bed configurations and slopes, beds with a grain size of 30 mm have higher roughness coefficients compared to those with a grain size of 20 mm. The models have shown that the roughness coefficient is inversely proportional to the discharge and directly proportional to the tailgate water levels. The coefficient of roughness and discharge coefficient are mainly influenced by the channel slopes, bed roughness, bed grain size, and bed configuration. A randomly configured bed with a 20 mm grain size gravel bed is preferred over a perpendicular bed configuration to handle high discharges. Using a 20 mm grain-size gravel bed in open-channel flow is more suitable than a 30 mm grain-size bed. Relying on the constant friction factor, Manning's n, is not recommended as it may result in design errors. These findings have the potential to improve hydraulic engineering design practices, enhancing the accuracy and efficiency of open-channel flow systems.

Investigating the Hydraulic Behaviours of an Alluvial Meandering River Reach Between Two Barrages

The Abassia-Shammia is a meandering stream in Najaf province. Predicting and estimating the flow behavior of meandering rivers is crucial for designing hydraulic structures in an accurate manner in the vicinity and conducting environmental and ecological studies. The hydraulic properties of an alluvial stream are typically subject to change due to its location between two barrages. In this study, HEC RAS 2D, developed by the Hydrologic Engineering Center’s River Analysis System, was employed to simulate the hydraulic performance of the Euphrates River reach between two series of barrages, i.e., Abbassia and Shammia. Reliable input data, such as Digital Elevation Models (DEMs), land cover classification, and data for the 2023 hydrograph as a boundary condition, were utilized to develop the hydraulic model. The model was calibrated by using the observed water surface elevation from field measurements downstream of Abbassia to match the ones calculated by the model. Hence, the hydraulic model of the Euphrates River was created using an appropriate Manning roughness coefficient value (n = 0.04) based on the most suitable values of statistical indices, correlation coefficient (R²), and root mean squared error (RMSE) to assess the agreement between the observed and simulated data throughout the calibration and validation phases. To visualize the HECRAS2D output, the hydraulic maps for the study region were presented. The ten cross-sections from the field study (investigated at the same period of flow hydrograph) were presented for modeling to emphasize the river's hydraulic behaviors. Based on the results, the water surface elevation ranged between 19.1–29.2 m.a.s.l., and the flow velocity was 2.50 m/s. Meanwhile, the values of bed shear stress (Pa) and the water depth (m) ranged between 0.1 Pa and 8.93 m for the entire river. The results also proved the superiority of the HEC RAS2D model to reliably represent the hydraulic performance of the Euphrates River reach located between the two barrages. Doi: 10.28991/CEJ-2024-010-05-013 Full Text: PDF

Improvement of photogrammetric joint roughness coefficient value by integrating automatic shooting parameter selection and composite error model

In order to improve the accuracy of the photogrammetric joint roughness coefficient (JRC) value, the present study proposed a novel method combining an autonomous shooting parameter selection algorithm with a composite error model. Firstly, according to the depth map-based photogrammetric theory, the estimation of JRC from a three-dimensional (3D) digital surface model of rock discontinuities was presented. Secondly, an automatic shooting parameter selection algorithm was novelly proposed to establish the 3D model dataset of rock discontinuities with varying shooting parameters and target sizes. Meanwhile, the photogrammetric tests were performed with custom-built equipment capable of adjusting baseline lengths, and a total of 36 sets of JRC data was gathered via a combination of laboratory and field tests. Then, by combining the theory of point cloud coordinate computation error with the equation of JRC calculation, a composite error model controlled by the shooting parameters was proposed. This newly proposed model was validated via the 3D model dataset, demonstrating the capability to correct initially obtained JRC values solely based on shooting parameters. Furthermore, the implementation of this correction can significantly reduce errors in JRC values obtained via photographic measurement. Subsequently, our proposed error model was integrated into the shooting parameter selection algorithm, thus improving the rationality and convenience of selecting suitable shooting parameter combinations when dealing with target rock masses with different sizes. Moreover, the optimal combination of three shooting parameters was offered. JRC values resulting from various combinations of shooting parameters were verified by comparing them with 3D laser scan data. Finally, the application scope and limitations of the newly proposed approach were further addressed.

