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Analysis of load and adaptability of disc cutters during shield tunneling in soft–hard varied strata

《结构与土木工程前沿（英文）》 2023年 第17卷 第4期   页码 533-545 doi: 10.1007/s11709-023-0946-1

摘要： The disc cutters of shield machines exhibit unsatisfactory adaptability and performance during the soft–hard varied strata tunneling process. To analyze the rotation state, cutting performance, and adaptability of disc cutters during shield tunneling in soft–hard varied strata, the Holmquist Johnson Cook and Federal Highway Administration constitutive models are introduced to numerically simulate the failure process of materials on the excavation face and to calculate the load of disc cutters. Additionally, the parameters of the models are modified based on laboratory disc cutter excavation test results. The results of numerical calculation can reflect the load level and the behavior of the disc cutters during operation. The tangential loads of the disc cutters during the cutting of four typical soft-strata excavation face models are numerically calculated, thus providing reference values for the starting torque of the disc cutters. A greater penetration is suggested for soft-strata tunneling to allow the disc cutters to rotate smoothly and continuously as well as to guarantee a better cutting effect. The disc cutters in the center of the cutterhead should be specified with a lower starting torque to prevent uneven wear, rotation stagnation, cutterhead clogging, and other adverse phenomena.

关键词： shield tunneling     disc cutter load     laboratory excavation test     numerical calculation     soft–hard varied strata    

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Crack evolution of soft–hard composite layered rock-like specimens with two fissures under uniaxial compression

《结构与土木工程前沿（英文）》 2021年 第15卷 第6期   页码 1372-1389 doi: 10.1007/s11709-021-0772-2

摘要： Acoustic emission and digital image correlation were used to study the spatiotemporal evolution characteristics of crack extension of soft and hard composite laminated rock masses (SHCLRM) containing double fissures under uniaxial compression. The effects of different rock combination methods and prefabricated fissures with different orientations on mechanical properties and crack coalescence patterns were analyzed. The characteristics of the acoustic emission source location distribution, and frequency changes of the crack evolution process were also investigated. The test results show that the damage mode of SHCLRM is related to the combination mode of rock layers and the orientation of fractures. Hard layers predominantly produce tensile cracks; soft layers produce shear cracks. The first crack always sprouts at the tip or middle of prefabricated fractures in hard layers. The acoustic emission signal of SHCLRM with double fractures has clear stage characteristics, and the state of crack development can be inferred from this signal to provide early warning for rock fracture instability. This study can provide a reference for the assessment of the fracture development status between adjacent roadways in SHCLRM in underground mines, as well as in roadway layout and support.

关键词： soft−hard composite layered rock mass     double cracks     crack evolution     acoustic emission     digital image correlation    

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Performance of soft-hard-soft (SHS) cement based composite subjected to blast loading with consideration

Jun WU,Xuemei LIU

《结构与土木工程前沿（英文）》 2015年 第9卷 第3期   页码 323-340 doi: 10.1007/s11709-015-0301-2

摘要： This paper presents a combined experimental and numerical study on the damage and performance of a soft-hard-soft (SHS) multi-layer cement based composite subjected to blast loading which can be used for protective structures and infrastructures to resist extreme loadings, and the composite consists of three layers of construction materials including asphalt concrete (AC) on the top, high strength concrete (HSC) in the middle, and engineered cementitious composites (ECC) at the bottom. To better characterize the material properties under dynamic loading, interface properties of the composite were investigated through direct shear test and also used to validate the interface model. Strain rate effects of the asphalt concrete were also studied and both compressive and tensile dynamic increase factor (DIF) curves were improved based on split Hopkinson pressure bar (SHPB) test. A full-scale field blast test investigated the blast behavior of the composite materials. The numerical model was established by taking into account the strain rate effect of all concrete materials. Furthermore, the interface properties were also considered into the model. The numerical simulation using nonlinear finite element software LS-DYNA agrees closely with the experimental data. Both the numerical and field blast test indicated that the SHS composite exhibited high resistance against blast loading.

