Stable Development Stage Research Articles

Fatigue Damage Behaviors of TRC-Strengthened RC Beams.

For the investigation of fatigue damage behavior of textile reinforced concrete (TRC)-strengthened RC beams, in this study, eight RC beams were fabricated, and five of them were strengthened with TRC and tested under fatigue loading until failure, using a four-point bending setup. Research parameters included reinforcement ratio, textile ratio, and strengthening methods (single-side and U-wrapped). The failure mode, fatigue life, fatigue deformation, and other properties of TRC-strengthened beams were analyzed. Experimental results revealed that there were two fatigue failure modes for TRC-strengthened RC beams. In the first mode, the textile was snapped, but the steel bars did not rupture. In the second mode, both the textile and steel bars broke. Fatigue failure modes depended on the textile ratio. The TRC-strengthened beam’s fatigue life was significantly higher than the non-strengthened RC beam. At the same textile ratio, the TRC-strengthened beam’s fatigue life using the single-side method was longer than that using the U-wrapped method. With the increase in fatigue loading time, the midspan deflection of the TRC-strengthened beam was developed in three stages, namely rapid development stage, stable development stage, and destabilized development stage. The residual deflection and strain damage accumulation of tensile steel bars of TRC-strengthened beams were significantly reduced with the increase in textile or reinforcement ratios; thus, the beam’s fatigue life was prolonged.

Thermocline dynamics in a thermally stratified water tank under different operation modes

The mantled solar heat storage (MSHS) tank can separate water utilization and heat collection, and its structure is not only conducive to the formation of temperature stratification, but also easy to be combined with the building, which has a wide range of application value. However, when it is in the simultaneous charging/discharging mode (CD-Mode), the mixing in the inner tank is affected by the heat transfer of the mantle exchanger, and the mixing mechanism and the development law need to be further explored. In this paper, the mixing mechanism of negative buoyancy jet at the inlet and the variation trend of thermocline in the tank under different operating modes were explored numerically and experimentally. As well as its influence on the overall thermal performance of the tank, a simple and feasible way to optimize the diffuser is discussed as well. It is found that in the CD-Mode, the mixing inside the water tank becomes more severe in the early stage of water use, and the thermocline thickness shows a trend of thickening first and then thinning over time. However, the mixing state is relatively stable during the whole water use period, and the change rate of thermocline thickness is smaller. But it is more affected by the inlet negative buoyancy jet than that in the discharging mode (D-mode), especially when the Rei number is large. Under the two operation modes, when the dimensionless time t* = 0.4–0.8, it enters the stable water use process, and the thermocline is in the stable development stage. The thickness of thermocline changes less in the CD-mode, which makes it easier for users to obtain longer hot water service time, reflecting the advantages of mantled heat exchange water tank in maintaining thermal stratification. For the working conditions studied, after optimized the diffuser, the hot water output rate can be 109.9% higher than the straight tube with the same tube length, and the hot water service time can be prolonged by 90.2%, which has practical application value.

Acoustic emission characteristics and damage law for prefabricated single‐crack sandstone under uniaxial compression

The cracks of rock seriously threaten the safety of building structures and underground space. Uniaxial compression tests were carried out on prefabricated single-crack sandstone samples with different angles and lengths. The results show that the existence of a prefabricated single-crack has a certain influence on the mechanical properties and acoustic emission response characteristics of sandstone samples. A function formula of the effect of uniaxial compression stress on the angle and length of prefabricated crack is established. It is found that there is an obvious moment of acoustic emission energy mutation in the three deformation and failure stages before sandstone failure. The change of angle and length of crack has a great influence on the stress value corresponding to the energy mutation at the stable development stage of the micro-crack. Meanwhile, the acoustic emission waveform characteristic parameters of sandstone samples under various fracture conditions are analyzed. Thus, the crack propagation mode of the sample with small angle can be judged. The damage variables based on real-time acoustic emission energy were defined, and the damage constitutive model of rock material with a single fracture under uniaxial compression was established based on real-time acoustic emission energy. The results show that the new model and method can not only reasonably explain the damage mechanism of prefabricated rock with a single fracture under uniaxial compression but also accurately simulate the full stress-strain process of rock with a single fracture at different angles and lengths, which has good rationality and feasibility.