Reliability of Runoff Hydrograph Model for Extreme Rainfall Events using HEC-RAS 2D Flow Hydrodynamics Rain-On-Grid

Hydrological modeling is a valuable tool for analyzing water resources and predicting the impacts of extreme rainfall events, particularly for flood risk mitigation. Accurate results from hydrological models rely heavily on detailed input of watershed characteristics, including morphometric factors, land cover, and slope. In the face of the increasing frequency and severity of floods due to climate change, hydrological modeling has become an essential tool for disaster risk mitigation and management. HEC-RAS is a widely used software for river flow modeling and floodplain analysis. HEC-RAS 2D with the rain-on-grid meteorological model is a powerful tool for simulating flood events in complex river systems. The rain-on-grid method enables the simulation of spatially distributed rainfall events and their impact on runoff, which is crucial for modeling extreme runoff hydrographs. Previous studies have demonstrated the accuracy and effectiveness of HEC-RAS 2D with rain-on-grid in modeling extreme runoff hydrographs. This study aims to validate the reliability of HEC-RAS 2D hydrodynamics in simulating unsteady flow with meteorological data will be examined within a laboratory-scale physical model of the watershed. Additionally, the performance of HEC-RAS 2D will be evaluated in a observed watershed, specifically the Bangga watershed in Central Sulawesi to assess the performance of the HEC-RAS 2D Hydrodynamics model. The runoff hydrograph reliability model using HEC-RAS 2D rain-on-grid yielded close results when compared to a laboratory-scale physical model with a rainfall simulator and HEC-RAS 2D simulation using meteorological input data. The error in Time of Peak (Tp) and Peak Discharge (Qp) between the physical and numerical models was 7% and 3.5%, respectively. Additionally, in the HEC-RAS 2D simulation, a Manning roughness coefficient value of 0.04 closely matched the results of the physical model, while there was some variability when comparing HEC-RAS 2D results with measured data in Bangga watershed of Central Sulawesi. However, the numerical model exhibited relatively approaching result with the HEC-HMS SCS hydrograph model.

Study on the Manufacturing of Composite Materials Made from Glass Fiber Reinforced Polymer (GFRP) in Indonesia for Use as Lining in Open Channels

This study explained the potential use of glass fiber-reinforced polymer (GFRP) composite materials as an alternative lined material for irrigation channels in Indonesia. Currently, only four recommended materials are used as lining in irrigation channels in Indonesia, i.e., stone masonry, concrete, soil-cement, and ferrocement. Almost all lined material's main constituents are sourced from nature/environment. The exploitation of these mined materials will impact environmental destruction. This study focused on the manufacturing process of GFRP material, GFRP surface roughness testing, and the water flow characteristics in the hydraulic model experimental testing. The manufacturing process of GFRP material used polyester resin as the polymer matrix, E-glass type with a combination of woven roving mat covered by non-woven standard mat as the glass fiber reinforcement, and manufacturing process with a combination of hand lay-up and spray-up techniques. The GFRP material product has an average surface roughness coefficient value of Ra around 5.19 to 5.97 μm. The GFRP manufacturing has a good uniform product, as the average surface roughness coefficients of GFRP material have relatively the same values. It is shown that a factory in Indonesia has sufficient capacity to manufacture GFRP material for lining in open channels. The water flow characteristics in the flume were turbulent during testing in the hydraulic laboratory. The experimental study concluded that the GFRP composite materials could be implemented as preliminary references for alternative lined material in irrigation channels in Indonesia.

A PROPOSED TECHNIQUE FOR IMPROVING THE ACCURACY OF TIDAL MODELING OF RIVER NETWORKS CONNECTING TO THE DADAHUP IRRIGATION AREA

