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Promoting prefabricated steel structures is considered one of the crucial approaches to meeting the objectives of "carbon peak" and "carbon neutrality" in the construction industry. Due to insufficient practical experience and incomplete fine engineering techniques in civil construction, the sustainable development of prefabricated building systems in China faces many challenges. Taking steel components as an example, the design process of tubular columns does not pay enough attention to the influence of the cold-working effect on material mechanical properties, and the constitutive relationship of cold-formed steels is not clear, which will cause an engineering economic burden and may affect the judgment of catastrophic problems. To serve the refined design and meet the intelligent construction technology using the computer platform, a modified Menegotto-Pinto model using a continuously derivable function is proposed in the paper. The proposed model can successfully describe the complete stress-strain curve of cold-formed circular mild steels as long as the basic mechanical parameters of the parent material are determined. Taking into account the influence of the strength and thickness of the parent steel sheets, as well as the internal bending radius r, on the cold-rolling effect, the model can also flexibly track the elastic-plastic nonlinearity of the cold-formed materials. In addition, the research shows that the cold-rolling effect will weaken with the increase of the yield strength fsy,0 of the parent steels and r/t ratio, and may disappear when fsy,0 reaches 1748 MPa or the r/t ratio is approximately 60, which can be used as economic indicators during the design process. [ABSTRACT FROM AUTHOR]

To obtain the impact mechanical response and establish the dynamic damage constitutive relationship of frozen sandstone at low temperature conditions, the impact test of Cretaceous red sandstone under different temperatures was conducted using a split Hopkinson pressure bar (SHPB) device. According to the characteristics of the stress-strain curves obtained by the test, a constitutive model considering the damage effect, temperature effect, and strain rate effect was established, which was improved by Zhu–Wang–Tang (Z–W–T) constitutive model. It was proved that the fitting curves of constitutive equation were in good agreement with the test curves. The fluctuation amplitude of fitting error was controlled within ± 4 MPa. The physical meaning of each parameter of the constitutive model is clear, and most of them are fixed values. The selection range of variable parameters and the related change rules are confirmed, which improves the practicability of constitutive model. The constitutive equation can well describe the nonlinear features of this kind of frozen sandstone under impact loading. It was also found that the constitutive equation was applicable to express the dynamic mechanical properties of rock-like materials such as hard rock, soft rock, frozen soil, raw coal, and concrete. It can be referred to the parameter determination method in this paper to study and determine the parameters, reduce the difficulty of parameter selection, and improve the practicability of the constitutive model and parameters, so as to guide the engineering practice better. [ABSTRACT FROM AUTHOR]

Determining the strength and deformation of jointed rock masses is an inevitable part of geomechanical projects. The strength and deformability of a rock mass with stochastic joint sets are conceivably anisotropic and are mainly controlled by joints' mechanical and geometrical properties. In this paper, the strength and deformation behavior of jointed rock masses against different scales and loading directions has been evaluated at the Tazareh coal mine, Iran. Field mappings through the scanline method have been used to collect joints' spatial features on rock surfaces. A statistical evaluation has been carried out on field data using Dips software. Then, the geomechanical properties of intact blocks have been measured by conducting a uniaxial compressive strength test. Finally, the rock mass is modeled using 3DEC, and its behavior is analyzed in some cases with different loading directions and block sizes to obtain representative elementary volume (REV) based on strength and deformation, respectively. [ABSTRACT FROM AUTHOR]

Coal seam water injection is widely used to prevent rockbursts in coal mines, and the duration of water injection is an important parameter related to the effectiveness of rockburst prevention, making it of practical importance to optimize the effective water injection duration. This paper presents the test results of the mechanical properties and pore structure of samples with different soaking time, obtained from a working face where rockburst occurred. Soaking time changes the mechanical properties of samples, and this time effect differs with the coal size (from centimeter to nanometer size). Results of numerical simulation and on-site tests in the Changgouyu coal mine demonstrated that water injection can effectively soften coal bodies and release or transfer stresses, and the time effect of water injection on rock prevention and control is apparent. [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]

