A new model to predict roadheader performance using rock mass properties

Prediction of roadheader performance plays a significant role in the plan of tunnel construction, which is influenced by different key parameters, including rock strength, discontinuity in rock mass, type and specifications of roadheader machine, and brittleness. The main aim of this study is to build a robust empirical equation based on rock mass properties for the roadheader performance prediction. For achieving the aim, a dataset composed of roadheader performance rate and rock properties is established using the dataset compiled from an underground coal mine located in a remote rugged desert environment some 85 km south of Tabas City in mid east Iran. By using gathered data, the statistical analyses are conducted between rock mass properties and roadheader performance to find whether there is a significant relationship between input variables and roadheader performance. The results show that rock mass properties have a considerable impact on the rate of the roadheader performance. It is demonstrated that the proposed model can accurately predict the roadheader performance as a function of rock mass properties.

New design equations for estimation of ultimate bearing capacity of shallow foundations resting on rock masses

Rock masses are commonly used as the underlying layer of important structures such as bridges, dams and transportation constructions. The success of a foundation design for such structures mainly depends on the accuracy of estimating the bearing capacity of rock beneath them. Several traditional numerical approaches are proposed for the estimation of the bearing capacity of foundations resting on rock masses to avoid performing elaborate and expensive experimental studies. Despite this fact, there still exists a serious need to develop more robust predictive models. This paper proposes new nonlinear prediction models for the ultimate bearing capacity of shallow foundations resting on non-fractured rock masses using a novel evolutionary computational approach, called linear genetic programming. A comprehensive set of rock socket, centrifuge rock socket, plate load and large-scaled footing load test results is used to develop the models. In order to verify the validity of the models, the sensitivity analysis is conducted and discussed. The results indicate that the proposed models accurately characterize the bearing capacity of shallow foundations. The correlation coefficients between the experimental and predicted bearing capacity values are equal to 0.95 and 0.96 for the best LGP models. Moreover, the derived models reach a notably better prediction performance than the traditional equations.

Mechanical properties and failure characteristics of fractured sandstone with grouting and anchorage

Based on uniaxial compression experimental results on fractured sandstone with grouting and anchorage, we studied the strength and deformation properties, the failure model, crack formation and evolution laws of fractured sandstone under different conditions of anchorage. The experimental results show that the strength and elastic modulus of fractured sandstone with different fracture angles are significantly lower than those of intact sandstone. Compared with the fractured samples without anchorage,the peak strength, residual strength, peak and ultimate axial strain of fractured sandstone under different anchorage increase by 64.5–320.0%, 62.8–493.0%, and 31.6–181.4%, respectively. The number of bolts and degree of pre-stress has certain effects on the peak strength and failure model of fractured sandstone. The peak strength of fractured sandstone under different anchorage increases to some extent, and the failure model of fractured sandstone also transforms from tensile failure to tensile–shear mixed failure with the number of bolts. The pre-stress can restrain the formation and evolution process of tensile cracks, delay the failure process of fractured sandstone under anchorage and impel the transformation of failure model from brittle failure to plastic failure.

Tree-Based Solution Frameworks for Predicting Tunnel Boring Machine Performance Using Rock Mass and Material Properties

Tunnel Boring Machines(TBMs)are vital for tunnel and underground construction due to their high safety and efficiency.Accurately predicting TBM operational parameters based on the surrounding environment is crucial for planning schedules and managing costs.This study investigates the effectiveness of tree-based machine learning models,including Random Forest,Extremely Randomized Trees,Adaptive Boosting Machine,Gradient Boosting Machine,Extreme Gradient Boosting Machine(XGBoost),Light Gradient Boosting Machine,and CatBoost,in predicting the Penetration Rate(PR)of TBMs by considering rock mass and material characteristics.These techniques are able to provide a good relationship between input(s)and output parameters;hence,obtaining a high level of accuracy.To do that,a comprehensive database comprising various rock mass and material parameters,including Rock Mass Rating,Brazilian Tensile Strength,and Weathering Zone,was utilized for model development.The practical application of these models was assessed with a new dataset representing diverse rock mass and material properties.To evaluate model performance,ranking systems and Taylor diagrams were employed.CatBoost emerged as the most accurate model during training and testing,with R2 scores of 0.927 and 0.861,respectively.However,during validation,XGBoost demonstrated superior performance with an R2 of 0.713.Despite these variations,all tree-based models showed promising accuracy in predicting TBM performance,providing valuable insights for similar projects in the future.

