Techno Press
Tp_Editing System.E (TES.E)
Login Search


gae
 
CONTENTS
Volume 18, Number 2, June10 2019
 

Abstract
Due to certain geological characteristics (high thickness, rocky properties), some underground coal mines require the use of explosives. This paper explores the effects of fragmentation of different decks detonated simultaneously in a single borehole with the use of numerical analysis. ANSYS/LS-DYNA code was used for the implementation of the models. The models include an erosion criterion to simulate the cracks generated by the explosion. As expected, the near-borehole area was damaged by compression stresses, while far zones and the free surface of the boundary were subjected to tensile damage. With the increase of the number of decks in the borehole, different changes in the fracture pattern were observed, and the superposition effects of the stress wave became evident, affecting the fragmentation results. The superposition effect is more evident in close distances to the borehole, and its effect attenuates when the distance to the borehole increase.

Key Words
distributed charges; coal blasting; tensile damage; explosion cracks

Address
Fei Liu, Shengli Yang, Huayong Lv and Jinwang Zhang: 1.) School of Energy and Mining Engineering, China University of Mining & Technology, Beijing 100083, China
2.) Coal Industry Engineering Research Center of Top-Coal Caving Mining, Beijing 100083, China

Jhon Silva: Department of Mining Engineering, University of Kentucky, Lexington, KY, 40506, U.S.A.

Abstract
This article discusses the phenomenon of plastic volumetric deformation of naturally structured clays before virgin yielding, i.e., subyielding behavior. A simple approach representing both the compression and shear responses of the clays during subyielding is demonstrated. A new compression model for structured clays based on the theoretical framework of the Structured Cam Clay (SCC) model via incorporation of the subyielding behavior is presented. Two stress surfaces are introduced to distinguish the subyielding and virgin yielding. The hardening and destructuring processes of structured clays under isotropic compression and shear are the focus of this work. The simulations of the compression and shear of eleven natural clays are studied for validation. The proposed work can accurately predict the subyielding behavior of structured clays both qualitatively and quantitatively and can be used for modeling structured clays under compression and shear responses in geological and geotechnical engineering problems.

Key Words
hardening; destructuring; structured cam clay; structured clay; subyielding

Address
Jirayut Suebsuk:Department of Civil Engineering, Faculty of Engineering and Architecture, Rajamangala University of Technology Isan, Nakhon Ratchasima, Thailand

Suksun Horpibulsuk: School of Civil Engineering and Center of Excellence in Innovation for Sustainable Infrastructure Development, Suranaree University of Technology, Nakhon Ratchasima, Thailand

Martin D. Liu: Faculty of Engineering, The University of Wollongong, New South Wales, Australia

Abstract
Strain-rate and temperature have significant effects on the one-dimensional (1D) compression behavior of soils. This paper focuses on the bonding degradation effect of soil structure on the time and temperature dependent behavior of soft structured clay. The strain-rate and temperature dependency of preconsolidation pressure are investigated in double logarithm plane and a thermal viscoplastic model considering the combined effect of strain-rate and temperature is developed to describe the mechanical behavior of unstructured clay. By incorporating the bonding degradation, the model is extended that can be suitable for structured clay. The extended model is used to simulate CRS (Constant Rate of Strain) tests conducted on structural Berthierville clay with different strain-rates and temperatures. The comparisons between predicted and experimental results show that the extended model can reasonably describe the effect of bonding degradation on the stain-rate and temperature dependent behavior of soft structural clay under 1D condition. Although the model is proposed for 1D analysis, it can be a good base for developing a more general 3D model.

Key Words
structured clay; strain-rate; bonding degradation; temperature; viscoplasticity

Address
Qi-Yin Zhu, Xiang-Yu Shang and Tuo Chen: State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining & Technology, Xuzhou 221116, China

Yin-Fu Jin: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China


Abstract
In this paper, it is aimed to present a detail investigation about the comparison of static and dynamic behavior of historical masonry arch bridges considering different arch curvature. Göderni historical masonry two-span arch bridge which is located in Kulp town, Diyarbakir, Turkey is selected as a numerical application. The bridge takes part in bowless bridge group and built in large measures than the others. The restoration projects were approved and rehabilitation studies have still continued. Finite element model of the bridge is constituted with special software to determine the static and dynamic behavior. To demonstrate the arch curvature effect, the finite element model are reconstructed considering different arch curvature between 2.86 m-3.76 m for first arch and 2.64 m-3.54 m for second arch with the increment of 0.10 m, respectively. Dead and live vehicle loads are taken into account during static analyses. 1999 Kocaeli earthquake ground motion record is considered for time history analyses. The maximum displacements, principal stresses and elastic strains are compared with each other using contour diagrams. It is seen that the arch curvature has more influence on the structural response of historical masonry arch bridges. At the end of the study, it is seen that with the increasing of the arch heights, the maximum displacements, minimum principal stresses and minimum elastic strains have a decreasing trend in all analyses, in addition maximum principal stresses and maximum elastic strains have unchanging trend up to optimum geometry.