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]

Metro-led underground space (MUS) plays a crucial role in modern underground space utilisation. Recent studies have shown its great potential for high-quality urban development. However, limited evidence about MUS was available on a national scale, resulting in incomplete and unsystematic knowledge of MUS utilisation. The interaction relationship between MUS and the surrounding built environment also remains unclear. To fill the research gap, an automatic method for MUS identification and development features extraction was proposed based on point of interest data. We applied the method to identify the MUS in 28 Chinese cities and estimated the development status of MUS in China for the first time. The nationwide statistics of MUS and correlation analysis of development features were conducted. Results show that complex MUS (CMUS) share is significantly lower than that of simple MUS. Besides, CMUS development in China is primarily dominated by public transport and does not have a solid functional link to its surroundings. The comparative analysis of MUS development in four primary urban agglomerations was also conducted, and their development characteristics were discussed. The study aims to expand the planning toolkit and construct the MUS database, which sheds light on the datadriven planning for MUS. [ABSTRACT FROM AUTHOR]

The rheological properties of soft rocks should be considered in the long-term design and maintenance of deep-buried tunnels using uniaxial single-stage loading and graded incremental cyclic-loading methods. In this article, creep tests were performed on deep-buried silty mudstone from a specific water conveyance tunnel in China, with a buried depth in the range of 1650–2320 m and subjected to high in situ stress. The creep curves of silty mudstone under different loading stresses were obtained, showing evident rheological mechanical behavior under complicated external environmental conditions. Based on the classic Burgers rheological model, a new nonlinear creep model was established based on the creep properties of deep-buried silty mudstone in the project area. Typically, the designated rheological models for certain projects are unsuitable or inadequate. A nonlinear dashpot was calculated using the Levenberg–Marquardt (L–M) method coupled with origin to account for the deterioration trend in the strength of the silty mudstone over time. With the determined parameters, the modified Burgers model exhibited good qualitative consistency with field monitoring data. The user-defined material mechanical behavior (UMAT) subroutine of the modified Burgers model was successfully achieved after it was implemented in the numerical code ABAQUS. Based on the full-rheological effect, the proper supporting time of a deep-buried tunnel was studied, and it was proposed that a second lining should be cast in situ approximately 150 days after the excavation of the tunnel. The outcomes of the proposed modified rheological model can accurately represent the creep behavior of deep-buried silty mudstones in a specific engineering instance. The research results can provide a basis for the rheological behavior and supporting time of deep-buried silty mudstone. [ABSTRACT FROM AUTHOR]

In this study, the uniaxial compressive mechanical properties of earth materials are tested, and the effects of four influencing factors, such as shape, size, curing age, and loading rate, on the strength, damage pattern, and stress-strain curve of the specimens are analyzed. The standard uniaxially compressed specimen size and the recommended loading rate are proposed for the earth specimens. The uniaxial compressive constitutive equations of earth materials are modified on the basis of the Illampas constitutive equation. By fitting the results of this study and typical literature tests, the applicability of the modified constitutive equation form to the uniaxial compressive test curves of soils in different regions of China based on standard sizes is verified. Finally, the formulae for calculating the parameters related to the constitutive equation of earth materials are established. In its application, only the compressive strength of 100-mm-cubic standard specimens with a curing age of 28 d needs to be measured to calculate and determine the specific values of the relevant parameters of the constitutive equation. This is a good reference value for promoting the development of computational analysis methods for earth structures and promoting the engineering design applications of earth structures. [ABSTRACT FROM AUTHOR]

