Wall Slope Research Articles

Landslide stabilization experience in Urtui open pit mine

Instability of pit wall slopes is the most critical accident in open pit mining. The risk of damages to pit walls is proportional to the height of exposed surfaces and to the time of exposure. Among many factors governing pit wall stability, the major factor is geological structure and weakening zones in rock mass. Deformation processes are initiated in host rock mass of coal seams mostly because of undercutting of weak interlayers. Alongside with local undercutting, another cause of landslides is transition of coal mining from down-dip extraction to up-dip extraction. The sequence of mining and morphology of weak interlayers also have influence on initiation and evolution of deformations. The basic component of engineering solutions on pit wall stability control is optimization of mining sequence and methods of accessing working horizons in open pit mines. Large-scale deformation of Western and Southeastern pit walls in Urtui mine could be avoided using the optimized sequence of mining operations. For example, mining advance mostly along the curve of the Urtui centroclinal fold, with early access and destress of the eastern and, first of all, western wings of the fold could make it possible to evade from up-dip mining of coal seams and, as a consequence, to solve the major geomechanical problems in the open pit mine.

Morphometric Analysis of Pluto’s Impact Craters

The scope of this work is to carry out a morphometric analysis of Pluto’s impact craters. A global Pluto digital elevation model (DEM) with a resolution of 300 m/px, created from stereoscopic pairs obtained by the New Horizons Mission, was used to extract the morphometric data of craters. Pluto’s surface was divided according to different morphometric characteristics in order to analyze possible differences in the impact dynamics and modification rate in each region. A Python code was developed, within the QGIS 3× software environment, to automate the process of crater outlining and collection of morphometric data: diameter (D), depth (d), depth variation, slope of the inner wall (Sw), diameter of the base (Db), and the width of the wall (Ww). Data have been successfully obtained for 237 impact craters on five distinct terrains over the west side of Sputnik Planitia on Pluto. With the collected data, it was possible to observe that craters near the equator (areas 3 and 4) are deeper than craters above 35°N (areas 1 and 2). Craters on the western regions (areas 2 and 3) contain the lowest depth values for a given diameter. The transition diameter from simple to complex crater morphology was found to change throughout the areas of study. Craters within areas 1 and 4 exhibit a transition diameter (Dt) of approximately 10 km, while Dt for craters within areas 3 and 5 the transitions occurs at 15 km approximately. The presence of volatile ices in the north and north-west regions may be the reason for the difference of morphometry between these two terrains of Pluto. Two hypotheses are presented to explain these differences: (1) The presence of volatile ices can affect the formation of craters by making the target surface weaker and more susceptible to major changes (e.g., mass waste and collapse of the walls) during the formation process until its final stage; (2) The high concentration of volatiles can affect the depth of the craters by atmospheric decantation, considering that these elements undergo seasonal decantation and sublimation cycles.

Estimating of Maximum Groundwater Level to Trigger Landslide in Batu Hijau Open Pit Mine, West Nusa Tenggara, Indonesia

The safety of the employees is essential in the mining activity area. Thus, the sloping wall of the pit needs to evaluate from time to time to avoid any loss due to landslide. One of the essential parameters to lead to slope failure is groundwater. Therefore, this paper highlights the limitations of the groundwater for the existing slope mine by analyzing it for several groundwater levels until it reached a safety factor below 1.2. The analysis was done using a finite element method for slope stability and finite element analysis for groundwater seepage for groundwater modeling. The results show that the safety factor of the slope showing a linearly decreasing trend and safety factor reached below 1.2 when 70 m increment in groundwater level from the original groundwater level model.

Boundary element method for wave trapping by a multi-layered trapezoidal breakwater near a sloping rigid wall

This study examines the multiple layers in a rubble mound breakwater and their effect on reflection and dissipation of incoming ocean waves. The numerical model is developed using multi-domain boundary element method for oblique water wave trapping near a sloping wall by a multi-layered trapezoidal porous structure, which is utilized to model armour, filter and core layers while examining the hydrodynamics in different configurations. Both, the constant element and linear element approaches to boundary element method are discussed. The cases of bottom-standing porous structures as being submerged and fully extended are considered. The wave hydrodynamics over the structure is described by the reflection and dissipation coefficients along with the forces acting on the sloping wall, and is influenced by wave and structural parametrics of the system. The influence of armour layer in different configurations is highlighted for various structural and wave parameters.

