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Xuan paper is one of the most famous handmade papers in China and is an important paper for conservation. However, the evenness of Xuan paper has not yet received much attention. In this study, the distribution of the in-plane grammage and mechanical properties of Xuan paper are measured. It is found that the distribution of the in-plane grammage and mechanical properties of Xuan paper is uneven. In the handmade direction, the grammage and mechanical properties of Xuan paper are overall largest in the lower area, followed by the upper and middle areas. The sheet forming process of Xuan paper has an important effect on the distribution of in-plane grammage, mechanical properties, and fiber orientation of Xuan paper. The folded state has a negative effect on the mechanical properties of the folded area of Xuan paper. This study will help raise awareness of the unevenness in physical properties of Xuan paper, which is important in both conservation and research applications. [ABSTRACT FROM AUTHOR]

A novel procedure has emerged in recent years within oilfields - namely, the utilization of a hybrid fracturing method employing pre-CO2 injection along with sand-carry slick water. In this paper, based on the real logging data of shale oil reservoirs in the second member of Cangdong Sag, Huanghua Depression, combined with the GOHFER, a coupled 3-D hydraulic fracture propagation model is proposed. This research delves into an examination of how engineering factors exert their influence on the process of fracture propagation. The quantitative analysis is conducted encompassing critical fracture parameters such as half-length, height, and width, and self-defined fracture seepage area and fracture front fractal dimension. The research findings indicate that as injection displacement increases, the fracture shape undergoes a transformation from being "long, low, and wide" to becoming "short, high, and narrow". [ABSTRACT FROM AUTHOR]

The prefabricated building with ultra-low energy consumption/near -zero energy consumption is one of the mainstream directions of future buildings in China. However, in the building of prefabricated ultra-low energy consumption frame structure, the weight of the outer window is too large to be directly built in the enclosure structure. Therefore, this paper designs a frame-type window opening, and studies the drawing performance, shear performance and bending performance of different types of self-tapping screws. The failure state and test data are analyzed. The results show that the use of square steel beam-column frame window openings can meet the ultra-low energy consumption requirements of aluminum-wood composite windows with excessive weight in prefabricated frame structures. When the wall thickness of square steel beam-column is 6 mm, ST5.5 screw can give full play to the drawing performance, and has good shear performance and bending performance, which provides a basis for the design of assembled ultra-low energy consumption frame structure. [ABSTRACT FROM AUTHOR]

The response characteristics of the mesostructure and macro-characteristics of the soil–rock mixture under repeated freeze–thaw action have an important influence on the safety and stability of the dump slope in low-temperature environments. In order to further understand the multi-scale response behavior of a soil–rock mixture under freeze–thaw cycles, this paper carried out indoor freeze–thaw cycles, uniaxial compression, and electrochemical impedance spectroscopy tests on a soil–rock mixture taken from a graphite mine dump in Jixi City, Heilongjiang Province, China. Combined with the simulation calculation of discrete element numerical software (PFC2D 7.0), the effects of freeze–thaw cycling on electrochemical impedance spectrometry (EIS) mesoscopic parameters, uniaxial compressive strength, and crack propagation of soil–rock mixtures were analyzed. The intrinsic relationship between mesoparameters and macroscopic mechanical properties was established. The results showed that as the number of freeze–thaw cycles increases from 0 to 15, the mesopores inside the soil–rock mixture gradually increase, and the angular similarity of distribution characteristics increases by 5.25%. The uniaxial compressive strength and the peak secant modulus increase exponentially with the increase in the number of freeze–thaw cycles, the uniaxial compressive strength decreases by 47.62%, and the peak secant modulus decreases by 75.87%. The peak strain and pore compaction stage showed an exponential increase and an increasing trend, respectively, and the peak strain increased from 2.115% to 4.608%. The failure mode was basically similar in different cycles; the failure cracks extended from the corners to the middle and lower parts before the failure finally occurred. The types of failure cracks were mainly tensile cracks, followed by tensile shear cracks and the fewest compression shear cracks. The similarity and uniaxial compressive strength conformed to a good linear relationship with the number of freeze–thaw cycles, with the uniaxial compressive strength decreasing linearly with the increase in similarity. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Alkali-activated materials are produced by chemically polymerizing the aluminosilicate materials using alkaline activators, which can effectively lower the greenhouse-gas emissions (approximately 73%) released by ordinary Portland cement (OPC). Silicomanganese slag is a large solid waste discharged from the ferroalloy industry in China that can pollute the environment and occupy resources. In this paper, the slag in alkali-activated material was replaced with silicomanganese slag to address the disposal of silicomangaese slag. The flowability, setting times, compressive and flexural strengths, micro-structure and freeze-thaw resistance of alkali-activated silicomanganese slag concrete (AASSC) with varied substitution ratios, volume fractions of steel fibers and alkali-activated modulus (MS) were exploited. As a results the compressive strengths at 56 days of AASSC with a 10% substitution ratio of silicomanganese slag reached over 80 MPa and over 132 MPa with the 3% steel fiber dosage. AASSC still reached 91 MPa and 45 MPa with 60% and 100% substitution ratios by cooperating 2% steel fibers, respectively. When the freeze-thaw cycle number reached 300, the compressive strengths of AASSC with the replacement ratios of 10%, 60% and 100% were 84%, 74% and 51% of their original values by cooperating 2% steel fibers, respectively; AASSC with the numerous substitutions of 60% and 100% were destroyed at 600 and 300 freeze-thaw cycles, respectively. AASSC with a 10% substitution ratio and 2% steel fiber content is suitable for excellent performance, and a 60% substitution ratio can also be applied to construction for the massive utilization of silicomanganese slag. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper reviewed the research progress in China on the durability, acid and alkali corrosion resistances, thermal insulation, sound insulation, and hygroscopic properties of basalt fibers (BFs) as well as the physicochemical and mechanical properties of BF-reinforced resin composites. The acidity coefficient and pH value of BFs and glass fibers (GFs) were tested, which showed that BFs had better chemical stability. Scanning electron microscopy observations showed that the acid corrosion of BFs gradually occurred from the outside to the inside, whereas the alkali corrosion of BFs occurred nearly simultaneously both inside and outside. Moreover, the reasons for these results were analyzed from a chemical reaction perspective. BFs met the thermal conductivity and sound absorption coefficient requirements of building thermal insulation and sound absorption materials. The hygroscopicity of BFs was 1/8–1/6 that of GFs, and BFs also had a smaller dielectric loss angle. Tests confirmed that BFRC exhibited great high-temperature resistance. As the short BF content increased, the flexural strength, splitting tensile strength and impermeability of BFRC significantly improved, and an optimal fiber length and content were proposed. A comparison showed that the mechanical properties of BF-reinforced resin were generally better than those of GF-reinforced resin. Finally, this review identified some concepts to be studied in this field and prospects for possible future research directions. [ABSTRACT FROM AUTHOR]

