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Model Test and Numerical Simulation Study on Soil Arching Effect Evolution Of Pile - Supported Reinforced Embankment

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SSRN 2024年

作者： Wang, Xin Yang, Guang-Qing Li, Hao-Ran Hebei GEO University Hebei Shijiazhuang050030 China The 6410th Factory of the People's Liberation Army of China Hebei Shijiazhuang050307 China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Hebei Shijiazhuang050043 China Shijiazhuang Tiedao University Hebei Shijiazhuang050043 China

The mechanical behavior of pile-supported reinforced embankment is complex, and the shape of soil arch has not been unified. It is of great scientific value to further study the mechanism of soil arch effect. Through three-dimensional model test, this paper studies the influence of embankment filling properties, pile spacing and horizontal reinforcement on soil arching effect. Based on the stress monitoring results of foundation surface and embankment internal, the formation process and evolution mechanism of soil arching effect in cohesive soil embankment were studied. The arch axis expressions of the central area between four piles and the strip area between two piles were proposed by numerical simulation. The results show: The differential settlement of pile-soil has a great influence on the degree of soil arching effect. The increase of pile spacing promotes the soil arching effect to a certain extent, but too large pile spacing will increase the settlement of roadbed;The cohesion of embankment has a certain promoting effect on load transfer. With the increase of cohesion, the differential settlement of pile-soil decreases gradually;Under the action of the reinforcement, the internal structure of the soil arch changes;The height of soil arch is related to the net spacing of pile cap. The maximum height of soil arch in the strip area between two piles is 1.10(s-a), and the maximum height of soil arch in the central area between four piles is 1.64(s-a). © 2024, The Authors. All rights reserved.

关键词： Piles

Evolution of Pore-Fracture and Permeability During Co2+O2 In-Situ Leaching Process of Fractured Sandstone

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SSRN 2024年

作者： Niu, Qinghe He, Jiabin Yuan, Wei Chang, Jiangfang Wang, Wei Yuan, Junhong Wang, Qizhi Zheng, Yongxiang Shang, Songhua Key Laboratory of Roads and Railway Engineering Safety Control Shijiazhuang Tiedao University Ministry of Education Shijiazhuang050043 China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Hebei Technology and Innovation Center on Safe and Efficient Mining of Metal Mines Shijiazhuang050043 China State Key Laboratory of Nuclear Resources and Environment East China University of Technology Nanchang330013 China School of Transportation Inner Mongolia University Hohhot010021 China School of Civil Engineering Hebei University of Science and Technology Shijiazhuang050018 China

This work is organized to reveal the influence mechanism and law of CO2+O2 in situ leaching on pore permeability characteristics of stimulated deposits. Results show that geochemical reactions during the CO2+O2 ISL process are complex, the dolomite and potassium feldspar are dissolved, while the clay mineral precipitates are formed. The response characteristics and mechanisms of pore-fracture structures differ between the single and multi-fractured samples during the CO2+O2 ISL process. The pore number density of the single-fractured sample increases while porosity decreases, causing larger pores to evolve into smaller ones. While the porosity and fracture volume of the multi-fractured sample increase significantly. The permeability characteristics of fractured samples are consistent with the evolution of pore-fracture structures. The multi-fractured sample possesses a higher fracture compression coefficient and lower PLR due to the larger compressive space, the self-supporting effect of fracture network and the scouring effect of leaching solution. Although creating a single fracture in reservoir stimulation can enhance the original deposit permeability, the conductivity will gradually decline during the subsequent CO2+O2 ISL process. Optimizing reservoir stimulation techniques to create complex fracture networks within deposits can enhance overall permeability and weaken the permeability reduction effect, ensuring the efficient extraction of uranium resources. © 2024, The Authors. All rights reserved.