Optimizing the operational management of tidal irrigation networks is a significant factor in the reactivation program of the swamp irrigation areas in Central Kalimantan Province. Appropriate water level and flow rate control in a tidal environment would provide a better solution for this effort. Monitoring water parameters and hydraulic modeling is an intelligent technique for evaluating irrigation canals' gate system operations. This paper focuses on providing more accurate hydraulic modeling that requires proper boundary conditions and calibration of the canal roughness coefficient. This study aims to obtain a more precise downstream boundary condition data calibration method with an appropriate river cross-sectional roughness coefficient value to improve the overall hydraulic modeling accuracy of the river network connecting to the Dadahup Irrigation Area. The hydraulic modeling utilized the HEC-RAS Software, where input data preparation used geometric data derived from the National Geospatial Agency's DEM in the form of river channel network chain, cross-section, and long-section data. Boundary condition data evaluation compared and selected data generated from references and the Tides Application Software. The results show that the tide prediction from the Tides Application Software provides the slightest difference between the predicted tide and the measured ones. The river network's channel roughness coefficient calibration utilized the generated boundary condition tide and simultaneously measured water level data at several locations. The results show that the most minor Root Mean Squared Error (RMSE) of the Manning roughness coefficient differences of the river channel network can reach 0.04 with a minimum RMSE value of 0.027.

The FC Algorithm to Estimate the Manning’s Roughness Coefficients of Irrigation Canals

Freshwater scarcity has driven the integration of technological advancements and automation systems in agriculture in order to attempt to improve water-use efficiency. For irrigation canals, water-use efficiency is, in great measure, limited by the performance of management systems responsible for controlling the flow and delivering water to the farmers. Recent studies show a significant sensitivity of the results obtained from irrigation canal control algorithms with respect to the Manning’s roughness coefficient value, thus, highlighting the importance of its correct estimation to ensure an accurate and efficient water delivery service. This is the reason why the friction coefficient algorithm was developed, to monitor the real behaviour of any irrigation canal by calculating the Manning’s roughness coefficient constantly. The friction coefficient algorithm was conceived as a powerful offline tool that is integrated in a control diagram of any irrigation canal, concretely in an optimization control algorithm, which can reconfigure canal gates according to the current crop water demand and the real Manning’s roughness coefficient values. The friction coefficient algorithm has been applied in several irrigation canals and different scenarios, with accurate results obtaining an average Manning coefficient deviation among 2 × 10−4 and 4.5 × 10−4.

Determination of the Canal Discharge Capacity Ratio and Roughness to Assess Its Maintenance Status: Application in Egypt

Waterlogging and soil salinity issues can be handled using surface or subsurface drainage networks, soil bed elevation, and soil and crop management patterns. A properly operating and maintained drainage system is important for both rural and urban inhabitants to protect lives and property from flooding and high groundwater levels, enhance health conditions, and safeguards water purity, soil salinity, and waterlogging. It also supports and increases crop yields and consequently rural incomes. This study assessed the maintenance condition of the main surface drains (Baloza and ELFarama) located in the Tina Plain (50,000 acres) and a portion of the Southeast El-Kantara regions (25,000 acres) in North Sinai, Egypt, based on the values of the Discharge Capacity Ratio (DCR) and Manning’s roughness (n). Ten measurement locations at the drain cross-section were used in the investigation. For the ELFarama Drain, the average values of n and DCR were found to be 0.029 and 86.2%, and for the Baloza Drain, they were 0.032 and 78.6%, respectively. Compared to the design values, the actual Manning’s roughness was higher, indicating that the drainage canals’ capacities had been reduced and that their upkeep was inadequate. In both drains, sedimentation is present and they need to be maintained, according to the hydrographic surveying results for the actual cross-sections compared to the planned cross-sections. A methodology for the channel maintenance method is presented. For removing vegetation and dredging sediment, a long-boom mechanical hydraulic excavator with a bucket is suggested and to be conducted every two years. To the results of this study, the amount of weed infestation in vegetated channels is the main factor that affects Manning’s roughness coefficient value. It is now easier to calculate the proportion of weeds that are submerged in vegetated channels using echo-sound sonar technology. The DCR is an affordable and simple methodology to assess the channel maintenance status for sustainable agriculture.

Roughness Coefficient in Euphrates River Reach between Haditha Dam to Ramadi Barrage

Accurate computation of the roughness coefficient is important in the studies of open channel flow. To measure and identify the hydraulic characteristics of the flow system, the model simulation is necessary to study and get the results of the hydraulic properties to specify Manning coefficient of the Euphrates River. In this study, the reach is extended along the Euphrates River from Haditha Dam to Ramadi Barrage with a distance of 169km. The HEC-RAS model was implemented to simulate the flow within the study reach. The geometry of the river was represented by more than two hundred cross-sections surveyed in 2013 and 2021. The model was calibrated using some observed discharges at the Heet gage station for records of the last five years. The Model was validated using five sets of observed water levels in different cases of manning coefficient in the model. The Root Mean Square Error (RMSE) was used for comparison of the model results. Results of the model showed that the roughness coefficient value for this reach is 0.026 for the river bed and 0.030 for the River bank. These values gave the best coincidence between the simulated and observed values of water levels.