Temperature has a significant impact on the structural performance of the China Railway Track System (CRTS) II slab ballastless track-bridge and the structure is susceptible to fatigue damage under long-term loading. Therefore, it is crucial to conduct cyclic-loading test on the track-bridge structure to reveal the evolution of its mechanical properties under coupled temperature-load effect. In this study, a 1:4 scaled-down model of a ballastless track-bridge was produced and placed in a large-size environmental chamber for temperature-load coupled cyclic-loading tests. The results showed that after 1x10-6 cycles of loading, no cracks were observed on the surface of the track structure. The structural workability and load capacity of the track-bridge met the required service standards. During the temperature-load coupling test, the load-displacement curves of the structural system exhibited intervals, with a more significant increase in static-deflection values. The dynamic deflection of the structural system under the coupling action experienced a higher growth rate and more abrupt changes compared to single-load conditions. These observations indicated that the ambient temperature amplified the deflection of the structural system. The strain values in the track structure exhibited significant non-linearity, with temperature amplifying this effect. The dynamic-response test results revealed a negative correlation between the inherent frequency of the track structure and the ambient temperature, further emphasizing the influence of temperature on the stability of the track structure. Consequently, it is essential to enhance the monitoring of track structures in high-temperature climates to ensure their safe operation. [ABSTRACT FROM AUTHOR]

With the rapid development of underground rail transportation in China, the demand for precast concrete pipe sheets in metro construction continues to increase, and the quality and safety of precast concrete pipe sheets profoundly affect the safety of tunnels. The quality and safety of precast concrete pipe sheets have a profound impact on the safety of tunnels. The maintenance of pipe sheets plays an important role in ensuring the strength and durability of concrete pipe sheets. Therefore, it is important to study the maintenance methods of concrete pipe sheets. The method of substituting immersion curing with spray curing is proposed in this paper. It has been shown that spray curing can overcome the challenges of high pollution and high cost caused by the immersion curing of precast concrete pipe (PCP) sheets. Experimental tests investigate the influence of macro-mechanical properties and microstructure of pipe sheet materials under various ages of the two curing conditions. The results highlighted that the conventional methods of water immersion for PCP have minimal effect on concrete's macro-mechanical characteristics or microstructure after a certain curing age. The comparative studies on both curing processes showed that after seven days of curing, the degree of moisture attained by the spray-cured samples was relatively lower than that of the water immersion approach. In addition, samples with the water spray curing process had larger pore sizes (which could degrade faster) with lower mechanical strength. Interestingly, after 28 days of curing age, both approaches attained complete hydration levels, resulting in a dense pore structure with reduced median pore size and higher mechanical performance. Investigations on two distinct methods indicated that the early strength properties (after seven days of curing) acquired with water immersion curing were higher than the mechanical properties obtained with spray curing. This difference in mechanical properties, in addition, was not significant after 28 days of curing age. As a result, the suggested technique of water spray curing is an appropriate method with minimum water use to some extent. [ABSTRACT FROM AUTHOR]

In harsh environments such as high altitude areas, the durability of rubber waterstops is a big concern. A long period of sunshine and the accompanying strong ultraviolet (UV) radiation accelerate the photooxidation and thermal oxygen aging of rubber waterstops, resulting in cracks, peeling off and even failure of waterstops. This study aims to investigate the performance of a widely used waterstop in simulated high altitude areas of western China by placing rubber waterstops in an UV aging chamber for 18, 36, 54, and 72 days. Mechanical properties, such as tensile strength, elongation, tear strength, compression set, and hardness, were measured. Moreover, scanning electron microscopy with X-ray microanalysis (SEM-EDS) and Fourier infrared spectroscopy-attenuated total reflection (FTIR-ATR) detection were performed on the damaged specimens to dissect the underlying mechanisms of deterioration in mechanical properties. The results showed that all the investigated mechanical properties of the rubber waterstop deteriorated with the increase in aging time. The increase in the UV aging time increased the surface cracks, decreased the unsaturated bonds, and increased the oxygen content and oxygen-containing functional groups of the rubber waterstop. It can also be found that the additive particles in the matrix gradually aggregated, and concurrently the carbon black particles decreased, which weakened the three-dimensionality of the cross section of the specimen. Findings from this paper provide new insights into the durability of rubber waterstops in high altitude areas. [ABSTRACT FROM AUTHOR]

In the actual exploitation process of coalbed methane (CBM), as the fluid in the wellbore continues to circulate, the surrounding rock of the CBM well will continuously exchange heat with the fluid in the wellbore, resulting in continuous changes in the temperature of the surrounding rock itself. Linfen, Shanxi is the main exploitation area for CBM in China. This paper aims further to improve the exploitation efficiency of CBM in this area and conducts experimental research on the change characteristics of coal-rock mechanical properties under varying temperature conditions. The experimental results show that under constant pressure conditions, the higher the temperature, the lower the stress value when the coal-rock breaks. In the process of reaching peak strength, the higher the temperature, the higher the proportion of coal-rock plastic deformation in its entire deformation stage. The compressive strength, elastic modulus, and main crack length of coal-rock will decrease with temperature. The Poisson's ratio and primary fracture angle will increase with the increase of experimental temperature. [ABSTRACT FROM AUTHOR]

Cement stabilized macadam semi-rigid base materials are widely used in road construction in China. However, a traditional static molding method and heavy compaction method cannot guide the design and engineering application of cement stabilized macadam mixture because it often appears that the compaction degree exceeds 100% in the practical engineering. In view of this, this paper carried out the research of an indoor vibration compaction method of cement stabilized macadam mixture, and compared the mechanical properties and void distribution characteristics of two kinds of compositions of mixtures under the vibration compaction method as well as static pressure molding and heavy compaction method and on-site sample after 7 days curing period, which was combined with the physical engineering project of Yu-Song Expressway in Jilin Province, China. The research results show that the maximum dry density of mixture under vibration compaction is larger and the best moisture content is smaller, which has a heavy incomparable advantage on the simulation of on-site compaction. And the compressive strength and splitting strength indexes of vibration compacted specimens are close to those of an on-site sample, which are all larger than static pressure specimen. Moreover, the void distribution characteristics of vibration compacted specimens is much closer to those of the on-site sample and more universal, while static pressure specimens lack in uniformity. In addition, different results caused by the two gradation are compared. All of the above research results can verify that the vibration compaction method has more reliability and accuracy to simulate the actual properties of base material. This study provides a reference for the application of vibration compaction method in road engineering design. [ABSTRACT FROM AUTHOR]

In recent years, the winter temperature in southern China decreases year by year, and the phenomenon of freeze-thaw damage is also widespread in hydraulic buildings. In this paper, the freezing-thawing cycle tests of fully graded concrete specimens and corresponding wet sieving suitable for climate conditions in southern China were carried out, and the effects of freezing-thaw cycles on the appearance, mass loss, relative dynamic elastic modulus, internal temperature and strain of fully graded concrete and wet sieving concrete were studied. The splitting tensile strength test of concrete specimens with specified salt freezing cycles was carried out, and the relationship between the strength reduction of fully graded concrete and wet sieving concrete specimens and the number of freeze-thaw cycles was analyzed. The results show that with the increase of freeze-thaw cycles, the properties of fully graded concrete and wet sieving concrete degraded, and the degradation of compressive strength was the most significant, followed by the splitting tensile strength. In the initial stage of the freeze-thaw cycles, the degradation of each property was not obvious, and the deterioration rate of each property increased significantly after 100 freeze-thaw cycles. Besides, the relationship between the splitting tensile strength of fully graded concrete and wet sieving concrete and the internal wave velocity after freeze-thaw cycles was established. The test results can provide theoretical basis for the design, repair, maintenance and life prediction of dams and offshore platforms in southern China. [ABSTRACT FROM AUTHOR]

