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Number of results: 4
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Abstract

The rheological behaviour of cemented paste backfill (CPB) has an important influence on the stability of its transportation in pipelines. In the present study, the time-dependent rheological behaviour of CPB was investigated to elucidate the effects of time and solid content. Experimental results showed that when CPB is subjected to a constant shear rate, the shear stress gradually decreases with time before finally stabilis ing. When the solid content was 60%~62%, a liquid network structure was the main factor that influenced the thixotropy of CPB, and the solid content had less influence. When the solid content was 64%~66%, a floc network structure was the main factor that influenced the thixotropy of CPB, and the solid content had a more significant influence on the thixotropy than the shear rate. The initial structural stability of CPB increased with the solid content, and this relationship can be described by a power function. Based on the experimental results, a calculation model of pipeline resistance considering thixotropy was proposed. The model was validated by using industrial experimental data. The current study can serve as a design reference for CPB pipeline transportation.
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Authors and Affiliations

Yingjie Chang
1
ORCID: ORCID
Youzhi Zhang
1
ORCID: ORCID
Deqing Gan
1
ORCID: ORCID
Xinyi Wang
1
ORCID: ORCID
Shuangcheng Du
1
ORCID: ORCID

  1. North China University of Science and Technology, College of Mining Engineering, China
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Abstract

Tunnel lay-by spacing is directly related to traffic safety and engineering investment. Nevertheless, its mechanism is not clear, and the rationality of the exiting norms with respect to tunnel lay-by spacing needs to demonstrate. A calculation model for tunnel lay-by spacing was derived by considering the headway and the physical kinematics of the two vehicles chasing and encountering. With it, the influence of various parameters on lay-by spacing were analysed and the rationality of the model were discussed through comparing with existing norms. Results shows longitudinal gradient rate, daily average traffic flow, rolling resistance coefficient, posted speed limit are significant to determine the lay-by spacing, and the most important parameter is longitudinal gradient rate. Existing tunnel lay-by spacing norm values are not reasonable enough, either too strict or too loose. These findings provide scientific support for how to select tunnel lay-by spacing value, which can improve tunnel traffic safety and make engineering investment reasonable.
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Authors and Affiliations

Bo Liang
1
ORCID: ORCID
Yao Xiao
2
ORCID: ORCID

  1. Chongqing Jiaotong University, School of Civil Engineering, State Key Laboratory of Mountain Bridge and Tunnel Engineering, Xuefu Avenue 66, Nanan District, Chongqing, China
  2. Chongqing Jiaotong University, School of Civil Engineering, Chongqing Rail Transit (Group) Co., Ltd, Xuefu Avenue 66, Nanan District, Chongqing, China
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Abstract

Coal is the main energy source in China, but its underground mining causes surface subsidence, which seriously damages the ecological and living environments. How to calculate subsidence accurately is a core issue in evaluating mining damage. At present, the most commonly used method of calculation is the Probability Integral Method (PIM), based on a normal distribution. However, this method has limitations in thick topsoil (thickness > 100 m), in that the extent of the calculated boundary of the subsidence basin is smaller than its real extent, and this has an undoubted impact on the accurate assessment of the extent of mining damage. Therefore, this paper introduces a calculation model for surface subsidence based on a Cauchy distribution for thick topsoil conditions. This not only improves the accuracy of calculation at the subsidence basin boundary, but also provides a universal method for the calculation of surface subsidence.

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Authors and Affiliations

Yue Jiang
Rafał Misa
ORCID: ORCID
Krzysztof Tajduś
ORCID: ORCID
Anton Sroka
ORCID: ORCID
Yan Jiang
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Abstract

Prediction of soft soil sub-grades settlement has been a big challenge for geotechnical engineers that are responsible for the design of roadbed embankment. The characteristics of low strength, poor permeability, high water contents, and high compressibility are dominant in soft soils, which result in a huge settlement in the case of long-term loading. The settlement prediction in soft soil subgrades of Jiehui Expressway A1, Guangdong, China, is the focus of this study. For this purpose, the necessary data of settlement is collected throughout the project execution. The numerical analysis is conducted by using the Richards model based on Linear Least Squares Iteration (LLS-I) method to calculate and predict the expected settlement. The traditional settlement prediction methods, including the hyperbolic method, exponential curve method, and pearl curve method, are applied on field settlement data of soft soil subgrades of Jiehui Expressway A1. The results show that the Richards model based on Linear Least Squares Iteration (LLS-I) method has high precision, and it has proven to be a better option for settlement prediction of soft soil sub-grades. The model analysis indicates that the mean absolute percentage error (MAPE) can be minimized as compared to other soft soil sub-grades settlement prediction methods. Hence, Richards's model-based LLS-I method has a capability for simulation and settlement prediction of soft soil subgrades.
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Authors and Affiliations

Muhammad Nadeem
1
Muhammad Akbar
2
Pan Huali
3
Li Xiaoqing
1
Ou Guoqiang
3
Azka Amin
4

  1. Graduate Student School of Civil Engineering and Mechanics, HUST, Wuhan, China
  2. PhD, Research Scholar, Department of Geotechnical Engineering Institute of Mountain Hazards and Environment, Chinese Academy of Science, Chengdu, China
  3. Prof, PhD., Eng., Department of Geotechnical Engineering Institute of Mountain Hazards and Environment, Chinese Academy of Science, Chengdu, China
  4. Assistant Professor, Department of Business Administration Iqra University, Main Campus, Karachi, Pakistan

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