Rainfall-triggered waste dump instability analysis based on surface 3D deformation in physical model test

Landslide is the second largest natural disaster after earthquake. It is of significance to study the evolution laws and failure mechanism of landslides based on its surface 3D deformation information. Based on the rainfall-triggered waste dump instability model test, we studied the failure mechanisms of the waste dump by integrating surface deformation and internal slope stress and proposed novel parameters for identifying landslide stability. We developed a noncontact measurement device, which can obtain millimeter-level 3D deformation data for surface scene in physical model test;Then we developed the similar materials and established a test model for a waste dump. Based on the failure characteristics of slope surface, internal stress of slope body and displacement contours during the whole process, we divided the slope instability process in model test into four stages: rainfall infiltration and surface erosion, shallow sliding, deep sliding, and overall instability. Based on the obtained surface deformation data, we calculated the volume change during slope instability process and compared it with the point displacement on slope surface. The results showed that the volume change can not only reflect the slow-ultra acceleration process of slope failure, but also fully reflect the above four stages and reduce the fluctuations caused by random factors. Finally, this paper proposed two stability identification parameters: the volume change rate above the slip surface and the relative velocity of volume change rate. According to the calculation of these two parameters in model test, they can be used for study the deformation and failure mechanism of slope stability.

Physical model test and numerical simulation on the failure mechanism of the roadway in layered soft rocks

To explore the failure mechanism of roadway in layered soft rocks,a physical model with the physically finite elemental slab assemblage(PFESA)method was established.Infrared thermography and a video camera were employed to capture thermal responses and deformation.The model results showed that layered soft roadway suffered from large deformation.A three-dimensional distinct element code(3 DEC)model with tetrahedral blocks was built to capture the characteristics of roadway deformation,stress,and cracks.The results showed two failure patterns,layer bending fracture and layer slipping after excavation.The layer bending fracture occurred at positions where the normal direction of layers pointed to the inside of the roadway and the layer slipping occurred in the ribs.Six schemes were proposed to investigate the effects of layered soft rocks.The results showed that the deformation of ribs was obviously larger than that of the roof and floor when the roadway passed through three types of strata.When the roadway was completely in a coal seam,the change of deformation in ribs was not obvious,while the deformation in the roof and floor increased obviously.These results can provide guidance for excavation and support design of roadways in layered soft rocks.

Physical model investigation on effects of drainage condition and cement addition on consolidation behavior of tailings slurry within backfilled stopes

Estimation of stressses within the tailings slurry during self-weight consolidation is a critical issue for cost-effective barricade design and efficient backfill planning in underground mine stopes.This process requires a good understanding of self-weight consolidation behaviors of the tailings slurry within practical stopes,where many factors can have significant effects on the consolidation,including drainage condition and cement addition.In this paper,the prepared tailings slurry with different cement contents(0,4.76wt%,and 6.25wt%)was poured into1.2 m-high columns,which allowed three drainage scenarios(undrained,partial lateral drainage near the bottom part,and full lateral drainage boundaries)to investigate the effects of drainage condition and cement addition on the consolidation behavior of the tailings slurry.The consolidation behavior was analyzed in terms of pore water pressure(PWP),settlement,volume of drainage water,and residual water content.The results indicate that increasing the length of the drainage boundary or cement content aids in PWP dissipation.In addition,constructing an efficient drainage boundary was more favorable to PWP dissipation than increasing cement addition.The final stable PWP on the column floor was not sensitive to cement addition.The final settlement of uncemented tailings slurry was independent of drainage conditions,and that of cemented tailings slurry decreased with the increase in cement addition.Notably,more pore water can drain out from the cemented tailings slurry than the uncemented tailings slurry during consolidation.