Mass transfer characteristics of chiral pharmaceuticals on membrane used for polar organic chemical integrative sampler

Passive sampling technology has good application prospects for monitoring trace pollutants in aquatic environments.Further research on the sampling mechanism of this technology is essential to improve the measurement accuracy and extend the application scope of this approach.In this study,adsorption and permeation experiments were performed to investigate the sorption and mass transfer properties of five chiral pharmaceuticals at the enantiomeric level on polyethersulfone(PES)and polytetrafluoroethylene(PTFE)membranes used in a polar organic chemical integrative sampler.Batch adsorption experiments showed that the PES membrane had an adsorption phenomenon for most selected pollutants and an insignificant sorption behavior was observed for all selected pharmaceuticals on the PTFE membrane except for R(S)-fluoxetine.The diffusion coefficients of selected pharmaceuticals onto the PTFE membrane were approximately one order of magnitude higher than those onto the PES membrane.The permeation experiment indicated that under different hydraulic conditions,the change of the relative pollutant concentration through the PTFE membrane for the composite pollutant system was more obvious than that for the single pollutant system,and mass transfer hysteresis exists for both contaminant systems through PES membranes.Using the first-order equation or 3-component model to estimate the overall mass transfer coefficients,the results showed that the overall mass transfer coefficient values of pollutants in the composite pollutant system onto both membranes were higher than those in the single pollutant system.This parameter was mainly influenced by the synergistic effects of the multi-analyte interaction and diminished water boundary layers during the mass transfer process.

Features and spatial distribution of circumpolar deep water in the southern Indian Ocean and the effects of Antarctic circum polar current

The data from the Southern Ocean observations of World Ocean Circulation Experiment （WOCE） are used for analysis and illustration of the features and spatial distributions of Circumpolar Deep Water （CDW） in the southern Indian Ocean. It is learnt from the comparison among the vertical distributions of temperature/ salinity/oxygen along the 30°E, 90°E and 145°E sections respectively that some different features of CDW and the fronts can be found at those longitudes, and those differences can be attributed to the zonal transoceanic flow and the merizonal movement in the Circumpolar Deep Water. In fact, the zonal transoceanic flow is the main dynamic factor for the water exchange between the Pacific Ocean and the /ndian Ocean or between the Atlantic Ocean and the Indian Ocean, and for the effects on the spatial distributions of the physical properties in CDW.

Deformation Analysis of LRC Underground Gas Storage

The risk during construction and in the operation of the underground gas storage （UGS） was analyzed. One of most important risk which should be prevented is large deformation or destruction of the steel lining. The specific deformation of the steel lining needs to be inside the acceptable value. This paper presents lined rock cavern （LRC） concept and specific deformations, which can occur under operation of underground gas storage. Analysis is performed with different （3D model and axis symmetrical） FEM models and analytical model. We made a comparison between analytical calculation and FEM calculation. Concrete wall is mechanically not regarded as reinforced concrete structure which means that concrete will crack. Finally, we determined the minimum value of Young＇s modulus, which satisfies the condition of maximum deformation of steel lining.

On orbit estimation of spacecraft dynamic property

Mass property of spacecraft needs to be estimated in certain circumstances.Based on the measurement of single point acceleration,angular acceleration and angular velocity,a discrete Kalman Filter(KF) based estimation method is developed to extract the inertia matrix and mass center.The simulation results show that the method can be used for continues online estimation without propellant consumption.Stability condition for the filter is given at last.

Hydrographic field investigations in the Northern South China Sea by open cruises during 2004-2013

In the past 10 years （2004-2013）, annual open cruise during late summer provided new opportunities for comprehensive studies in the Northern South China Sea （NSCS）. The 10-year field investigation program was carried out by the South China Sea Institute of Oceanology, Chinese Academy of Sciences （SCSIO, CAS）. Measurements inclu- ded water mass property, ocean circulation, atmospheric structure, and chemical and biological elements. The observation data collected during these open cruises have been intensively used in the studies of marine oceanographic, meteorological, chemical, and biological processes in the NSCS. In this study, comprehensive assessment of data application in oceanographic and meteorological studies is provided： （1） the property and variability of water masses in different layers; （2） the distribution of main currents and three-dimensional structure of mesoscale eddies; and （3） atmospheric structure and its feedback to the ocean. With the continuance of open cruises, it is feasible to construct high- quality, gridded climatological marine meteorological datasets in the NSCS in the near future.

Impact of carbon paper structural parameters on the performance of a polymer electrolyte fuel cell cathode via lattice Boltzmann method

Polymer electrolyte fuel cells(PEFCs)being employed in fuel cell electric vehicles(FCEVs)are promising power generators producing electric power from fuel stream via porous electrodes.Structure of carbon paper gas diffusion layers(GDLs)applying in the porous electrodes can greatly affect the PEFC performance,especially at the cathode side where electrochemical reaction is more sluggish.To discover the role of carbon paper GDL structure on the mass transfer properties,different cathode electrodes with dissimilar structural parameters are simulated via lattice Boltzmann method(LBM).3D contours of oxygen and water vapor concentration through the GDL as well as the 2D contours of current density on the catalyst layer are illustrated and examined.The results indicate that the carbon fiber diameter has a negligible impact on the current density while the impact of carbon paper thickness and porosity is significant.In fact,increasing of carbon paper thickness or porosity leads to lack of cell performance.