Effects of Sublevel Open Stope Underground Mining on Surface and Open Pit Slopes

Underground mining is an economically viable option for exploiting ore reserves deemed uneconomic after open pit mining. However, underground development can have adverse effects on the above existing open pit slope walls. As a goal of this paper, identification and assessment of potential slope instabilities prior to underground development is crucial for safe and sustainable mining. Towards goal achieving, this paper gives a comprehensive parametric study to investigate the influence of sublevel open stope (SLOS) underground mining on the surface and open pit slope walls. By means of numerical simulation, the SLOS design is tried against the existing open pit followed by adjustments of important slope parameters which are overall slope height (OSH) and overall slope angle (OSA). We found that underground mining may induce slope failure, particularly on the hangingwall side of the pit. Subsidence is prominent on the hanging wall and the surface, whereas, the uplift dominates the footwall and pit bottom. Pit wall closure is observed during underground mining. Although the assigned dimensions in the parametric study show a negligible effect of OSH and OSA, the high OSH experience low subsidence in comparison with low OSH. Overall, the results demonstrate that the slope walls on the hanging wall side are mostly affected by the underground mining and high-stress concentration prevails near slope toes and pit bottom. Additionally, slope deformation decrease from pit bottom towards the slope crest and surface. The results of this study add knowledge to open pit and underground mining interaction.

Macrofaunal diversity and community structure of the DeSoto Canyon and adjacent slope

Northern Gulf of Mexico canyons are centers of organic matter accumulation and biodiversity, but studies of their finer-scale (sub-100 km) ecological patterns are scarce. Detailed sampling of macrofauna within the DeSoto Canyon was undertaken along 3 depth transects on the canyon wall, axis, and adjacent slope. Sediment, terrain, and water mass parameters were also compiled for the same stations. Within the canyon, macrofaunal abundance decreased, evenness increased, and richness followed the expected parabolic curve with depth, peaking at 1100 m. Cluster analysis identified 3 canyon depth groups that conformed to established bathymetric boundaries for the non-canyon Gulf of Mexico slope: Group I at <500 m, Group II at 669-1834 m, and Group III at >2000 m. Explanatory environmental models indicate that canyon community structure was strongly correlated with oxygen concentration and fluorescence, with a weaker potential influence from any of salinity, particulate organic carbon, sediment organic carbon, or slope. Comparisons of the habitats indicated that abundances were highest on the canyon wall. Slope community structure differed from that of either of the canyon habitats. Environmental models consisted of single variables including oxygen concentration, sediment organic carbon, slope, and temperature with similar explanatory values. Community differences within the canyon and between the canyon and adjoining slope contradict previous findings of a single faunal zone for the whole study area. Factors that may contribute to inter-habitat heterogeneity include potential hydrocarbon seepage, organically enriched sediment deposits along channels, or remnant influence from the Deepwater Horizon spill, warranting more research into this dynamic ecosystem.

Динамика восстановления нарушенных земель горнодобывающей отрасли в соответствии с принципом самоорганизации природных систем и ее прогнозирование по спутниковым данным

Environmental issues associated with the development of mineral deposits are largely caused by the need to store mining and processing waste which becomes a source of environmental pollution. Large areas of dumped ore processing wastes determine the expediency of applying satellite data to monitor the environmental condition of the disturbed lands in order to make justified decisions on restoring the integrity of natural landscapes, which is crucial for the Arctic regions. The purpose of the research is to use the satellite data as the basis to reveal the dynamics of plant formation on the surrounding natural terrain when implementing the technology developed in the Mining Institute of the Kola Scientific Center of the Russian Academy of Sciences in accordance with the self-organizing principle of natural systems in the framework of the rock-biota system evolution. This is achieved by introducing a gramineous plant community without creating a fertile layer, which creates a biologically active environment. Analysis of the vegetation index obtained from a time series of the satellite data that characterizes the introduced vegetational change of the gramineous plant community on the bund wall slopes at the Khibiny group of apatite-containing ore deposits demonstrates the determinant influence of phytocoenotic factors on the recovery dynamics of natural ecosystems. A geobotanical study of the monitoring site has shown that in transition from the introduced gramineous to the forest stage of vegetational change, we observe a tier structure and large-scale resettlement of species from the adjacent natural areas, which is consistent with an increase in the vegetation index and allows to predict the dynamics of the natural ecosystem recovery.