关键词： high strength concrete (SHS)     engineered cementitious composite     interface     blast test     strain rate effect    

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Realtime prediction of hard rock TBM advance rate using temporal convolutional network (TCN) with tunnel

Zaobao LIU; Yongchen WANG; Long LI; Xingli FANG; Junze WANG

《结构与土木工程前沿（英文）》 2022年 第16卷 第4期   页码 401-413 doi: 10.1007/s11709-022-0823-3

摘要： Real-time dynamic adjustment of the tunnel bore machine (TBM) advance rate according to the rock-machine interaction parameters is of great significance to the adaptability of TBM and its efficiency in construction. This paper proposes a real-time predictive model of TBM advance rate using the temporal convolutional network (TCN), based on TBM construction big data. The prediction model was built using an experimental database, containing 235 data sets, established from the construction data from the Jilin Water-Diversion Tunnel Project in China. The TBM operating parameters, including total thrust, cutterhead rotation, cutterhead torque and penetration rate, are selected as the input parameters of the model. The TCN model is found outperforming the recurrent neural network (RNN) and long short-term memory (LSTM) model in predicting the TBM advance rate with much smaller values of mean absolute percentage error than the latter two. The penetration rate and cutterhead torque of the current moment have significant influence on the TBM advance rate of the next moment. On the contrary, the influence of the cutterhead rotation and total thrust is moderate. The work provides a new concept of real-time prediction of the TBM performance for highly efficient tunnel construction.

关键词： hard rock tunnel     tunnel bore machine advance rate prediction     temporal convolutional networks     soft computing     construction big data    

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Stability and agility: biped running over varied and unknown terrain

Yang YI,Zhi-yun LIN

《信息与电子工程前沿（英文）》 2015年 第16卷 第4期   页码 283-292 doi: 10.1631/FITEE.1400284

摘要： We tackle the problem of a biped running over varied and unknown terrain. Running is a necessary skill for a biped moving fast, but it increases the challenge of dynamic balance, especially when a biped is running on varied terrain without terrain information (due to the difficulty and cost of obtaining the terrain information in a timely manner). To address this issue, a new dynamic indicator called the sustainable running criterion is developed. The main idea is to sustain a running motion without falling by maintaining the system states within a running-feasible set, instead of running on a periodic limit cycle gait in the traditional way. To meet the precondition of the criterion, the angular moment about the center of gravity (COG) is restrained close to zero at the end of the stance phase. Then to ensure a small state jump at touchdown on the unknown terrain, the velocity of the swing foot is restrained within a specific range at the end of the flight phase. Finally, the position and velocity of the COG are driven into the running-feasible set. A five-link biped with underactuated point foot is considered in simulations. It is able to run over upward and downward terrain with a height difference of 0.15 m, which shows the effectiveness of our control scheme.

关键词： Underactuated running biped     Dynamic balance     Varied and unknown terrain    

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Effect of strata restraint on seismic performance of prefabricated sidewall joints in fabricated subway

《结构与土木工程前沿（英文）》 2023年 第17卷 第5期   页码 763-779 doi: 10.1007/s11709-023-0917-6

摘要： A disadvantage of the conventional quasi-static test method is that it does not consider the soil restraint effect. A new method to test the seismic performance of prefabricated specimens for underground assembled structures is proposed, which can realistically reflect the strata restraint effect on the underground structure. Laboratory work combined with finite element (FE) analysis is performed in this study. Three full-scale sidewall specimens with different joint forms are designed and fabricated. Indices related to the seismic performance and damage modes are analyzed comprehensively to reveal the mechanism of the strata restraint effect on the prefabricated sidewall components. Test results show that the strata restraint effect effectively improves the energy dissipation capacity, load-bearing capacity, and the recoverability of the internal deformation of the precast sidewall components. However, the strata restraint effect reduces the ductility of the precast sidewall components and aggravates the shear and bending deformations in the core region of the connection joints. Additionally, the strata restraint effect significantly affects the seismic performance and damage mode of the prefabricated sidewall components. An FE model that can be used to conduct a seismic performance study of prefabricated specimens for underground assembled structures is proposed, and its feasibility is verified via comparison with test data.

关键词： underground structures     precast sidewall specimen     seismic test method     bearing capacity     energy dissipation capacity     plastic deformation    

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Advances in molecular dynamics simulation of ultra-precision machining of hard and brittle materials

Xiaoguang GUO,Qiang LI,Tao LIU,Renke KANG,Zhuji JIN,Dongming GUO

《机械工程前沿（英文）》 2017年 第12卷 第1期   页码 89-98 doi: 10.1007/s11465-017-0412-7

摘要：

Hard and brittle materials, such as silicon, SiC, and optical glasses, are widely used in aerospace, military, integrated circuit, and other fields because of their excellent physical and chemical properties. However, these materials display poor machinability because of their hard and brittle properties. Damages such as surface micro-crack and subsurface damage often occur during machining of hard and brittle materials. Ultra-precision machining is widely used in processing hard and brittle materials to obtain nanoscale machining quality. However, the theoretical mechanism underlying this method remains unclear. This paper provides a review of present research on the molecular dynamics simulation of ultra-precision machining of hard and brittle materials. The future trends in this field are also discussed.