Hydrodynamic Performance of a Newly-Designed Pelagic and Demersal Trawls Using Physical Modeling and Analytical Methods for Cameroonian Industrial Fisheries

This study proposed the newly-designed Pelagic and demersal trawls for the fishing vessels operating in Cameroonian waters in pelagic and demersal fishing grounds. The engineering performances of both trawls were investigated using physical modelling method and analytical method based on the predicted equations. In a flume tank, a series of physical model tests based on Tauti’s law were performed to investigate the hydrodynamic and geometrical performances of both trawls and to assess the applicability of the analytical methods based on predicted equations. The results showed that in model scale, the working towing speed and door spread for the pelagic trawl were 3.5 knots and 1.85 m, respectively, and for the bottom trawl net they were 4.0 knots and 1.8 m. At that speed and door spread, the drag force, net opening height, and wing-end spread of the pelagic model trawl were 36.73 N, 0.89 m, and 0.86 m, respectively, and the swept area was 0.76 m2. Bottom trawl speed and door spread were 30.43 N, 0.38 m, and 0.45 m, respectively, and the swept area was 0.25 m2. The maximum difference between the experimental and analytical results of hydrodynamic performances was less than 56.22% and 41.45%, respectively, for pelagic and bottom trawls, the results of the geometrical performances obtained using predicted equations were close to the experimental results in the flume tank with a maximum relative error less than 12.85%. The newly developed pelagic and bottom trawls had advanced engineering performance for high catch efficiency and selectivity and could be used in commercial fishing operations in Cameroonian waters.

Model test of the influence of cyclic water level fluctuations on a landslide

Many landslides in reservoir areas continuously deform under cyclic water level fluctuations due to reservoir operations. In this paper,a landslide model, developed for a typical colluvial landslide in the Three Gorges Reservoir area, is used to study the effect of cyclic water level fluctuations on the landslide. Five cyclic water level fluctuations were implemented in the test, and the fluctuation rate in the last two fluctuations doubled over the first three fluctuations. The pore water pressure and lateral landslide profiles were obtained during the test. A measurement of the landslide soil loss was proposed to quantitatively evaluate the influence of water level fluctuations. The test results show that the first water level rising is most negative to the landslide among the five cycles. The fourth drawdown with a higher drawdown rate caused further large landslide deformation. An increase of the water level drawdown rate is much more unfavorable to the landslide than an increase of the water level rising rate. In addition, the landslide was found to have an adaptive ability to resist subsequent water level fluctuations after undergoing large deformation during a water level fluctuation. The landslide deformation and observations in the field were found to support the test results well.

Separation and Preliminary Identification of Intestinal Probiotics of Laying Hens

[Objective] The paper was to isolate and identify probiotics in the intestine of laying hens. [Method] The intestinal probiotics in laying hens at peak period were isolated using conventional separation methods; the physical and chemical properties of target strains and in vitro antibacterial effects were measured. Moreover, the safety test of chicks was conducted. [Result] Four strains of lactobacillus were isolated from the jejunum of laying hens, including Lactobacillus plantarum, Bacillus acidophilus, L. delbrueckii subsp. Delbrueckii and L. delbrueckii subsp. Lactis, and their inhibition zone diameters were 18.30, 16.07, 11.45, 17.26 mm, respectively. One strain of Lactobacillus, L. brevis, was isolated from the cecum, with the inhibition zone diameter of 10.26 mm. Three strains of bacillus were isolated from the cecum, including Bacillus subtilis, B. cereus and B. licheniformis, and their inhibition zone diameters were 9.25, 8.46 and 8.37 mm, respectively. Daily drinking 2 billion units of viable bacteria was the safe dosage for chicks. [Conclusion] Eight strains of probiotics had certain inhibitory effect on Escherichia coli O;, and had no toxic side effects to chicks. Lactobacillus had strong antibacterial effect on E. coli O;, while the antibacterial effect of bacillus was relatively weak.

Failure mechanism of a large-scale composite deposits caused by the water level increases

The failure of slope caused by variations in water levels on both banks of reservoirs is common.Reservoir landslides greatly threaten the safety of reservoir area.Taking large-scale composite deposits located on the Lancang River in Southwest China as a study case,the origin of the deposits was analyzed based on the field investigation and a multi-material model was established in the physical model test.Combined with numerical simulation,the failure mechanism of the composite deposits during reservoir water level variations was studied.The results indicate that the deformation of the large-scale composite deposits is a staged sliding mode during the impoundment process.The first slip deformation is greatly affected by the buoyancy weight-reducing effect,and the permeability of soil and variation in the water level are the factors controlling slope deformation initiation.The high water sensitivity and low permeability of fine grained soil play an important role in the re-deformation of deposits slope.During the impoundment process,the deformation trend of the deposit slope is decreasing,and vertical consolidation of soil and increasing hydrostatic pressure on the slope surface are the main reasons for deformation attenuation.It is considered that the probability of large-scale sliding of the deposits during the impoundment period is low.But the damage caused by local bank collapse of the deposit slope still needs attention.The results of this paper will further improve our understanding of the failure mechanism of composite deposits caused by water level increases and provide guidance for the construction of hydropower stations.

