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CONTENTS
Volume 19, Number 5, December10 2019
 

Abstract
The objective of this paper is to study the two dimensional deformation in transversely isotropic thermoelastic medium without energy dissipation due to time harmonic sources using new modified couple stress theory, a continuum theory capable to predict the size effects at micro/nano scale. The couple stress constitutive relationships have been introduced for transversely isotropic thermoelastic medium, in which the curvature tensor is asymmetric and the couple stress moment tensor is symmetric. Fourier transform technique is applied to obtain the solutions of the governing equations. Assuming the deformation to be harmonically time-dependent, the transformed solution is obtained in the frequency domain. The application of a time harmonic concentrated and distributed sources have been considered to show the utility of the solution obtained. The displacement components, stress components, temperature change and couple stress are obtained in the transformed domain. A numerical inversion technique has been used to obtain the solutions in the physical domain. The effects of angular frequency are depicted graphically on the resulted quantities.

Key Words
new modified couple stress theory; length scale parameters; transversely isotropic; concentrated and distributed sources; harmonic behavior; Fourier transform; angular frequency

Address
Parveen Lata and Harpreet Kaur: Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab, India

Abstract
How to safely and economically dispose mining tailings is a challenge to mine operators. This paper presents an alternative upstream method for tailings dam construction, termed as the template construction method (TCM), which has been successfully implemented at Zhelamuqing tailings impoundment since 2004. By the beginning of 2015, the tailings dam wall had reached 95 m in height for the 46 upstream raises, with the total height of the dam including the starter dyke being 128 m. The proposed TCM is relatively simple and cost-effective and provides a good way for constructing rapidly raising tailings dam based on this case.

Key Words
tailings; waste disposal; template construction method (TCM); environmental engineering

Address
Zuoan Wei,Guangzhi Yin and Yonghao Yang: 1.) State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030, China
2.) School of Resource and Safety Engineering, Chongqing University, Chongqing 400030, China

Yulong Chen: School of Energy and Mining Engineering, China University of Mining and Technology, Beijing 100083, China

Weimin Shu: Yuxi Mining Company Ltd., Yuxi Yunnan 653100, China

Abstract
This paper evaluates the geotechnical and geo-engineering properties of the South Pars Zone (SPZ) marls in Assalouyeh, Iran. These marly beds mostly belong to the Aghajari and Mishan formations which entail the gray, cream, black, green, dark red and pink types. Marls can be observed as rock (soft rock) or soil. Marlstone outcrops show a relatively rapid change to soils in the presence of weathering. To geotechnically characterise the marls, field and laboratory experiments such as particle-size distribution, hydrometer, Atterberg limits, uniaxial compression, laboratory direct-shear, durability and carbonate content tests have been performed on soil and rock samples to investigate the physico-mechanical properties and behaviour of the SPZ marls in order to establish empirical relations between the geo-engineering features of the marls. Based on the experiments conducted on marly soils, the USCS classes of the marls is CL to CH which has a LL ranging from 32 to 57% and PL ranging from 18 to 27%. Mineralogical analyses of the samples revealed that the major clay minerals of the marls belong to the smectite or illite groups with low to moderate swelling activities. The geomechanical investigations revealed that the SPZ marls are classified as argillaceous lime, calcareous marl and marlstone (based on the carbonate content) which show variations in the geomechanical properties (i.e., with a cohesion ranging from 97 to 320 kPa and a friction angle ranging from 16 to 35 degrees). The results of the durability tests revealed that the degradation potential showed a wide variation from none to fully disintegrated. According to the results of the experiments, the studied marls have been classified as calcareous marl, marlstone and argillaceous lime due to the variations in the carbonate and clay contents. The results have shown that an increase in the carbonate content leads to a decrease in the degradation potential and an increase in the density and strength parameters such as durability and compressive strength. A comparison of the empirical relationships obtained from the regression analyses with similar studies revealed that the results obtained herein are reasonably reliable.