关键词： Fracture

Studies of Turbulent Heat Transfer Properties in Combined Solar Chimneys and Their engineering Applications

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SSRN 2023年

作者： Cui, Huimin Han, Mengjiao Zhang, Jitao Han, Zhiming Xu, Feng Liu, Qingkuan State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province Shijiazhuang050043 China Department of Mathematics and Physics Shijiazhuang Tiedao University Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China School of Physical Science and Engineering Beijing Jiaotong University Beijing100044 China

Solar chimneys can induce natural ventilation through solar radiation. However, sufficient theoretical studies are needed as a basis in order to fully exploit passive design in practical green building design. In this study, the heat transfer properties of turbulent natural convective flows in a combined solar chimney with a thermal flux at the absorption wall are investigated by theoretical analysis and numerical simulations. Two different flow patterns have been discovered, one with an obvious thermal boundary layer flow pattern and the other without, based on the high Rayleigh number. For the flow development in these two flow regimes, the transient scaling analysis is performed separately and the control mechanism for each phase is presented. Scaling correlations of air flow speed, temperature, and mass flow rate have been established to describe the ventilation properties of solar chimneys. The corresponding numerical simulation data is used for scaling verification. Ventilation times are calculated for a solar chimney with aspect ratio A=7.5 to provide a basis for the devise of a solar chimney. © 2023, The Authors. All rights reserved.

关键词： Boundary layers

The Effects of Row Spacing and Ground Clearance On the Wind Load of Photovoltaic (Pv) Arrays

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SSRN 2023年

作者： Xu, Ang Ma, Wenyong Yuan, Huanxin Lu, Lihe 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 Shijiazhuang Hebei050043 China Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province Hebei050043 China School of Civil Engineering Wuhan University Wuhan430072 China Inner Mongolia Electric Power Survey & Design Istitute Co. Ltd. Huhehot Inner Mongolia 010011 China

Row spacing and ground clearance have a significant effect on the wind load of a photovoltaic (PV) array. Based on wind tunnel tests and numerical simulations with the self-sustainable equilibrium atmospheric boundary layer, the influences of row spacing and ground clearance on the wind load of PV arrays are analysed, and the mechanism of the wind-induced interference effect is determined by flow field analysis. The results show that the ground clearance affects the wind load distribution on the PV module, and this effect has an inconsiderable impact on the net wind pressure on the PV modules. The effect of row spacing on the wind load of PV arrays is more significant, and this effect is mainly manifested in the shielding effect. The tilt angle is the main factor that affects the size of the vortex scale which significantly influences the wind load. The ground clearance, row spacing and tilt angle all affect the torque coefficient on the PV module. The larger the ground clearance is, the larger the torque coefficient. Finally, the wind load coefficients and reduction factors are presented as a recommendation for wind resistance design of PV arrays. © 2023, The Authors. All rights reserved.

关键词： Atmospheric boundary layer

Curing Stress Effect on Stability, Microstructure, Matric Suction and Electrical Conductivity of Cementitious Tailings Backfills

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SSRN 2022年

作者： Chen, Shunman Yilmaz, Erol Wang, Wei Wang, Yi-Ming School of Civil Engineering and Architecture East China Jiaotong University Jiangxi Nanchang330013 China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Hebei Province Shijiazhuang050043 China Jiangxi Key Laboratory of Disaster Prevention-mitigation and Emergency Management East China Jiaotong University Jiangxi Nanchang330013 China Department of Civil Engineering Geotechnical Division Recep Tayyip Erdogan University Fener RizeTR53100 Turkey School of Civil and Resources Engineering University of Science and Technology Beijing Beijing100083 China

Cementitious tailings backfill (CTB) is a regularly used technique for most mines at home and aboard since it has a significant meaning for the recycling of total tailings and enhances the safety of underground mines. Thus, studying the behavior of the CTB materials exposed to diverse curing stresses is fairly vital to guarantee the whole stability and long-term ageing of underground mining structures. This paper inspects the effect of diverse curing stresses (0 kPa – witness, 180 kPa, 360 kPa and 540 kPa) on physico-mechanical characteristics of CTB materials subjected to a curing age of up to 28 days. Based on lab tests, uniaxial compression and microstructure analyses are performed for all the specimens. To well characterize the self-desiccation behavior of CTB specimens, suction and electrical conductivity are also scrutinized during their curing processes. Results indicate that curing of CTBs under stress ranging from 0 to 540 kPa can improve their strength gains to some extent. Irrespective of curing stress, CTB’s suction is enlarged while its porosity is dropped once increased with curing age and stress, respectively. There exists a robust power function between suction and strength while there is a linear link between electrical conductivity and strength. One can state from this study that curing stress must be significantly taken into account during the backfill mixture proportions’ design. © 2022, The Authors. All rights reserved.

