Effect of Elevated Temperatures on Mechanical Performance of Normal and Lightweight Concretes Reinforced with Carbon Nanotubes

An experimental program was developed to evaluate the effect of multi-walled carbon nanotubes (MWCNTs) inclusion on elevated temperature properties of normal weight concrete (NWC) and lightweight concrete (LWC). The mechanical performance was assessed by conducting material property tests namely compressive strength (f’_c,_T), tensile strength (f’_t,T), mass loss (M_T), elastic modulus (E_T), compressive toughness (T_c) and stress–strain response under unstressed and residual conditions in the range of 23°C to 800°C. The mechanical properties were measured by heating 100?×?200 mm cylindrical specimens to 200°C, 400°C, 600°C and 800°C at a heating rate of 5°C/min. Results show that the inclusion MWCNTs in cementitious matrices enhanced the fire endurance. The relative retention of mechanical strength and mass of concretes modified with MWCNTs was higher. The stress–strain response of specimens modified with MWCNTs was more ductile. Microstructural study of cyrofractured samples evidenced the homogenous dispersion of nano-reinforcements in host matrix. Furthermore, the data obtained from high temperature material property tests was utilized to develop mathematical relationships for expressing mechanical properties of modified mixes as a function of temperature.     

An investigation on the mechanisms of instabilities and safe design of the south slope at a lignite pit (SW Turkey) based on a sensitivity approach

Turkey has significant lignite reserves which are generally being extracted using open pit mining methods. The Hüsamlar pit is one of the operated lignite pits in the well-known Mugla lignite province in SW Turkey. Some local failures and one large failure, which caused the evacuation of the Hüsamlar village located next to the slope crest and interruption in coal production, occurred along the south slope of this pit. This paper outlines the results of the field and laboratory geotechnical investigations associated with the causes and mechanisms of the instabilities, and assessments on the possible modifications in the current and planned final slope geometries to improve the stability of the south slope. Since no sufficient data on groundwater conditions in the pit were available, in order to reduce the uncertainty associated with groundwater, different pore pressure ratios (r _u) were considered and a sensitivity approach was used in the stability assessments. The back-analyses of the observed instabilities including one or more benches in the overburden indicated that the most critical modes of failure for the south slope are circular and composite sliding surfaces. Although kinematical analyses suggested that structurally controlled failures would not be expected, one local planar failure that occurred in the south slope emphasizes that the possibility of local planar sliding should be considered when the dip of bedding planes locally exceed 20° and pore pressure becomes high. In addition, the back-analyses revealed that r _u was probably between 0.3 and 0.4 and the residual shear strength along the bedding planes was critical when slope instabilities occurred along the south slope. The stability assessments for the current and the final south slope, which was planned by the mining organization operating the pit, indicated that some modifications in bench and slope geometries are necessary to achieve a factor of safety of 1.3, which is a commonly used value in open pit practice. In addition, these assessments also suggested that the most critical zone in the overburden was the thinly bedded marl in terms of stability, and at the thickest part of this material (30 m), the overall slope angles satisfying F = 1.3 at r _u values of 0.2, 0.3 and 0.4 should be 18°, 17° and 15°, respectively. Except those in the thinly bedded marl, bench widths in the overburden units and coal seam are reduced and steeper slopes with F ≥ 1.3 were achieved.     

Investigation of correlations between shear wave velocities and CPT data: a case study at Eskisehir in Turkey

Seismic waves result from fault movement during earthquakes. Depending on the features of the physical environment through which they pass, there are variations in the velocity and amplitude of body waves, which occur underground, and surface waves, which occur on the Earth’s surface. The ratio of shear wave velocity (V _s) to near-surface velocity is a parameter used widely in land use planning to predict the potential for amplified seismic shaking, especially in urban areas. The main objective of this study was to estimate V _s by using cone resistance (q _c) and lateral friction (f _s) for a study area at Eskisehir Graben, to help mitigate geotechnical earthquake engineering problems in civil engineering and land use planning. In geotechnical shallow soil research, certain geophysical methods are used for measuring V _s —a major form of seismic energy propagation—at the near surface. In this study, cone penetrometer data collected from seismic cone penetration tests (SCPT) includes q _c, f _s, and downhole V _s. S-type seismic energy waveforms, which are produced on the surface, were measured at different depths using an S-type geophone in the city center of Eskisehir via SCPT. With SCPT, q _c, friction ratios (R _f), and V _s values were measured at 42 different test points. R _f properties are associated with soil thickness, and these were compared with dynamic soil properties (V _s) using a standard statistical method; we calculated correlations amongst V _s, q _c, and R _f measured from cone penetration tests.     

