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CONTENTS
Volume 22, Number 1, July10 2020
 

Abstract
This paper presents an investigation of the ground response of a gob-side gateroad suffering mining stress induced by a 21 m-thick coal seam extraction. A field observation, including entry convergence and stress changes monitoring, was first conducted in the tailgate 8209. The observation results of entry convergence showed that, during the adjacent panel 8210 retreating period, the deformation of the gob-side gateroad experienced a continuous increase stage, subsequently, an accelerating increase stage, and finally, a slow increase stage. However, strong ground response, including roof bending deflection, rib extrusion and floor heave, occurred during the current panel 8209 retreating period, and the maximum floor heave reached 1530 mm. The stress changes within coal mass of the two ribs demonstrated that the gateroad was always located in the stress concentrated area, which responsible for the strong response of the tailgate 8209. Subsequently, a hydraulic fracture technique was proposed to pre-fracture the two hard roofs above the tailgate 8209, thus decreasing the induced disturbance on the tailgate. The validity of the above roof treatment was verified via field application. The finding of this study could be a reference for understanding the stability control of the gob-side gateroad in extra thick coal seams mining.

Key Words
field observation; gob-side gateroads; mining-induced stress; hard and thick roofs; an extra thick coal seam

Address
Fulian He: School of Energy and Mining Engineering, China University of Mining and Technology (Beijing), Beijing, 100083, China

Sheng Gao: 1.) School of Energy and Mining Engineering, China University of Mining and Technology (Beijing), Beijing, 100083, China
2.) CCTEG Energy Technology Development Co., Ltd., Beijing, 100013, China

Guangchao Zhang: 1.) School of Energy and Mining Engineering, China University of Mining and Technology (Beijing), Beijing, 100083, China
2.) College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao, 266590, China
3.) CCTEG Energy Technology Development Co., Ltd., Beijing, 100013, China

Bangyou Jiang: College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao, 266590, China

Abstract
In this study, a new analytical-numerical procedure is developed to give the stresses and strains around a circular tunnel in rock masses exhibiting different stress-strain behavior. The calculation starts from the tunnel wall and continues toward the unknown elastic-plastic boundary by a finite difference method in the annular discretized plastic zone. From the known stresses in the tunnel boundary, the strains are calculated using the elastic-plastic stiffness matrix in which three dimensional Hoek-Brown failure criterion (Jiang and Zhao 2015) and Mohr-Coulomb potential function with proper dilation angle (i.e., non-associated flow rule) are employed in terms of stress invariants. The illustrative examples give ground response curve and show correctness of the proposed approach. Finally, from the results of a great number of analyses, a simple relationship is presented to find out the closure of circular tunnel in terms of rock mass strength and tunnel depth. It can be valuable for the preliminary decision of tunnel support and for prediction of tunnel problems.

Key Words
circular tunnel; stress and strain; stiffness matrix; analytical solution; three dimensional Hoek-Brown criterion; stress invariants

Address
Masoud Ranjbarnia and Nima Rahimpour: Department of Geotechnical Engineering, Faculty of Civil Engineering, University of Tabriz, 29 Bahman Blvd, Tabriz, Iran

Pierpaolo Oreste: Department of Environmental, land and infrastructure Engineering, Politecnico di Torino, Corso Duca degli Abruzzi, Torino 24-10129, Italy

Abstract
In metropolitan areas, the quantity and density of the underground structure increase rapidly in recent years. Even though most damage incidents of the underground structure were minor, there were still few incidents causing a great loss in lives and economy. Therefore, the safety evaluation of the underground structure becomes an important issue in the disaster prevention plan. Liquefaction induced uplift is one important factor damaging the underground structure. In order to perform a preliminary evaluation on the safety of the underground structure, simplified prediction equations were introduced to provide a first order estimation of the liquefaction induced uplift. From previous studies, the input motion is a major factor affecting the magnitude of the uplift. However, effects of the input motion were not studied and included in these equations in an appropriate and rational manner. In this article, a numerical simulation approach (FLAC program with UBCSAND model) is adopted to study effects of the input motion on the uplift. Numerical results show that the uplift and the Arias Intensity (Ia) are closely related. A simple modification procedure to include the input motion effects in the Sasaki and Tamura prediction equation is proposed in this article for engineering practices.

