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CONTENTS
Volume 16, Number 2, October10 2018
 

Abstract
Under repeated loading, the residual stresses within the subgrade and subsoil can accelerate the deformation of the road structures. In this paper, a series of laboratory cyclic loading model tests and small-scale model tests were conducted to investigate the dynamic stress response within soils under different loading conditions. The experimental results showed that a dynamic stress accumulation effect occurred if the soil showed cumulative deformation: (1) the residual stress increased and accumulated with an increasing number of loading cycles, and (2) the residual stress was superimposed on the stress response of the subsequent loading cycles, inducing a greater peak stress response. There are two conditions that must be met for the dynamic stress accumulation effect to occur. A threshold state exists only if the external load exceeds the cyclic threshold stress. Then, the stress accumulation effect occurs. A higher loading frequency results in a higher rate of increase for the residual stress. In addition to the superposition of the increasing residual stress, soil densification might contribute to the increasing peak stress during cyclic loading. An increase in soil stiffness and a decrease in dissipative energy induce a greater stress transmission within the material.

Key Words
subgrade; subsoil; dynamic stress; accumulation; traffic load; time-dependent

Address
Lian Sheng Tang: 1.) Department of Earth Science and Geological Engineering, Sun Yat-sen University, No. 135 Xingang Road West, Guangzhou 510275, Guangdong Province, China
2.) Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resources Survey, Guangzhou 510275, China

Hao Kun Chen, Yin Lei Sun, Qing Hua Zhang and Hua Rong Liao: Department of Earth Science and Geological Engineering, Sun Yat-sen University, No. 135 Xingang Road West, Guangzhou 510275, Guangdong Province, China

Abstract
Tianjin, which is located on the west shore of the Bohai Sea, is part of China\'s Circum-Bohai-Sea Region, where very weak clay is deposited. From the 1970s to the early 21st century, Tianjin marine clay deposits have been the subject of numerous geotechnical investigations. Because of these deposits\' geological complexity, great depositional thickness, high water content, large void ratio, excessive settlement, and low shear strength, the geotechnical properties of Tianjin marine clay need to be summarized and evaluated based on various in situ and laboratory tests so that Tianjin can safely and economically sustain more infrastructure in the coming decades. In this study, the properties of Tianjin marine clay, especially its consolidation properties, are summarized, evaluated and discussed. The focus is on establishing correlations between the geotechnical property indexes and mechanical parameters of Tianjin marine clay. These correlations include the correlations between the water content and the void ratio, the depth and the undrained shear strength, the liquid limit and the compression index, the tip resistance and the constrained modulus, the plasticity index and the ratio of undrained shear strength and the preconsolidation pressure. In addition, the primary consolidation properties of Tianjin marine clay, such as the intrinsic compression line (ICL), sedimentation compression line (SCL), compression index, Cc, coefficient of consolidation, Cv, and hydraulic conductivity change index, Ckv, are evaluated and discussed. A secondary consolidation property, i.e., the secondary compression index, Ca, is also investigated, and the results show that the ratio of Ca/Cc for Tianjin marine clay can be used to calculate Ca in secondary consolidation settlement predictions.

Key Words
marine clay; consolidation; correlations; secondary consolidation

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:Department of Civil Engineering, Tianjin University, Tianjin 300072, China

Yan Jiang: Terracon Consultants, Inc., 2201 Rowland Ave., Savannah, Georgia 31404, U.S.A.


Abstract
In this current work a quasi 3D \"trigonometric shear deformation theory\" is proposed and discussed for the dynamic of thick orthotropic plates. Contrary to the classical \"higher order shear deformation theories\" (HSDT) and the \"first shear deformation theory\" (FSDT), the constructed theory utilizes a new displacement field which includes \"undetermined integral terms\" and presents only three \"variables\". In this model the axial displacement utilizes sinusoidal mathematical function in terms of z coordinate to introduce the shear strain impact. The cosine mathematical function in terms of z coordinate is employed in vertical displacement to introduce the impact of transverse \"normal deformation\". The motion equations of the model are found via the concept of virtual work. Numerical results found for frequency of \"flexural mode\", mode of shear and mode of thickness stretch impact of dynamic of simply supported \"orthotropic\" structures are compared and verified with those of other HSDTs and method of elasticity wherever considered.