Strength and deformation characteristics of irregular columnar jointed rock mass: A combined experimental and theoretical study

The irregularity of jointed network poses a challenge to the determination of field mechanical param-eters of columnar jointed rock mass(CJRM),and a reasonable prediction of deformation and strength characteristics of CJRM is important for engineering construction.The Voronoi diagram and three-dimensional printing technology were used to make an irregular columnar jointed mold,and the irregular CJRM(ICJRM)specimens with different dip directions and dip angles were prepared.Uniaxial compression tests were performed,and the anisotropic strength and deformation characteristics of ICJRM were described.The failure modes and mechanisms were revealed in accordance with the final appearances of the ICJRM specimens.Based on the model test results,the empirical correlations for determining the field deformation and strength parameters of CJRM were derived using the dip angle and modified joint factor.The proposed empirical equations were used in the Baihetan Project,and the calculated mechanical parameters were compared with the field test results and those obtained from the tunneling quality index method.Results showed that the deformation parameters determined by the two proposed methods are all consistent with the field test results,and these two methods can also estimate the strength parameters effectively.

Physical model test on the support characteristic for quasi-NPR bolt under asymmetric stress

With the continuous increase in tunnel construction,the significant deformation of the surrounding tunnel rock is often difficult to predict and control.In addition,the lithology,structure,and various asymmetric large deformation of surrounding rock mass during operation and maintenance severely affect the ultimate bearing and stability of the tunnel.To explore the deformation mechanisms and failure modes of surrounding rock under large asymmetric stress and complex geological conditions,a physical model of a tunnel through granite was constructed based on the similarity theory.The model had 30°dip lithology under asymmetric stress and was emplaced a new quasi-negative Poisson’s ratio(NPR)bolt.By analyzing the variation law of displacement and axial force of the bolt under an asymmetric load,the asymmetric deformation and failure mechanism of the granite tunnel and the support effect of the quasi-NPR bolt were determined.The energy absorbed by the surrounding rock was analyzed,and the influence mechanism and control countermeasures of asymmetric stress on the granite tunnel were explored.This work provides a reference for the design of asymmetric support of tunnels with similar engineering backgrounds.

Does Locomotive Syndrome, Associated with Sarcopenia or otherwise, Influence Quality of Life in Individuals Aged over 80 years? Third Wave of the LOCOMOV Project

Introduction:Locomotion is a determinant of intrinsic capacity of older people and can be limited by dysfunction in locomotory organs,characterizing Locomotive Syndrome(LoS).Knowledge on locomotive problems and sarcopenia,and their interface with quality of life,in the oldest old in the literature is scarce.Objective:To evaluate the correlation between LoS and sarcopenia and their influence on quality of life in oldest old.Methods:A cross-sectional study of an observational,descriptive and analytical epidemiological survey in independent older adults aged 80 and over from São Paulo,Brazil and who participated in the third wave of the LOCOMOV Project,was carried out.Sociodemographic data,comorbidities,functioning in activities of daily living,physical functioning,quality of life,and presence of sarcopenia and LoS were assessed.The statistical analyses included the Test-for-Comparing-Two-Proportions,Pearson's Correlation Coefficient,the chi-Square test and Student´s t-test.Results:Thirty oldest old with a mean age of 89.1 years were evaluated.The prevalence of LoS was high(53.3%)and correlated significantly with chronic pain(p-value 0.024),worse performance on the SPPB and Gait speed(p-value<0.001).Sarcopenia was not correlated with LoS,but worse quality of life on the physical domain was significantly associated with LoS(p-value<0.001)regardless of the presence of sarcopenia.Conclusions:LoS was highly prevalent among the oldest old studied and negatively impacted their quality of life,regardless of the presence of sarcopenia.