关键词： Pore structure

Data-Driven Turbulence Model for Unsteady Cavitating Flow

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SSRN 2022年

作者： Zhang, Zhen Wang, Jingzhu Huang, Renfang Qiu, Ruidi Ye, Shuran Wang, Yiwei Liu, Qingkuan State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences Beijing100190 China School of Future Technology University of Chinese Academy of Sciences Beijing100049 China School of Engineering Science University of Chinese Academy of Sciences Beijing100049 China

Reynolds-averaged Navier-Stokes (RANS) equations have been widely used in engineering fields to investigate cavitating flow owing to their low computational cost and excellent robustness. However, it is challenging to accurately obtain the unsteady characteristics of cavitating flow owing to cavitation-induced phase transitions. In this study, we propose an implicit data-driven RANS (DD-RANS) framework based on a higher-order eddy viscosity model to analyze the unsteady characteristics of cavitating flow. In the DD-RANS framework, a basic computational model is developed by introducing a cavitation-induced phase transition into the equations of Reynolds stress in the process of turbulence modeling. To improve the computational accuracy and generalization performance of the basic model, the linear and nonlinear parts of the anisotropic Reynolds stress tensor are predicted through implicit and explicit methods, respectively. A data fusion approach, allowing the input and output of characterized parameters at multiple time points, is presented to obtain the unsteady characteristics of the model dataset. The neural networks in the DD-RANS model are trained using the numerical results obtained via large eddy simulation (LES). The training data consists of two parts: (i) the results obtained at cavitation numbers of 2.0, 2.2, and 2.7 for a Venturi flow, and (ii) those obtained at cavitation numbers of 0.8 and 1.5 for a NACA66 hydrofoil. The DD-RANS model is used to predict the cavitating flow at cavitation numbers of 2.5 for a Venturi flow and 0.8 for a Clark-Y hydrofoil. It is found that the DD-RANS model is superior to the baseline RANS model in predicting the instantaneous periodic shedding of a cavity and the mean flow fields. Furthermore, the developed DD-RANS exhibited excellent generalization abilities. © 2022, The Authors. All rights reserved.

关键词： Cavitation

Causal inference approach to appraise long-term effects of maintenance policy on functional performance of asphalt pavements

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arXiv

arXiv 2024年

作者： You, Lingyun Guo, Nanning Long, Zhengwu Wang, Fusong Si, Chundi Diab, Aboelkasim School of Civil and Hydraulic Engineering Huazhong University of Science and Technology Hubei Province Wuhan430074 China State Key Laboratory of Mechanical Behaviour and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Hebei Province Shijiazhuang050043 China Department of Civil Engineering College of Engineering Fahad Bin Sultan University Tabuk71454 Saudi Arabia Department of Civil Engineering Aswan University Aswan81542 Egypt

Asphalt pavements as the most prevalent transportation infrastructure, are prone to serious traffic safety problems due to functional or structural damage caused by stresses or strains imposed through repeated traffic loads and continuous climatic cycles. The good quality or high serviceability of infrastructure network is vital to the urbanization and industrial development of nations. In order to maintain good functional pavement performance and extend the service life of asphalt pavements, the long-term performance of pavements under maintenance policies needs to be evaluated and favourable options selected based on the condition of the pavement. A major challenge in evaluating maintenance policies is to produce valid treatments for the outcome assessment under the control of uncertainty of vehicle loads and the disturbance of freeze-thaw cycles in the climatic environment. In this study, a novel causal inference approach combining a classical causal structural model and a potential outcome model framework is proposed to appraise the long-term effects of four preventive maintenance treatments for longitudinal cracking over a 5-year period of the upkeep. Three fundamental issues were brought to our attention: 1) detection of causal relationships prior to variables under environmental loading (identification of causal structure);2) obtaining direct causal effects of treatment on outcomes excluding covariates (identification of causal effects);and 3) sensitivity analysis of causal relationships. The results show that the method can accurately evaluate the effect of preventive maintenance treatments and assess the maintenance time to cater well for the functional performance for different preventive maintenance approaches. This framework could help policymakers to develop appropriate maintenance strategies for pavements. Copyright © 2024, The Authors. All rights reserved.

