Roughness Coefficient Research Articles

Fracture surface morphology characterization and its influence on plugging performance of granular lost circulation materials

The irregularity and complexity of formation fracture morphology lead to great uncertainty in lost circulation control. At present, the fracture morphology is simplified to be smooth in the process of fracture plugging investigation, thus the influence of fracture surface morphology on the retention behavior and pressure bearing capacity of granular lost circulation materials (LCMs) remains unknown. To fill this gap, the reverse engineering technology was utilized for investigating the influence of fracture surface morphology on plugging performance. In this study, the three-dimensional (3D) reverse reconstruction and quantitative characterization of fracture surface were realized based on the 3D coordinates of real fracture surfaces, which were obtained through the 3D structured light scanning. A new parameter “particle size matching factor” was established to analysis the retention behavior of LCM particles. A new method for fracture plugging experiments was established based on 3D printing technology, which can obtain the structure of the sealing zone in fracture with real morphology. The results show that the irregularity of the real fracture surface leads to the local shrinkage of the flow channels, while provide support force to LCMs, which has an important influence on the plugging performance of LCMs. The larger the “particle size matching factor”, the easier to form retention in fractures. With the increase of Joint Roughness Coefficient (JRC) and fractal dimension, the pressure bearing capacity of the sealing zone is significantly improved. The research results are helpful to more accurately realize the plugging mechanism of granular LCMs, which contributes to improve efficiency of lost circulation control.

Impact of Beam Deflection Geometry on the Surface Architecture and Mechanical Properties of Electron-Beam-Modified TC4 Titanium Alloy.

This paper aims to investigate the impact of beam deflection geometry on the structure, surface architecture, and friction coefficient of electron-beam-modified TC4 titanium alloys. During the experiments, the electron beam was deflected in the form of different scanning geometries, namely linear, circular, and matrix. The structure of the treated specimens was investigated in terms of their phase composition by employing X-ray diffraction experiments. The microstructure was studied by scanning electron microscopy (SEM). The surface architecture was examined by atomic force microscopy (AFM). The friction coefficient was studied by a mechanical wear test. It was found that the linear and circular deflection geometries lead to a transformation of the phase composition, from double-phase α + β to α' martensitic structure. The application of a linear manner of scanning leads to a residual amount of beta phase. The use of a matrix does not tend to structural changes on the surface of the TC4 alloy. In the case of linear geometry, the thickness of the modified zone is more than 800 μm while, in the case of EBSM using circular scanning, the thickness is about 160 μm. The electron-beam surface modification leads to a decrease in the surface roughness to about 27 nm in EBSM with linear deflection geometry and 31 nm in circular deflection geometry, compared to that of the pure TC4 substrate (about 160 nm). The electron-beam surface modification of the TC4 alloy leads to a decrease in the coefficient of friction (COF), with the lowest COF values obtained in the case of linear deflection geometry (0.32). The results obtained in this study show that beam deflection geometry has a significant effect on the surface roughness and friction coefficient of the treated surfaces. It was found that the application of a linear manner of scanning leads to the formation of a surface with the lowest roughness and friction coefficient.

Can the splitting joint reproduce the characteristics of the natural joint in the lab? —A comparison study based on the roughness analysis and shear test

Splitting joints have been widely used to study the morphology characteristic and shear behavior of rock joints in the laboratory. There are some differences between the splitting joint and natural joint both in morphology characteristic and shear behavior. To quantitatively compare the differences, the present study used several splitting joints and natural joints to carry out the roughness analysis and direct shear test. Six profiles were extracted from each joint surface with a 30° interval to calculate the 2D roughness parameters (i.e., amplitude roughness parameter, average asperity inclination, root-mean-square of profile slope, and joint roughness coefficient). These parameters of the natural joints have a wide range and have obvious fluctuation. On the contrary, these parameters of the splitting red sandstone joints converge on a small range with tiny fluctuation, even calculated from different joint surfaces. The directional parameter (θ⁎max(C + 1)) was adopted to calculate the 3D roughness with a 5° interval. The directional parameter of the natural joints in range of 0° ∼ 360° forms a peanut, a prolate ellipse, or a gourd shape, presenting significant anisotropy. For the splitting joints, it forms a circle or a roughly circular shape, presenting insignificant anisotropy. The asperity heights of natural joints mainly present an irregular distribution, and they present an approximately normal distribution in few joints. For the splitting joints, the asperity heights generally obey a normal distribution. It indicates that there are huge differences between natural joint and splitting joint in morphology characteristic. To study the shear behavior, two types of joint were reconstructed for repeated test. The mechanical performance and failure characteristic of the splitting joint under different shear directions are similar. On the contrary, those of the natural joints under different shear directions are different, presenting obvious anisotropy. Based on the comparative analysis of the natural joints and the sandstone splitting joints in the present study, there is substantial difference between two types of joints both in morphology characteristic and shear behavior. The splitting joints cannot reproduce the characteristics of the natural joints well.