Обоснование методов гидравлических расчетов оросительных каналов

Purpose: justification of the applicability of various methods of hydraulic calculations of irrigation canals of land reclamation systems. It is recommended to use five types of hydraulic tasks allowing determining the following main parameters of irrigation canals for each type: conveying capacity (first type), canal slope (second type), roughness coefficient (third type), water flow depth (fourth type), cross-section dimensions of the irrigation canal (fifth type). Materials and methods. The well-known classical methods and dependences of N. N. Pavlovsky, B. A. Bakhmetev, R. R. Chugaev, A. A. Agroskin, Shezi and other scientists were taken as a basis during the research. Results. Methods for determining the main hydraulic characteristics of irrigation canals, including: canal discharge and slope and roughness coefficient are considered. These methods allow making calculations by the selection and graphical methods. The fifth type of problems is a series of independent solutions, where the effective width also calculated graphically is used. An analysis of the calculation results shows that for problems of the first type, the Chezy coefficients and hydraulic discharge decrease with an increase in the channel roughness coefficient values. Based on the calculated data obtained, canal discharge change chart depending on the roughness coefficient of the channel was constructed. Conclusions. The conditions for application of various methods of hydraulic calculation of irrigation canals were determined based on the results of the research. The values of the roughness coefficients of irrigation canals in impervious lining – concrete monolithic and reinforced concrete from prefabricated slabs are given. Summary calculation results for six different examples are presented.

An inverse problem for modeling open channel flow with movable bed

Abstract In this research, an explicit finite difference two steps scheme developed by Richtmyer is presented for simulation of 1D steady/unsteady flow and bed morphology in alluvial channels. Some laboratory experiments were performed in a mobile-bed flume for both of steady an unsteady flow to validate the proposed model. For improving the simulation, first, the role of sediment transport formulas, coupled–uncoupled approaches and simplification in the mass continuity equation are investigated. Comparisons between experimental data and model performance highlight the advantage of coupled method over the uncoupled method, domain role of sediment transport model in the bed morphological simulation and inaccuracy of aggradation processes due to simplifying the mixture continuity equation. Second, the importance of changing alluvial roughness is established by testing the model with calibrated and optimized friction factors. The inverse problem of estimating alluvial flow roughness is solved using a genetic algorithm (GA) optimization model coupled with alluvial flow model. The study demonstrates that the application of GA in the search for optimal values of roughness coefficients can significantly reduce computational errors and improve the computed water stage hydrographs. Role of the choice of the objective function is also mentioned.

ВИЗНАЧЕННЯ КОЕФІЦІЄНТУ ШОРСТКОСТІ ДЛЯ РОЗРАХУНКУ ПОТОКУ НЕУСТАЛЕНОГО РУХУ РІДИНИ

The analysis of the literature devoted to calculation of hydrotechnical structures showed that there are recommendations that take into account the influence roughness of the channel on magnitude transformation transit flow of liquid along the length of the channel. But these recommendations are difficult to apply to reclamation systems, which include complexes of hydraulic engineering and transport facilities, because they do not take into account the characteristic features of unsteady fluid movement in such systems. Unfortunately, as of today, this issue has not been adequately addressed in modern scientific literature. The article considers the issue of determining the roughness coefficient based on the materials of field experiments on irrigation systems of Ukraine for its further use in the Saint-Venant equations for unsteady water movement in open prismatic channels. At one time, professor V.O. Bolshakov applied the method of running according to the implicit difference scheme, provided that the roughness coefficients are known, to solve the Saint-Venant equations. The authors conducted an analysis errors of field measurements of maximum depths, calculation area of live sections, etc. The absolute error of finding the drop in water levels in individual sections of the channel was determined. The results. Among the issues that were covered in the discussed publication, the main attention was paid to the issue of studying the influence of the roughness coefficient on flow elements during unsteady motion in meliorational (irrigation) systems. Also, the characteristics conducted field measurements are given, a detailed overview field data is provided, and the measured parameters at different sections research channel are listed. Conclusions. An indicative evaluation and analysis errors of the performed measurements was carried out, and recommendations were given for determining the average values of roughness coefficients for irrigation channels (channels) with a well-planned bottom and slopes, as well as for banks not covered with vegetation. The results of data processing of field observations are summarized in a table, which presents a comparison calculated values of the roughness coefficients.

