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Experimental Study on Shear Strength Characteristics of Frozen Soil - Cast-in-Situ Concrete Interface

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SSRN 2022年

作者： Sun, Tiecheng Dong, Chuangqi Zhang, Jiao Zong, Zihang Wu, Kai State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Key Laboratory of Roads and Railway Engineering Safety Control Ministry of Education Shijiazhuang050043 China Hebei Province Technology and Innovation Center on Intelligent Construction of Infrastructure Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China

The roughness of contact surface is closely related to the friction coefficient and shear strength characteristics of pile-soil interface. At present, there is no recognized and unified quantitative characterization method of contact surface roughness. In this paper, the roughness formula is corrected in combination with the proposed form factor, and the low temperature direct shear test of the frozen soil-cast-in-situ concrete interface is carried out. The influence of several test factors, such as contact surface roughness, normal pressure and moisture content of soil sample, on frozen shear strength of frozen soil-cast-in-situ concrete contact surface is analyzed. The test results show that: (a) The frozen shear strength at the contact surface is mainly determined by the cementation of ice cementation force, cohesion and the bite force between frozen soil and concrete. The roughness corrected by the form coefficient can accurately characterize the contribution of bite force to the frozen shear strength of the contact surface. (b) The primary and secondary order of the influence of test control factors on the frozen shear strength of contact surface is normal pressure > moisture content of soil sample > test temperature > roughness > dry density. The normal pressure and moisture content have a strong and significant influence on the test results, the influence of dry density is not significant, and the influence of test temperature and roughness is in the middle. (c) The frozen shear strength of the contact surface increases with the increase of roughness, but the increase of normal pressure can weaken the effect of roughness on the enhancement of shear strength. © 2022, The Authors. All rights reserved.

关键词： Temperature

Solar Energy-Based Active Heating Method for Frost-Resistant Embankments: A Case Study in China

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SSRN 2022年

作者： Hu, Tianfei Sun, Tiecheng Wang, Tengfei Zhang, Zongkai Wang, Li State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University 17 Northeast Second Inner Ring Hebei Province Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China MOE Key Laboratory of High-Speed Railway Engineering Southwest Jiaotong University Chengdu610031 China

The primary objective of this study is to address embankment frost heave issues in cold regions with an active heating method. A real-time and efficient method of solar heating is developed based on the concept of actively controlling the balance between heat absorption and heat loss. The applicability of various heat sources was compared with the heating demands of embankment. The case study demonstrates that the seasonally frozen areas of China are rich in solar energy resources. A dedicated embankment heating device was designed, including a solar collector section and an embankment heater section. The device integrates energy conversion, storage, and transfer without any moving part, and thus can be used in an "isolated island" scenario for self-driven operations. Performance tests showed that the maximum heating temperature exceeds 60 °C, with an average range of 20–40 °C, which increases with solar radiation. The effective heat utilization rate of soil is approximately 26%. A predictive model that considers latitude and daily ordinal number was proposed for heating temperature. A numerical simulation of the actual embankment long-term heating performance was performed. The results revealed that the heating mode in all seasons could effectively enhance the potential of frost-resistant embankments in winter. © 2022, The Authors. All rights reserved.

关键词： Solar energy

Study on mechanical properties and failure characteristics of rock mass with weak interlayer subjected to freezing–thawing treatment

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Arabian Journal of Geosciences 2022年第10期15卷 1-9页

作者： Fang, Zhichun Zhu, Zhengguo Zhang, Shuai Wu, Siqi Ma, Chaoyi Wang, Renyuan State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuag Tiedao University Shijiazhuang People’s Republic of China State Key Laboratory for Track Technology of High-Speed Railway China Academy of Railway Sciences Beijing People’s Republic of China Hebei Province Technical Innovation Center of Safe and Effective Mining of Metal Mines Shijiazhuang People’s Republic of China School of Traffic and Transportation Shijiazhuag Tiedao University Shijiazhuang People’s Republic of China