Dynamic Mechanical Behavior of Rock Specimens with Varying Joint Roughness and Inclination under Impact Load

The influence of joint roughness and inclination on the dynamic mechanical properties of rocks is a prominent research area. In order to investigate the effects of joint roughness and inclination on the dynamic mechanical properties of jointed rocks, impact tests were conducted using a spilt Hopkinson pressure bar (SHPB) apparatus for prefabricated serrated joint cement mortar specimens with varying joint roughness and inclination. The failure mode, stress wave propagation characteristics, peak stress, and stress wave energy transfer law under impact load were analyzed. The results indicate that both joint inclinations and joint roughness coefficients (JRC) have a strong influence on the failure mode, peak stress, and stress wave energy transfer of jointed specimens. The jointed specimens exhibit three distinct failure modes under impact load, namely splitting tensile failure, shear slip failure, and compound failure of splitting tensile and shear. The peak stress initially decreases then increases with the increase in joint inclination angle, namely a V-shape variation, while it gradually increases with JRC increasing from 0 to 20. Jointed specimens exhibit the lowest peak stress at an inclination angle of 45° and JRC of 0. The variation of transmitted energy coefficient is similar to the peak stress, while the variation of reflected energy coefficient is opposite to the peak stress. At joint inclination angles of 0° or 90°, the reflected energy coefficient increases with the increase of JRC from 0 to 20, while the transmitted energy decreases. However, when the joint inclination angle is in the range of 30° to 60°, the reflected energy coefficient gradually decreases with JRC increasing, while the transmitted energy coefficient gradually increases.

Effect of temperature on pure mode Ⅲ fracture behavior and fracture morphology of granite after thermal shock

To investigate the effect of temperature on the pure mode III fracture behavior and fracture morphology of granite after thermal shock, edge-notched disc bend granite specimens are selected for heat treatment and a series of fracture tests. Firstly, the effect of temperature on the macroscopic fracture behavior of the rock is analyzed regarding the physical and mechanical properties and fracture toughness. Then, the impact of temperature on the microscopic fracture morphology of the rocks is discussed based on a fractal theory using 3D laser scanning techniques. The results show that temperature affects the fracture behavior of rock by changing its physical parameters and mechanical properties. High temperatures can change the fracture mode of rocks and have a softening effect on rocks. The heat treatment temperature of 325 °C above can convert rocks from brittle to ductile failure. When the heat treatment temperature is above 525 °C can evolve rocks from pure mode III fracture to mixed mode I/III fracture. The fracture toughness of the rock and the joint roughness coefficient are highly linearly correlated with temperature. The fracture toughness of the rock decreases by 0.5 MPa∙m0.5, and the joint roughness coefficient increases by 1.7 for every 100 °C increase in temperature in the range of 25 °C to 625 °C. The asperity height and slope angle of the rock obey a normal distribution. The higher the temperature, the larger the fracture surface area, the larger the fractal dimension, the stronger the anisotropy of the surface protrusions, and the rougher the rock surface.