Influence of river channel deflector hydraulic structures on lowland river roughness coefficient values: the Flinta river, Wielkopolska Province, Poland

River channel deflectors are environmentally friendly low head hydraulic structures constructed from wood, stones and coarse gravel Their aim is to protect river banks against erosion, to change the direction of river flow making the river course naturally meandrous instead of artificially straight, to provide natural refugia for fish and invertebrates and finally to improve hydraulic discharge conditions. However, from the designing point of view they are difficult to represent in hydrodynamic models since they are constructed and fixed in the river bed differently. For this reason, in hydraulic models’ deflectors may be treated as modifications to the value of the watercourse bed roughness or reduction in the active part of the cross-section. Thus, to test the suitability of one-dimensional models for river restoration involving river deflectors, a 1-D numerical model of the lower section of the Flinta river (Wielkopolska Province, Poland) was prepared. To do that, firstly three channel flow deflectors were constructed and installed in the lower section of the Flinta river. Secondly, hydrometric measurements were continued systematically over three years. Next, based on field studies and field data, calculations were made using the HEC-RAS 1-D software. Several variants of the shape and the effect of deflectors were tested. On this basis, the variability of the roughness coefficient value for the Flinta riverbed after the implementation of deflectors was analyzed. The novelty of the research is that the obtained results show that river channel deflectors have a significant influence on the processes of morphological changes (such as: velocity distribution, grain size changes, tendency towards channel meandering, channel slope) of the riverbed and thus also on changes in hydromorphological parameters of river flow. The presented case study confirmed the potential for effective deflector operation for the velocity range of 0.10 – 0.30 m·s−1. The maximum changes of the river bed elevation after the deflectors had been introduced reached 0.10 m. It was also found that the effect of deflectors on roughness at high water levels was non-significant and did not increase the risk of flooding. For Q1% flow, the implementation of flow deflectors had no significant effect on the capacity of the studied river section. Only slight subduction of 0.02 – 0.03 m of the water surface in the vicinity of the deflectors could be observed compared to the model from before the restoration activities. The greatest impact of the channel deflectors is seen at low water levels and low flows that do not exceed average flow values. Finally, it was shown that the best solution to implement deflectors into a one-dimensional model is to consider their influence as a change in the value of Manning's coefficient. The obtained results can be considered universal in relation to typical transformed small lowland watercourses that have been straightened and regulated and are to be subjectedto the process of river restoration.

Flood Inundation Modeling by Integrating HEC–RAS and Satellite Imagery: A Case Study of the Indus River Basin

Floods are brutal, catastrophic natural hazards which affect most human beings in terms of economy and life loss, especially in the large river basins worldwide. The Indus River basin is considered as one of the world’s large river basins, comprising several major tributaries, and has experienced severe floods in its history. There is currently no proper early flood warning system for the Indus River which can help administrative authorities cope with such natural hazards. Hence, it is necessary to develop an early flood warning system by integrating a hydrodynamic model, in situ information, and satellite imagery. This study used Hydrologic Engineering Center–River Analysis System (HEC–RAS) to predict river dynamics under extreme flow events and inundation modeling. The calibration and validation of the HEC–RAS v5 model was performed for 2010 and 2015 flood events, respectively. Manning’s roughness coefficient (n) values were extracted using the land use information of the rivers and floodplains. Multiple combinations of n values were used and optimized in the simulation process for the rivers and floodplains. The Landsat 5 Thematic Mapper (TM), Landsat 8 Operational Land Imager (OLI), Moderate Resolution Imaging Spectroradiometer (MODIS) MOD09A1, and MOD09GA products were used in the analysis. The Normalized Difference Water Index (NDWI), Modified NDWI1 (MNDWI1), and MNDWI2, were applied for the delineation of water bodies, and the output of all indices were blended to produce standard flood maps for accurate assessment of the HEC–RAS-based simulated flood extent. The optimized n values for rivers and floodplains were 0.055 and 0.06, respectively, with significant satisfaction of statistical parameters, indicating good agreement between simulated and observed flood extents. The HEC–RAS v5 model integrated with satellite imagery can be further used for early flood warnings in the central part of the Indus River basin.