Key Words
uplift; underground structure; liquefaction; FLAC; ground motion

Address
Jui-Ching Chou: Department of Civil Engineering, National Chung Hsing University, 145 Xingda Rd., South Dist., Taichung 40227, Taiwan, R.O.C.

Der-Guey Lin: Department of Soil and Water Conservation, National Chung Hsing University, 145 Xingda Rd., South Dist., Taichung 40227, Taiwan, R.O.C.

Abstract
This paper provides methods for the deterministic and reliability-based design of the support pressures necessary to prevent tunnel face collapse. The deterministic method is developed by extending the use of the unique load multiplier, which is embedded within OptumG2/G3 with the intention of determining the maximum load that can be supported by a system. Both two-dimensional and three-dimensional examples are presented to illustrate the applications. The obtained solutions are validated according to those derived from the existing methods. The reliability-based method is developed by incorporating the Response Surface Method and the advanced first-order second-moment reliability method into the bisection algorithm, which continuously updates the support pressure within previously determined brackets until the difference between the computed reliability index and the user-defined value is less than a specified tolerance. Two-dimensional reliability-based support pressure is compared and validated via Monte Carlo simulations, whereas the three-dimensional solution is compared with the relationship between the support pressure and the resulting reliability index provided in the existing literature. Finally, a parametric study is carried out to investigate the influences of factors on the required support pressure.

Key Words
tunnel face stability; necessary support pressure; strength reduction analysis; reliability-based design; bisection method

Address
Bin Li and Hong Li: School of Transportation, Wuhan University of Technology, Hubei Highway Engineering Research Center, 1178 Heping Avenue, Wuhan, China

Kai Yao: 1.)School of Qilu Transportation, Shandong University, 12550 East Second Ring Road, Jinan, 250002, China
2.) Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, Singapore, 117576, Singapore

Abstract
Studying the critical response characteristics of box culverts with diverse geometrical configurations under seismic excitations is a necessary step to develop a reasonable design method. In this work, a numerical parametric study is conducted on various soil-culvert systems, aiming to highlight the critical difference in the seismic performances between three- and four-sided culverts. Two-dimensional numerical models consider a variety of burial depths, flexibility ratios and foundation widths, assuming a visco-elastic soil condition, which permits to compare with the analytical solutions and previous studies. The results show that flexible three-sided culverts at a shallow depth considerably amplify the spectral acceleration and Arias intensity. Larger racking deformation and rocking rotation are also predicted for the three-sided culverts, but the bottom slab influence decreases with increasing burial depth and foundation width. The bottom slab combined with the burial depth and structural stiffness also significantly influences the magnitude and distribution of the dynamic earth pressure. The findings of this work shed light on the critical role of the bottom slab in the seismic responses of box culverts and may have a certain reference value for the preliminary seismic design using R-F relation.

Key Words
box culvert; earthquake; numerical model; flexibility ratio

Address
Qiangqiang Sun: Laboratory 3SR, Grenoble Alpes University, Grenoble, France

Da Peng: Department of Civil and Environmental Engineering, University of Cincinnati, Cincinnati, U.S.A.

Daniel Dias: 1.) Laboratory 3SR, Grenoble Alpes University, Grenoble, France
2.) School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei, China

Abstract
This paper presents a theoretical investigation on the response of the thermo-mechanical bending of FG plate on variable elastic foundation. A quasi-3D higher shear deformation theory is used that contains undetermined integral forms and involves only four unknowns to derive. The FG plates are supposed simply supported with temperature-dependent material properties and subjected to nonlinear temperature rise. Various homogenization models are used to estimate the effective material properties such as temperature-dependent thermoelastic properties. Equations of motion are derived from the principle of virtual displacements and Navier\'s solution is used to solve the problem of simply supported plates. Numerical results for deflections and stresses of FG plate with temperature-dependent material properties are investigated. It can be concluded that the proposed theory is accurate and simple in solving the thermoelastic bending behavior of FG thick plates.