关键词： MD simulation     ultra-precision machining     hard and brittle materials     machining mechanism     review    

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浅埋深两硬条件下特厚煤层综放开采技术

张忠温,吴吉南

《中国工程科学》 2011年 第13卷 第11期   页码 107-112

摘要：

针对平朔矿区4号煤层条件，采用理论分析方法研究了浅埋深两硬条件下4号煤层顶煤的冒放性及合理采煤方法。以提高顶煤冒放性为目标，采用数值模拟的方法进行了综放工作面参数及设备选型配套研究。实践表明，浅埋深两硬煤层条件下通过加大综放工作面长度与割煤高度，可以实现安全、高效、高回收率开采。

关键词： 浅埋深     两硬煤层     顶煤冒放性     大采高综放    

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Primary cilia in hard tissue development and diseases

《医学前沿（英文）》 2021年 第15卷 第5期   页码 657-678 doi: 10.1007/s11684-021-0829-6

摘要： Bone and teeth are hard tissues. Hard tissue diseases have a serious effect on human survival and quality of life. Primary cilia are protrusions on the surfaces of cells. As antennas, they are distributed on the membrane surfaces of almost all mammalian cell types and participate in the development of organs and the maintenance of homeostasis. Mutations in cilium-related genes result in a variety of developmental and even lethal diseases. Patients with multiple ciliary gene mutations present overt changes in the skeletal system, suggesting that primary cilia are involved in hard tissue development and reconstruction. Furthermore, primary cilia act as sensors of external stimuli and regulate bone homeostasis. Specifically, substances are trafficked through primary cilia by intraflagellar transport, which affects key signaling pathways during hard tissue development. In this review, we summarize the roles of primary cilia in long bone development and remodeling from two perspectives: primary cilia signaling and sensory mechanisms. In addition, the cilium-related diseases of hard tissue and the manifestations of mutant cilia in the skeleton and teeth are described. We believe that all the findings will help with the intervention and treatment of related hard tissue genetic diseases.

关键词： primary cilia     bone     mechanical sensing     hard tissue     cilium-related bone disease     tooth    

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Crystalline mesoporous transition metal oxides: hard-templating synthesis and application in environmental

Zhen MA, Bei ZHOU, Yu REN

《环境科学与工程前沿（英文）》 2013年 第7卷 第3期   页码 341-355 doi: 10.1007/s11783-012-0472-1

摘要： Mesoporous silicas such as MCM-41 and SBA-15 possess high surface areas, ordered nanopores, and excellent thermal stability, and have been often used as catalyst supports. Although mesoporous metal oxides have lower surface areas compared to mesoporous silicas, they generally have more diversified functionalities. Mesoporous metal oxides can be synthesized via a soft-templating or hard-templating approach, and these materials have recently found some applications in environmental catalysis, such as CO oxidation, N O decomposition, and elimination of organic pollutants. In this review, we summarize the synthesis of mesoporous transition metal oxides using mesoporous silicas as hard templates, highlight the application of these materials in environmental catalysis, and furnish some prospects for future development.

关键词： mesoporous materials     silica     metal oxide     hard-templating     environmental catalysis    

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Field and laboratory experimental studies on hard-rock tunnel excavation based on disc cutter coupled

《结构与土木工程前沿（英文）》   页码 1370-1386 doi: 10.1007/s11709-023-0947-0

摘要： The tunnel boring machine (TBM) is typically used in hard-rock tunnel excavation. Owing to the unsatisfactory adaptability of TBM to the surrounding rock, when crossing high-strength and high-wear strata, the TBM can easily cause defects, such as abnormal wear on cutters and overload damage to bearings, thus affecting the construction efficiency and cost. Therefore, high-pressure waterjet technology should be applied to assist in rock breaking for efficient TBM tunneling. In this study, the effects of water pressure, nozzle diameter, and nozzle speed on cutting are investigated via laboratory experiments of cutting hard rock using high-pressure waterjets. The penetration performance of the TBM under different water pressures is investigated via a field industrial penetration test. The results show that high-pressure waterjets are highly efficient for rock breaking and are suitable for industrial applications, as they can accommodate the advancing speed of the TBM and achieve high-efficiency rock breaking. However, during the operation of high-pressure waterjets, the ambient temperature and waterjet temperature in the tunnel increase significantly, which weakens the cooling effect of the cutterhead and decreases the construction efficiency of the TBM. Therefore, temperature control and cooling measures for high-pressure waterjets during their long-term operation must be identified. This study provides a useful reference for the design and construction of high-pressure water-jet-assisted cutterheads for breaking road headers.