Strength and failure characteristics of jointed marble under true triaxial compression

The rock structure and three-dimensional stress state play a vital role in the mechanical behaviour of rock masses. Here, a series of true triaxial compression tests (σ₁ > σ₂ > σ₃) are conducted on jointed marble (50 × 50 × 100 mm³) containing a natural stiff joint, taken from the China Jinping Underground Laboratory (CJPL-II) project. The purposes of this study are to investigate the joint effect and estimate the stress dependency of jointed marble. The test results show that jointed marble can fail in four distinct forms, namely, splitting or shearing of intact marble, opening of the joint or sliding along the joint, and these failure modes are influenced by the joint configuration and the minimum and intermediate principal stresses. Generally, jointed marble has more brittle post-peak behaviour than intact marble. The linear Mogi-Coulomb failure criterion can be modified to describe the strength of the jointed marble under true triaxial compression. The jointed marble strength is more sensitive to the minimum principal stress than to the intermediate principal stress. A maximum decline of 25% in strength is observed, which corresponds to a joint dip angle of 60° at σ₂ = 60 MPa and σ₃ = 30 MPa. The link between the experimental results and in situ fracturing at CJPL-II is also demonstrated.

     

The ultrasonic P-wave velocity-stress relationship of rocks and its application

When a rock sample is extracted from an underground rock mass, it is subject to unloading, which will cause changes in the physical and mechanical properties. This article describes a laboratory experiment to determine the change of P-wave velocity of rock samples during a uniaxial compression test. It was found that the P-wave velocity vs. stress curves (V-S curves) of the rock samples could reflect three stages of bulk volume deformation commonly observed in a uniaxial compression test of rocks. When the applied stress was less than σ _c (about 0.25–0.33 of the uniaxial compressive strength), the P-wave velocities increased rapidly with the increase of stress; this part of the V-S curves could be fitted with a power function. When the stress was greater than σ _c, the P-wave velocities of rock samples increased more slowly and gradually approached the peak before decreasing dramatically near failure; the V-S curves above σ _c could be fitted with a polynomial function of the second degree. During the V-S experiment, it could be also observed that the increasing rate of P-wave velocity decreased dramatically when the applied stress reached the overburden stress. An unloading index was defined as the ratio of the P-wave velocity under in situ overburden stress to the P-wave velocity at free stress and could be calculated from the measured V-S curves. Based on the calculated unloading index, the calculation of the intactness index of rock mass could be modified, and then an improvement of the basic quality (BQ) classification method of rock masses, which is used widely in China, was made.     

A Method to Assess the Accuracy of Pseudo-Random Number Sampling Methods from Evacuation Datasets

We propose a method for assessing the accuracy of pseudo-random number sampling methods for evacuation modelling purposes. It consists of a systematic comparison between experimental and generated distributions. The calculated weighted relative error (E _{w_rel} ) is based on the statistical parameters as central moments (mean, standard deviation, skewness and kurtosis) to shape the distribution. The case study involves the Box–Muller transform, the Kernel-Epanechnikov, the Kernel-Gaussian and the Piecewise linear generating samples from eight evacuation datasets fitted against normal, lognormal and uniform distributions. Keeping in mind that the Bos Muller method has two potential sources of error (i.e. distribution fitting and sampling), this method produces plausible results when generating samples from the three types of distributions (E _{w_rel}  < 0.30 for normal, lognormal and uniform distributions). We also fund that the Kernel Gaussian and the Kernel Epanechnikov methods are well accurate in generating samples from normal distributions (E _{w_rel}  < 0.1) but potentially inaccurate when generating samples from uniform and lognormal distributions (E _{w_rel}  > 0.80). Results suggest that the Piecewise linear is the most accurate method (E _{w_rel}  = 0.01 normal; E _{w_rel}  = 0.04 lognormal; E _{w_rel}  = 0.009 uniform). This method has the advantage of sampling directly from empirical datasets i.e. no previous distribution fitting is needed. While the proposed method is used here for evacuation modelling, it can be extended to other fire safety engineering applications.     