Influenced by the geological activity, there are a lot of weak interlayers in the surrounding rock of tunnels along railway in China, and the severe cold climate has a great influence on the engineering properties of rock in cold region. To better understand the influence of interlayer dip and freezing–thawing (F-T) cycles on the mechanical properties and failure characteristics of tunnel surrounding rock and therefore providing a theoretical basis for the tunnel support design, rock samples with different dips of weak interlayer and different F-T cycles were prepared in laboratory, and the triaxial compression test was carried out. The results show that (1) the deformation of hard rock part with weak interlayer is small, while the failure of soft rock interlayer is more severe. When the dip angle of the interlayer is small (β = 0° and 30°), the fracture crack is nearly parallel to the dip angle of the interlayer after rock failure. When the dip angle of the interlayer is large, the fracture surface of the rock mass and the interlayer present an X-shaped intersection. The more F-T cycles, the stronger the damage degree of rock mass. (2) Triaxial compression strength (TCS) and elastic modulus of rock mass decrease first and then increase with the increase of dip angle of interlayer, and the compressive strength and elastic modulus are the minimum when the dip angle of interlayer β = 45°. Compared with the rock mass with horizontal weak interlayer, the compressive strength decreases by 35.27%, and the elastic modulus decreases by 34.84%. (3) F-T cycles have a significant deterioration effect on the mechanical properties of rock mass. The bearing capacity of rock mass decreases with the increase of F-T cycles, but the plastic deformation capacity increases. There is a negative exponential correlation between TCS, elastic modulus, and F-T cycles and a positive linear correlation between peak strain and F-T cycles.

关键词：

Load Distribution Uniformity of Assembled Emergency Steel Bridge Pier Columns

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SSRN 2024年

作者： Liu, Zi-Yu Chen, Shi-Tong Zhi, Mo-Mo Cheng, Shuai-Qi Fan, Xin Collaborative Innovation Center for Performance and Security of Large-scale Infrastructure Shijiazhuang Tiedao University Shijiazhuang China Hebei Eng. Innovation Center for Traffic Emergency and Guarantee Shijiazhuang Tiedao University Shijiazhuang China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang China

Throughout the utilization of assembled emergency steel bridge piers, there is a significant discrepancy in the load carried between different columns, which can lead to premature failure of individual columns and potentially trigger the collapse of the entire structure. Currently, there is no mature method for calculating and implementing load distribution. Based on an improved Fourier series and energy principle, this paper proposes a universal calculation method for the load distribution of columns in assembled emergency steel piers. A specific assembled emergency steel pier is selected as the research subject to conduct model tests and simulation experiments. Through mutual verification of theory, experiments, and simulations, this study analyzes the key factors affecting the load distribution of columns, examines the mechanisms and patterns of their impacts, and explores general principles for the even distribution of loads. The research shows: As the column height or diameter-to-thickness ratio increases, the proportion of load borne by the corner columns and transverse edge columns increases, while the central and longitudinal edge columns see a reduction in their load proportions. A pier-beam linear stiffness ratio based on an overall consideration is proposed. As the height of the columns or the diameter-to-thickness ratio increases, the pier-beam linear stiffness ratio tends to decrease. Using the coefficient of variation of column loads as the standard for evaluating the pier-beam linear stiffness ratio, the recommended threshold for the application of the pier-beam linear stiffness ratio in engineering should be between 3 and 3.86. © 2024, The Authors. All rights reserved.