Bed entrainment plays an important role in the run-out process of a flow-like landslide. A limited number of studies have investigated the influence of entraining loose materials on the mechanical properties of a landslide, and some of them have considered bed entrainment either by mechanical or empirical methods. In this paper, a modified finite difference model was used to analyze the propagation process of a typical flow-like landslide with bed entrainment that occurred in the Jingyang loess tableland, China. In this model, the mechanical parameters of the sliding mass were modified according to the local entrainment depth. Triaxial Consolidated Undrained (CU) tests and ring shear tests were conducted to obtain the mechanical parameters needed in the numerical simulation. The triaxial CU tests were conducted on three intact loess samples taken at the back scarp of the landslide, and the ring tests were conducted on gravelly sand samples taken from the first terrace of the Jinghe River, which includes the landslide deposit. The results show that both the simulated run-out distance and final covering area agreed well with the field data. The modified model revealed the propagation process of this landslide. A major contribution of this study is that entraining the saturated gravelly sand contributed to the flow-like movement of the landslide. The case study investigated here is helpful for better an understanding of the flow-like transformation mechanism. In addition, the numerical model adopted in this paper can be effectively used to assess or predict the propagation processes of similar landslides. • The propagation process of a loess flow-like landslide with bed entrainment is analyzed. • The significant shear strength loss of loess contributes to the rapid acceleration of this landslide. • Entraining saturated terrace material contributes to the flow-like transformation of this landslide. [ABSTRACT FROM AUTHOR]

Using undrained triaxial shear tests, this study investigates the mechanical properties of fine-grained materials (silty clay and sand) which are extensively used for China's Qinghai–Tibet Railway (QTR) under different confining pressures (σ3) and freezing temperatures (T). The results show that a reduction in T causes an increase in the shear strength and elastic modulus of all the materials tested in the present study. In addition, the freezing of the silty clay has no significant effect on the type of soil behaviour (strain-hardening), whereas the freezing of the sand changes its strain-hardening behaviour to strain-softening. Supposing that the deviatoric stress–strain curves of the silty clay and sand can be divided into two segments due to a reverse bending point, it was assumed that the first segment follows a hyperbolic function. Meanwhile, the second segment is also a hyperbola, with the reverse bending point as the origin and the residual strength as the asymptote. Accordingly, a nonlinear relation constitutive model that considers σ3 and T is derived. All model parameters are identified. The reasonability of the new model was verified using the test results of the materials. A comparison of the predicted and test results shows that this model can well simulate the deviatoric stress–strain response in the failure process of the tested materials. In particular, it can reflect the residual deviatoric stress after the materials' failure. [ABSTRACT FROM AUTHOR]

Abstract: Engineering construction in cold regions and artificial ground freezing projects require an understanding of the mechanical properties of frozen soils. An understanding of properties such as strength and deformation are important for engineering design purposes. In the past decades of years, because of the increase of the engineering, such as the Qinghai–Tibet Railway (QTR), the Qinghai–Tibet Highway and the Golmud–Lhasa Oilpipe (GLO), constructed in frozen soil regions on the Qinghai–Tibet Plateau, the study on the material properties of frozen soils in China was being developed quickly, and numerous research results were achieved. This paper summarizes these research fruits in four aspects: (1). Strength property of frozen soils, (2). Deformation behavior of frozen soils, (3). Constitutive models for frozen soils, (4). Dynamical property of frozen soils. This summary would be helpful for their convenient application in practical engineering, as well as for supplying foundation and developing direction of mechanical property research on frozen soils. [Copyright &y& Elsevier]

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]

Abstract: Completely decomposed granite (CDG) is abundant in Hong Kong. It has been used extensively as fill materials in various applications, such as back-filling materials for retaining structures and pavements. In this paper, results of a series of triaxial tests, including isotropic and anisotropic compression, and drained and undrained shearing tests, on a medium-fine-grained re-compacted CDG with overconsolidation ratio ranged between 1 and 8 are reported. The tests aim to understand the mechanical behavior of the soil in its saturated state under various initial states, stress paths and drainage conditions. It is found that the material is highly compressible during virgin isotropic and anisotropic compression. Moreover, the virgin compression lines are uniquely associated with their stress ratios and they appear to parallel to each other in an e-lnp′ plane. All specimens exhibit strain-hardening type response during drained shearing. In undrained shear, normally consolidated specimens reveal contractive response until the ultimate states are reached. Overconsolidated specimens, however, show complex stress paths and volumetric tendency. Dilatancy responses of the soil during a constant stress ratio compression and deviatoric shear are discussed respectively. Unique isotropic compression line (ICL) and critical state line (CSL) are reported for the studied soil. [Copyright &y& Elsevier]