Occupants’ interactions with windows in 8 residential apartments in Beijing and Nanjing,China

Occupants’ interactions with windows influence both building energy consumption and exposure to airborne pollutants indoors. Occupants’ window opening behavior varies from region to region due to physical environmental factors and social reasons. China is now confronting severe atmospheric pollution, which may affect occupants’ window opening behaviors. A field study was conducted in 8 naturally ventilated residential apartments in Beijing and Nanjing, China. This involved periodically monitoring window states of eight residential apartments within each season from October 2013 to December 2014 by magnetic induction devices (TJHY, CKJM-1). Relationships between the probability of window opening (p) and explanatory variables, including outdoor air temperature (t _o), outdoor relative humidity (RH), outdoor wind speed (V _s), and ambient PM2.5 (particles with aerodynamic diameter less than 2.5 microns) concentrations (C _p), were analyzed. Stochastic models of occupants’ interactions with windows in monitored residences were established via univariate and multivariate linear logistic regression for both cities. According to the results, t _o is the most important explanatory variable affecting occupants’ interactions with windows in monitored residences. The best multivariate linear logistic model result from the “backward selection” procedure based on “Akaike Information Criterion” (AIC) includes t _o, RH, V _s and C _p as explanatory variables, which implied that outdoor air quality, represented by C _p, has become a concern affecting Chinese residents’ interactions with windows.     

Utilizing the strength conversion factor in the estimation of uniaxial compressive strength from the point load index

The strength conversion factor (k) is the ratio between the uniaxial compressive strength (UCS) and the point load index (PLI). It has been used to estimate the UCS from the PLI since the 1960s. Many researchers have investigated the relationship between UCS and PLI for various rock types of different geological origins, such as igneous, sedimentary, and metamorphic rocks. In this study, the k values for subclasses of igneous (pyroclastic, volcanic, and plutonic), sedimentary (chemical and clastic), and metamorphic (foliated and nonfoliated) rocks were evaluated. For this purpose, UCS and PLI data for a total of 410 rock samples extracted from literature published around the world as well as UCS and PLI data obtained in this work for 80 rock samples taken from the Eastern Black Sea Region in Turkey were evaluated together to determine the k values of different rock classes. Strength conversion factors were obtained using zero-intercept regression analysis, formulation, and a graphical approach. This study confirmed that there is no single k value that is applicable to all rock classes. According to statistical analyses, k varied between 12.98 and 18.55 for the rocks studied. These findings demonstrate that the k values derived in this work can be reliably used to estimate the strengths of rock samples with specific lithologies.     

Variation of total toxicity of cationic SAS solutions in ozonization,UV radiation,and O<Subscript>3</Subscript>/UV treatment

Variation of total toxicity of cationic SAS (surface-active substance) solutions in ozonization, UV radiation, and O₃/UV treatment was evaluated by the change of bioluminescence intensity of the bacteria Vibrio fisheri B 7070 or Photobacterium phosphoreum B 7071 and chemiluminescence intensity in a reaction of luminole with H₂O₂ caused by exometabolites Daphnia magna. It has been shown that the least toxicity is characteristic of reaction blends after O₂/UV treatment of cationic SAS solutions.     

Classification and assessment of rock mass parameters in Choghart iron mine using P-wave velocity

Engineering rock mass classification,based on empirical relations between rock mass parameters and engineering applications,is commonly used in rock engineering and forms the basis for designing rock structures.The basic data required may be obtained from visual observation and laboratory or field tests.However,owing to the discontinuous and variable nature of rock masses,it is difficult for rock engineers to directly obtain the specific design parameters needed.As an alternative,the use of geophysical methods in geomechanics such as seismography may largely address this problem.In this study,25 seismic profiles with the total length of 543 m have been scanned to determine the geomechanical properties of the rock mass in blocks Ⅰ,Ⅲ and Ⅳ-2 of the Choghart iron mine.Moreover,rock joint measurements and sampling for laboratory tests were conducted.The results show that the rock mass rating(RMR) and Q values have a close relation with P-wave velocity parameters,including P-wave velocity in field(V_(PF)).P-wave velocity in the laboratory(V_(PL)) and the ratio of V_(PF) V_(PL)(i.e.K_p = V_(PF)/V_(PL).However,Q value,totally,has greater correlation coefficient and less error than the RMR,In addition,rock mass parameters including rock quality designation(RQD),uniaxial compressive strength(UCS),joint roughness coefficient(JRC) and Schmidt number(RN) show close relationship with P-wave velocity.An equation based on these parameters was obtained to estimate the P-wave velocity in the rock mass with a correlation coefficient of 91%.The velocities in two orthogonal directions and the results of joint study show that the wave velocity anisotropy in rock mass may be used as an efficient tool to assess the strong and weak directions in rock mass.     