COAST GEOMORPHOSYSTEMS OF THE RIGHT BANK OF THE VOTKINSK RESERVOIR

Methods and results of field studies of the complex of coastal processes on the right Bank of the Votkinsk reservoir are presented. They include observations of the rate of destruction and retreat of the walls of landslide-scree slopes, cut by abrasion, and processes that develop on the emerging shallows. For the first time, the processes of slow mass displacement of material entering the shallows due to the destruction of the banks were established and quantified within the shallow coastal waters. The main morphological types of coastal geomorphosystems are identified and the rates of re-formation are determined for their surface and underwater parts. It is noted that the most productive processes in relation to the flow of loose material into the reservoir bowl are the processes of shedding. Accordingly, weathering, as a source of loose material formation, acquires the importance of the most important shore-forming factor in the surface part of coastal geomorphosystems in the reservoir conditions. Among the most important lithodynamic flows of underwater sections of the coastal zone, the underwater "creep" is singled out. It was found that the layer of loose sediment lining the bench with a layer of 20-25 cm by the beginning of ice formation completely slides in the drying zone at a distance of 15-20 meters by the beginning of spring water discharge. Mass displacement of fine-grained earth occurs in the summer, but the slid material is actively replenished with abrasive products in the summer. Banks are destroyed by parallel retreat of the underwater and surface parts of the coast. At present, the rate of coastal destruction often increases rather than decreases, which makes it necessary to review some theoretical provisions concerning the laws of coastal development and forecast estimates. The results obtained can be used to estimate the rate of siltation of the reservoir basin.

What lithic clasts and lithic-rich facies can tell us about diatreme processes: An example at Round Butte, Hopi Buttes volcanic field, Navajo Nation, Arizona

Round Butte (Hopi Buttes volcanic field, Arizona) exposes a diatreme 170–190 m across, 190 m below the pre-eruptive surface. The central part of the massif is 130–150 m in diameter, displaying 20–30 m-high subvertical cliffs. The well-known layer-cake stratigraphy of the sedimentary rocks of the Colorado Plateau permits identification of the largest lithic fragments preserved in the Round Butte diatreme. We define three main groups of pyroclastic facies: undisturbed beds, disturbed beds and non-bedded rocks. Two other minor facies groups were mapped: megablocks (blocks over 2 m in long axis), and small-volume debris avalanche deposits. Pyroclastic megablocks are finer grained and richer in lithic clasts than most diatreme rocks surrounding them. These pyroclastic megablocks are interpreted as subsided portions of the maar ejecta ring. Sedimentary megablocks originate either from above, or from the same level, relative to their current location, i.e. no megablock has a net upward displacement. Small-volume debris avalanche deposits are poorly sorted deposits resulting from gravitational destabilization of the surrounding country rocks into the syn-eruptive crater. Small-volume debris avalanches and individual megablock collapse are the main ways in which the crater grew in size laterally during the eruption.We combine the componentry of the disturbed bedded pyroclastic facies, the non-bedded pyroclastic facies and the pyroclastic megablocks with a series of conceptual models for country rock fragmentation. This exercise further allows us to estimate diatreme wall slopes of 70° below the Bidahochi Formation to approximately the depth of the root zone around 440 m below the pre-eruptive surface. Lithic fragments at the current level of exposure come from elevations up to 190 m above (i.e., up to the pre-eruptive surface) and up to 250 m below (i.e., down to the root zone) their current locations. Pyroclastic units displaying the richest content of lithic clasts with a deep origin are typically the non-bedded facies interpreted to have formed from debris jets during the eruption.

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

Abstract 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%.