The hydrological and mechanical properties of granitic residual soils can be significantly altered by periodical wetting and drying (W-D) cycles. The soil structure degradation induced by W-D cycles can lead to soil mass failure and collapsing gully erosion in granitic hilly slopes in south China. However, limited attempts have been made at a comprehensive investigation of the effects of W-D cycles on the structure degradation of granitic residual soils, especially at the pedon scale. The purpose of this paper is to investigate the structural degradation of granite soils induced by W-D cycles and explore its potential influence on the development of collapsing gully erosion. The granitic soil properties, including hydraulic properties, shear strength, and disintegration characteristics, were performed after W-D cycles. The results indicated that the W-D cycles altered the soil pore structure, leading to variations in soil hydraulic properties. Specifically, with increasing alternate W-D cycles, the initial saturated water content and residual water content decreased, while the saturated hydraulic conductivity increased. Meanwhile, increasing W-D cycles contributed significantly to variations in cohesion and internal friction strength by decreasing the shear strength variables, especially the soil cohesion strength. Correspondingly, soil disintegration was increased during W-D cycles. Furthermore, most degradation of soil structure was recorded within the first two cycles of W-D. The obtained results indicate that the W-D cycles weaken soil structure, increase rainwater infiltration, decrease soil shear strength and disintegration resistance, and accelerate soil erosion. A vicious cycle of granitic slope failure induced by W-D cycles is eventually formed. This study provides useful information about the mechanism of soil mass failure and collapsing gully erosion in granitic hilly slopes. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Chinese traditional mortise-tenon joints have some advantages and can be considered for application in modern timber construction. • It is an efficient, economical and convenient way to reinforce mortise-tenon joints with self-tapping screws (STS). • Different STS insertion methods had different reinforcement effects for mortise-tenon joints. • The reinforced joints had better mechanical properties compared with the unreinforced joint. The mortise-tenon (MT) joints are kind of traditional connection for structural components in China, which can get better connection performance by reinforcement. In this paper, different self-tapping screw (STS) insertion methods were applied to reinforce the MT joints, and cyclic loading were carried out for one group of unreinforced joint and three groups of reinforced joints. The load-carrying capacity, strength, stiffness, ductility, and energy dissipation capacity of each group were evaluated. The results showed that STS inserted horizontally could significantly reduce the pull-out of the tenon and improve the load-carrying capacity of the joints. The joints reinforced by two horizontally inserted STS had a higher load-carrying capacity than those reinforced by one STS with horizontal insertion, although the former might accelerate the damage to joints. Inclined insertion of STS for joints provided higher stiffness, ductility and energy dissipation capacity, while the load-carrying capacity was inferior to that of the reinforced joints with STS horizontally inserted. This paper provides data for reinforcing MT joints with STS, so as to select different reinforcement methods for different engineering requirements. [ABSTRACT FROM AUTHOR]

Nowadays, the challenges of the industry increasingly demand the manufacture of complex shapes with great design flexibility without waste by 3D printing. Additive manufacturing, unlike traditional manufacturing techniques such as casting and machining, enables designers to rapid prototype while lowering operating costs and material waste during this process. In this way, understanding the current state of the literature related to additive manufacturing processes and the mechanical properties of 3D printed materials is of high importance to determine a research horizon in developing future works of this topic. In this paper, a bibliometric analysis, also named Scientometric science, was implemented. The tendencies and transcendental topics were determined using the Bibliometrix package for R and VOSviewer. Data were exported directly from the Scopus database with a search equation. The results showed that, of the 1271 documents analyzed, 2015 is a year where the research began its developing stage, with a growth rate of 20.8%. The USA resulted to be a leading country in publications followed by China and the UK. Likewise, it is observed that the author with the highest number of publications and h-index is C.B. Williams, followed by A.A. Zadpoor and J. Muller. Besides, the evolution in time of the keywords most used by researchers, and trends and research gaps in the study of additive manufacturing with the mechanical properties of the 3D printing materials are presented. [ABSTRACT FROM AUTHOR]

The cement manufacturing industry, a resource- and energy-intensive sector, took up more than 15% of total greenhouse gas emissions in China, thus finding a clean technology option for sustainable development is essential. CO 2 curing has emerged as a promising novel method for large-scale carbon sequestration and mechanical properties improvement of cement-based composites. Currently, a body of related works is mainly investigated in the laboratory, and understandings of the behaviors of CO 2 -cured cement-based composites are still less than complete, including, 1) the CO 2 storage potential has plenty of room for improvement due to the influence mechanism of variables factors remains unclear; 2) previous evaluations were mostly based on the subsets of individual result rather than an integrated dataset; 3) whether CO 2 curing is suitable for the manufacturing process of reinforced concrete. Therefore, this paper presents a comprehensive overview covering a wide range of parameters as well as fabrication, mechanical (compressive strength), and environmental (CO 2 uptake value) performances on the basis of a correct understanding of the differences between active and passive carbonation reactions. Notably, the influences of critical factors, including those less understood, e.g., types of curing setup (flow-able, enclosed, and others), components of binder, and aggregate/binder ratio, are also analyzed and the corresponding mechanisms discussed to achieve satisfied curing efficiency. Besides, corrosion-related challenges are also be pointed out to convince the widespread acceptance of this technology. Finally, based on this paper, limitations of existing research are identified and future scope on CO 2 curing regime is proposed. • 170 studies related to CO 2 /carbonation-cured cement-based composites are analyzed. • The differences between active/passive-carbonation together with reaction mechanisms are expounded. • Fabrication and influence factors on engineering and environmental properties are systematically reviewed. • CO 2 -cured cement-based composites exhibit excellent resistance to aggressive conditions. • The challenges and opportunities in the CO 2 curing method are innovatively discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A gully erosion area affected by weathering-related process is focused. • Comprehensive dataset of granite chemical weathering is given. • Applicability of chemical weathering index is critically assessed. • Weathering index is quantitatively corelated to mechanical property. • Various aspects of mechanical property of granite regolith are considered. In most cases, chemical weathering reduces the strength and stability of granite regolith and increases its water sensitivity. When combined with external agents such as climate, these alterations facilitate geomorphological evolution, such as gully erosion in hilly regions. The lack of fundamental understanding about how gully erosion forms have led to an increasing trend of gully erosion in recent years. Because the weathering-controlled properties of granite regolith have a significant effect on gully development, it is vital to assess the chemical weathering degree. However, despite extensive studies on quantifying weathering degree using chemical weathering indices, less is known about how these parameters are correlated with the mechanical properties of granite regolith. To this end, a typical weathering profile is established for granite in Jiangmen, China. This paper investigates the chemical weathering of granite, evaluates the appropriateness of previous chemical weathering indices, and correlates them with the mechanical parameters of granite regolith. Several suitable indices, including CIA, Bases/Al 2 O 3 , Bases/R 2 O 3 , ba 1 , ba 3 , CIW, I mob , and PIA, are selected and correlated with the mechanical parameters. These indices apply well, with some scattering when they are correlated with the internal frictional angle of granite residual soil. This paper provides a comprehensive datset regarding the physical, mineralogical, petrographical, geochemical, and mechanical properties of granite regolith, and enhances the understanding of chemical weathering, especially its correlations with the mechanical properties of regolith. [ABSTRACT FROM AUTHOR]