Research and Application of the Calculation Method of River Roughness Coefficient with Vegetation

The roughness coefficient is a comprehensive parameter reflecting river resistance, which is widely used in the planning and design of river regulation and flood control projects. In recent years, as the upstream water conservancy and hydro-power projects have been put into operation, the frequency of low flow in the middle and lower reaches has increased, and the frequency of flood flow has decreased. All kinds of vegetation in the river floodplain grow luxuriantly, which causes a change in the river resistance and roughness coefficient. The present study was carried out with theoretical analysis and laboratory tests. A formula for the roughness coefficient calculation was derived based on the momentum equilibrium equation and momentum exchange between the vegetation layer and upper layer. The relationship between the depth-averaged velocity within the vegetation layer and depth-averaged velocity of the whole flow was analyzed. The reliability of the formula was verified by a large amount of previous experimental data. Based on the derived formula, the variation law of the roughness coefficient with vegetation density, vegetation height, and water depth were obtained. For the emerged vegetation flow, the Manning coefficient tended to increase with the increase in the vegetation density and water depth. For the submerged vegetation flow, the Manning coefficient showed a trend of decreasing with the increase in the water depth and increased with the increase in the vegetation height. Finally, the derived formula was applied in the Yueyang reach of the Yangtze River and the Duliujian River. The study can be applied in the fields of water level-flow discharge relationship analysis and the water surface line calculation of vegetated rivers.

A wellbore-fracture coupled fracturing model to simulate non-uniform fracture propagation under multiple clusters of fracturing

Multiple clusters of fracturing within one stage have been widely used in the unconventional reservoir production. However, the non-uniform fracture propagation under multiple clusters of fracturing has not yet fully been understood, due to the fluid flow in the wellbore being neglected in the fracturing model. In view of this, a wellbore-fracture coupled fracturing model was established to simulate fracture non-uniform propagation under multiple clusters of fracturing. In this model, the governing equation was firstly given based on the pressure continuity and flow conservation, to obtain the flow distribution in each fracture. Then, equations of fracture propagation, fracture height growth and stress shadow were combined to determine the fracture geometric parameters. Substituting fracture geometric parameters into the governing equation, the wellbore-fracture coupled fracturing model was finally solved. The proposed model was validated by a ABAQUS cohesive elements numerical by comparing the fracture parameters, respectively considering conditions of wellbore-fracture coupling and non-wellbore-fracture coupling, within a maximum deviation that did not exceed 6.14%. Using the proposed model, the parametric analyses were performed, including energy-related parameters and wellbore-related parameters. For energy-related parameters, with the increase of surface energy density of rock and the minimum principal stress, the fracture length and height decreased, while the fracture width increased to some extent. In addition, with the increase of pumping rate of fracturing fluid, the fracture length, height and width increased significantly. For wellbore-related parameters, with the decrease of diameter of perforation and perforation number as well as the increase of wellbore roughness coefficient and viscosity of fracturing fluid and cluster distance, the flow distribution in each fracture and the injection pressure became more uniform and the non-uniform propagation of each fracture was reduced, but fracture dimensions were simultaneously decreased.

Hydraulic Planning in Insular Urban Territories: The Case of Madeira Island—Ribeira Brava, Tabua

This study’s primary goal was to conduct an analysis of the flood propensity of the Tabua (Ribeira Brava) drainage basin’s main watercourse. In addition to that, this study also recommends two different methodologies in order to mitigate flood impacts, namely by dimensioning a detention basin and adjusting the riverbed roughness coefficient. Regarding the study on the flood propensity, it was necessary to resort to geomorphological data, which were obtained when characterizing the watershed; these data were crucial to determining the expected peak flow rate, according to the Gumbel distribution methodology and considering a 100-year return period, and to perform necessary tasks in the SIG ArcGIS 10.5 software. Lastly, the drainage capacity of this drainage basin’s river mouth was also analyzed in order to conclude whether it would have the capacity to drain the total volume of rainwater if an extreme flood event were to happen. Indeed, the main results show that this watershed’s river mouth does not have the necessary drainage capacity to cope with an extreme event for the return period that was considered. As a consequence, the two aforementioned mitigation measures were developed considering the Tabua (Ribeira Brava) drainage basin’s specific features. The size of the detention basin was estimated through the Dutch method and the simplified triangular hydrograph method, while the adjustment of the roughness coefficient was considered a valid solution to enhance the drainage capacity of this river mouth.