Abstract: The relationship between kaolinite structure and the temperature of thermal transformation of phase was discussed in this paper through grinding and heating treatment. The results show that the structure of kaolinite is destroyed rapidly with increasing mechanical grinding time, and the kaolinite structure collapses completely after 1h grinding. The temperature of thermal transformation of phase decreases with the destruction of kaolinite structure. This result has a great significance for the utilization of kaolinite associated with coal measures in China. [Copyright &y& Elsevier]

Abstract: The rare-earth doped cemented carbides have being investigated and developed for mass production in China since 1990 due to their obvious physical and mechanical properties as hardness, transverse rupture strength, impact toughness, wear resistance, cutting life and so on. The studies on rare-earth doped cemented carbides in China are reviewed in this paper. The doped compositions and contents, addition approaches, processing scheme, strengthening mechanism, microstructure and mechanical properties of rare-earth doped cemented carbides are described and discussed according to the processing techniques. The typical brand, chemical and physical properties of rare-earth doped cemented carbides in Chinese production are introduced briefly. In order to further improve the cemented carbides quality, more research works should be focused on the chemical co-precipitation mixing method and the increment of the contents of α-Co binder with fcc structure in WC/Co alloys in China in future. [Copyright &y& Elsevier]

Sliding liquefaction is considered to be the cause of high-speed and long-distance sliding of some homogeneous loess landslides in western China. However, there is still a lack of necessary experimental research and analysis on the effects of sliding liquefaction on these landslides. In this work, the effects of sliding liquefaction on irrigation-induced, high-speed and long-distance loess landslides on the South Jingyang Tableland area in China are studied by performing large-scale ring shear tests and using the sled mode. The results are as follows. (1) There are two kinds of long-runout sliding modes of loess landslides on the South Jingyang Tableland: sliding along the terrace surface and sliding within the saturated terrace alluvium, which is associated with sliding liquefaction. Both sliding modes can lead to long-runout sliding. (2) There are some differences in the inclination of the sliding surface between the two sliding modes. Based on the inclination of the sliding surface, the corresponding sliding mode can be distinguished. (3) Under the two sliding modes, the large shear mechanical properties of the two-layer soil composed of loess and alluvial sandy silt show significant differences. The friction between the loess and dry terrace alluvium increases with increasing normal stress and shear rate, while the friction between the loess and saturated terrace alluvium presents the opposite trend. The results show that the sliding distances under different sliding modes present opposite trends with the change in sliding speed. (4) Based on the test results from the ring shear tests and the morphological characteristics of the sliding surface, the sliding mode and sliding distance of a loess landslide can be identified and predicted. [ABSTRACT FROM AUTHOR]

Cemented paste backfill (CPB) mining is widely applied in coal mines throughout China, where gangue rock is commonly used as an aggregate. However, some mining areas do not have an abundant supply of gangue. This paper proposes a sand-based cemented paste backfill material (SCPB) with widely distributed and low-cost Yellow River sand as the filling aggregate with cement and fly ash as the binders based on the mining conditions of the Zhaoguan Coal Mine located in the Shandong province of China. The conveying and mechanical properties of the material were tested and optimized. This study found that (i) the initial SCPB have a large bleeding rate, while the early and late strengths are generally low; (ii) simultaneously adding polycarboxylate and quicklime can significantly improve the engineering performance of the filling material, where the bleeding rate is 3.2%–3.9%, the early strength is 0.2–0.39 MPa, and the late strength is 7.53–8.86 MPa; and (iii) the optimal mixing ratio of the SCPB concentration is 78%, the F/S ratio is 0.6, the C/S ratio is 0.2, the P/S ratio is 0.004, and the L/S ratio is 0.15. Furthermore, the X-ray diffraction (XRD) and scanning electron microscopy (SEM) results show that the optimized SCPB was denser than the initial SCPB and exhibited a greater degree of fly ash hydration. Image 10755 • Engineering performance metrics of cemented paste backfill materials were given. • Weaknesses of sand-based cemented paste backfill materials and their causes were analyzed. • Best ratio of sand-based cemented paste backfill material was obtained. • Microstructural features of sand-based cemented paste backfill materials were analyzed. [ABSTRACT FROM AUTHOR]