Reconstruction of rough rock joints: 2D profiles and 3D surfaces

The 3D reconstruction of rock joint surfaces is crucial for quantifying rock joints. Through the uniform discretization of 2D and 3D rock joints, it was determined that both the climbing angles along the shear direction and the projection lengths of the consecutive ascending/descending segments follow normal distributions . This statistical distribution of climbing angles and projection lengths provides an important reference for rock joint reconstruction, although hypothesis testing indicated that some joint profiles/surfaces do not follow normal distributions. A normal distribution-based method and a bubbling method were used to reconstruct the 2D joint profiles. The bubbling method demonstrated good applicability for the generation of 3D rock joint surfaces, especially because it included surfaces with different roughness in two orthogonal directions. Therefore, ten typical 3D rock joint surfaces were reconstructed using the bubbling method, where both the size of asperities (waviness or unevenness) and the joint roughness coefficient values were quantified. To reconstruct a joint surface with a certain roughness coefficient, scaling the elevation of a generated surface was demonstrated as an effective supplementary approach. • Rock joints were statistically analyzed via normal distributions owing to a uniform discretization operation. • The normal distribution-based method and the bubbling method were both suitable for reconstructing 2D joint profiles. • The bubbling method could generate 3D joint surfaces with different roughness in two orthogonal directions. • Rock joints with different joint roughness coefficients were reconstructed by scaling their elevation coordinates.

Effects of Bed Materials to Flow Characteristics on Open Channel and Gradually Varied Flow Simulation Using Genetic Algorithm (GA)

Determination of accurate roughness coefficient was realized necessary for hydraulic parameters estimation in open channel flow. For the purpose this study was planned to carry out on experimental basis in hydraulic laboratory hall of campus itself. In this study, a combination between experimental and numerical models study were carried out to investigate the influence of bed roughness on flow characteristics. Experiments were conducted on six bed materials (Sand, Gravel, Cement plaster, Grass, Formica and cast iron (original bed of channel)) in three conditions. Firstly the discharge was varied at same tail water level. Secondly the depths were varied for same discharge and thirdly the depths were measured for different discharges for each bed material Results were analyzed and were graphically presented .The Manning roughness coefficient was estimated for each bed material using the experimental and discharge optimization technique. The percentages of errors between the observed and predicted were reported. Since the channel represents compound case having glass wall and different bed material, the roughness coefficient of each bed materials were predicted by optimization on genetic algorithm to the lotter’s modified equation in which the exponent alpha value varies from 1.28 to 1.76 The shear stress distribution was examined by first and second approximation theory on smooth rectangular channel on Knight et al (1984) model. It was compared with the experimental average shear stress and was found the first approximation theory over estimated to the experimental value whereas second approximation result was within the average relative error of 1.61% for bed. Side wall/bed stress ration was found of 0.61. Similarly gradually varied flow was simulated in python using optimal value of roughness coefficient.