关键词： Sensitivity analysis

Soft-Landing Dynamics of a Type of Four-Legged Space Lander

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SSRN 2024年

作者： Shi, Tengfei Shi, Tengfei Yang, Yinping Zhang, Zhijuan Liu, Cuicui Liu, Caishan Ma, Daolin Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and Aerospace Engineering Southwest Jiaotong University Chengdu610031 China State Key Laboratory for Turbulence and Complex Systems College of Engineering Peking University Beijing100871 China Institute of Dynamics and Control College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology Beijing100871 China China Academy of Space Technology Beijing100094 China School of Naval Architecture Ocean and Civil Engineering Shanghai Jiao Tong University Shanghai200240 China Key Laboratory of Marine Intelligent Equipment and System Ministry of Education Shanghai200240 China

Analyzing the landing dynamics response is essential for enhancing the success rate of surface explorations on Mars, the moon, or asteroids. This paper develops a comprehensive dynamics model for a space lander equipped with four sets of buffer legs, each consisting of a primary strut, two secondary struts, and a footpad, during its soft landing process. The degrees of freedom of the main body and the footpads are defined as generalized coordinates to describe the motion of the space lander. The compression force of the buffer struts is obtained by interpolating real experimental data, and the contact force between the footpad and the ground is calculated using Archimedes law for granular media. Then, the dynamical model for the lander in terms of minimal degrees of freedom can be constructed by applying the Lagrange equations of the second kind. The proposed dynamics model is validated by the experiments of a single-legged lander vertical touchdown and a four-legged lander free touchdown. Moreover, histories of buffer force, acceleration of the main body, and other key physical quantities are computed to investigate the landing process. This highly efficient and accurate dynamics model provides a method to perform extensive simulations to design and optimize a soft landing process. © 2024, The Authors. All rights reserved.

关键词： Landing

NUMERICAL STUDY ON TRANISENT NATURAL CONVECTION IN COAL SHED ENCLOSED OF SINGLE COAL PILE

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Gongcheng Lixue/engineering Mechanics 2023年第10期40卷 237-246页

作者： Wang, Wen-Yue Cui, Hui-Min Han, Zhi-Ming Liu, Qing-Kuan Department of Mathematics and Physics Shijiazhuang Tiedao University Hebei Shijiazhuang050043 China State Key Laboratory of Mechanical Behavior System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Hebei Shijiazhuang050043 China Innovation Center for Wind Engineering Wind Energy Technology of Hebei Province Hebei Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Hebei Shijiazhuang050043 China

In recent years, the environmentally friendly closed coal shed has been widely used in actual production and life. The heat released from the coal pile will cause local overheating of the environment, which will affect the comfort and health of workers. So the problem of convective heat transfer in coal shed has attracted extensive attention. In order to reduce the harm of coal heap heat release, it is necessary to understand the mechanism of heat transfer and flow in the process of coal heap heat release. CFD numerical simulation method is used to study the natural convection phenomenon in the closed large span coal shed with a single coal pile. Under unsteady conditions, the heat transfer characteristics and flow transition around coal pile with fixed Rayleigh number are studied. The emergence time of symmetric and asymmetric flow structures in coal shed under different Rayleigh numbers are studied. The unsteady characteristics of flow in full development stage are given. The results show that the transient flow in the coal shed will go through three different stages: initial stage, transitional stage and quasi-steady stage. During the transitional stage, the separation and shedding of the plume will promote the formation of asymmetric structure in coal shed, and the emergence time of asymmetric phenomenon will advance with the increase of Rayleigh number. In the quasi-steady stage, the flow in the coal shed presents the characteristics of irregular unsteady turbulent flow, and the time to reach full-development state is delayed with the increase of Rayleigh number. © 2023 Tsinghua University. All rights reserved.

关键词： Coal