Key Words
plate theory; vibration; orthotropic plate

Address
Mohamed Sadoun and Mohammed Sid Ahmed Houari: 1.) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2.) Department of Civil Engineering, University Mustapha Stambouli of Mascara, Mascara, Algeria

Ahmed Bakora: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria

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

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

Afaf S. Alwabli: Department of Biology, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia

Abstract
The constrained conditions of roof and floor for the coal pillar affect the strength of coal pillar very seriously. To analyze the influence of rock mass for the roof and floor on the stability of coal pillar comprehensively, one method based on the mechanical method for the composite rock mass was proposed. In this method, the three rock layers of roof, floor and coal pillar are taken as the bedded composite rock mass. And the influence of rock mass for the roof and floor on the elastic core of coal pillar has been analyzed. This method can obtain not only the derived stress by the cohesive constraining forces for the coal pillar, but also the derived stress for the rock mass of the roof and floor. Moreover, the effect of different mechanical parameters for the roof and floor on the stability of coal pillar have been analyzed systematically. This method can not only analyze the stability of strip coal pillar, but also analyze the stability of other mining pillars whose stress distribution is similar with that of the strip coal pillar.

Key Words
influence; strip coal pillar; stress distribution; derived stress; roof and floor

Address
W. Gao: Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,
College of Civil and Transportation Engineering, Hohai University, Nanjing 210098, P. R. China


Abstract
In this study, a real-time grouting management system based on the clogging theory was established to manage injection procedure in real time. This system is capable of estimating hydraulic permeability with the passage of time as the grout permeates through the ground, and therefore, capable of estimating real time injection distance and flow rate. By adopting the Controlled Injection Pressure (CoIP) model, it was feasible to predict the grout permeation status with the elapse of time by consecutively updating the hydraulic gradient and flow rate estimated from a clogging-induced alteration of pore volume. Moreover, a method to estimate the volume of the fractured gap according to the reduction in injection pressure was proposed. The validity of the proposed system was successfully established by comparing the estimated values with the measured field data.

Key Words
real time grouting management system; permeation grouting; clogging theory

Address
Young-Sam Kwon and In-Mo Lee: School of Civil, Environmental and Architectural Engineering, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul, Republic of Korea

Jinchun Kim: Korea Institute of Geo Technology Inc., 14 Sagimakgol-ro 45beon-gil, Jungwon-gu, Seongnam-si, Gyeonggi-do, Republic of Korea

Abstract
An attempt has been made here to study the propagation of SH-type surface waves in an elastic medium, which is initially stressed and heterogeneous and has a point source inside the medium. The upper portion of the composite medium is a sandy layer. It is situated on an initially stressed heterogeneous half-space, whose density, rigidity and internal friction are function of depth. The analysis has been carried out by using Fourier transform and Green\'s function approach. The phase velocity has been investigated for several particular situations. It has been shown that the results of the study agree with those the case of Love wave propagation in a homogeneous medium in the absence of the sandy layer, when the initial stress is absent. In order to illustrate the validity of the analysis presented here, the derived analytical expression has been computed numerically, by considering an illustrative example and the variances of the concerned physical variables have been presented graphically. It is observed that the velocity of shear wave is amply influenced by the initial stress and heterogeneity parameters and the presence of the sandy layer. The study has an important bearing on investigations of different problems in the earth\'s interior and also in seismological studies.

Key Words
surface wave; green function; dispersion equation; phase velocity; heterogeneity

Address
Santanu Manna: 1.)Discipline of Mathematics, Indian Institute of Technology Indore, Simrol-453552, India
2.) Discipline of Civil Engineering, Indian Institute of Technology Indore, Simrol-453552, India

J.C. Misra: Indian Institute of Engineering Science and Technology Shibpur, Howrah 711103, India

Santimoy Kundu and Shishir Gupta: Department of Applied Mathematics, Indian Institute of Technology (ISM), Dhanbad, Jharkhand-826004, India


Abstract
The subsidence mechanism of ground surface is a complex phenomenon when multiple seam coal mining operations are carried out. Particularly, the coal mining beneath karstic formations causes a very special form of subsidence. The subsidence causes elasto-plastic deformation of the karstic layers and the collapse of cavities leads to dolinization and/or sinkhole formation. In this study, a sinkhole with a depth of 90 m and a width of 25 m formed in Gelik district within the coal-basin of Zonguldak (NW, Turkey) induced by multiple seam coal mining operations in the past has been presented as a case-history together with two-dimensional numerical simulations and InSAR monitoring. The computational results proved that the sinkhole was formed as a result of severe yielding in the close vicinity of the faults in contact with karstic formation due to multiple seam longwall mining at different levels.