含节理大理岩变形和强度特性的试验研究

 锦屏二级水电站处于高地应力区域,引水隧洞开挖后岩体变形和稳定问题十分突出。从辅助洞取样制备含节理试件,采用MTS815.03岩石三轴试验机,开展了含天然节理大理岩试件的常规三轴压缩试验。试验中,节理面与最大主应力夹角θ为29.3°～56.0°,围压为5～40 MPa。通过试验结果分析,主要得到如下结论：(1) 试件共有两类破坏形式：穿切节理面破坏和沿节理面滑移。试件破坏形式主要取决于节理面与最大主应力夹角大小。在试验围压范围内,围压高低对试件破坏形式没有影响。(2) 试件变形特征取决于节理面与最大主应力夹角的大小,并受围压高低影响。(3) 试件轴向变形曲线均具有较好的线性段,但其轴向等效弹性模量均显著低于完整岩石弹性模量。(4) 试件强度首先取决于θ的大小,θ＞40.0°的试件破坏强度与完整岩石相当;θ＜40.0°的试件破坏强度较完整岩石有显著降低,不同节理强度差异是导致不同试件破坏强度差异的主要原因。     

Numerical simulation of a jointed rock block mechanical behavior adjacent to an underground excavation and comparison with physical model test results

Mechanical behavior of a jointed rock mass with non-persistent joints located adjacent to a free surface on the wall of an excavation was simulated under without and with support stress on the free surface using approximately 0.5 m cubical synthetic jointed rock blocks having 9 non-persistent joints of length 0.5 m, width 0.1 m and a certain orientation arranged in an en echelon and a symmetrical pattern using PFC^3D software package. The joint orientation was changed from one block to another to study the effect of joint orientation on strength, deformability and failure modes of the jointed blocks. First the micro-mechanical parameters of the PFC^3D model were calibrated using the macro mechanical properties of the synthetic intact standard cylindrical specimens and macro mechanical properties of a limited number of physical experiments performed on synthetic jointed rock blocks of approximately 0.5 m cubes. Under no support stress, the synthetic jointed rock blocks exhibited the same three failure modes: (a) intact rock failure, (b) step-path failure and (c) planar failure under both physical experiments and numerical simulations for different orientations. The jointed blocks which failed under intact rock failure mode and planar or step-path failure mode produced high and low jointed block strengths, respectively. Three phases of convergence of free surface were discovered. The joint orientation and support stress played important roles on convergence magnitude. The average increment of jointed block strength turned out to be about 10, 7.9 and 6.6 times the support stress when support stresses of 0.06 MPa, 0.20 MPa and 0.40 MPa were applied, respectively. The modeling results offer some guideline in support design for underground excavations.     

Effects of inner sleeves on the inner frictional resistance of open-ended piles driven into sand

In open-ended piles, inner friction is developed between inner pile shaft and the inner soil. Inner frictional resistance depends largely on the degree of soil plugging, which is influenced by many factors including pile diameter, relative density and end conditions of piles. In this paper, effects of inner sleeves on inner frictional resistance are discussed. The experiments were conducted on a medium-dense sandy ground using laboratory-scale piles. It was observed that the piles penetrated under partially-plugged or unplugged state. The results suggest that inner frictional resistance, Q_in increases with sleeve height, l linearly and requires 2D (D is pile outer diameter) of l to produce a large as 50% of Q_t by Q_in (Q_t is total resistance). The results also indicate that bearing capacity increases with wall thickness at the pile tip, which can be attributed to the increase in annular area. The results also indicate that soil plug height is independent of sleeve height. The results also reveal that the penetration of straight piles is closer to unplugged state than the sleeved piles. The results of incremental filling ratio and plug length ratio also indicate that the degree of soil plugging is affected by the sleeve height.     

The internal force relationship of rectangular and I-section for bi-linear hardening material with limit strain

Based on bilinear stress-strain constitutive law σ = f (ε), the elastic to fully plastic analysis of bending of rectangular-section and bi-symmetrical I-section beams with the influence of axial load is presented for hardening material with limit strain. The variation of the applied bending moment with the axial force for the fully elastic, elastic-plastic, and fully plastic conditions is given in analytical form. The Internal force relationship of the elastic limit is the same for both hardening and non-hardening material and independent of the geometry of the beam section. However, for the elastic-plastic and plastic limits, the relationships are dependent of the hardening parameter β _q, limit strain ε _lim and the geometry of the beam section for neutral axis (N.A) inside the cross section. When N.A outside the cross section, the relationships are dependent of hardening parameter β _q and limit strain ε _lim but independent of the geometry of the beam section. The results given by the analytical expressions reduce to the ones for non-hardening material are in good agreement with the existing results.     