Since a high-density polyethylene membrane has good mechanical properties and stable chemical properties, it is widely used in all kinds of anti-permeable layers. But for a sewage pool of a drilling engineering in the western desert oil field, it is not only facing a high temperature and drying environment, but also quite a complex drilling fluid composition. Yet an experimental study system on application has not set up in China. According to the working environment of the high-density polyethylene membrane, a series of aging tests are carried out in the paper. Measured the change value of the high-density polyethylene membrane, mechanical properties are expressed directly the aging properties of high-density polyethylene membranes. [ABSTRACT FROM AUTHOR]

A lot of cultural heritages in the world made up of or supported by stones are damaged seriously because of long-term weathering. It is necessary to assess the weathered degrees and stabilities of these heritages. In this paper, a procedure to assess the weathered degrees and stabilities of stone relics was put forward on the base of ultrasonic CT techniques. The procedure was applied to an ancient stone bridge in eastern China, Guyue Bridge constructed about 820 years ago. Firstly, P-wave velocity distribution profiles of stone ashlars of the bridge were obtained with ultrasonic CT techniques. Secondly, according to velocity ratio of the in situ P-wave velocities of the stone ashlars to the P-wave velocity of the fresh rock specimens of the same lithology with those of the stone ashlars, the weathered degrees of the stone ashlars were determined. Finally, the same rock specimens with different weathered degree, which were collected from a quarry near the historic bridge, were tested to get their P-wave velocities, UCS and elastic moduli, and the relations between the P-wave velocity and these mechanical properties were put forward. On the base of these relations, the mechanical property distributions of the detected stones could be obtained. In this study, two vertical sections of an ashlar in the historic stone bridge were detected by the assessment procedure. According to the assessment results, the two cross sections have different weathered degrees because of different stress states: higher weathered degree and lower compressive strength present to the section near the joint connecting two stone ashlars, where pressive stress is much stronger than that of the section far away from the joint. Correspondingly, the higher weathered section had worse physical and mechanical properties, which would be the key location for the stability of the old bridge. [ABSTRACT FROM AUTHOR]

Though a large amount of research has been carried out on recycled aggregate concrete (RAC) during recent years, the application cases of RAC in real structures are still very few in China. This paper reports the application of RAC in a real project. Two beams made of RAC and commercial natural aggregate concrete (NAC) respectively were cast in-situ to carry out the tests. The two beams were subjected to the similar service loading, so that the performance of the RAC beam could be compared with that of the NAC one. Compressive strength, degree of density and uniformity were tested for both types of concrete at representative ages, and concrete strain of the two target beams was monitored regularly from the age from 1 d to 420 d. The results from laboratory tests and on-site monitoring have proved the feasibility and reliability of the application of RAC in real structures though RAC is generally inferior to NAC. [ABSTRACT FROM AUTHOR]

Highlights • Fatigue testing on full-scale CRTS III track model subjected to 30 million cycles. • Study on the evolution of fastener and isolation layer stiffness with fatigue load. • Prediction of the service life of key components of the track structure. • Study on the dynamic response of CRTS III track structure with fatigue load. Abstract Ballastless slab track have been developed and used worldwide to carter for high speed, high stability, high riding comfort, and low maintenance cost requirements of High Speed Railway (HSR) operations. To this ends, the Chinese Rail Track System (CRTS) III was designed and developed independently in China and adopted in new railway lines. The CRTS III is believed to have improved performance over the previously used CRTS I and II, severe structural damages in the form of cracks and delamination at the interface between the prefabricated slab and the SCC filling layer have been reported in service. This cannot be ignored because of the detrimental effects they have on bearing capacity and stiffness of the track. This paper presents an experimental study to evaluate the evolution of stiffness of fasteners and the isolation layer of CRTS III ballastless slab track. The experiments are based on full-scale test on three CRTS III slab track-subgrade structure model subjected to cyclic fatigue loadings up to 30 million cycles. The results of the study revealed the following: (1) The dynamic and static stiffness of the fastener increase by 116% and 30%, respectively. After 10 million cycles of fatigue loading, the ratio of dynamic to static stiffness become larger than 1.5. (2) the stiffness of isolation layer changes in accordance with quadratic function with a correlation coefficient of 0.999. The maximum stiffness obtains 2.4 times than its initial value at 30 million cycles of fatigue loading. (3) the acceleration of rail and slab track reduce by 63% and 34% respectively, while the acceleration of support foundation increases by 54%. The findings of this research can serve as a useful guide in the design and maintenance scheduling of the CRTS III slab track structure as well as references for future studies. [ABSTRACT FROM AUTHOR]

Polymer-modified concrete and fiber concrete are two excellent paving materials that improve the performance of some concrete, but the performance of single application material is still limited. In this paper, polymer-modified concrete with strong deformation and fiber concrete with obvious crack resistance and reinforcement effect were compounded by using the idea of composite material design so as to obtain a high-performance pavement material. The basic mechanical properties of high-content hybrid fiber–polymer-modified concrete, such as workability, compression, flexural resistance, and environmental durability (such as sulfate resistance) were studied by using the test regulations of cement concrete in China. The main results were as follows. (1) The hybrid fiber–polymer concrete displayed reliable working performance, high stiffness, and a modulus of elasticity as high as 35.93 GPa. (2) The hybrid fiber–polymer concrete had a compressive strength of 52.82 MPa, which was 31.2% higher than that of the plain C40 concrete (40.25 MPa); the strength of bending of the hybrid concrete was 11.51 MPa, 191.4% higher than that of the plain concrete (3.95 MPa). (3) The corrosion resistance value of the hybrid fiber–polymer concrete was 81.31%, indicating its adjustability to sulfate attack environments. (4) According to cross-sectional scanning electron microscope (SEM) images, the hybrid fiber–polymer concrete was seemingly more integrated with a dense layer of cementing substance on its surface along with fewer microholes and microcracks as when compared to the ordinary concrete. The research showed that hybrid fiber–polymer concrete had superior strength and environmental erosion resistance and was a pavement material with superior mechanical properties. [ABSTRACT FROM AUTHOR]

This research presents a dual-pronged bibliometric and systematic review of the integration of phase change materials (PCM) in asphalt pavements to counteract the urban heat island (UHI) effect. The bibliometric approach discerns the evolution of PCM-inclusion asphalt research, highlighting a marked rise in the number of publications between 2019 and 2022. Notably, Chang'an University in China has emerged as a leading contributor. The systematic review addresses key questions like optimal PCM types for UHI effect mitigation, strategies for PCM leakage prevention in asphalt, and effects on mechanical properties. The findings identify polyethylene glycols (PEGs), especially PEG2000 and PEG4000, as prevailing PCM due to their wide phase-change temperature range and significant enthalpy during phase transitions. While including PCM can modify asphalt's mechanical attributes, such mixtures typically stay within performance norms. This review emphasises the potential of PCM in urban heat management and the need for further research to achieve optimal thermal and mechanical balance. [ABSTRACT FROM AUTHOR]