Key Words
quasi-3D solution; FG thick plates; homogenization models; temperature-dependent material; thermo-mechanical bending

Address
Mohamed Ali Rachedi and Abdelhakim Bouhadra: 1.) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Algeria
2.) Department of Civil Engineering, Faculty of Science and Technology, University of Abbés Laghrour Khenchela, Algeria

Samir Benyoucef, Mohamed Sekkal and Abdelkader Benachour: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Algeria

Rabbab Bachir Bouiadjra: 1.) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Algeria
2.) Department of Civil Engineering, University Mustapha Stambouli of Mascara, Algeria

Abstract
Measurement of the unconfined compressive strength (UCS) of the rock is critical to assess the quality of the rock mass ahead of a tunnel face. In this study, extensive field studies have been conducted along 3,885 m of the new Nagasaki tunnel in Japan. To predict UCS, a hybrid model of artificial neural network (ANN) based on genetic algorithm (GA) optimization was developed. A total of 1350 datasets, including six parameters of the Measurement-While- Drilling data and the UCS were considered as input and output parameters respectively. The multiple linear regression (MLR) and the ANN were employed to develop contrast models. The results reveal that the developed GA-ANN hybrid model can predict UCS with higher performance than the ANN and MLR models. This study is of great significance for accurately and effectively evaluating the quality of rock masses in tunnel engineering.

Key Words
unconfined compressive strength; measurement-while-drilling data; ANN; genetic algorithm; tunnel face

Address
Jiankang Liu, Yuanchao Zhang and Yujing Jiang: Graduate School of Engineering, Nagasaki University, 1-14 Bunkyo-machi, 852-8521 Nagasaki, Japan

Hengjie Luan: College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao 266590, China

Osamu Sakaguchi: Department of Civil Engineering, Konoike Construction Co., Ltd., 3-6-1, Kitakyuhoji-machi, Chuo-ku, 541-0057 Osaka, Japan

Abstract
The time-consuming and less objectivity are the main problems of conventional micromechanical parameters calibration method of Particle Flow Code simulations. Thus this study aims to address these two limitation of the conventional \"trial-and-error\" method. A new calibration method for the linear parallel bond model (CM-LPBM) is proposed. First, numerical simulations are conducted based on the results of the uniaxial compression tests on limestone. The macroscopic response of the numerical model agrees well with the results of the uniaxial compression tests. To reduce the number of the independent micromechanical parameters, numerical simulations are then carried out. Based on the results of the orthogonal experiments and the multi-factor variance analysis, main micromechanical parameters affecting the macro parameters of rocks are proposed. The macro-micro parameter functions are ultimately established using multiple linear regression, and the iteration correction formulas of the micromechanical parameters are obtained. To further verify the validity of the proposed method, a case study is carried out. The error between the macro mechanical response and the numerical results is less than 5%. Hence the calibration method, i.e., the CM-LPBM, is reliable for obtaining the micromechanical parameters quickly and accurately, providing reference for the calibration of micromechanical parameters.

Key Words
discrete element method; particle flow code; parallel bond model; micromechanical parameters; calibration method

Address
Z.H. Xu: 1.) Geotechnical and Structural Engineering Research Center, Shandong University, Jinan, Shandong 250061, China
2.) School of Qilu Transportation, Shandong University, Jinan, Shandong 250061, China
3.) SinoProbe Center - China Deep Exploration Center, Chinese Academy of Geological Sciences, Beijing 100037, China

W.Y. Wang and Y. Xiong: 1.) Geotechnical and Structural Engineering Research Center, Shandong University, Jinan, Shandong 250061, China
2.) School of Qilu Transportation, Shandong University, Jinan, Shandong 250061, China

P. Lin, Z.Y. Liu and S.J. He: Geotechnical and Structural Engineering Research Center, Shandong University, Jinan, Shandong 250061, China


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