Effects of geometry on the sound field in atria

The atria in commercial buildings are widespread. However, the sound environment has not been given sufficient consideration. Geometry affects the acoustics in the atria. The concept of geometry in this paper includes five parameters, namely, length (l), height (h), aspect ratio of length to width (l/w), skylight form and slope, to provide suggestions for the acoustic environment design in atria. A series of computer models are simulated to analyse the effects of the form parameters on the acoustic environment, such as sound pressure level (SPL) and reverberation time (T₃₀ in this paper). The results indicate that with an increase in the length or height, the values of the average SPL decrease, and the trends of the curves are logarithmic. For an increasing length, the T₃₀ increases first sharply and then slowly. With the scattering increasing, the increment of the T₃₀ is smaller. For an increasing height, the changes of T₃₀ are determined by the absorption and scattering. In terms of the aspect ratio of l/w increasing for a given volume and area, the average SPL values approximately decrease linearly; furthermore, the T₃₀ decreases unless the atrium is extremely high. The T₃₀ is the longest for a flat skylight compared to that of other forms, and it is shorter when the skylight has a slope, including either a single or a double-pitch skylight. It can decrease nearly by 40% when the angle of the lean-to skylight is 7°. The T₃₀ is lower and the amount of decrease is considerably smaller for an increasing slope. When the absorption is evenly distributed in the atria, the skylight has minimal effect on the average SPL or T₃₀ values. Additionally, the classical formula can approximately calculate the SPL distribution unless the atrium is in a form of long space. The Arau-Purchades formula is generally appropriate to predict T₃₀ with uneven absorption distributions unless the absorption or scattering coefficient is low.     

Stability analysis of stratified rock slopes with spatially variable strength parameters: the case of Qianjiangping landslide

Jurassic strata prone to slope failure are widely distributed in the Three Gorges Reservoir region. The limit equilibrium method is generally used to analyze the stability of rock slopes that have a single failure plane. However, the stability of a stratified rock mass cannot be accurately estimated by this method because different bedding planes have variable shear strength parameters. A modified limit equilibrium method is presented with variable water pressure and shear strength used to estimate the stability coefficient of a sloping mass of stratified rock and to identify the potential sliding surface. Furthermore, an S-curve model is used to define the spatial variations of the shear strength parameters c and ? of the bedding plane and the tensile strength of the rock mass. This model can also describe the variation of strength parameters with distance from the slope surface, which depends on the reservoir water level. Also, it is used to evaluate the stability of the Qianjiangping landslide, located at Shazhenxi Town, Zigui County, Three Gorges Reservoir area, China. The results show the most probable sliding surface is the interface between a slightly weathered layer and subjacent bedrock. When reservoir water rises above the elevation of the slide mass toe, the stability coefficient of the slope declines sharply. When the reservoir water level is static at 135 m, the stability coefficient decreases gradually as the phreatic line changes as a result of heavy rainfall.     

Numerical Studies on Thermally-Induced Air Flow in Sloping Tunnels with Experimental Scale Modelling Justifications

Study of smoke movement or air flow due to fire in sloping tunnels is important in designing smoke control systems. In contrast to a horizontal tunnel, there is an acceleration along the longitudinal axis due to smoke buoyancy. This phenomenon together with thermal radiation would lead to a complicated heat transfer mechanism of the ceiling jet in sloping tunnels. In the present work, thermally induced air flow arising from fire in sloping tunnels was studied via numerical simulations using the Computational Fluid Dynamics code FLUENT. Prior to the application of FLUENT in simulating the air flow under different conditions, scale model experiments were carried out and the results were compared with simulation results, to establish the reliability of FLUENT in simulating fires in sloping tunnels. For this purpose, a tunnel section model of length 3 m, width 0.8 m and height 1 m was constructed, with a 1.5 kW electrical heating source to model fire. Hot air movement pattern driven by the electric heater was studied with the tunnel inclined at 0°, 10°, 20° and 30° to the horizontal. Four cases of the same configuration as the scale tunnel experiments were simulated using FLUENT, with predicted results agreeing well with experimental results. Having established the suitability of FLUENT in simulating air flow due to fire in sloping tunnels, numerical simulations were carried out to study air flow in sloping tunnels with different scenarios, that is, for tunnels with different gradients and with fire located at different positions in the tunnel. Macroscopic number on heat transfer, including the Rayleigh number Ra, the average and local Nusselt number Nu_ave for sloping tunnels were also studied from the measured results. The correlation between Nu_ave and Ra, which shows the effect of hydrodynamic properties on relative dominance of heat transfer in tunnel fire, was also discussed.     