Key Words
Assalouyeh; marl; physio-mechanical properties; carbonate content; South Pars Zone

Address
Mohammad Azarafza and Akbar Ghazifard: Department of Geology, University of Isfahan, Isfahan, Iran

Haluk Akgün: Geotechnical Unit, Department of Geological Engineering, Middle East Technical University (METU), Ankara, Turkey

Ebrahim Asghari-Kaljahi: Department of Earth Sciences, University of Tabriz, Tabriz, Iran


Abstract
This paper illustrates the results of a series of seismic geotechnical centrifuge experiments to explore dynamic structure-soil-structure interaction (SSSI) of two structures (named S1 and S2) installed on ground surface. A dense homogeneous ground is prepared in an equivalent shear beam (ESB) container. Two structural models are designed to elicit soil-foundation-structure interaction (SFSI) with different masses, heights, and dynamic characteristics. Five experimental tests are carried out for: (1) two reference responses of the two structures and (2) the response of two structures closely located at three ranges of distance. It is found that differential settlements of both structures increase and the smaller structure (S2) inversely rotates out of the other (S1) when they interact with each other. S2 structure experiences less settlement and uplift when at a close distance to the S1 structure. Furthermore, the S1 structure, which is larger one, shows a larger rocking and a smaller sliding response due to the SSSI effects, while S2 structure tends to slide more than that in the reference test, which is illustrated by an increase in sliding response and rocking stiffness as well as a decrease in moment-to-shear ratio (M/H.L) of the S2 structure.

Key Words
structure-soil-structure interaction; over-turning moment; base-shear force; rocking stiffness; moment-to-shear ratio

Address
Van-Linh Ngo: Department of Civil and Environmental Engineering, Chonnam National University, Yeosu 550-749, Korea

Jae-Min Kim: Department of Civil Engineering, Chonnam National University, Gwangju 500-757, Korea

Changho Lee: Department of Marine and Civil Engineering, Chonnam National University, Yeosu 550-749, Korea

Abstract
It is of great significance to study the mechanical properties and failure mechanism of the defected rock for geological engineering. The defected sandstone modeling with power-law distribution of pre-cracks was built in this paper by Particle Flow Code software. Then the mechanical properties of sandstone and the corresponding failure process were meticulously analyzed by changing the power-law index (PLI) and the number of pre-cracks (NPC). The results show that (1) With the increase of the PLI, the proportion of prefabricated long cracks gradually decreases. (2) When the NPC is the same, the uniaxial compressive strength (UCS) of sandstone increases with the PLI; while when the PLI is the same, the UCS decreases with the NPC. (3) The damage model of rock strength is established based on the Mori-Tanaka method, which can be used to better describe the strength evolution of damaged rock. (4) The failure mode of the specimen is closely related to the total length of the pre-crack. As the total length of the pre-crack increases, the failure intensity of the specimen gradually becomes weaker. In addition, for the specimens with the total pre-crack length between 0.2-0.55 m, significant lateral expansion occurred during their failure process. (5) For the specimens with smaller PLI in the pre-peak loading process, the concentration of the force field inside is more serious than that of the specimens with larger PLI.

Key Words
numerical statistical study; mechanical property; failure mechanism; power-law distribution; defected sandstone

Address
Hao Shi:1.) State Key Laboratory for Geomechanics & Deep Underground Engineering, School of Mechanics & Civil Engineering, China University of Mining and Technology, Xuzhou, 221008, People\'s Republic of China
2.) University of Nottingham, GeoEnergy Research Centre, Nottingham NG7 2RD, U.K.

Lei Song, Houquan Zhang, Keke Xue, Guotao Yuan, Zhenshuo Wang and Guozhu Wang: State Key Laboratory for Geomechanics & Deep Underground Engineering, School of Mechanics & Civil Engineering, China University of Mining and Technology, Xuzhou, 221008, People\'s Republic of China

Abstract
A series of element tests with different drainage conditions and strain rates were performed on compacted unsaturated non-plastic silt in unconfined conditions. Soil samples were compacted at water contents from dry to wet of optimum with the degree of saturation varying from 24 to 59.5% while maintaining the degree of compaction at 80%. The tests performed were shear infiltration tests in which specimens had constant net confining pressure, pore air pressure was kept drained and constant, just before the shear process pore water pressure was increased (and kept constant afterwards) to decrease matric suction and to start water infiltration. In constant water content tests, specimens had constant net confining pressure, pore air pressure was kept drained and constant whereas pore water pressure was kept undrained. As a result, the matric suction varied with increase in axial strain throughout the shearing process. In both cases, maximum shear strength was obtained for specimens prepared on dry side of optimum moisture content. Moreover, the gradient of stress path was not affected under different strain rates whereas the intercept of failure was changed due to the drainage conditions implied in this study.