Evaluation of geometrical parameters affecting on the optimal slope design of Shadan Gold-Copper Open Pit Mine

The main objective of this research is to present a stable and optimal design of the ultimate slope of the eastern wall of Shadan Gold-Copper open pit mine based on the calculation of minimum factor of safety (1.20) by numerical modeling method under different conditions of slope geometry. Numerical modeling was performed using finite difference method (FDM) and FLAC3D software which is capable of calculating the factor of safety (FOS) by shear strength reduction method. Therefore, a set of 3D numerical models in different scenarios were investigated by varying the geometrical properties of the pit slope (width, height and face angle of bench, pit depth and overall slope angle). Based on the analysis carried out during the different scenarios, finally the fifth scenario with minimum safety factor of 1.20 was introduced as the proposed pattern. According to the initial design (first scenario) with a safety factor of 1.39, in the fifth scenario by decreasing the benches width from 6.8 m to 5 m and increasing their height from 10 m to 12 m which increases the slope angle of the bench face (from 70 degrees to 73 degrees) and overall slope angle (from 43 degrees to 52 degrees), safety factor of the ultimate slope was reduced to a minimum of 1.20. The maximum impact of the change in the safety factor is related to shear strain and horizontal displacement in the model such that the maximum shear strain (1.12 e-2 m) and the maximum horizontal displacement (-25.75 cm) are related to the fifth scenario with minimum safety factor (1.20). Whereas, the maximum vertical displacement (29.63 cm) is related to the first scenario model (FOS = 1.39) with the maximum slope height (pit height) of about 219 m, which shows the least influence on the value of the safety factor.

Ensuring Wall Stability in the Course of Blasting at Open Pits of Kyzyl Kum Region

Involvement of deep deposits in mining predetermined the trend of development of open pit mining towards increasing the depth of open pits. The main limitation imposed on drilling and blasting in the near-contour zone of an open pit is the need to protect the pit walls and engineering structures on the walls from seismic effects of huge blasts. As practice shows, the most effective and proven method of protecting pit walls is the use of blasting by presplitting method, creation of a shielding gap and a shielding layer of blasted rock mass, i.e. pre-splitting of the pit walls, preceding the huge blast. Therefore, the study of stress-strain state of the near-contour rock mass, determination of the parameters of blastholes for edge pre-splitting (preliminary shielding gap formation) in open pits is an urgent task. The analysis of the pit wall design and stress-strain state of rock mass at Kokpatas deposit exploited by Navoi Mining and Metallurgical Combine allowed to determine the model, as well as the method for calculating stress-strain state of the rock mass. When assessing stability of the pit walls, an approach known as the displacement method was used. Applying the boundary integral equations method allowed to develop an algorithm for calculating stresses in the rock mass for the conditions of Kokpatas deposit. A technique has been developed for experimental studies of blasting contour blasthole charges (blasting by pre-splitting method) using models, allowing to study fracturing on volumetric models and wave interaction by the method of high-speed video recording of the blasting process in transparent models, as well as to determine the parameters of stress waves during blasting in samples of real rocks. A method for formation of stable pit wall slopes, an excavator method for bench pre-splitting on ultimate envelope (contour) of a pit, and a method for initiating blasthole charges in the near contour zone of a pit have been developed and implemented in the industry.

Optimisation of the Half-Skip Total Focusing Method (HSTFM) parameters for sizing surface-breaking cracks

The Half-Skip Total Focusing Method (HSTFM) is an ultrasonic array post-processing (imaging) technique. The method allows surface-breaking cracks (SBCs) to be imaged and also sized using 6 dB drop rule. The HSTFM has previously been used to size SBCs initiating from flat and horizontal walls. However, there has been limited research to optimise the method in a rigours manner and quantitatively determine the performance of the HSTFM to size cracks accurately. In this paper, the SBCs characterization capability of the HSTFM was tested and applied on both numerically simulated and experimentally generated data. Under numerical simulation, considering the travel time of ultrasonic signals as per the ray theory, first, a mathematical framework was developed for the HSTFM imaging algorithm. Then, a quantitative parametric study, using the finite element method and point reflector model, was performed to evaluate the sizing capability of the HSTFM under different scenarios. These scenarios include the position of the ultrasonic array relative to the crack, the accuracy of the acoustic velocity, the height of the sample, the slope of the back wall, and the tilting angle of the defect. For each of the array configuration, the crack-sizing range (the smallest and largest Through Wall Extent (TWE) of a crack) that can be measured using the HSTFM was calculated. Thereafter, experimental validation was performed, where an excellent match with the numerical results was observed.