Exploring the capabilities of portable device photogrammetry for 3D surface roughness evaluation

ABSTRACT The feasibility of using a portable photogrammetric device to digitalise rock surface roughness is investigated. Structured light 3D scanner, terrestrial LiDAR scanner, and portable photogrammetry device are used to scan precast different roughness lab-scale specimens. The reconstructed 3D surface is evaluated for accuracy using point cloud distance, joint roughness coefficient, and 3D roughness parameters. Results show that the portable device can reconstruct a 3D model comparable in accuracy to a structured light 3D scanner in 15 minutes. The proposed method is applied to laboratory-scale model reconstruction, with the potential to scan rock surfaces efficiently and economically in a mine.

Library of rough hailstone backscattering coefficients at 2.8 GHz

The rough hailstone scattering library is created to fill the need for results of non-spheroidal hailstone backscattering characteristics. The listed backscattering coefficients at the S-band (2.8 GHZ) are specifically tailored for computing the polarimetric variables. The National Weather Service’s radar operates in this band; hence the library is pertinent to those studying hail in the USA. The library contains several axis ratios and a range of hail sizes from 5 mm to 100 mm. Moreover, hailstone surface roughness is expressed as a percentage of the equatorial diameter. Our computational electromagnetic approach to modeling hailstones is compared with typically employed simpler methods. The polarimetric variables calculated using our models can be compared to observations. Furthermore, we illustrate the potency of the CEM approach to hydrometeors with extreme axis ratios for which simpler methods (i.e., the T-matrix) fail.

Morphological classification method and data-driven estimation of the joint roughness coefficient by consideration of two-order asperity

Abstract The roughness of the joint surface plays a significant role in evaluating the shear strength of rock. The waviness (first-order) and unevenness (second-order) of natural joints have different effects on the characterization of joint surface roughness. To accurately quantify the influence of the two-order asperity on the joint roughness coefficient (JRC) prediction of joint surface profile curve, the optimal sampling interval of the asperity was determined through the change of the R p {R}_{{\rm{p}}} value of the joint surface profile curve. The separation of the two-order asperity of 48 joint surface profile curves was completed at the optimal sampling interval, and morphological parameters of the asperity such as i ave {i}_{{\rm{ave}}} , R max {R}_{{\rm{\max }}} , and R p {R}_{{\rm{p}}} were counted from three aspects: asperity angle of the profile curve, asperity degree, and the trace length. Based on the statistical results of the morphological parameters considering the two-order asperity, the new nonlinear prediction models were proposed. The results showed that the curve slope mutation point SI = 2 mm is the optimal separation distance of the two-order asperity of the joint surface profile curve. The refined separation method that considers the waviness and unevenness of morphological parameters can characterize the detailed morphological features of the joint surface in more dimensions. The support vector regression (SVR) and random forest (RF) models that take into account a two-order asperity separated results have higher accuracy than traditional models. The prediction accuracy has improved by 7–8% in SVR model compared with SVR(SO) and RF(SO). The SVR nonlinear model that considering separation of two-orders of joint surface roughness is more suitable for the prediction of JRC.

Geometric transformation of finite element methods: Theory and applications

We present a new analysis of finite element methods for partial differential equations over curved domains. In many applications, a change of variables translates a physical Poisson problem over a curved physical domain into a parametric Poisson problem over a polytopal parametric domain. Whilst this change of variables greatly simplifies the geometry and numerical implementations, the coordinate transformation typically features only low regularity. In the parametric Poisson problem, this manifests as rough coefficients and data, which diminish the elliptic regularity, and as roughness of the parametric solution. Our main result addresses how to nevertheless recover high-order finite element convergence rates, the key component being a recently developed broken Bramble-Hilbert lemma. This analysis has numerous applications, where the geometric transformation is either computable or merely a theoretical tool. We propose a simplified technique as easier, more broadly applicable, yet just as powerful as previous isoparametric methods. In particular, we reassess the error analysis of isoparametric finite element methods and prove high-order error estimates for isoparametric FEM even when the physical solution is not continuous. Numerical examples confirm our theoretical predictions.