Research on three-dimensional, randomly distributed BFRC in China is analyzed and summarized in relative depth in this study. The results indicate that the effect of the fiber component and alkali corrosion temperature on the alkali resistance of BF is significant; the BF has little effect on the compressive strength of the concrete; the tensile and flexural strengths of the composites significantly increase compared with plain concrete, and the fiber content has a significant effect on the strength. In light of some problems in the current research, six possible research topics are suggested: (1) investigating the alkali resistance of the BF under dynamic temperatures, lower alkali concentrations, and longer alkali corrosion times; (2) improving the alkali resistance of the BF by increasing its hydrophobicity; (3) determining the optimal fiber distribution orientation of the BF with various characteristic parameters; (4) establishing the calculation formulas for the critical content and critical aspect ratio of various types of BF; (5) determining the optimal mixture ratio of two or more fibers in the FRC while studying the complementary mechanisms between each other; and (6) improving the dispersion of the BF and the BF/matrix interfacial properties. [ABSTRACT FROM AUTHOR]

Using two fencing swords manufactured in Europe and China, we investigated the typical materials used for fencing blades and compared the experimental results with the nominal compositions of a variety of steels. We found that spring steels and maraging steels were the primary metals used in fencing blades. The review then provides an overview of the chemical compositions, heat treatment processes, microstructures and associated mechanical properties of these materials. By combining the requirements for the safety of athletes, mechanical behaviors of different steels, and production costs for industry, we introduced possible directions for the heat treatments and processing methods that have the potential to enhance performance and overcome the limitations of previous materials. In addition, an ultra-strong steel, Fe-9.95Mn-0.44C-1.87Al-0.67V which could be a promising new candidate in this area, was recommended. Finally, we suggested that successful cooperation between manufacturers and researchers is necessary to reach the various requirements of fencing blades to meet the growing popularity of fencing in China. [ABSTRACT FROM AUTHOR]

In order to model perpetual pavement response, the traffic loads, pavement temperature, and mechanics responses collected from the Shandong perpetual pavement test road were used to develop axle load spectrums, temperature probability functions, and response regression models with load and temperature variables. The random sample methods of a probability distribution function were developed and the numerical simulation of parameter inputs and mechanical responses under a whole year of traffic volume and temperature cycles was realized. The results showed that the simulated mechanical response conformed to the actual response and both followed an approximate normal distribution. The response of different pavement structures was also compared. The research proves that the Monte Carlo method can help to understand the pavement mechanical response under the influence of both load and temperature. Finally, based on the simulated tensile strain distributions, the pavement fatigue life of all sections was compared. [ABSTRACT FROM AUTHOR]

To rationally use low-grade phosphorous limestone as the raw materials for cement production, the influence of phosphorous introduced by fluorapatite during the clinker calcination process on the mechanical properties of cementitious materials is investigated. Hydration kinetics, phase evolutions, and microstructure of cement pastes have been studied by using calorimetry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicate that the mechanical properties of cementitious materials can be slightly improved due to the mineralization effect of the small amount of phosphorous in the clinker and significantly decreased with an increase of phosphorous. High content of phosphorous will reduce the content of C3S and make the formation of α′-C2S-xC3P(x: 0–0.05), whose hydration reactivity is rather lower, such that on the one hand less-hydrated products, such as calcium silicate hydrate (C-S-H) gel, can be obtained, and on the other hand, the hydration reaction will be slowed by severely prolonging the induction period. Interestingly, small particles can be observed on the surface of hydration products, but no new phase can be detected by XRD. When the content of P2O5 is 2.0%, the cement can meet the requirements of P·II 42.5 cement in China. Hopefully, this can provide significant guidance for the use of cement prepared by fluorapatite as raw material. [ABSTRACT FROM AUTHOR]