Kinematic reverse flood routing in natural rivers using stage data

In many developing countries, due to economic constraints, a single station on a river reach is often equipped to record flow variables. On the other hand, hydrographs at the upstream sections may also be needed for especially assessing flooded areas. The upstream flow hydrograph prediction is called the reverse flood routing. There are some reverse flood routing pocedures requiring sophisticated methods together with substantial data requirements. This study proposes a new reverse flood routing procedure, based upon the simple kinematic wave (KW) equation, requiring only easily measurable downstream stage data. The KW equation is first averaged along a channel length at a fixed time, t, assuming that channel width is spatially constant, and then the spatially averaged equation is averaged in time, Δt. The temporally averaged terms are approximated as the arithmetical mean of the corresponding terms evaluated at time t and t + Δt. The Chezy roughness equation is employed for flow velocity, and the upstream flow stage hydrograph is assumed be described by a two parameter gamma distribution (Pearson Type III). The spatially averaged mean flow depth and lateral flow are related to the downstream flow stage. The resulting routing equation is thus obtained as a function of only downstream flow stage, meaning that the method mainly requires measurements of downstream flow stage data besides the mean values of channel length, channel width, roughness coefficient and bed slope. The optimal values of the parameters of reverse flood routing are obtained using the genetic algorithm. The calibration of the model is accomplished by using the measured downstream hydrographs. The validation is performed by comparing the model-generated upstream hydrographs against the measured upstream hydrographs. The proposed model is applied to generate upstream hydrographs at four different river reaches of Tiber River, located in central Italy. The length of river reaches varied from 20 to 65 km. Several upstream hydrographs at different stations on this river are generated using the developed method and compared with the observed hydrographs. The method predicts the time to peak with less than 5% error and peak rates with less than 10% error in the short river reaches of 20 km and 31 km. It also predicts the time to peak and peak rate in other two brances of 45 km and 65 km with less than 15% error. The method satisfactorily generates upstream hydrographs, with an overall mean absolute error (MAE) of 42 m3/s.

Investigation on the Shear Behavior of Rough Rock Joints Prepared by Three-Dimensional Engraving Technique

Abstract Laboratory shear test is an important and widely used method to investigate the shear behavior of rock joints, and the preparation of joint specimens is a key factor that influences test results. In order to study the shear mechanism of rough rock joints with different morphologies in the laboratory, an innovative three-dimensional (3D) engraving technique was employed to produce specimens with rough joints. Intact sandstone and cement mortar blocks were used as model materials. The engraving parameters were determined to ensure a satisfactory engraving precision and to save as much time as possible for an engraving process. Three Barton profiles with joint roughness coefficient (JRC) values of 2.8, 10.8, and 18.7 were selected as the morphology prototypes for automatically engraving the model material blocks to obtain rough joint specimens. Shear tests were then conducted under four normal stress levels in the laboratory. In addition, numerical simulations on joints with the same physico-mechanical properties, surface morphology, and boundary conditions as the joint tested in the laboratory were performed. The failure characteristics, shear behavior curves, and shear strength obtained from numerical and experimental studies were analyzed considering the effect of joint materials, joint roughness, and applied normal stress. The shear mechanism of rough joints was investigated, and the analysis indicated that the results of shear tests by simulation and experiment were similar. The results revealed that it is feasible to make rough joints by engraving either real rocks or commonly used model materials (e.g., cement mortar).

Remote Sensing Methodology for Roughness Estimation in Ungauged Streams for Different Hydraulic/Hydrodynamic Modeling Approaches

This study investigates the generation of spatially distributed roughness coefficient maps based on image analysis and the extent to which those roughness coefficient values affect the flood inundation modeling using different hydraulic/hydrodynamic modeling approaches ungauged streams. Unmanned Aerial Vehicle (UAV) images were used for the generation of high-resolution Orthophoto mosaic (1.34 cm/px) and Digital Elevation Model (DEM). Among various pixel-based and object-based image analyses (OBIA), a Grey-Level Co-occurrence Matrix (GLCM) was eventually selected to examine several texture parameters. The combination of local entropy values (OBIA method) with Maximum Likelihood Classifier (MLC; pixel-based analysis) was highlighted as a satisfactory approach (65% accuracy) to determine dominant grain classes along a stream with inhomogeneous bed composition. Spatially distributed roughness coefficient maps were generated based on the riverbed image analysis (grain size classification), the size-frequency distributions of river bed materials derived from field works (grid sampling), detailed land use data, and the usage of several empirical formulas that used for the estimation of Manning’s n values. One-dimensional (1D), two-dimensional (2D), and coupled (1D/2D) hydraulic modeling approaches were used for flood inundation modeling using specific Manning’s n roughness coefficient map scenarios. The validation of the simulated flooded area was accomplished using historical flood extent data, the Critical Success Index (CSI), and CSI penalization. The methodology was applied and demonstrated at the ungauged Xerias stream reach, Greece, and indicated that it might be applied to other Mediterranean streams with similar characteristics and flow conditions.