关键词： Steel bridges

Effects of the Cuo Additive Nanoparticles on the Internal Strain Homogenization and Microstructure Evolution in Ag-Sno2 Composites

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SSRN 2022年

作者： Li, Guijing Ma, Yuanyuan Feng, Wenjie Zhang, Chuanzeng Yan, Zhen Fang, Xueqian Tian, Ruilan Shijiazhuang Tiedao University Shijiazhuang050043 China Provincial Collaborative Innovation Center of Mechanics of Intelligent Materials Hebei China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures China Department of Civil Engineering University of Siegen SiegenD-57068 Germany Department of Engineering Mechanics Germany

Stress concentration caused by reinforcements has very unfavorable effects on the metal matrix composites, which will inevitably induce localized strains and crack initiation. In this paper, an effective approach is presented to relieve stress concentrations near the reinforcements in metallic composites. The Ag-SnO2 contact materials with CuO additive are prepared by electroless plating combined with powder metallurgy method. The CuO nanoparticles in-situ formed on the SnO2 reinforcements are adopted to relieve local stress concentrations near the Ag/SnO2 interfaces and promote strain homogenization. The mechanical properties, deformation characteristics and microstructure evolution of the Ag-SnO2 composites without and with CuO additive are systematically studied by experiments and numerical simulations. The results show that the CuO nanoparticles formed on the surfaces of the SnO2 reinforcements dramatically improve the mechanical properties of the Ag-SnO2 composites, particularly the plasticity at a higher loading rate. It is demonstrated that the dislocation tangle around the CuO nanoparticles effectively relieves the adverse effect of the stress concentration near the SnO2 and results in the strain homogenization in the Ag matrix. Furthermore, the damage evolution of the Ag-SnO2 composites without and with CuO nanoparticles is investigated by the Gurson-Tvergaard-Needleman (GTN) models under uniaxial tension. The nucleation and growth of voids at the interfaces of the Ag-SnO2 composites are numerically simulated and discussed. This study provides a fundamental basis for developing novel high-performance metal matrix composites. © 2022, The Authors. All rights reserved.

关键词： Stress concentration

Study on the Band Gap and Directional Wave Propagation Mechanism of Novel Single-Phase Metamaterials

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SSRN 2022年

作者： Cheng, Shu-Liang Yang, Hong-Yun Yan, Qun Wang, Bin Sun, Yong-Tao Xin, Ya-Jun Ding, Qian Yan, Hao Wang, Liang Key Laboratory of Mechanical Reliability for Heavy Equipment and Large Structure of Hebei Province Yanshan University Qinhuangdao China Tianjin Key Laboratory of Soft Soils and Engineering Environment Tianjin Chengjian University Tianjin China Department of Mechanics Tianjin Key Laboratory of Nonlinear Dynamics and Control Tianjin University Tianjin China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang China Key Laboratory of Aeroacoustics and Dynamics Aircraft Strength Research Institute Xi’an China Key Laboratory of Green Construction and Intelligent Maintenance for Civil Engineering of Hebei Province Yanshan University Qinhuangdao China

In this paper, a new type of single-phase metamaterial is proposed. Based on the finite element method, the band gap characteristics of the structures with different branches are comprehensively analyzed, and the existence of the band gap is further verified by the frequency response transmission spectrum. Then, the propagation characteristics of elastic waves of different frequencies in different combinations of structures are investigated respectively. The results show that the proposed single-phase metamaterial structure has an excellent band gap range, and under the action of relatively low-frequency elastic waves, the wave propagation in the structure has a certain direction and regionality, while the elastic waves at higher frequencies are applied, the propagation direction of the wave tends to propagate in all directions. This paper provides a new idea for studying the structural design of metamaterials with specific wave propagation directions. © 2022, The Authors. All rights reserved.

关键词： Energy gap

Heat Transfer-Based Frost Heave Deformation and structure Optimization of High-Speed Railway Foundation Bed in Frozen Areas

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SSRN 2024年

作者： Qing, Caolin Jie, Shaolong Yue, Zurun Mao, Shuai Zhai, Zhongang State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China College of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China Shijiazhuang University Shijiazhuang050035 China College of Transportation Shijiazhuang Tiedao University Shijiazhuang050043 China