Liquid hydrogen is the main fuel of large-scale low-temperature heavy-duty rockets, and has become the key direction of energy development in China in recent years. As an important application carrier in the large-scale storage and transportation of liquid hydrogen, liquid hydrogen cryogenic storage and transportation containers are the key equipment related to the national defense security of China's aerospace and energy fields. Due to the low temperature of liquid hydrogen (20 K), special requirements have been put forward for the selection of materials for storage and transportation containers including the adaptability of materials in a liquid hydrogen environment, hydrogen embrittlement characteristics, mechanical properties, and thermophysical properties of liquid hydrogen temperature, which can all affect the safe and reliable design of storage and transportation containers. Therefore, it is of great practical significance to systematically master the types and properties of cryogenic materials for the development of liquid hydrogen storage and transportation containers. With the wide application of liquid hydrogen in different occasions, the requirements for storage and transportation container materials are not the same. In this paper, the types and applications of cryogenic materials commonly used in liquid hydrogen storage and transportation containers are reviewed. The effects of low-temperature on the mechanical properties of different materials are introduced. The research progress of cryogenic materials and low-temperature performance data of materials is introduced. The shortcomings in the research and application of cryogenic materials for liquid hydrogen storage and transportation containers are summarized to provide guidance for the future development of container materials. Among them, stainless steel is the most widely used cryogenic material for liquid hydrogen storage and transportation vessel, but different grades of stainless steel also have different applications, which usually need to be comprehensively considered in combination with its low temperature performance, corrosion resistance, welding performance, and other aspects. However, with the increasing demand for space liquid hydrogen storage and transportation, the research on high specific strength cryogenic materials such as aluminum alloy, titanium alloy, or composite materials is also developing. Aluminum alloy liquid hydrogen storage and transportation containers are widely used in the space field, while composite materials have significant advantages in being lightweight. Hydrogen permeation is the key bottleneck of composite storage and transportation containers. At present, there are still many technical problems that have not been solved. [ABSTRACT FROM AUTHOR]

The disposal of waste coal gangue (WCG) is still a serious problem for areas that rely on the coal mine industry, especially in the northern part of China. This paper investigated the improving behavior and corresponding mechanism by waste coal gangue on the dispersivity, water stability and mechanical properties of dispersive soil. Dispersive soil samples with different contents of natural waste coal gangue, varying from 1% to 10%, were prepared and cured for 0, 1, 3, 7, 14 and 28 days. Dispersivity and water stability of soil samples were evaluated by pinhole test, cube sample crumb test and remoulded sphere sample crumb test. Electric conductivity and pH of soil samples were monitored during 28 days of curing. Unconfined compression test and splitting test were performed to determine the compressive and tensile strength of soil samples. Microstructural and mineral analysis methods such as SEM, EDS and XRD were conducted to determine the microstructural and mineral changes during curing time. Experiments show that waste coal gangue could restrain the dispersivity and enhance the water stability of dispersive soil, subsequently changing dispersive soil into nondispersive soil. Increases of 591% and 192% are observed when WCG content increases from 1% to 10% and curing time increases from 0 to 28 days for compressive and tensile strength, respectively. Increasing in waste coal gangue content and curing time would better promote the positive effect of waste coal gangue, on both the dispersivity modification and strength improvement of dispersive soil. Microstructural and mineral analyses show that newly generated products among soil particles increase the friction and cohesion between soil particles. Results indicate that reusing of waste coal gangue as an admixture in dispersive soil is a feasible way, which would solve the disposal of waste coal gangue and optimize the poor properties of dispersive soil at the same time. Enhancing water stability of dispersivity soil would ensure the safety and normal operation of soil structures. • Modification experiment of dispersive soil by waste coal gangue is studied. • Waste coal gangue is capable of changing dispersive soil into nondispersive soil. • Water stability of dispersive soil is enhanced by waste coal gangue. • Mechanical property of dispersive soil is improved by waste coal gangue. [ABSTRACT FROM AUTHOR]

Bamboo belongs to the grass family and is an important non-timber forest product in tropic and sub-tropic countries. The global trade of bamboo products is worth billions of dollars and is mainly dominant with monopodial bamboo grown in sub-tropic countries such as China and Japan. Many researchers globally discuss that in addition to species and region, bamboo quality can differ based on its rhizome types because the physiology is different for both monopodial and sympodial bamboo. However, there is a massive competition within the yearly forest products due to the challenges posed by underground root system in agroforestry. This review studied the properties of bamboo with regards to their differences in terms of monopodial and sympodial types of rhizomes. It was found that most of the structural, chemical organic, and mechanical properties are higher in monopodial bamboo, but there is a greater fibre morphology and decay resistance in the sympodial bamboo. [ABSTRACT FROM AUTHOR]

Granite is the host rock of the Beishan Underground Research Laboratory (URL) for geological disposal of high-level radioactive waste in China. The mechanical behavior of Beishan granite is the key in determining whether the repository can serve safely for a long time. The surrounding rock of the repository will be exposed to thermal environment induced by radionuclide decay, resulting in significant changes in the physical and mechanical properties of the Beishan granite. This study investigated the pore structure and mechanical properties of Beishan granite after thermal treatment. The T2 spectrum distribution, pore size distribution, porosity, and magnetic resonance imaging (MRI) were obtained through nuclear magnetic resonance (NMR); uniaxial compressive strength (UCS) and acoustic emission (AE) signal characteristic of granite were investigated through uniaxial compression tests. The results showed that high temperature significantly affected the T2 spectrum distribution, pore size distribution, porosity, compressive strength, and elastic modulus of granite, and porosity gradually increases, whereas the strength and elastic modulus gradually decline with increasing temperature. The porosity of granite has a linear relationship with UCS and elastic modulus, indicating that the essential mechanism for the deterioration of macroscopic mechanical properties lies in changes of microstructure. In addition, the thermal damage mechanism of granite was revealed, and a damage variable was defined based on porosity and uniaxial compressive strength. [ABSTRACT FROM AUTHOR]

In order to study the variation of mechanical properties of steel under acid rain corrosion conditions in northern China, monotonic tensile tests were conducted on Q235 steel with a thickness of 3.0 mm and 4.5 mm using a method of artificially prepared simulated acid rain solution for indoor accelerated corrosion. The results show that the failure mode of corroded steel standard tensile coupon includes normal fault and oblique fault. The failure patterns of the test specimen show that the thickness of the steel and corrosion rate affected the corrosion resistance. Larger thicknesses and lower corrosion rates will delay the failure mode of corrosion on steel. The strength reduction factor (Ru), deformability reduction factor (Rd) and energy absorption reduction factor (Re) decrease linearly with the increasing corrosion rate from 0% to 30%. The results are interpreted also from the microstructural point of view. The number, size, and distribution of the pits are random when the steel is subjected to sulfate corrosion. The higher the corrosion rate, the clearer, denser, and more hemispherical the corrosion pits. The microstructure of steel tensile fracture can be divided into intergranular fracture and cleavage fracture. As the corrosion rate increases, the dimples at the tensile fracture gradually disappear and the cleavage surface gradually increases. An equivalent thickness reduction model is proposed based on Faraday's law and the meso-damage theory. [ABSTRACT FROM AUTHOR]