Key Words
sinkhole, subsidence; karstic cave; underground coal mining

Address
Melih Genis:Department of Mining Engineering, Zonguldak Bülent Ecevit University, Zonguldak, Turkey

Hakan Akcin: Department of Geomatics Engineering, Zonguldak Bülent Ecevit University, Zonguldak, Turkey

Omer Aydan: Department of Civil Engineering and Architecture, Ryukyus University, Nishihara, Okinawa, Japan

Gurkan Bacak: Department of Geological Engineering, Zonguldak Bülent Ecevit University, Zonguldak, Turkey

Abstract
Application the pile group foundation to reduce overall settlement of the foundation and also avoid a very fruitful settlement of foundations, inconsistent was carried out. In such a case, in event that the Foundation, not as a mere pile group, which as a system consisting of a broad foundation with pile Group, economic design criteria will be provided in spite of high safety. A new approach in the design of the Foundation can be introduced as the piles are just a tool to improve the parameters of soil hardness; that it can work with detachable piles from raft. Centralized arrangement of piles as the most optimal layout of piles in reducing inconsistent settlement, which is the lowest value of resulting layout in this differential settlement. Using the combination of piles connected and disconnected to form the raft, bending moment created in the raft is reduced. It also concentrated arrangements have greatest effect in reducing amount of moment applied to the raft.

Key Words
pile intervals; numerical analysis; piled raft foundations; settlement of raft; bending moment

Address
Vahed Ghiasi and Mobin Moradi: Civil Engineering Department, Malayer University, Malayer, Iran

Abstract
Based on theories of rock mechanics, rock fragmentation, mechanics of elasto-plasticity, and energy dissipation etc., a method is presented for evaluating the rock fragmentation efficiency by using plastic energy dissipation ratio as an index. Using the presented method, the fragmentation efficiency of rocks with different strengths (corresponding to soft, intermediately hard and hard ones) under indentation is analyzed and compared. The theoretical and numerical simulation analyses are then combined with experimental results to systematically reveal the fragmentation mechanism of rocks under indentation of indenter. The results indicate that the fragmentation efficiency of rocks is higher when the plastic energy dissipation ratio is lower, and hence the drilling efficiency is higher. For the rocks with higher hardness and brittleness, the plastic energy dissipation ratio of the rocks at crush is lower. For rocks with lower hardness and brittleness (such as sandstone), most of the work done by the indenter to the rocks is transferred to the elastic and plastic energy of the rocks. However, most of such work is transferred to the elastic energy when the hardness and the brittleness of the rocks are higher. The plastic deformation is small and little energy is dissipated for brittle crush, and the elastic energy is mainly transferred to the kinetic energy of the rock fragment. The plastic energy ratio is proved to produce more accurate assessment on the fragmentation efficiency of rocks, and the presented method can provide a theoretical basis for the optimization of drill bit and selection of well drilling as well as for the selection of the rock fragmentation ways.

Key Words
rock indentation; rock fragmentation mechanism; ductile-brittle failure; plastic energy dissipation ratio; rock fragmentation efficiency

Address
Xiaohua Zhu: School of Mechatronic Engineering, Southwest Petroleum University, Chengdu 610500, China

Weiji Liu: 1.) School of Mechatronic Engineering, Southwest Petroleum University, Chengdu 610500, China
2.) Postdoctoral Research Station for Oil and Gas Engineering, Southwest Petroleum University, Chengdu, Sichuan, 610500, China


Abstract
Strain-based criteria are known as a direct method in determining the stability of the geomechanical structures. In spite of the widely use of Sakurai critical strain criterion, it is so conservative to make use of them in rocks with initial plastic deformation on account of the considerable difference between the failure and critical strains. In this study, a new criterion has been developed on the basis of the failure strain to attain more reasonable results in determining the stability status of the tunnels excavated in the rocks mostly characterized by plastic-elastic/plastic behavior. Firstly, the stress-strain curve was obtained having conducted uniaxial compression strength tests on 91 samples of eight rock types. Then, the initial plastic deformation was omitted making use of axis translation technique and the criterion was presented allowing for the modified secant modulus and by use of the failure strain. The results depicted that the use of failure strain criterion in such rocks not only decreases the conservativeness of the critical strain criterion up to 42%, but also it determines the stability status of the tunnel more accurately.

Key Words
failure strain; critical strain; modified secant modulus; tunneling

Address
Ako Daraei and Shokrollah Zare: Faculty of Mining, Petroleum and Geophysics Engineering, Shahrood University of Technology, Shahrood, 3619995161, Iran


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