Study on failure mechanism of room and pillar with different shapes and configurations under uniaxial test and numerical simulation compression using experimental test and numerical simulation

Experimental and discrete element methods were used to investigate the failure behavior of room and pillar with different configura-tions under uniaxial loading.Concrete samples with dimension of 15 cm×15 cm×5 cm were prepared.Within the specimens,rooms and pillars with different configurations were provided.The room dimension was 1 cm×1 cm,and the pillar dimension was according to the room configuration.Twelve different configurations were chosen for rooms and pillars.The axial load was applied to the model by rate of 0.05 mm/min.The results show that the failure process was mostly governed by both the non-persistent joint angle and joint number.The compressive strength of the specimens was related to the fracture pattern and failure mechanism of the pillars.It was shown that the shear behaviour of pillars was related to the number of the induced tensile cracks,which increased by increasing the room angle.The compressive strength of samples increased with the increase of the room angle.The failure pattern and failure strength are similar in both methods,i.e.,the experimental testing and the numerical simulation.

Numerical Analysis on the Effects of Submerged Depth of the Grid and Direction of Incident Wave on Gravity Cage

In this paper, the numerical model of the net cage with the grid mooring system in waves is set up by the lumped mass method and rigid kinematics theory, and then the motion equations of floating system, net system, mooring system, and floaters are solved by the Runge-Kutta fifth-order method. For the verification of the numerical model, a series of physical model tests have been carried out. According to the comparisons between the simulated and experimental results, it can be found that the simulated and experimental results agree well in each condition. Then, the effects of submerged depth of grid and direction of incident wave propagation on hydrodynamic behaviors of the net cage are analyzed. According to the simulated results, it can be found that with the increase of submerged depth of grid, the forces acting on mooring lines and bridle lines increase, while the forces on grid lines decrease; the horizontal motion amplitudes of floating collar decrease obviously, while the vertical motion amplitudes of floating collar change little. When the direction of incident wave propagation changes, forces on mooring lines and motion of net cage also change accordingly. When the propagation direction of incident wave changes from 0° to 45°, forces on the main ropes and bridle ropes increase, while the forces on the grid ropes decrease. With the increasing propagation direction of incident wave, the horizontal amplitude of the forces collar decreases, while the vertical amplitude of the floating collar has little variation.

Numerical Simulation of Dynamic Response of A Net Cage for Flatfish in Waves

A numerical model of flatfish cage is built based on the lumped mass method and the principle of rigid body kinematics. To validate the numerical model, a series of physical model tests are conducted in the wave flume. The numerical results correspond well with the data sets from physical model test. The effect of weight of bottom frame, height of fish net and net shape on motion responses of fish cage and tension force on mooring lines is then analyzed. The results indicate that the vertical displacements of float collar and bottom frame decrease with the increase in the weight of bottom frame; the maximum tension force on mooring lines increases with the increasing weight of bottom frame. The inclination angles of float collar and bottom frame decrease with the increasing net height; the maximum tension force increases obviously with the increase of net height.

Study on Global Performances and Mooring-Induced Damping of A Semi-Submersible

The harsh environmental conditions bring strong nonlinearities to the hydrodynamic performances of the offshore floating platforms, which challenge the reliable prediction of the platform coupled with the mooring system. The present study investigates a typical semi-submersible under both the operational and the survival conditions through numerical and experimental methods. The motion responses, the mooring line tensions, and the wave loads on the longitudinal mid-section are investigated by both the fully non-linearly coupled numerical simulation and the physical experiment. Particularly, in the physical model test, the wave loads distributed on the semi-submersible＇s mid-section were measured by dividing the model into two parts, namely the port and the starboard parts, which were rigidly connected by three six-component force transducers. It is concluded that both the numerical and physical model can have good prediction of the semi-submersible＇s global responses. In addition, an improved numerical approach is proposed for the estimation of the mooting-induced damping, and is validated by both the experimental and the published results. The characteristics of the mooring-induced damping are further summarized in various sea states, including the operational and the survival ~nvironments. In order to obtain the better prediction of the system response in deep water, the mooring-induced damping of the truncated mooring lines applied in the physical experiment are compensated by comparing with those in full length. Furthermore, the upstream taut and the downstream slack mooring lines are classified and investigated to obtain the different mooring line damping performances in the comparative study.