Evaluation of valley topography effects on the seismic stability of earth-rockfill dams via a modified valley topography coefficient

This paper presents the impact of valley topography on the stability of an earth-rockfill dam slope during earthquakes. The valley site is simplified as an ideal trapezium. A series of three-dimensional numerical models with different valley floor widths and valley wall slopes are used to represent different geometries of the valley topography. A modified dimensionless valley topography coefficient ς is proposed to describe the shape characteristics of the valley topography quantitatively. Considering the most commonly used parameter, the length-height ratio of the dam (L/H), ς replaces L with the length of the median line, Lm, and introduces a shape index, S, as a correction factor on the basis of Lm/H. Comparing to L/H, data from previous studies indicate that ς has a better correlation with the increment ratio of FoS3D to FoS2D. The shear strength reduction technique and the pseudo-static approach are adopted to calculate the factor of safety and the associated critical slip surface of the dam slopes. The results show that the valley topography plays a positive role in the seismic stability of the dam in the cases investigated in this study, especially for narrow valleys and that the valley topography effect will decrease with increasing earthquake intensity.

Studying ore field structure and rock properties of the Delken deposit to substantiate the optimal pit walls design

Introduction. In order to determine a key design parameter substantiated by technical-economic and geomechanical analyses, the critical angle of slope of the nonmining wall in Delken deposit pit which depends on the properties and the state of rock building up the wall and its structures, and in order to determine the forms and the elements of mineral occurrence, the authors carried out comprehensive research consisting of the of deposit’s geological and structural features determination, including endogeneous and exogeneous jointing, and the detailed examination of physical and mechanical properties of rock and ore. Research aim is to study geological-structural properties of the deposit in order to analyze and substantiate the optimal and safe structure of pit walls when developing ore at the Delken gold deposit. Methodology. The structural features of Vodorazdelny ground were determined by carrying out the comparative analysis of geological sections and maps, structural description of core and building the scheme of rock blocking according to the level of destruction during deposit opencast. Physical and mechanical properties of rock were determined in laboratory conditions. Numerical analysis of wall stability was fulfilled with modern software. Results. The comprehensive research consisting of the analysis of mining and geological conditions of development, deposit’s geological and structural features determination, detailed examination of the properties of rock building up the slopes of the quarry have made it possible to substantiate the rational design of pit walls when developing ore reserves of the deposit. Summary. The results of the research carried out at the deposit may be applied when substantiating the safest technology of uncovering the deposit and the safest mining sequence.

Flame acceleration in a narrow channel with flow compressibility and diverging or converging walls

We study the effects of non-parallel (diverging or converging) channel walls on flame propagation and acceleration in planar and cylindrical narrow channels, closed at the ignition end and open at the other, accounting for thermal expansion in both the zero Mach number and weakly compressible flow limits. For parallel channel walls, previous work has shown that thermal expansion induces an axial flow in the channel, which can significantly increase the propagation speed and acceleration of the flame. In this study, we consider examples of diverging/converging linear walls, although our asymptotic analysis is also valid for curved walls. The slope of the channel walls is chosen so that the magnitude of the thermal-expansion induced flow through the channel obtained for parallel walls is modified at leading-order, thereby influencing the leading-order flame propagation. For zero Mach number flows, the effect of the diverging/converging channel walls is moderate. However, for weakly compressible flows, the non-parallel walls directly affect the rate at which pressure diffuses through the channel, significantly inhibiting flame acceleration for diverging walls, whereas the flame acceleration process is enhanced for converging walls. We consider several values of the compressibility factor and channel wall slopes. We also show that the effect of a cylindrical channel geometry can act to significantly enhance flame acceleration relative to planar channels. The study reveals several new physical insights on how non-parallel channel walls can influence the ability of flames to accelerate by modifying the flow and pressure distribution induced by thermal expansion.

Influence of geometry on the thermal performance of water pit seasonal heat storages for solar district heating

The aim of the study is to investigate the influence of geometry on the thermal capacity and stratifications of a water pit heat storage for solar district heating. A TRNSYS component model for a truncated cone water pit was developed based on the coordinate transformation method and validated by experimental results from the water pit heat storage in Huangdicheng in 2018. The thermal performance of 26 water pits with different heights and side wall slopes was calculated for 10 consecutive years. It takes four to six years for the water pit to reach steady-state operation. The operation data from the tenth year was selected to evaluate the thermal performance of each configuration. The results show that because of the thermal insulation on top of the water pit, the height to diameter ratio of a water pit with minimum annual heat loss was always smaller than 1.0. The annual storage efficiency of a water pit increases with side wall slope due to the reduced side wall area. There is an almost linear increase in the thermal stratification number of a water pit with height. With an increase in the height, thermal stratification in water pits with a steeper slope increased more gradually than water pits with a lower slope. The findings in this paper are relevant for the design optimization of water pits as seasonal thermal energy storages.