Key Words
arch bridge; dynamic behavior; finite element model; masonry; curvature effect

Address
Ahmet Can Altunsik, Burcu Kanbur and Ebru Kalkan: Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey

Ali Fuat Genc: Department of Civil Engineering, Karadeniz Technical University, Of Technology Faculty, Trabzon, Turkey

Abstract
This paper examines the results from three-dimensional dynamic finite element analysis undertaken to develop a new dynamically installed anchor (DIA). Several candidate shapes of new DIAs were selected after an investigation into previous researches of existing DIA designs. The performances of selected DIAs during the installation and loading in non-homogeneous clay were investigated through large deformation finite element (LDFE) analyses. Findings were compared to the current anchors in operation (i.e., Torpedo and Omni-Max DIA) to assess the viability of the new designs in the field. Overall, the anchor embedment depths of the novel DIAs lied under the results of OMNI-Max DIA. And also, the tracked anchor trajectory confirmed that, the novel DIAs dove deeper with stiffer travelling angle, compared to the OMNI-Max DIA. These elements are more critical and beneficial especially in a field where the achieved embedment depths are generally low.

Key Words
anchors; clays; numerical modelling; offshore engineering

Address
Youngho Kim and Lachlan Thomas Rosher: Centre for Offshore Foundation Systems (COFS), The University of Western Australia, 35 Stirling highway, Crawley, WA 6009, Australia

Abstract
In this research, a simple quasi 3D hyperbolic shear deformation model is employed for bending and dynamic behavior of functionally graded (FG) plates resting on visco-Pasternak foundations. The important feature of this theory is that, it includes the thickness stretching effect with considering only 4 unknowns, which less than what is used in the First Order Shear Deformation (FSDT) theory. The visco-Pasternak\'s foundation is taken into account by adding the influence of damping to the usual foundation model which characterized by the linear Winkler\'s modulus and Pasternak\'s foundation modulus. The equations of motion for thick FG plates are obtained in the Hamilton principle. Analytical solutions for the bending and dynamic analysis are determined for simply supported plates resting on visco-Pasternak foundations. Some numerical results are presented to indicate the effects of material index, elastic foundation type, and damping coefficient of the foundation, on the bending and dynamic behavior of rectangular FG plates.

Key Words
vibration; bending; FGM; plate; visco-pasternak foundations; quasi-3D HSDT

Address
Laid Boulefrakh: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria

Habib Hebali, Abdelbaki Chikh: 1.) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2.) Ibn Khaldoun University, BP 78 Zaaroura, 14000 Tiaret, Algeria

Abdelmoumen Anis Bousahla: 1.) Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria
2.)Centre Universitaire Ahmed Zabana de Relizane, Algeria

Abdelouahed Tounsi:1.) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2.) Civil and Environmental Engineering Department, King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia

S.R. Mahmoud: Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia

Abstract
This paper presents an experimental study to evaluate the effect of palm oil on the selected basic physical-chemical and geotechnical properties of kaolin. The experimental findings are further compared with literature outcomes investigating similar properties of fine grained soils subjected to contamination by different types of oils. To this end, palm oil was mixed with oven dried kaolin samples–aiding oil\'s interaction (coating) with dry particles first, in anticipation to emphasize the effect of oil on the properties of kaolin, which would be difficult to achieve otherwise. Oil content was limited to 40% by dry weight of kaolin, supplemented at intervals of 10% from clean kaolin samples. Observations highlight physical particle-to-particle bonding resulting in the formation of pseudo-silt sized clusters due to palm oil\'s interaction as evinced in the particle size distribution and SEM micrographs. These clusters, aided by water repellency property of the oil coating the kaolin particles, was analyzed to show notable variations in kaolin\'s consistency–measured as liquid and plastic limits. Furthermore, results from compaction tests indicates contribution of oil\'s viscosity on the compaction behavior of kaolin – showing decrease in the maximum dry unit weight (gammad,max) and optimum moisture content (wopt) values with increasing oil contents, while their decrease rates were directly and inversely proportional in gammad,max and wopt values with oil contents respectively. Comparative study in similar terms, also validates this lower and higher decrease rates in gammad,max and wopt values of the fine grained soils respectively, when subjected to contamination by oil with higher viscosity.

Key Words
oil contamination; ground improvement; laboratory analysis; plasticity; soil behavior

Address
Anirudh Subramanya Sriraam: Civil Engineering Discipline, School of Engineering, Monash University Malaysia, 47500 Bandar Sunway, Selangor, Malaysia

Mavinakere Eshwaraiah Raghunandan: 1.) Civil Engineering Discipline, School of Engineering, Monash University Malaysia, 47500 Bandar Sunway, Selangor, Malaysia
2.) Advanced Engineering Platform, Monash University Malaysia, 47500 Bandar Sunway, Selangor, Malaysia

Tey Beng Ti: 1.) Chemical Engineering Discipline, School of Engineering, Monash University Malaysia, 47500 Bandar Sunway, Selangor, Malaysia
2.) Advanced Engineering Platform, Monash University Malaysia, 47500 Bandar Sunway, Selangor, Malaysia

Jayantha Kodikara: Department of Civil Engineering, Monash University, Clayton, Victoria 3800, Australia