How Is Construction Land Transition Related to Rural Transformation? Evidence from a Plain County in China Based on the Grey Correlation Model

Under the background of urban-rural integration, the frequent flow of urban and rural elements has promoted the close connection between rural transformation (RT) and construction land transition (CLT). How is CLT related to RT? By taking the plain area Linqing County in China as the study area, basing the study on the RT and CLT coupling framework of relevance theory, building an RT and CLT evaluation index system, using the multi-factor evaluation method for the evaluation of RT and CLT from 2010 to 2018, and using the grey correlation model to measure the RT and CLT coupling relationship, the results showed that the level of RT was from 0.04 to 97.42, and the level of CLT was from 14.89 to 82.47, showing the trends of gradual increase and fluctuating increase, respectively. Taking 2013 and 2016 as the time point, RT could be divided into the initial stage, growth stage I, and growth stage II, corresponding to the initial stage, high growth stage, and stable development stage of CLT. The coupling degree between the two was in the range of 0.6–0.8 and was in the stage of a medium to high coupling degree. The correlation degree between the subsystem of RT and CLT was over 0.65. In the subsystem of CLT, the correlation degrees between quantitative structure transition and RT and efficiency transition and RT were both lower than 0.65, which were relatively low. Controlling the scale of construction land and taking efficiency transition are the effective methods to guide the deep exploration of potential and are the inevitable way to strengthen the relationship between CLT and RT and promote urban-rural integration development.

Research on Fatigue Performance of the Rib Beam Bridge Carriageway Slab Based on Cumulative Damage Theory

The purpose of this paper is to study the development law of fatigue damage of the carriageway slab of reinforced concrete ribbed girder bridge and to provide theoretical support for carriageway slab design. The fatigue test of reinforced concrete rib beam bridge carriageway slabs was conducted. Based on the material fatigue damage theory, the fatigue damage model was established by ABAQUS software. The fatigue performance, failure mechanism, and the effect of fatigue level on the fatigue performance of the carriageway slab were studied. The experimental research results show that when the slab of the rib beam bridge was fatigued, and the radial crack appeared at the bottom of the slab, which belonged to punching shear failure. The fatigue failure process was divided into three stages as follows: in the initial stage of fatigue, the deflection and reinforcement strain increased linearly with fatigue times, and in the stable development stage, the bottom deflection and reinforcement strain increased steady progression. With the increase in fatigue cycles, the fatigue accumulation damage was gradually accumulated, and the stiffness of the carriageway slab gradually decreases. In the rapid development stage, the deflection, reinforcement strain, and crack growth speed were significantly increased. According to the fatigue damage model, the simulation analysis results show that the accumulated damage to the bridge carriageway was more serious with the increase in fatigue load level. The fatigue damage degree was lower when the design fatigue load level is not greater than 0.55.

Hot Topics and Frontier Evolution of Broadcasting and Hosting Art Talent Cultivation Research：Keyword Co-Occurrence Analysis Based on CiteSpace

Based on the method of bibliometrics, this paper conducts a visual analysis of the related researches on the cultivation of broadcasting and hosting artistic talents. The research finds that the research on the training of broadcasting and hosting artistic talents has entered a stage of stable development. "Modern Communication" is an important publication platform for broadcasting and hosting art Talent Cultivation Research; the number of scientific research institutions has greatly increased since 2010. Communication University of China, Sichuan Film & Television College, and Jilin University of Arts are important research units for the cultivation of broadcasting and hosting artistic talents; a stable research team and cooperation network have not yet formed in this field ; Focus on the three major themes of "research on training mode under technological and industrial transformation", "research on characteristic training mode based on the college's own positioning" and "research on curriculum construction, classroom teaching and practical teaching based on training mode", and presents Out of the research trend from macro to micro. From the perspective of research evolution, the training of broadcasting and hosting art talents is divided into three stages. The information entropy value of each development stage is fluctuating, and the overall information entropy value of the latter stage is higher than that of the previous stage, that is As the research is further refined, less new knowledge is generated; the research on the training mode of broadcasting and hosting art talents has become more refined, and the amount of information has gradually decreased, but the overall fluctuation state shows that this field is still full of vitality.