Near the coast of China, a large amount of sediment is produced during construction work. In order to mitigate the environmental damage caused by sediment and enhance the performance of rubber-modified asphalt effectively, solidified silt material and waste rubber were prepared to modify asphalt, and its macroscopic properties, such as viscosity and chemical composition, were determined via a routine physical test, DSR, Fourier Transform Infrared Spectroscopy (FTIR), and Fluorescence Microscopy (FM). The results show that, with the increase in powder particles and the addition of a certain amount of hardened mud, the mixing and compaction temperature of modified asphalt can be significantly increased—still reaching the design standard. In addition, the high thermal stability and fatigue resistance of the modified asphalt were clearly better than those of the ordinary asphalt. From the FTIR analysis, rubber particles and hardened silt only exhibited mechanical agitation with the asphalt. Considering that excessive silt might result in the aggregation of matrix asphalt, the addition of an appropriate amount of hardened solidified silt material can eliminate the aggregation. Therefore, the performance of modified asphalt was optimum when solidified silt was added. Our research can provide an effective theoretical basis and reference values for the practical application of compound-modified asphalt. Therefore, 6%HCS(6:4)-CRMA have better performance. Compared to ordinary rubber-modified asphalt, the composite-modified asphalt binder has better physical properties and a more suitable construction temperature. The composite-modified asphalt uses discarded rubber and silt as raw materials, which can effectively protect the environment. Meanwhile, the modified asphalt has excellent rheological properties and fatigue resistance. [ABSTRACT FROM AUTHOR]

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In water-related projects, the application of steel sheet pile cofferdams is becoming more and more widespread, and the influence of tunnel construction on the mechanical properties of adjacent cofferdams is important. In this study, the object of research was the mechanical properties of large-span steel sheet pile cofferdams. The open-cut tunnel project was located in Suzhou Yinshan Lake, China. According to the actual construction steps of the tunnel foundation pit, assuming that the soil was a small strain hardening soil model, combined with on-site monitoring data, a three-dimensional elastoplastic finite difference model was established. The results show that during tunnel construction, the maximum settlement of the cofferdam appeared at 0.27~0.53 m on the side of the foundation pit; the maximum horizontal displacement of the steel sheet pile occurred at the pile bottom of foundation pit side, and the seepage gradually increased during construction, eventually resulting in water gushing at the bottom of the foundation pit. After the completion of tunnel construction, the settlement value of the cofferdam presented a pattern that first increased and then decreased from the side of the foundation pit to the side of the adjacent lakeside; the steel cofferdam tilted toward the side of the foundation pit, with a maximum inclination angle of 3.37°. It should be pointed out that as the construction progressed, the axial force of the tie rods in the steel cofferdam changed from a U-shaped distribution to a V-shaped distribution. This study could provide a reference for the impact of tunnel foundation pit construction on adjacent steel cofferdam and could also provide a reference for the safety research of open-cut tunnel construction. [ABSTRACT FROM AUTHOR]

The abundant reserve of shale gas in Sichuan Basin has become a significant natural gas component in China. To achieve efficient development of shale gas, it is necessary to analyze the stress state, pore pressure, and reservoir mechanical properties such that an accurate geomechanical model can be established. In this paper, Six wells of Neijiang-Dazu and North Rongchang (NDNR) Block were thoroughly investigated to establish the geomechanical model for the study area. The well log analysis was performed to derive the in-situ stresses and pore pressure while the stress polygon was applied to constrain the value of the maximum horizontal principal stress. Image and caliper data, mini-frac test and laboratory rock mechanics test results were used to calibrate the geomechanical model. The model was further validated by comparing the model prediction against the actual wellbore failure observed in the field. It was found that it is associated with the strike-slip (SS) stress regime; the orientation of SHmax was inferred to be 106–130° N. The pore pressure appears to be approximately hydrostatic from the surface to 1000 m true vertical depth (TVD), but then becomes over-pressured from the Xujiahe formation. The geomechanical model can provide guidance for the subsequent drilling and completion in this area and be used to effectively avoid complex drilling events such as collapse, kick, and lost circulation (mud losses) along the entire well. Also, the in-situ stress and pore pressure database can be used to analyze wellbore stability issues as well as help design hydraulic fracturing operations. [ABSTRACT FROM AUTHOR]

To study the mechanical properties and energy evolution characteristics of the shallow fractured coal in the Western China mining area, a series of triaxial compression tests was carried out on fractured coal specimens. The stress–strain curve, mechanical properties and failure characteristics were analyzed. Then, the fractal characteristics and energy evolution law were investigated. Results show that with the increase of prefabricated crack number, the post-peak stage of the stress–strain curve changed from a linear drop to a stepped drop, indicating that the damage degree tends to moderate. Both the elastic modulus and peak strength decreased as the prefabricated crack number increased, whereas the peak strain did not exhibit a clear trend. The failure mode changed from overall tensile failure to tensile-shear mixed failure as the prefabricated crack number increased. With the increase of prefabricated crack number, the failure shape dimension increased linearly. The total energy and elastic energy decreased gradually with the increase of prefabricated crack number, whereas the dissipation energy increased gradually. The results can provide a better understanding of the failure mechanism of fractured coal and its application for control design. [ABSTRACT FROM AUTHOR]

Poplar is a common tree species that is extensively cultivated in China, and its density is relatively low. The low density of poplar results in low mechanical properties, which restrict its application range. However, the density of wood can be increased by compressing the porous structure in the transverse direction. Before compression, the wood needs to be softened from a rigid state to a thermoplastic flow state. After compression, the compressive deformation needs to be fixed. The hot water pretreatment and heat post-treatment is by far the most convenient and environment-friendly way for the manufacture of the densified wood. This study presents the mechanical properties of densified poplar by hot water pretreatment with different compression ratio and thermal modification time, and explores the engineering application potential of densified poplar as wooden dowel to connect timber members instead of steel dowel. [ABSTRACT FROM AUTHOR]

The mechanical properties of gas-containing coal and rock mass play important roles in controlling the occurrence and development of coal and gas outbursts. The gradual increase in mining depth will change the failure mechanism of gas-containing coal and rock mass. In order to further study the failure mechanism of gas-containing coal and rock mass, samples were taken from the gas-containing coal seam in the Wuhushan Coal Mine of the Wuhai Mining area of China. The mechanical parameters of coal samples during the failure process under different gas pressure conditions were measured and analyzed with the SAW-2000 rock mechanics testing machine, the gas-containing coal uniaxial compression device and inflation system. Meanwhile, the failure process and mechanical parameters of coal samples under different gas pressure were simulated by RFPA2D gas plate numerical simulation software. The results show that with increasing gas pressure in the coal there is decrease in Compressive strength, Elastic modulus, Strain, Peak strength and Bearing capacity and increase in Poisson's ratio. When the failure state appears in the coal, the cracks are longer and wider, more random cracks are genareted, and the damage degree of the coal is greater. The numerical analysis' results are in good agreement with experimental results. The research results are applicable to the gas bearing coal with the same or similar gas geological conditions. The tests can be carried out repeatedly and reasonable results can be obtained according to the physical and mechanical parameters of the actual coal seam and the occurrence of gas. On this basis, physical experiments and numerical simulations of triaxial compression can also be carried out to further study the mechanical characteristics of deformation and the failure of gas-containing coal under gas pressure and provide technical support for revealing the mechanism of coal and gas outbursts. [ABSTRACT FROM AUTHOR]