The deformation of the subgrade surface caused by frost heave and thawing settlement is the main cause of railway subgrade deformation in the frozen area, and controlling the deformation of the subgrade surface by reducing the freezing depth is the key to ensure the stability of train operation. Based on the measured temperature field and deformation field of the subgrade of the HQTJ-5 bid section of the Haqi passenger special project, and taking the freezing depth and frost heave deformation in the center of the subgrade on the minimum temperature date as the control standards, the simulation models of the subgrade temperature field and the deformation field were established, and the thermal insulation effects of 13 different types of subgrade surface structures were explored. The results show that under the premise of not considering the hot blanket effect of asphalt mixture layer, both asphalt mixture and cement-stabilized gravel have thermal insulation effect, and laying on the surface layer of subgrade bed can reduce the freezing depth. Appropriately increasing the 2.36-4.75mm particles in the asphalt mixture can reduce the thermal conductivity, the rubber powder cement stabilized gravel can further improve the thermal insulation capacity, and when the surface structure of the foundation bed adopts "10cm thick AC-16 C asphalt mixture reinforced layer + 30% rubber powder cement stabilized gravel", the thermal insulation effect is the best, and the freezing depth can be controlled within 0.97m, and the frost heave deformation can be controlled within 3.23mm. The structure is of great significance to the design of thermal insulation and waterproof roadbed in the frozen area. © 2024, The Authors. All rights reserved.

关键词： Structural optimization

Snow Load Shape Coefficients and Snow Prevention Method on Stepped Flat Roofs

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SSRN 2023年

作者： Zhang, Zhibo Ma, Wenyong Li, Qiang Li, Sai State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang051132 China Key Laboratory of Road and Railway Engineering Safety Ministry of Education Shijiazhuang Tiedao University Hebei Shijiazhuang050043 China Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province Hebei 050043 China

Excessive snow load and nonuniform snow deposition are the main factors leading to building collapses. The snow load shape coefficient represents the dimensionless snow load, and its value is related to the unbalanced distribution of snow. There are differences in the codes of different countries for applying snow load shape coefficients on stepped flat roofs. Therefore, through the combination of field measurements and numerical simulations, this study probed into the snow accumulation processes and snow load shape coefficients on stepped flat roofs, and thus proposed a viable design option to minimize the potential for any drift. It is found that the windward drift on the lower roof is similar to a "triangle" shape, while the downwind drift is close to being evenly distributed. Based on these, the equation of snow load shape coefficients is summarized, which combines with the discrepancies between counties’ codes and the regularity of snow distributions. In this study, the dynamic grid technology under the Eulerian framework is used to predict snow accumulation on stepped flat roofs. The formation mechanism of snow erosion and deposition in each process is analyzed with the wind field. Finally, an effective approach to prevent snow on stepped flat roofs is conceived. © 2023, The Authors. All rights reserved.

关键词： Snow

Response Characteristics of a Piezoelectric Semiconductor Layer Under a Rigid Spherical Indenter

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SSRN 2024年

作者： Liu, Jinxi Gao, Shijing Ju, Chengjian Nie, Guoquan Chen, Weiqiu State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China School of Mechanical Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China Department of Engineering Mechanics Hebei Key Laboratory for Mechanics of Intelligent Materials and Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Key Lab of CAD & CG Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Department of Engineering Mechanics Zhejiang University Hangzhou310027 China

This paper considers the axisymmetric frictionless indentation responses of a piezoelectric semiconductor (PSC) layer, which is perfectly bonded to a rigid substrate and acted on by a rigid spherical indenter. While both the indenter and the rigid substrate are assumed to be electrically insulating, the interaction of piezoelectricity and semiconducting property of PSC is fully taken into consideration. By the Hankel integral transformation, the indentation problem is reduced to a Fredholm integral equation of the second kind, which is solved numerically. The variations of the indentation force, electric potential and contact radius with the indentation depth are obtained. The effects of the layer thickness, indenter size and semiconducting on the variation relationships are analyzed in detail to achieve a better understanding of the response of the PSC layer under indentation. Furthermore, the theoretical results based on the singular integral equation method are verified by the finite element simulation. © 2024, The Authors. All rights reserved.

关键词： Piezoelectricity