Development of a computer program from photogrammetry for assisting Q-system rating

A computer program to assist the Q-system rating of jointed rock mass is herein developed based on the photogrammetric analysis of point clouds. Three major rating terms, namely, rock quality designation (RQD), joint set number (Jn), and joint roughness number (Jr), are evaluated using predefined algorithms in the computer program without the input of an engineering expert. The random sample consensus algorithm is adopted to identify major outcrop joint surfaces. Thereafter, the major joint surface is determined to calculate the weighted joint density (wJd) and its corresponding RQD. In addition, a spherical K-means clustering is utilized to obtain the number of dominant joint sets and further convert it to the Jn value. Moreover, the a/L method is adopted to calculate the joint roughness coefficient (JRC) of those facets and convert it to Jr. The analysis results agree with manual Q-system rating results, revealing that the proposed computer program is practicable. Furthermore, we evaluate the limitation of the proposed computer program as applied to interlayered sedimentary rocks. Finally, we found that doubling the standard deviation of the distance between fitted facets to the point cloud is a reasonable estimate of the JRC20 and Jr of rock joints.

Hydraulic Response and Overtopping Performance of Single-Layer Double Cube Unit Armored Mound Breakwater

A newly developed friction-interlocking armor unit called the ‘Double cube’ (DC) was designed to improve the performance of a concrete armor unit used in river/marine structures against currents/waves actions. The DC unit is an octagonal-shaped block made up of two parts: an upper cube set on a lower base that is either square or octagonal in shape. The innovative design aims to provide good performance in terms of stability, to allow for high tolerance placement with various contact points, and to allow for ease of placement. The DC’s shape and placement enhance the unit’s stability by bringing the center of gravity closer to the underlayer and by providing a large contact surface with the surrounding blocks that reduces the chance of extraction and limits movements (rocking, lifting) via the “keystone” effect. The characteristics of this new unit provide a relatively high hydraulic stability number for the armor layer (NS = 2.9), a favorable hydraulic performance due to energy dissipation from turbulence and aeration, as well as a high roughness coefficient (γf ≈ 0.46), helping to reduce overtopping.

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.

Fatigue life analysis of offshore wind turbine tower under combined action of wind and wave

In order to obtain the fatigue life of an 8 MW offshore wind turbine tower, the fatigue damage characteristics of tower under combined action of wind and wave were analyzed. The calculation method of fatigue damage degree of the tower under different working conditions in unit cycle time is given. Based on the linear extension theory of fatigue damage, the annual fatigue damage degree of the tower under different working conditions was calculated, and the fatigue life of the tower was obtained. The calculation results show that the fatigue life of the tower is 31.2 years when the ideal S-N curve is adopted, which is longer than the design life of 25 years. The influences of average stress, roughness and structure size on S-N curve are analyzed. When Goodman method is selected for average stress correction, roughness coefficient is 0.473, and dimension correction coefficient is 0.639, the fatigue life of the tower is 26.7 years, decreasing by 14%. The fatigue life of the tower under different roughness is calculated. The calculated results show that the fatigue life of the tower decreases with the decrease of the roughness coefficient. When the roughness coefficient is 0.287, the fatigue life of the tower is about 25 years.

Study on the characterization of differential weathering feature based on surface roughness theory and 3D laser scanning: A case study of the Suoyang Ancient City

Earthen heritage sites have been undergoing lengthy surface weathering since they were built, which can pose a severe threat to the protection and utilization of these cultural treasures. Especially for differential weathering, one of the most common surface weathering patterns of earthen heritage sites in northwestern China, has not been well studied yet. Hence, in this paper, Suoyang Ancient City was selected as the study area, and six analysis domains (S1 to S6) exhibiting various differential weathering degrees were determined on wall faces and their morphological data were collected by a 3D laser scanner. Based on the point cloud data, the morphology of each domain was digitalized and reconstructed, and ten typical profiles were selected for roughness analysis. Concretely, for these profiles, six roughness parameters, including average asperity inclination (Ai), mean curvature (R′da), textural slope parameter (Z2), roughness coefficient (Rp), self-affine fractal dimensions (A and D) and directional roughness metric (G(i)) were calculated to characterize their differential weathering features. The results show that the wall with a higher differential weathering degree has greater values of Rp, G(i), A and D. It can also be found that different roughness indicators can reflect different wall surface morphological characteristics. In addition, the main driver of differential weathering developing is the prevailing sediment-laden wind, and the degree of differential weathering is also affected by the building techniques, wall endowment environment, wall orientation and morphology. Finally, according to the roughness values and wall surface morphology, the differential weathering degrees were classified into five grades (from level I to level V). In this case, the differential weathering degrees of S2 (level IV) and S5 (level IV) are the highest, followed by S3 (level III), S6 (level III), S1 (level II) and S4 (level II) respectively. Overall, the proposed approach based on 3D scanning and surface roughness is feasible to characterize the differential weathering degree, contributing to better prevention and mitigation of damage on earthen heritage sites.