Three-dimensional experimental study of loose top-coal drawing law for longwall top-coal caving mining technology

Based on the loose medium flow field theory, the loose top-coal drawing law of longwall top-coal caving（LTCC） mining technology is studied by using self-developed three-dimensional（3D） test device. The loose top-coal drawing test with shields and the controlled test without shields are performed in the condition without any boundary effect. Test results show that shields will cause reduction in drawing volume of coal in the LTCC mining. The deflection phenomenon of drawing body is also observed in the controlled test, which is verified that the deflection of drawing body is caused by shield. It is found that the deflection angle decreases with increasing caving height, with the maximum value of atailand the minimum value of 0. In addition, the formula to calculate the drawing volume is proposed subsequently.The deflection of drawing body is numerically simulated using particle flow code PFC3 Dand the proposed formula to calculate drawing volume in LTCC is also verified.

Experimental Study on Scouring and Silting Deformation of Artificial Beach Under Storm Surge−Wave Coupling

With the increasing construction of artificial beach in coastal areas, it is of practical significance to study the beach surface deformation of artificial beach profile. Previous studies only focus on a single wave dynamic factor, and it is difficult to predict the beach deformation of artificial beach profile under the storm surge-wave co-action. To solve this problem, the cross-section physical model test method was used to study the beach surface deformation of a typical artificial beach profile in Shuangdao Bay, Weihai, Shandong Province, after continuous wave actions till they stabilize. The characteristics of beach surface deformation under the conditions of constant water levels, laddershaped water level combined with corresponding wave elements and storm surge-wave co-action are compared and analyzed. A beach profile model which satisfies the theory of Bruun model is proposed. The test results show that the maximum scour depth of beach under storm surge-wave co-action is smaller and the scour range is obviously larger than that under the condition of constant water levels or ladder-shaped water level. The evaluation of the maximum scour depth by traditional model test tends to be conservative while the evaluation of the scour range is insufficient.The research results can provide scientific reference for designing artificial beaches.

Analytical and Experimental Studies on Wave Scattering by a Horizontal Perforated Plate at the Still Water Level

This research investigates water-wave scattering via a horizontal perforated plate fixed at the still water level through analytical studies and physical model tests.The velocity potential decomposition method is combined with an efficient iterative algorithm to develop an analytical solution in which the quadratic pressure drop condition is imposed on the horizontal perforated plate.The analytical results are in good agreement with the results of an independently developed iterative boundary element method(BEM)solution.Experimental tests are carried out in a wave flume to measure the reflection coefficient and transmission coefficient of the horizontal perforated plate,and the analytical results agree reasonably well with the experimental data.The influence of various structural parameters of the horizontal perforated plate on the hydrodynamic parameters of reflection coefficient,transmission coefficient,energy-loss coefficient,and wave force are analyzed on the basis of the analytical solution.Useful results for the practical engineering application of horizontal perforated plates are also presented.

Model test and numerical simulation of a new prefabricated double-row piles retaining system in silty clay ground

This paper introduces a new prefabricated recyclable double-row piles retaining system for excavations in silty clay ground.Laboratory model test and numerical simulation are conducted to study the system behavior upon excavation.The horizontal displacement(δ_(h)),Von Mises stress(δ_(M)),strain(ε),ground surface settlement(δ_(v)),and earth pressure are systematically investigated.Furthermore,the monitoring data of 13 excavation cases supported by double-row piles retaining system are presented and discussed.The experimental results can basically match the numerical results,and the maximumδ_(M),maximum bending moment(M_(max)),maximum horizontal displacement(δ_(hm))of structural members are all less than the tolerance limits.The ground surface settlement model of double-row piles retaining system consists of three zones,i.e.,rebound influence zone,primary influence zone and secondary influence zone.The dhm values are 0.07%–1.42%of the excavation depth(He).The maximum ground surface settlement(δ_(vm))is generally less than dhm.The ratio ofδ_(vm)=δ_(hm)varies between 0.09 and 0.76,with an average value of 0.5.The observed earth pressure on the retained side of front pile(paf)is about 0.53–0.57γH below the excavation surface.Above the excavation surface,p_(af)decreases dramatically when getting closer to the ground surface.