Experimental Study on Ultrasonic Velocity, Suction Curve, and Gas Permeability of Damaged Granite

The excavation damaged zone (EDZ) of a high-level radioactive waste (HLW) disposal repository is a key factor related to long-term safety. The essence of the damage evolution of rocks is the development of microcracks, which change the ultrasonic velocity, suction curve, and gas permeability of rocks. In this work, some granite samples with different damage degrees were generated by uniaxial compression, which is similar to the stress condition of the surrounding rocks of HLW disposal tunnels. The ultrasonic velocity was simultaneously tested during the compression process. The suction curve was then obtained by drying the damaged samples under different levels of relative humidity. The gas permeability was finally measured at different levels of water saturation. Test results indicated that the unstable development of microcracks led to a decrease in Young’s modulus and enlarged the horizontal deformability of granite. The development of microcracks did not change the longitudinal wave velocity, which tended to remain constant when the ratio of the axial stress to the crack damage stress was greater than one. However, the shear wave velocity of damaged granite was significantly decreased. Such effect indicated that the microcracks generated at the stable and unstable development stages mainly extended along the axial direction rather than the radial direction. The suction curve of damaged granite was obtained and was found to comply with van Genuchten’s model and the dual-porosity model. The results of the permeability tests revealed that almost no new gas pathways were generated at the stable development stage of the microcracks. Meanwhile, the unstable development of microcracks led to a great increase in gas permeability. Moreover, the gas permeability of the intact and damaged granite tended to be constant when the water saturation level was less than 0.5. These results will benefit the performance assessment of the EDZs in the surrounding rocks of HLW disposal repositories.

Study on Acoustic Emission Characteristics and Damage Evolution Law of Red Sandstones under Different Loading Rates

Uniaxial compression experiments with different loading rates and acoustic emission tests were conducted to study the loading rate effects on the mechanical and acoustic emission characteristics of red sandstones. The mechanical and acoustic emission parameters of red sandstones were analyzed with varying loading rates. Furthermore, the red sandstone damage evolution model was established based on the acoustic emission cumulative ringing count. The results show that: (1) The elastic modulus decreases linearly with the increase of the logarithm of loading rate, while the peak strength generally shows a gradually increasing trend with the logarithm of the loading rate. (2) With the increase of loading rate, the AE event rate’s peak value increases gradually, and the cumulative number of AE events decreases. (3) The evolution law of the characteristic stresses determined by the AE event rate and cumulative AE event number is the same as that of the loading rate. That is, with the increase of the loading rate, it shows a gradually decreasing evolution trend. (4) The damage evolution model of red sandstone can better describe the damage evolution process of red sandstone. According to the evolution characteristics of damage variables, the damage evolution process of red sandstone can be divided into three stages: the initial damage stage, the damage stable development stage, and the damage accelerated stage. (5) The damage variable at the damage stress point can reflect the actual damage degree of rock, and the size of the damage variable is closely related to the initiation, propagation, and transfixion of microcracks inside the rock. When the loading rate is low, the damage degree of red sandstone at the damage stress is usually more prominent because the rock’s microcrack develops more fully.

Mapping Global Research on Green Finance from 1989 to 2020: A Bibliometric Study

Green finance is considered to be the financial support for green growth. It acts on the environmental protection industry through financial activities to reduce greenhouse gas emissions. It is a new financial model that combines financial and environmental protection activities. In order to explore the origin and development of this new financial model, namely, green finance, this study adopts the method of bibliometrics. Based on the database based on the Science Citation Index Expanded and Social Sciences Citation Index databases, the historical evolution of green finance and the classification of research hotspots are explored. The results show that green finance research has gone through three stages: the budding stage, the stable development stage, and the booming development stage. The research topics have also changed from the establishment of the green financial system to the difficulties faced by the green financial systems of various countries to the empirical evidence of the vigorous development of green finance. In addition, we have also established a three-dimensional framework (i.e., purpose, process, and participants, or 3P) of research hotspots in green finance to show a road map for future research directions.