关键词： tunnel boring machine     hard-rock cutting     free face     disc cutter     rock-cutting efficiency    

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Improved CO

Mahboube Ghahramaninezhad, Fatemeh Mohajer, Mahdi Niknam Shahrak

《化学科学与工程前沿（英文）》 2020年 第14卷 第3期   页码 425-435 doi: 10.1007/s11705-019-1873-5

摘要： Post-synthetic functionalization or modification has been regarded as a promising strategy to treat surfaces of adsorbents for their applications in targeted adsorption and separation processes. In this work, a novel microporous adsorbent for carbon capturing was developed via functionalization of zeolitic imidazolate framework-91 (ZIF-91) to generate a hard/hard (metal-oxygen) structure named as lithium-modified ZIF-91 (ZIF-91-OLi compound). To this purpose, the ZIF-91 compound as an intermediate product was achieved by reduction of ZIF-90 in the presence of NaBH as a good reducing agent. Afterwards, acidic hydrogen atoms in the hydroxyl groups of ZIF-91 were exchanged with lithium cations via reaction of -BuLi compound as an organo lithium agent through an appropriate procedure. In particular, the as-synthesized ZIF-91-OLi operated as an excellent electron-rich center for CO adsorption through trapping the positive carbon centers in the CO molecule. DFT calculations revealed that the presence of lithium over the surface of ZIF-91-OLi adsorbent plays an effective role in double enhancement of CO storage via creating a strong negative charge center at the oxygen atoms of the imidazolate linker as a result of the lithium/hydrogen exchange system. Finally, the selectivity of CO /N was investigated at different temperatures, revealing the ZIF-91-OLi as a selective adsorbent for industrial application.

关键词： hard/hard structure     acidic hydrogen     ZIF-91     carbon capture     ZIF-91-OLi    

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A biofilter model for simultaneous simulation of toluene removal and bed pressure drop under varied inlet

Jinying XI,Insun KANG,Hongying HU,Xian ZHANG

《环境科学与工程前沿（英文）》 2015年 第9卷 第3期   页码 554-562 doi: 10.1007/s11783-014-0671-z

摘要： In this study, a biofiltration model including the effect of biomass accumulation and inert biomass growth is developed to simultaneously predict the Volatile Organic Compounds (VOCs) removal and filter bed pressure drop under varied inlet loadings. A laboratory-scale experimental biofilter for gaseous toluene removal was set up and operated for 100 days with inlet toluene concentration ranging from 250 to 2500 mg?m . According to sensitivity analysis based on the model, the VOCs removal efficiency of the biofilter is more sensitive to Henry’s constant, the specific surface area of the filter bed and the thickness of water layer, while the filter bed pressure drop is more sensitive to biomass yield coefficient and original void fraction. The calculated toluene removal efficiency and bed pressure drop satisfactorily fit the experimental data under varied inlet toluene loadings, which indicates the model in this study can be used to predict VOCs removal and bed pressure drop simultaneously. Based on the model, the effect of mass-transfer parameters on VOCs removal and the stable-run time of a biofilter are analyzed. The results demonstrate that the model can function as a good tool to evaluate the effect of biomass accumulation and optimize the design and operation of biofilters.

关键词： Volatile Organic Compounds (VOCs)     biofilters     modelling     biomass accumulation     pressure drop    

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Development of soft kernel durum wheat