Error estimates for a finite volume scheme for advection–diffusion equations with rough coefficients

We study the implicit upwind finite volume scheme for numerically approximating the advection–diffusion equation with a vector field in the low regularity DiPerna–Lions setting. That is, we are concerned with advecting velocity fields that are spatially Sobolev regular and data that are merely integrable. We prove that on unstructured regular meshes the rate of convergence of approximate solutions generated by the upwind scheme towards the unique solution of the continuous model is at least one. The numerical error is estimated in terms of logarithmic Kantorovich–Rubinstein distances and provides a bound on the rate of weak convergence.

Numerical Modeling of Rock Blocks with Nonpersistent Rough Joints Subjected to Uniaxial Compressive and Shear Loadings

Characterizing the mechanical behavior of jointed rocks is important to understand the behavior of structures in rock masses. Jointed rocks can be composed of persistent and nonpersistent joints where the impact of nonpersistent joints requires careful consideration for an accurate rock mass mechanical characterization. Most previous investigations into nonpersistent jointed rocks focused on joints with smooth surfaces, and a few experimental studies focused on nonpersistent rough joints and nothing specific has been reported numerically. Therefore, this study investigated several synthetic jointed rocks with nonpersistent rough joints numerically under uniaxial compressive and shear loadings. The PFC2D-based synthetic rock mass (SRM) approach was adopted to assess the impact of bridge angle (γ) and length (L), joint roughness coefficient (JRC), and normal stress (σn) on the shear strength (τn) and cracking in jointed rocks with nonpersistent rough joints. In addition, the impacts of γ, L, JRC, and joint inclination (θ) on the uniaxial compressive strength (UCS or σcm), elastic modulus (Em), and failure pattern in the jointed blocks were examined numerically. First, several numerical models were developed and verified by the laboratory data, followed by an extensive parametric study to assess the effects of the defined parameters further. The effects of JRC and σn on τn were more pronounced than γ and L due to the formation of interlocking cracks, which could cause significant shear resistance during shear loading. In addition, the numerical results under axial loading revealed that an increase in θ could reduce the deformation modulus and the value of the other parameters, in particular the JRC, could lead to an increase in the strength of jointed samples.

Biofilm analyses and exoproduct release by clinical and environmental isolates of Burkholderia pseudomallei from Brazil

Objective: To characterize biofilm production by clinical (n=21) and environmental (n=11) isolates of Burkholderia pseudomallei and evaluate the production of proteases, hemolysins and siderophores. Methods: Initially, the 32 strains were evaluated for biofilm production in Müller-Hinton broth-1% glucose (MH-1% glucose) and BHI broth-1% glucose, using the crystal violet staining technique. Subsequently, growing (48 h) and mature (72 h) biofilms were evaluated by confocal microscopy. Finally, the production of proteases, hemolysins and siderophores by planktonic aggregates, growing biofilms and mature biofilms was evaluated. Results: All isolates produced biofilms, but clinical isolates had significantly higher biomass in both MH-1% glucose (P<0.001) and BHI-glucose 1% (P=0.005). The structural analyses by confocal microscopy showed thick biofilms, composed of multiple layers of cells, homogeneously arranged, with mature biofilms of clinical isolates presenting higher biomass (P=0.019) and thickness of the entire area (P=0.029), and lower roughness coefficient (P=0.007) than those of environmental isolates. Protease production by growing biofilms was significantly greater than that of planktonic (P<0.001) and mature biofilms (P<0.001). Hemolysin release by planktonic aggregates was higher than that of biofilms (P<0.001). Regarding siderophores, mature biofilms presented higher production than growing biofilms (P<0.001) and planktonic aggregates (P<0.001). Conclusions: Clinical isolates have higher production of biofilms than their environmental counterparts; protease and siderophores seem important for growth and maintenance of Burkholderia pseudomallei biofilms.