Sustainability and challenges in biodiesel production from waste cooking oil: An advanced bibliometric analysis

Biodiesel production from waste cooking oil (WCO) has become an economic and environmental strategy to help address global renewable energy challenges and contribute to a sustainable society. A systematic and extensive assessment of WCO-based biodiesel production research has become increasingly important. However, scant literature based on the bibliometric analysis of this field, including publication trends, geographical distribution, co-citation references analysis, and future research trends are available. To visualize and map the developments and sustainable future challenges in this research area more thoroughly, a comprehensive bibliometric analysis was conducted. A total of 2,750 publications from the Web of Science Core Collection databases (from 2000–2020) were analyzed using ArcGIS 10.2, VOSviewer, and CiteSpace. The results demonstrated that the three stages of development in this field included the initial stage (2000–2007), the exploration stage (2008–2015), and the stable development stage (2016–2020). China, India, and Malaysia are the most active countries with the highest number of publications. The top three prolific research organizations included the Indian Institute of Technology System, Universiti Putra Malaysia, and Universiti Malaya. These 2,750 publications are found in the following journals Fuel, Renewable Energy, and Energy Conversion and Management. The most fruitful authors and literatures have also been included in this research field. Cluster analysis indicates that two constant research fields were transesterifications and diesel engines. Future studies should concentrate on life cycle assessment, lipase, WCO, ultrasound, and deoxygenation. Two augmented insights involve the application of soft computing techniques and thermodynamic-based sustainability assessment analysis. This is the first study to use bibliometric analysis method to provide an overview of WCO-based biodiesel production research. By conducting a systematic survey of the current research, this study offers a tool that industry practitioners and renewable energy policymakers can use in their work.

Swelling Properties and Permeability of GMZ Bentonite-Sand Mixtures during Different Solutions Infiltration

In China, Gaomiaozi (GMZ) bentonite is recognized as a barrier material for isolating nuclear waste. Different chemical solutions may change the hydraulic conductivity and swelling capacity of bentonite. Consequently, a series of swelling pressure and permeability experiments was carried out on bentonite-sand mixtures with various dry densities and infiltrating solutions. X-ray diffraction (XRD) and the field emission scanning electron microscope (FESEM) were carried out on the samples experiencing the tests to identify the influence of chemistry pore solutions upon the mineralogical and microstructure changes. The results show that the swelling pressure experienced rapid swelling, slow expansion, and the stable expansion stage for the specimens of infiltrating solutions except for NaOH. For the specimens infiltrated with NaOH solutions, the swelling pressure experienced rapid increases, slow decreases, and a stable development stage. With hyper-alkaline and hyper-salinity infiltration, the swelling pressure decreased, and the permeability increased. In addition, swelling pressure attained stability more quickly on contact with hyper-alkaline and hyper-salinity solutions. Comparing the test results, the results indicate that the influence of NaOH on the expansion and permeability was higher than NaCl-Na2SO4 at the same concentration.

Analysis on Several Issues Concerning Sustainable Development of Urban Fringe Green Open Space in Chinese Megalopolis: Taking Three Types of Leisure and Recreation Projects as Examples