Influence of degree of interlock on confined strength of jointed hard rock masses

The strength of jointed rock mass is strongly controlled by the degree of interlock between its constituent rock blocks. The degree of interlock constrains the kinematic freedom of individual rock blocks to rotate and slide along the block forming joints. The Hoek–Brown (HB) failure criterion and the geological strength index (GSI) were developed based on experiences from mine slopes and tunneling projects in moderately to poorly interlocked jointed rock masses. It has since then been demonstrated that the approach to estimate the HB strength parameters based on the GSI strength scaling equations (called the ‘GSI strength equations’) tends to underestimate the confined peak strength of highly interlocked jointed rock masses (i.e. GSI > 65), where the rock mass is often non-persistently jointed, and the intact rock blocks are strong and brittle. The estimation of the confined strength of such rock masses is relevant when designing mine pillars and abutments at great depths, where the confining pressure is high enough to prevent block rotation and free sliding on block boundaries. In this article, a grain-based distinct element modeling approach is used to simulate jointed rock masses of various degrees of interlock and to investigate the influences of block shape, joint persistence and joint surface condition on the confined peak strengths. The focus is on non-persistently jointed and blocky (persistently jointed) rock masses, consisting of hard and homogeneous rock blocks devoid of any strength degrading defects such as veins. The results from this investigation confirm that the GSI strength equations underestimate the confined strength of highly interlocked and non-persistently jointed rock masses. Moreover, the GSI strength equations are found to be valid to estimate the confined strength of persistently jointed rock masses with smooth and non-dilatant joint surfaces.     

Simulation of excavations in jointed rock masses using a practical equivalent continuum approach

A simple practical equivalent continuum numerical model previously presented by Sitharam et al. (Int. J. Rock Mech. Min. Sci. 38 (2001) 437) for simulating the behaviour of jointed rock mass has been incorporated in the commercial finite difference programme fast Lagrangian analysis of continua (FLAC). This model estimates the properties of jointed rock mass from the properties of intact rock and a joint factor (J_f), which is the integration of the properties of joints to take care of the effects of frequency, orientation and strength of joint. A FISH function has been written in FLAC specially for modelling jointed rocks. This paper verifies the validity of this model for three different field case studies, namely two large power station caverns, one in Japan and the other in Himalayas and Kiirunavara mine in Sweden. Sequential excavation was simulated in the analysis by assigning null model available in FLAC to the excavated rock mass in each stage. The settlement and failure observations reported from field studies for these different cases were compared with the predicted observations from the numerical analysis in this study. The results of numerical modelling applied to these different cases are systematically analysed to investigate the efficiency of the numerical model in estimating the deformations and stress distribution around the excavations. Results indicated that the model is capable of predicting the settlements and failure observations made in field fairly well. Results from this study confirmed the effectiveness of the practical equivalent continuum approach and the joint factor model used together for solving various problems involving excavations in jointed rocks.     

Erosion resistance and scouring depth of fine-grained seabed of the Huanghe River estuary,China

Numerical calculation is an effective method to predict the scouring depth of fine-grained sediments. However, as many soil properties affect sediment erodibility, numerically simulated parameters, such as critical erosion stress τ _c , may result in wrong prediction. To understand the erosion resistance and scouring depth of fine-grained seabed in the Huanghe (Yellow) River estuary, China, the authors calculated the critical erosion stress τ _c of the bottom sediments using regression equations that correlated physical properties to critical shear stress of silty fine-grained sediment of the research area and predicted the scouring depth of the study area using different available formulae. The results indicate that τ _c ranges from 0.48 to 1.74 Pa. Comparisons show that the results calculated from the empirical formula proposed by Kandiah are close to the measured data, and choosing the right parameters of sediment in the formula decides the accuracy of the scouring depth calculation. With the Kandiah τ _c value, the seabed scouring amplitudes in wave action periods of 5, 10, 25 and 50 years were simulated. The calculated results of scouring depth are between 0 and 0.23 m and the corresponding scouring center was predicted to be in the region of depths between 5 and 9 m. Meanwhile, the scouring center was found to be highly correlated with wave breaking and sediment properties.