Reverse engineering is conducted based on the analysis of an already existing product. The results of such an analysis can be used to improve the functioning of the product or develop new organizational, economic, information technology, and other solutions that increase the efficiency of the entire business system, in particular 3D printed products. Therefore, the main aim of this research is to focus on evaluation of the load-bearing capacity of already existing 3D printed metals in order to see their suitability for the intended application and to obtain their relevant mechanical properties. To this end, 3D printed metallic bars with almost square cross-sections were acquired from an external company in China without any known processing parameters, apart from the assumption that specimens No. 1–3 are printed horizontally, and specimens No. 4–7 are printed vertically. Various experiments were conducted to study microstructural characteristics and mechanical properties of 3D printed metals. It was observed that specimens No. 1–6, were almost similar in hardness, while specimen No. 7 was reduced by about 4.5% due to the uneven surface. The average value of hardness for the specimens was found to be approximately 450 HV, whereas the load-extension graphs assessed prior point towards the conclusion that the specimens' fractured in a brittle status, is due to the lack of plastic deformation. For different specimens of the 3D printed materials, the main defects were identified, namely, lack of fusion and porosity are directly responsible for the cracks and layer delamination, prevalent in SLM printed metals. An extensive presence of cracks and layer delamination prove that the printing of these metallic bars was completed in a quick and inaccurate manner, which led to higher percentages of lack of fusion due to either low laser power, high scan speed, or the wrong scan strategy. [ABSTRACT FROM AUTHOR]

A uranium tailing pond in southern China is the largest in Asia. For historical reasons, uranium tailings stored in the pond have been in an acidic environment for a long time, which has caused great difficulties for decommissioning treatment of the pond. In this study, uranium tailings were taken from the beach surface of the pond as the research object. Then, 11 kinds of solidified samples of uranium tailings with different compositional ratios were prepared using water glass and sodium hydroxide, as alkali activators, and mixed with metakaolin, fly ash, and PVA or basalt fibers. The resulting solidified samples were examined in terms of microscopic characterization, compressive strength, tensile strength, resistivity, and U(VI) leaching. The results showed that, with increased fiber content, the compressive strength of samples first increased and then decreased, while the tensile strength increased continuously. The body volume resistivities first increased and then decreased and, with increased time, the leaching rate decreased continuously and finally tended to stabilize. The compressive strength and volume resistivity of samples were negatively correlated with the U(VI) leaching rate and cumulative leaching fraction. Considering the physical mechanics and U(VI) leaching resistance properties of these bodies, the best fiber proportion was concluded to be the addition of 0.2-wt% PVA fiber and 0.6-wt% basalt fiber. [ABSTRACT FROM AUTHOR]

With people's awareness of environmental protection, the requirement of eco‐quality is increasingly demanding, particularly a more profound reflection in the field of materials. Polylactic acid (PLA) is a hopeful biodegradable thermoplastic material while its adverse nature restricts the practical applications. In this work, a one‐step reactive extrusion method was adopted to improve some properties of PLA by melt blending with some active additives, including commercial epoxy‐based chain extender, that is, ADR4468 of BASF, Germany; thermoplastic polyurethane thermoplastic polyurethane (TPU) elastomer, that is, DN‐5380 of Dawn, China, and mineral nucleating agent talc, that is, AH250CL of Aihai, China. Their influences on mechanical properties and crystallization behaviors of PLA were explored, and the detailed mechanisms were also discussed. It is found that ADR chain extender played a key role in improving the strength and rigidity of the composites, and methylenediphenyl diisocyanate type TPU elastomer could significantly enhance the toughness and ductility of PLA materials, while talc had a positive impact on regulating the cooling crystallization behavior of PLA. In particular, only trace ADR4468 (0.4 wt%) could effectively enhance its tensile and flexural strengths of neat PLA by 6.3% and 13.4%, respectively. Reactive polyurethane with 5 wt% significantly improved its elongation at break by 36.5%. The micro‐sized talc‐nucleating agent enhanced the cooling crystallization degrees to 24.7% from 4.8% for PLA blended with trace chain extender. The analysis results indicated that the functional group reactions between the active additives and PLA played key roles in improving the related properties. The output has certain reference values for PLA modification strategy, and will pave a route for endowing PLA materials with specific and required nature. [ABSTRACT FROM AUTHOR]

The swelling characteristics of swelling soft rocks (SSRs) in the Yanji Basin, Northeastern China, have posed huge challenges to the construction of local highways. Based on the geological background, the swelling properties and strength characteristics of undisturbed and reconstructed SSRs, especially the constitutive relationship, are studied, which is of great significance to engineering practice. In this study, X-ray diffraction and scanning electron microscopy were used to determine SSRs' mineral composition and microstructural characteristics. Swelling test, shear test, and unconfined compression test were used to identify the relationship between different water content of SSRs and free swell ratio (δe), swelling pressure (Pe), stress–strain characteristics, and strength, respectively. The results showed that (1) the mixed layer content of illite-montmorillonite in SSRs reached 95%. (2) δe and Pe were negatively linearly and exponentially related to the initial moisture content (ωs), respectively. Rapid and intense swelling mainly occurred at the initial swelling stage. (3) ωs were negatively linearly related to the shear stress (τ), cohesion (c) and the angle of internal friction (φ). In addition, SSRs with lower ωs suffered "strain softening" failure, while SSRs with higher ωs suffered "strain hardening" failure. (4) δe and the moisture content after swelling were both linearly related to the logc and logφ. Furthermore, the optimum moisture content (21–26%) of SSRs of the Yanji Basin's project was determined for the first time. These results have already been applied to engineering practice in the Yanji Basin and other regions where SSRs are widely distributed. Highlights: The mechanical properties of undisturbed and reconstructed specimens were studied by three geotechnical tests. The moisture content of swelling soft rocks has an important role in the expansion behavior and strength characteristics. The optimal water content of swelling soft rocks' engineering construction in Yanji Basin was determined to be 21-26%. [ABSTRACT FROM AUTHOR]

Abstract: Fracture data available for one of the rock masses (limestone) in the dam site of Yujian River Reservoir were used to build and validate a stochastic 3-D fracture network model, and to perform a REV and equivalent continuum study in 3-D. A number of relations are developed in the paper between the rock mass mechanical parameters and fracture tensor components in 3-D. Based on the mechanical parameter values obtained in every 45° direction in 3-D, the principal parameter values, principal directions and tensors are developed for rock mass mechanical parameters to represent the REV block size properties. An incrementally linear elastic, orthotropic constitutive model is suggested to represent the equivalent continuum pre-failure mechanical behavior of the jointed rock mass by incorporating the effect of joint geometry network by the fracture tensor components. [Copyright &y& Elsevier]

• The EBW test of different weld penetration and scale FW with W/Cu sheets was realized. • When the weld penetration is small, the surface focus welding is the best. Otherwise, the lower focus welding is the best. • Reduced scale FW welding with weld width less than 4 mm and good surface forming is realized. Water- cooled ceramic breeder (WCCB) blanket is one of the candidate blanket for China Fusion Engineering Test Reactor (CFETR) independently developed by China Institute of plasma physics. The first wall (FW) is a component of WCCB, which directly faces the plasma. FW contains flow channels and has complex shape structure, therefore, it is difficult to complete the full-scale manufacturing by one kind of welding process. Hence, in the development process, the components of FW are first connected by hot isostatic pressing (HIP), and then connected by electron beam welding (EBW), so as to form the full-scaled FW connection. In this paper, the EBW process of FW was studied. The results showed that when the electron beam current was 50 mA and the focus was on the surface, the welded joint with 20 mm penetration and good shape can be formed. After the one time welding and the twice welding (overlapping first welding) of the weld, the tensile test fracture occurred in the base metal. The impact energy of the one time welding was 13 MPa, 18 MPa, and 21 MPa, respectively, and the impact energy of the twice welding was 19 MPa, 20 MPa, and 51 MPa, respectively. The microstructure of the joint was composed of δ-ferrite and lath martensite. When the weld penetration was increased to 50 mm, the lower the focus is, the smaller the porosity at the bottom of the weld is. Similarly, when the lower focus was used, the porosity at the bottom of the weld disappeared basically; The EBW test on the scaled FW with W/Cu sheets showed that when the we took the test pieces with the W-Cu sheet spacing is 4 mm, the welded joint with good surface shape and no internal defects can be formed without scanning deflection electron beam welding, and ultrasonic testing showed that EBW does not affect on the HIP interface. This provides a favorable basis for the future test of equal ratio FW test piece and the welding of actual FW. [ABSTRACT FROM AUTHOR]