Taking country parks, sightseeing agriculture and golf courses as cases, the paper analyzes the law of the emergence and development of green open space leisure and recreation projects in the fringe of megalopolis in China, based on building of a comparative model of the correlation between different project development stages and the economy and the analysis of the preference of three types of projects in the location of space, transportation and scenic resources. The results show that: ① The three representative recreation projects have basically gone through the "embryonic stage-accelerated development / upgrading transformation stage-sustained and stable development stage", as well as the different development stages of the three kinds of projects are related to some specific nodes of urban per capita GDP. ② The higher the degree of public welfare of the type of recreation project, the later the start and development, and vice versa. The emergence of golf courses is earlier than that of sightseeing agriculture, while the emergence of country parks is much later than both. At the same time, the non-public welfare recreation projects driven by market capital obviously have a more sustainable and strong development power than the public welfare recreation projects led by government investment. ③ The three types of recreation projects are consistent in the location of space, transportation and scenic resources, and are bound to face fierce spatial competition in the limited urban fringe of megalopolis. ④ From the three aspects of strengthening the development guidance of recreation projects, gradually optimizing the spatial layout of recreation projects and optimizing the allocation of traffic infrastructure, this paper puts forward some countermeasures and suggestions for optimizing the recreation utilization of green open space in urban fringe.

Mapping publication status and exploring hotspots in a research field: Rheumatoid arthritis with depression.

To make a bibliometric analysis of the current research status and hot spots in the field of rheumatoid arthritis (RA) -related depression. Systematic review. Based on the Web of Science database, studies in the past 5years from 1 January 2015-5 November 2019 have been included. Data were analysed from annual number of published papers, main research institutions, core authors, core teams and research topics by using bibliometric approaches. Related papers (N=1,073) were obtained. The field of RA-related depression is in a stable development stage, forming core authors and core teams. The epidemiological characteristics, influencing factors, prediction effect and the intervention of RA-related depression are common research directions and themes. The common role of auto-antibodies and inflammatory factors in the development of RA and depression, the risk of cardiovascular events and disease burden caused by RA-related depression are newly emerging research topics. The RA-related depression has been widely concerned by scholars and the research field is gradually mature. However, the research on the prevention and intervention of RA-related depression is still wanting, which needs to be strengthened. WHERE AND ON WHOM WILL THE RESEARCH HAVE AN IMPACT?: The research revealed the most popular institutions, authors, research teams, emerging issues and 'hot topics' in the RA-related depression field, which might suggest avenues for future research in this field.

Damage Characteristics and Constitutive Model of Deep Rock under Frequent Impact Disturbances in the Process of Unloading High Static Stress

During the mining of deep mineral resources, the rock is in the complex mechanical environment of high crustal stress and blasting excavation unloading, and the improved SHPB test system is used to carry out frequent impact disturbance test of deep rock in the process of unloading high static stress. Firstly, the general characteristics of dynamic stress-strain curve envelope of the whole process trend can be divided into four stages: the stable development stage of micro cracks, the non-stable development stage of micro cracks, the fatigue damage stage, and the fatigue failure stage. Then, the damage variables of the rock are defined by continuous factors, strain equivalence principle and statistical damage theory, which are based on the whole deformation characteristics of rock during the test. And the derived damage variable equation of rock in the damage process is proved to be reasonable, and the damage constitutive model of rock under frequent disturbances in the process of unloading high static stress is established by the combined model method. Finally, the rationality of constitutive equation is verified by test data, which shows that the dynamic stress-strain curve envelope is in good consistency with the theoretical curve of constitutive equation.

Numerical Analysis of Fracture Characteristics of Elliptic Porous Sandstone and its Filling Gypsum Based on Statistical Damage Theory

In view of the fact that less attention has been paid to the failure characteristics of rock mass structures with different elliptical shapes, based on the statistical damage theory, the finite element calculation model of sandstone with elliptical holes and its filled gypsum is established, the meso-parameters are calibrated by laboratory test results, and the fracture damage process, peak intensity and acoustic emission law are numerical simulated. Based on the acoustic emission results, the concept of damage degree is defined, and the damage process of the specimen is quantitatively described. The results show that with the increase of k value, the "main crack" produced by tensile stress in the hole gradually evolves into a tension-shear compound "wing crack". After the grain "," main crack "and" wing crack "developed to a certain extent, shear failure appeared on the left and right sides of the hole, and then developed into horizontal inclined tension-shear composite failure. The peak strength of elliptical pores and sandstone filled with gypsum sandstone increased at first and then decreased. The peak strength of filled gypsum sandstone increased by 6.92%, 4.61%, 11.21%, 13.64%, 15.31%, 10.6% and 11.50%, respectively, compared with that of unfilled gypsum sandstone, and the peak strength of sandstone filled with gypsum sandstone increased by 6.92%, 4.61%, 11.21%, 13.64%, 15.31%, 10.6% and 11.50%, respectively. Damage and variation of concrete during loading. There are four stages: linear elastic deformation stage, crack initiation stage, crack acceleration stage and damage stable development stage. With the increase of k value, the maximum damage degree increases at first and then decreases, and the damage degree of sandstone filled with gypsum is larger than that of unfilled sandstone sample as a whole.