Intracrater Sediment Trapping and Transport in Arabia Terra, Mars

AbstractCraters are the most prevalent basins and potential depocenters of sediment on Mars. Within these craters and extending from them, terminal dune fields and wind streaks are abundant, indicating active sediment transport and providing a way to study how wind and sediment interact with crater topography. Here we explore the role of craters as both sources and sinks in the modern Martian sedimentary cycle. Our results show that craters with low albedo wind streaks (indicative of sediment transport out of a crater and downwind dust removal) have lower crater wall slopes (9.4° ± 5.5°) compared to craters without wind streaks (17° ± 5.8°). We interpret that crater wall slopes play a dominant role in whether sediment is transported out of a crater basin and infer, from measurements of craters on Mars, that a crater transitions from being a net sediment sink to a net sediment source when crater wall slopes decrease to ~15°. This threshold value is consistent with limits of bedform climb observed on Earth and elsewhere on Mars.

Sediment infilling and geomorphological change of a mud-capped Raccoon Island dredge pit near Ship Shoal of Louisiana shelf

To restore degraded barrier shorelines of the Mississippi River Delta of coastal Louisiana, sand is dredged from high-quality borrow areas on the adjacent continental shelf. This dredging process generally creates a topographic low that facilitates the rapid capture of sediments. Our understanding of sedimentary processes and influences on seabed morphologic evolution is still limited. In this study, Raccoon Island dredge pit in a paleo-river channel on the Louisiana shelf was studied via multiple bathymetric surveys. Physical parameters include pit geometry and topographic change from post-dredging, and infilling sediment sources were analyzed. Raccoon Island pit was 100% filled up less than six years after dredging. The average infilling rate in the Raccoon Island pit was 1.10 m/year from 2013 to 2018. During the surveying period, the pit wall slope decreased by 6.8° within two years. The sediment infilling process in the Raccoon Island pit was likely under the combined influence of topography, wind-driven currents, storm waves, and the dynamic Atchafalaya River dispersal system. The Atchafalaya River reached high discharge in 2016, which likely contributed to a surprisingly high sediment infilling rate at Raccoon Island pit between 2015 and 2018. Raccoon Island pit is in a mixed texture environment in which the sandy pit was fully filled with mud. Mud is useful for marsh restoration but is not considered a quality resource for barrier island or beach restoration. Thus, the Raccoon Island pit is not regarded as a renewable resource for future barrier island restoration.

Wave Interaction with Single and Twin Vertical and Sloped Slotted Walls

The interaction between waves and slotted vertical walls was experimentally studied in this research to examine the performance of the structure in terms of wave transmission, reflection, and energy dissipation. Single and twin slotted barriers of different slopes and porosities were tested under random wave conditions. A parametric analysis was performed to understand the effect of wall porosity and slope, the number of walls, and the incoming relative wave height and period on the structure performance. The main focus of the study was on wave transmission, which is the main parameter required for coastal engineering applications. The results show that reducing wall porosity from 30% to 10% decreases the wave transmission by a maximum of 35.38% and 38.86% for single and twin walls, respectively, increases the wave reflection up to 47.6%, and increases the energy dissipation by up to 23.7% on average for single walls. For twin-walls, the reduction in wall porosity decreases the wave transmission up to 26.3%, increases the wave reflection up to 40.5%, and the energy dissipation by 13.3%. The addition of a second wall is more efficient in reducing the transmission coefficient than the other wall parameters. The reflection and the energy dissipation coefficients are more affected by the wall porosity than the wall slope or the existence of a second wall. The results show that as the relative wave height increases from 0.1284 to 0.2593, the transmission coefficient decreases by 21.2%, the reflection coefficient decreases by 15.5%, and the energy dissipation coefficient increases by 18.4% on average. Both the transmission and the reflection coefficients increase as the relative wave length increases while the energy dissipation coefficient decreases. The variation in the three coefficients is more significant in deep water than in shallower water.