Abstract
Brine leakage is a common phenomenon during construction facilitated by artificial freezing technique, threatening the stability of frozen wall due to the continual thawing of already frozen domain. This paper takes the frequently encountered soft clay in Wujiang District as the study object, and remolded specimens were prepared by mixing calcium chloride solutions at five levels of concentration. Both the deformation and pore water pressure of frozen specimens during thawing were investigated by two-stage loading tests. Three sections were noted from the changes in the strain rate of specimens during thawing at the first-stage load, i.e., instantaneous, attenuated, and quasi-stable sections. During the second-stage loading, the deformation of post-thawed soils is closely correlated with the dissipation of pore water pressure. Two characteristic indexes were obtained including thaw-settlement coefficient and critical water content. The critical water content increases positively with salt content. The higher water content of soil leads to a larger thaw-settlement coefficient, especially at higher salt contents, based on which an empirical equation was proposed and verified. The normalized pore water pressure during thawing was found to dissipate slower at higher salt contents, with a longer duration to stabilize. Three physical indexes were experimentally determined such as freezing point, heat conductivity and water permeability. The freezing point decreases at higher salt contents, especially as more water is involved, like the changes in heat conductivity. The water permeability maintains within the same order at the considered range of salt contents, like the development of the coefficient of consolidation. The variation of the pore volume distribution also accounts for this.

Key Words
thaw consolidation; frozen soil; freezing point; heat conductivity; water permeability

Address
Songhe Wang, Qinze Wang, Jiulong Ding and Fengyin Liu: Institute of Geotechnical Engineering, Xi\'an University of Technology, Xi\'an University of Technology, Xi\'an, Shaanxi, 710048, China

Jian Xu: School of Civil Engineering, Xi\'an University of Architecture and Technology, Xi\'an, Shaanxi, 710055, China

Jilin Qi: College of Civil and Transportation Engineering, Beijing University of Civil Engineering and Architecture, Beijing 100044, China

Yugui Yang: State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221008, China

Abstract
A calculation model of reservoir pressure field distribution around multiple production wells in a heavy oil reservoir is established, which can overcome the unreasonable uniform-pressure value calculated by the traditional mathematical model in the multiwell mining areas. A calculating program is developed based on the deduced equations by using Visual Basic computer language. Based on the proposed mathematical model, the effects of drainage rate and formation permeability on the distribution of reservoir pressure are studied. Results show that the reservoir pressure drops most at the wellbore. The farther the distance away from the borehole, the sparser the isobaric lines distribute. Increasing drainage rate results in decreasing reservoir pressure and bottom-hole pressure, especially the latter. The permeability has a significant effect on bottom hole pressure. The study provides a reference basis for studying the dynamic pressure field distribution before thermal recovery technology in heavy oilfield and optimizing construction parameters.

Key Words
thermal recovery; reservoir pressure; stress sensitivity; exploitation; numerical simulation

Address
Xing Zhang: Research Institute of Petroleum Engineering Technology, Shengli Oilfield,SINOPEC, Xisan Road No. 306, Dongying, 257000, Shandong, People\'s Republic of China

Ting T. Jiang, Jian H. Zhang, Yu B. Li, Chun Y. Zhang,Bing B. Xu and Peng Qi: Hubei Province Key Laboratory of Processing of Mineral Resources and Environment, School of Resource and Environmental Engineering, Wuhan University of Technology, Luoshi road No.122, Wuhan 430070, Hubei, People\'s Republic of China

Bo Li: Key Laboratory Geotechnical Mechanics and Engineering of the Mechanics and Engineering of the Minister of Water Resources,
Changjiang River Scientific Research Institute, Huangpu Road No.23, Wuhan, 430070, Hubei, People\'s Republic of China

Abstract
Excavation of long tunnels by shielded TBMs is a safe, fast, and efficient method of tunneling that mitigates many risks related to ground conditions. However, long-distance tunneling in great depth through adverse geological conditions brings about limitations in the application of TBMs. Among various harsh geological conditions, squeezing ground as a consequence of tunnel wall and face convergence could lead to cluttered blocking, shield jamming and in some cases failure in the support system. These issues or a combination of them could seriously hinder the performance of TBMs. The technique of excavation has a strong influence on the tunnel response when it is excavated under squeezing conditions. The Golab water conveyance tunnel was excavated by a double-shield TBM. This tunnel passes mainly through metamorphic weak rocks with up to 650 m overburden. These metamorphic rocks (Shales, Slates, Phyllites and Schists) together with some fault zones are incapable of sustaining high tangential stresses. Prediction of the convergence, estimation of the creeping effects and presenting strategies to overcome the squeezing ground are regarded as challenging tasks for the tunneling engineer. In this paper, the squeezing potential of the rock mass is investigated in specific regions by dint of numerical and analytical methods. Subsequently, several operational solutions which were conducted to counteract the challenges are explained in detail.

Key Words
squeezing; tunnel deformation; shield jamming; double shield TBM

Address
Abbas Eftekhari and Ali Aalianvari: Department of Mining Engineering, Faculty of Engineering, University of Kashan, Kashan, Iran


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2020 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-2-736-6801, Email: info@techno-press.com