Research hotspots and tendency of intelligent manufacturing

<p indent="0mm">During the past few years, many countries have put forward their national manufacturing strategies. Although these strategies are proposed and developed under different backgrounds, their common objective is to achieve intelligent manufacturing, which has the potential to revolutionise manufacturing industry and is being nurtured through national projects such as “Industry 4.0” in Germany, “Made Smarter” in the UK, “Industrial Internet” in the US, and “Intelligent Manufacturing” in China, etc. These projects promote a new manufacturing philosophy to guide the development of industrial manufacturing in a digital, intelligent and networked global environment, as well as upgrade the traditional manufacturing to intelligent manufacturing. With taking advantages of artificial intelligence and advanced manufacturing technologies, intelligent manufacturing connects all manufacturing facilities and enables physical processes and information flows to be available when and where they are needed across holistic manufacturing supply chains, this will benefit optimizing manufacturing resources, improving product quality, system productivity and sustainability, and reducing costs. Intelligent manufacturing has attracted intense attention due to the broad application of artificial intelligence and information science technology in manufacturing industry. In this study, 1370 papers in intelligent manufacturing are taken as data sources, which are retrieved from the Web of Science Core Collection Database between 1987 to 2017. The present paper aims to reveal the development status, the number of documents by leading countries, hotspots and trends of intelligent manufacturing by VOSviewer tool. Based on annual outputs and growth rate of literatures, the initial development stage (1987−1997), the stable development stage (1998−2012) and the rapid development stage (2013−2017) of intelligent manufacturing are proposed. On the whole, to date, China takes a leading position out of more than 100 countries or regions, followed by America and England. With more than <sc>30 years</sc> of evolution, the connotation of intelligent manufacturing mainly goes through the process from digitalization to networking and then to intellectualization. In the recent research (since 2013), new enabling technologies for intelligent manufacturing have been developed, including Internet of Things (IoT), Big Data, Digital Twin (DT), Cloud Manufacturing, and Cyber-Physical System (CPS), which endow the manufacturing process with intelligence. For instance, IoT devices can communicate and interact with each other, and thus enable the real-time monitoring and dynamic control. Big data analytics together with AI can help to mine out potential rules, knowledge and patterns, in order to smart prediction, evaluation, optimization and decision-making. DT aims at constructing interactive virtual mirrors for physical assets and fusing both real and simulated data to give more insights. Cloud Manufacturing transforms manufacturing resources and manufacturing capabilities into manufacturing services, which can be managed and operated in an intelligent and unified way to enable the full sharing and circulating of manufacturing resources and manufacturing capabilities. These technologies can be combined with each other and greatly promote the innovation of manufacturing in design, production, operation and maintenance, etc. The findings presented in this study reveal the technical developing tendency and current hot topics in intelligent manufacturing and will facilitate scholars’ investigation in the related fields, a comprehensive taxonomy of Intelligent Manufacturing can also be developed through analyzing the results of this review.