Craig F. MORRIS

《农业科学与工程前沿（英文）》 2019年 第6卷 第3期   页码 273-278 doi: 10.15302/J-FASE-2019259

摘要：

Kernel texture (grain hardness) is a fundamental and determining factor related to wheat ( spp.) milling, baking and flour utilization. There are three kernel texture classes in wheat: soft and hard hexaploid ( ), and very hard durum ( subsp. ). The genetic basis for these three classes lies with the Puroindoline genes. Phenotypically, the easiest means of quantifying kernel texture is with the Single Kernel Characterization System (SKCS), although other means are valid and can provide fundamental material properties. Typical SKCS values for soft wheat would be around 25 and for durum wheat≥80. Soft kernel durum wheat was created via homeologous recombination using the mutation, which facilitated the transfer of ca. 28 Mbp of 5DS that replaced ca. 21 Mbp of 5BS. The 5DS translocation contained a complete and intact locus and both puroindoline genes. Expression of the puroindoline genes in durum grain resulted in kernel texture and flour milling characteristics nearly identical to that of soft wheat, with high yields of break and straight-grade flours, which had small particle size and low starch damage. Dough water absorption was markedly reduced compared to durum flour and semolina. Dough was essentially unchanged and reflected the inherent gluten properties of the durum background. Pasta quality was essentially equal-to-or-better than pasta made from semolina. Agronomically, soft durum germplasm showed good potential with moderate grain yield and resistance to a number of fungal pathogens and insects. Future breeding efforts will no doubt further improve the quality and competitiveness of soft durum cultivars.

关键词： soft durum wheat     grain hardness     puroindolines     milling     baking     pasta     noodles    

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Microstructure investigation of dynamic recrystallization in hard machining: From thermodynamic irreversibility

Binxun LI, Xinzhi ZHANG, Song ZHANG

《机械工程前沿（英文）》 2021年 第16卷 第2期   页码 315-330 doi: 10.1007/s11465-020-0612-4

摘要： The drastically changed thermal, mechanical, and chemical energies within the machined surface layer during hard machining tend to initiate microstructural alteration. In this paper, attention is paid to the introduction of thermodynamic potential to unravel the mechanism of microstructure evolution. First, the thermodynamic potential-based model expressed by the Helmholtz free energy was proposed for predicting the microstructure changes of serrated chip and the machined surface layer. Second, the proposed model was implemented into a validated finite element simulation model for cutting operation as a user-defined subroutine. In addition, the predicted irreversible thermodynamic state change in the deformation zones associated with grain size, which was reduced to less than 1 m from the initial size of 1.5 m on the machined surface, was provided for an in-depth explanation. The good consistency between the simulated results and experimental data validated the efficacy of the developed model. This research helps to provide further insight into the microstructure alteration during metal cutting.

关键词： thermodynamic irreversibility     Helmholtz free energy     microstructure evolution     dynamic recrystallization     hard milling    

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标题 作者 时间 类型 操作

Analysis of load and adaptability of disc cutters during shield tunneling in soft–hard varied strata

期刊论文

Crack evolution of soft–hard composite layered rock-like specimens with two fissures under uniaxial compression

期刊论文

Performance of soft-hard-soft (SHS) cement based composite subjected to blast loading with consideration

Jun WU,Xuemei LIU

期刊论文

Realtime prediction of hard rock TBM advance rate using temporal convolutional network (TCN) with tunnel

Zaobao LIU; Yongchen WANG; Long LI; Xingli FANG; Junze WANG

期刊论文

Stability and agility: biped running over varied and unknown terrain

Yang YI,Zhi-yun LIN

期刊论文

Effect of strata restraint on seismic performance of prefabricated sidewall joints in fabricated subway

期刊论文

Advances in molecular dynamics simulation of ultra-precision machining of hard and brittle materials

Xiaoguang GUO,Qiang LI,Tao LIU,Renke KANG,Zhuji JIN,Dongming GUO

期刊论文

浅埋深两硬条件下特厚煤层综放开采技术

张忠温,吴吉南

期刊论文

Primary cilia in hard tissue development and diseases

期刊论文

Crystalline mesoporous transition metal oxides: hard-templating synthesis and application in environmental

Zhen MA, Bei ZHOU, Yu REN

期刊论文

Field and laboratory experimental studies on hard-rock tunnel excavation based on disc cutter coupled

期刊论文

Improved CO

Mahboube Ghahramaninezhad, Fatemeh Mohajer, Mahdi Niknam Shahrak

期刊论文

A biofilter model for simultaneous simulation of toluene removal and bed pressure drop under varied inlet

Jinying XI,Insun KANG,Hongying HU,Xian ZHANG

期刊论文

Development of soft kernel durum wheat

Craig F. MORRIS

期刊论文

Microstructure investigation of dynamic recrystallization in hard machining: From thermodynamic irreversibility

Binxun LI, Xinzhi ZHANG, Song ZHANG

期刊论文