Key Words
unsaturated soil; shear strength; matric suction; pore water pressure; water infiltration; constant water content tests; drained shear tests

Address
Ali Murtaza Rasool: National Engineering Services Pakistan (NESPAK), Lahore, Pakistan

Mubashir Aziz: Department of Civil Engineering, National University of Computer and Emerging Sciences (NUCES), Lahore, Pakistan

Abstract
The vacuum preloading method has been used in many countries for ground improvement and land reclamation works. A sand cushion is required as a horizontal drainage channel for conventional vacuum preloading. In terms of the dredged-fill foundation soil, the treatment effect of the conventional vacuum preloading method is poor, particularly in Tianjin, China, where a shortage of sand exists. To solve this problem, straight-line vacuum preloading without sand is widely adopted in engineering practice to improve the foundation soil. Based on the engineering properties of dredged fill in Lingang City, Tianjin, this paper presents field instrumentation in five sections and analyzes the effect of a prefabricated vertical drain (PVD) layout and a vacuum pumping method on the soft soil ground treatment. Through the arrangement of pore water pressure gauges, settlement marks and vane shear tests, the settlement, pore water pressure and subsoil bearing capacity are analyzed to evaluate the effect of the ground treatment. This study demonstrates that straight-line vacuum preloading without sand can be suitable for areas with a high water content. Furthermore, the consolidation settlement and consolidation degree system is developed based on the grey model to predict the consolidation settlement and consolidation degree under vacuum preloading; the validity of the system is also verified.

Key Words
field instrumentation; straight-line vacuum preloading; consolidation settlement prediction; grey model

Address
Huayang Lei: 1.) Department of Civil Engineering, Tianjin University, Tianjin, 300072 China
2.) Key Laboratory of Coast Civil Structure Safety of Education Ministry, Tianjin University, Tianjin, 300072 China

Shuangxi Feng and Lei Wang:Department of Civil Engineering, Tianjin University, Tianjin, 300072 China

Yawei Jin: Jiangsu Xintai Geotechnical Technology Co. Ltd, Jiangsu, 214213, China

Abstract
The mode perturbation method (MPM) is suitable and efficient for solving the eigenvalue problem of a nonuniform soil deposit whose property varies with depth. However, results of the MPM do not always converge to the exact solution, when the variation of soil deposit property is discontinuous. This discontinuity is typical because soil is usually made up of sedimentary layers of different geologic materials. Based on the energy integral of the variational principle, a new mode perturbation method, the energy-based mode perturbation method (EMPM), is proposed to address the convergence of the perturbation solution on the natural frequencies and the corresponding mode shapes and is able to find solution whether the soil properties are continuous or not. First, the variational principle is used to transform the variable coefficient differential equation into an equivalent energy integral equation. Then, the natural mode shapes of the uniform shear beam with same height and boundary conditions are used as Ritz function. The EMPM transforms the energy integral equation into a set of nonlinear algebraic equations which significantly simplifies the eigenvalue solution of the soil layer with variable properties. Finally, the accuracy and convergence of this new method are illustrated with two case study examples. Numerical results show that the EMPM is more accurate and convergent than the MPM. As for the mode shapes of the uniform shear beam included in the EMPM, the additional 8 modes of vibration are sufficient in engineering applications.

Key Words
soil deposit; perturbation method; characteristic equation; variational principle; dynamic characteristics

Address
Danguang Pan: 1.) Department of Civil Engineering, University of Science and Technology Beijing, Beijing, China
2.) State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai, China

Wenyan Lu: Department of Civil Engineering, University of Science and Technology Beijing, Beijing, China

Qingjun Chen: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai, China

Pan Lu: Department of Transportation and Logistics/Upper Great Plains Transportation Institute,
North Dakota State University, Fargo, North Dakota, U.S.A.


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