Experimental research on seismic damage of a full-web SRC frame structure

An experiment was conducted to investigate the seismic damage of a full-web steel-reinforced concrete (SRC) frame structure. A 1/3 scale, 2-bay, 3-story model of the full-web SRC frame was designed and constructed, and the load-displacement hysteretic curve, stiffness and strength degradation, displacement ductility, energy dissipation, crack propagation, failure mechanism, damage parameter, and evolution of seismic damage were investigated under low-reversed cyclic lateral loading. Based on an existing seismic damage model, the damage index was calculated and cumulative damage of the frame model was determined. The experimental results showed that the damage process of the full-web SRC frame structure consisted of four stages - namely, the undamaged stage, initial damage stage, stable development stage, the rapid development stage. Frame beams were damaged first, followed by damage to frame columns; Frame beams experienced the greatest damage. The damage value was largest for the first floor of the structure. Damage values calculated with the two methods were similar and accurately reflected the evolution of seismic damage. The research results can provide a theoretical basis for post-earthquake damage assessment of a full-web SRC frame structure.

Analysis and Application of Port Enterprise Management Mode Based on Profit Mode Analysis

Liu, R.; Shen, W.-Q., and Zhang, M., 2019. Analysis and application of port enterprise management mode based on profit mode analysis. In: Gong, D.; Zhu, H., and Liu, R. (eds.), Selected Topics in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 94, pp. 722–726. Coconut Creek (Florida), ISSN 0749-0208.Nowadays, the maritime transport has entered a stable development stage, and port enterprises are trying to win the market and profit with lower prices, however, the results are not satisfactory. For port enterprises, the acquisition of profits should depend on reasonable cost management. With a domestic port enterprise as an example, this paper analyzes its current operation status, finds out problems existing in the cost management, and proposes corresponding improvement solutions. The research shows that the operating income and net profit of the target port enterprise have declined to a certain extent, and its overall profitability is not good. There are big problems in the cost management of the enterprise, such as the operating cost is unstable, the sales cost and financial cost increase slightly, and the retirees-related expenditure is relatively large; and these cost problems of the enterprise could be improved via optimizing human resources and organizational allocation, and enhancing investment management, etc.

Damage and failure characteristics of rock similar materials with pre-existing cracks

In order to further study the damage and failure mechanism for rock similar materials, this study investigated the mechanical properties and failure characteristics, law of damage space development, and damage evolution characteristics for rock similar materials with pre-existing cracks of varying length under uniaxial compression load. The equipment used in this study is the self-developed YYW-II strain controlled unconfined compression apparatus and the PCIE-8 acoustic emission monitoring system. Results show that, as the length of pre-existing crack increases: (1) the peak and residual strength reduces, and the peak axial strain and the strain during the initial compression phase increases; (2) the major failure mode is changed from shear failure to tensile failure along a vertical plane that passes the middle of the pre-existing crack; (3) The damage increases during the stable and accelerated development stage, and the effect of the pre-existing cracks is more during the accelerated development stage than the stable development stage.

Mechanical behaviors of the brittle rock-like specimens with multi-non-persistent joints under uniaxial compression

The stability of rock engineering applications is significantly influenced by the mechanical behavior of jointed rock masses. However, the deformability, strength and failure characteristics of non-persistent jointed rock specimens have not been examined comprehensively. In this paper, laboratory tests and discrete element method simulations are used to investigate the influence of angle (α), spacing (S), joint length (L), and rock bridge length (B) on uniaxial compressive strength (UCS), Young’s modulus and failure processes of brittle rock-like specimens with multi-non-persistent joints. The orthogonal experimental method is used to quantify the influence of four geometric factors on the UCS and Young’s modulus through comparing different range values. The results show that the joint inclination angle has the most significant influences on UCS and Young’s modulus. The failure patterns can be classified into six categories: (1) stepped path failure caused by wing cracks; (2) stepped path failure caused by wing cracks and shear cracks; (3) vertical failure caused by wing cracks; (4) stepped path failure caused by anti-wing cracks; (5) transfixion failure along the diagonal caused by shear cracks; (6) intact failure. The evolution of micro-cracks divides the numerical stress-strain curve into four stages: stage I, linear elastic stage; stage II, stable development stage of micro-cracks; stage III, increment stage of micro-cracks before peak strength; stage IV, increment stage of micro-cracks after peak strength. Comparison between the experimental and numerical results confirms the capacity of the DEM model to simulate the non-persistent jointed rock specimens. These experimental and numerical results enhance our understanding of the influence of joints on the mechanical behavior of rock masses.