The typical sandstone of the Shendong mining area, China, was considered as the research object in order to determine the mechanical properties and fracture evolution characteristics under true triaxial stress and different moisture contents by X-ray diffraction, true triaxial mechanical test, and CT scanning. The results show that the main mineral components of the sandstone are quartz, plagioclase, potassium feldspar, siderite, and clay minerals (kaolinite, illite, and chlorite), with clay minerals accounting for 25.7%. When σ2 > σ3, after sandstone failure, compressive deformation occurs in the ε2 direction, while expansion deformation occurs in the ε3 direction. A larger σ3 corresponds to a higher moisture content and a greater ductility of sandstone. σ3 influences the sandstone failure mode more significantly, compared with σ2 and moisture content. For a constant moisture content, the sandstone's compressive strength and the Young's modulus increase with increase in σ3. On the contrary, as σ2 increases, the compressive strength and the Young's modulus first increase and then decrease for all moisture contents. Additionally, when the stress state is kept the same, as the moisture content increases, the compressive strength and the Young's modulus of the sandstone decrease. Similarly, for the same moisture content, with increase in σ2, the smaller the number of fractures after sandstone failure and the more regular the fracture distribution. Moreover, under the same stress conditions, dry sandstone has the least regular fracture development after failure, followed by saturated sandstone, while the sandstone with natural moisture content has the most regular fracture development after failure. [ABSTRACT FROM AUTHOR]

• Strength and stiffness of calcareous sand is enhanced by using PFA for chemical stabilization. • The influence of PFA on calcareous sand characteristics are different for varying particle gradation. • The shear strength as well as CBR of calcareous sand is greatly improved when stabilized by PFA. • The test results are useful in determining the optimum content of PFA to be used in a particular calcareous sand with specific particle gradation. The calcareous sand existing at the South China sea is characterized by low shear strength with high compressibility. Associated with particle breakage, foundations built on such problematic soil initiates undrained failure with uneven foundation settlement, unless adequate ground improvement technique is adopted. In this paper, chemical soil stabilization is carried out by applying Polyurethane Foam Adhesive (PFA) to the virgin soil. Improvement of strength and stiffness of the treated soil have been investigated in detail by a series of triaxial consolidation and drainage tests followed by California bearing ratio tests. The effect of particle gradation on the stress–strain curve and CBR values of the stabilized calcareous sand as well as the influence on peak shear stress and shear strength index has been studied. The test results show that the PFA is effective in improving the mechanical properties of calcareous sand. The particle gradation has significant effects on the stress–strain response of the stabilized calcareous sand under different PFA contents. Optimal PFA content for each grading of calcareous sand was proposed. The test results of this work would be beneficial for engineering practice in dealing with the bearing capacity and settlement of foundations involving calcareous sand. [ABSTRACT FROM AUTHOR]

• 52 tensile coupons of high-performance bolt material are tested. • Effects of test strain-rate on the elevated temperatures are clarified. • Elevated-temperature behaviour of the steel is elucidated at microstructure level. • Prediction equations are proposed for elevated-temperature performance. • Constitutive model of full-range stress-strain relation is developed. Mechanical properties of steel at elevated temperatures are critical to the fire-resistant analysis and the fire safety design of steel structures. Thus, one solution for improving the fire resistance is use of high-performance (HP) steel, such as fire-resistant (FR) steel. However, practical use of the FR steel in steel structures implies requirements of sufficient fire resistance for the high-strength (HS) bolts as well, so that the loading capacities of bolted connections commonly used in steel structures can be guaranteed in case of fire. In this paper, material properties of grade 10.9 HP bolts recently developed in China, possessing both fire resistance and corrosion resistance, are tested at various elevated temperatures. Their stress-strain curves, modulus of elasticity, yield strength, ultimate tensile strength (UTS), and elongation percentage after fracture are obtained. These results are compared with that of conventional HS bolts and with reduction factors given in national standards. Constitutive models and prediction equations of the HP bolts at elevated temperatures are proposed. Besides, the relationship between degradation in macro mechanical properties and change in microstructure is clarified. The research outcomes may provide essential bases for the fire response analysis of steel structures applying the FR steel and the HP bolts. [ABSTRACT FROM AUTHOR]

Issues of fossil fuel and plastic pollution are shifting public demand toward biopolymer-based textiles. For instance, silk, which has been traditionally used during at least 5 milleniums in China, is re-emerging in research and industry with the development of high-tech spinning methods. Various arthropods, e.g. insects and arachnids, produce silky proteinic fiber of unique properties such as resistance, elasticity, stickiness and toughness, that show huge potential for biomaterial applications. Compared to synthetic analogs, silk presents advantages of low density, degradability and versatility. Electrospinning allows the creation of nonwoven mats whose pore size and structure show unprecedented characteristics at the nanometric scale, versus classical weaving methods or modern techniques such as melt blowing. Electrospinning has recently allowed to produce silk scaffolds, with applications in regenerative medicine, drug delivery, depollution and filtration. Here we review silk production by the spinning apparatus of the silkworm Bombyx mori and the spiders Aranea diadematus and Nephila Clavipes. We present the biotechnological procedures to get silk proteins, and the preparation of a spinning dope for electrospinning. We discuss silk's mechanical properties in mats obtained from pure polymer dope and multi-composites. This review highlights the similarity between two very different yarn spinning techniques: biological and electrospinning processes. [ABSTRACT FROM AUTHOR]

Membrane structures deteriorate with time. This results in reduction of their resistance, and consequently, of their reliability. Material aging is one of the main causes of structure deterioration. This paper investigates statistical characteristics of naturally aged polyvinylidene fluoride PVDF-coated fabrics' mechanical properties and calculates reliability indexes on the basis of Central Point Method and Rackwitz-Fiessler Method. Five groups of experimental fabrics were taken from different existing engineering structures or indoor warehouse in China, which have been naturally aged for more than 10 years. First, series of tearing tests, uniaxial and biaxial tensile tests were carried out to study the mechanical properties. Then, the uncertainties of material properties, material's dimension, computational model and load effects were discussed and the reliability indexes were studied by two methods according to the ultimate limit state. Finally, reliability indexes of aged PVDF-coated fabrics were compared with that of unaged coated fabrics. Results show that the impact of natural ageing on the properties of PVDF-coated fabric can not be ignored in reliability analysis and membrane structures design. These data offer a further understanding of aged PVDF-coated fabrics' mechanical properties and provide references for the durability analysis of tensioned membrane structures. • Five groups of naturally aged PVDF-coated fabris were taken from engineering structures or indoor warehouse in China. • Series of tests were carried out to study their mechanical properties. • Uncertainties of material properties, material's dimension, computational model and load effects were studied. • Reliability indexes were calculated by two methods. • Reliability indexes of aged coated fabrics were compared with those of unaged fabrics. [ABSTRACT FROM AUTHOR]