Techno Press
Tp_Editing System.E (TES.E)
Login Search
You logged in as

gae
 
CONTENTS
Volume 29, Number 6, June25 2022
 


Abstract
In this study, the reliability analysis of internal and external stabilities of Reinforced Soil Walls (RSWs) under static and seismic loads are investigated so that it can help the geotechnical engineers to perform the design more realistically. The effect of various variables such as angle of internal soil friction, soil specific gravity, tensile strength of the reinforcements, base friction, surcharge load and finally horizontal earthquake acceleration are examined assuming the variables uncertainties. Also, the correlation coefficient impact between variables, sensitivity analysis, mean change, coefficient of variation and type of probability distribution function were evaluated. In this research, external stability (sliding, overturning and bearing capacity) and internal stability (tensile rupture and pull out) in both static and seismic conditions were investigated. Results of this study indicated sliding as the predominant failure mode in the external stability and reinforcing rupture in the internal stability. First-Order Reliability Method (FORM) are applied to estimate the reliability index (or failure probability) and results are validated using the Monte Carlo Simulation (MCS) method. The results showed among all variables, the internal friction angle and horizontal earthquake acceleration have dominant impact on the both reinforced soil wall internal and external stabilities limit states. Also, the type of probability distribution function affects the reliability index significantly and coefficient of variation of internal friction angle has the greatest influence in the static and seismic limits states compared to the other variables.

Key Words
random variables; reinforced soil; reliability; seismic; stability

Address
Rebin Ahmadi: Geotechnical Engineering, Shahid Rajaee Teacher Training University, Iran
Saeed Ghaffarpour Jahromi: Faculty of Civil Engineering, Shahid Rajaee Teacher Training University, Iran
Naser Shabakhty: School of Civil Engineering, Iran University of Science and Technology, Iran

Abstract
The soft clays are widely distributed, and one of the prominent engineering problems is the creep behavior. In order to predict the creep deformation of soft clays in an easier and more acceptable way, a simple creep constitutive model has been proposed in this paper. Firstly, the triaxial creep test data indicated that, the strain-time (e-t) curve showing in the e-lgt space can be divided into two lines with different slopes, and the time referring to the demarcation point is named as tEOP. Thereafter, the strain increments occurred after the time tEOP are totally assumed to be the creep components, and the elastic and plastic strains had occurred before tEOP. A hyperbolic equation expressing the relationship between creep volumetric strain, stress and time is proposed, with several triaxial creep test data of soft clays verifying the applicability. Additionally, the creep flow law is suggested to be similar with the plastic flow law of the modified Cam-Clay model, and the proposed volumetric strain equation is used to deduced the scaling factor for creep strains. Therefore, a creep constitutive model is thereby established, and verified by successfully predicting the creep principal strains of triaxial specimens.

Key Words
clay; constitutive model; creep; flow rule; triaxial test

Address
G. Chen, J.G. Zhu and Z. Chen: Minist Educ Geomech & Embankment Engn, Key Lab, Hohai Univ, Nanjing 210098, Jiangsu, China
W.L. Guo: Geotech Engn Dept, Nanjing Hydraul Res Inst, Nanjing 210024, Jiangsu, China

Abstract
Water-rock interactions have a significant influence on the mechanical behavior of rocks. In this study, uniaxial compression and tension tests on different water-treated sandstone samples were conducted. Acoustic emission (AE) monitoring and micro-pore structure detection were carried out. Water-rock interactions and their effects on rock mechanical behavior were discussed. The results indicate that water content significantly weakens rock mechanical strength. The sensitivity of the mechanical parameters to water treatment, from high to low, are Poisson ratio (u), uniaxial tensile strength (UTS), uniaxial compressive strength (UCS), elastic modulus (E), and peak strain (e). After water treatment, AE activities and the shear crack percentage are reduced, the angles between macro fractures and loading direction are minimized, the dynamic phenomenon during loading is weakened, and the failure mode changes from a mixed tensile-shear type to a tensile one. Due to the softening, lubrication, and water wedge effects in water-rock interactions, water content increases pore size, promotes crack development, and weakens micro-pore structures. Further damage of rocks in fractured and caved zones due to the water-rock interactions leads to an extra load on the adjoining coal and rock masses, which will increase the risk of dynamic disasters.

Key Words
acoustic emission; mechanical behavior; pore structure; sandstones; water content; water-rock interaction

Address
Kunyou Zhou and Linming Dou:Key Laboratory of Deep Coal Resource Mining, Ministry of Education, China University of Mining and Technology,
Xuzhou, Jiangsu, 221116, China;
School of Mines, China University of Mining and Technology, Xuzhou, Jiangsu, 221116, China
Siyuan Gong, Yanjiang Chai, Jiazhuo Li and Xiaotao Ma: School of Mines, China University of Mining and Technology, Xuzhou, Jiangsu, 221116, China
Shikang Song: Shaanxi Zhengtong Coal Industry Co., Ltd., Xianyang, Shaanxi, 713600, China

Abstract
Granular columns have recently found widespread use in underground construction. The behaviour of granular columns under vertical loads has been extensively studied, specifically in relation to vertical load capacity obtained by bulging of the column body, including the behaviour after encasement of material. Determining the shear strength of loose soils reinforced with granular columns has received less attention. After the observations of lateral deformation near the toe of the embankment, attempts have been made to strengthen the lateral strength of granular columns. The purpose of this research is to look into the effects of different encasement conditions on the lateral load capacity of granular columns. This was accomplished by three-dimensional finite element analysis with FEM software. Various normal pressures and two different encasement configurations, namely single layer encasement and double layer encasement, with differing tensile strengths, were used in this study to determine their effect on lateral resistance. The failure envelope for a single column planted in loose sand was used to analyse the findings for three different granular column diameters, as well as the impact of different encasement conditions. According to the findings, the inclusion of a Granular Column enhanced the shear strength and overall stiffness of the loose sand bed, and the encasement of the Granular Column helped in deriving higher lateral resistance.

Key Words
encasement; FEM; granular column; lateral load; numerical analysis

Address
Akash Jaiswal and Rakesh Kumar: Department of Civil Engineering MANIT, Bhopal,462003, India

Abstract
Lightweight foamed soils are geomaterials that can be used when the lateral earth pressure needs to be reduced. Lightweight foamed soil typically consists of dredged soil, cement, and foam. Additives have been used to enhance the performance of lightweight foamed soils, and waste fishing nets are materials that can be used for tensile reinforcement of geomaterials. In this study, a waste fishing net was used in lightweight foamed soil, and laboratory tests were conducted to optimize the composition of lightweight foamed soil in terms of water content, cement ratio, foam ratio, and net type. A dredged soil in situ was collected to use. A waste fishing net was retreated for experiments. The waste fishing net cut into pieces and some were unthreaded. A form generator was used to produce foam. The comprehensive evaluation of lightweight foamed soil reinforced with waste fishing net was performed in terms of the sample preparation time, rheology, unit weight, and strength associated with lightweight foamed soils. The normalized factor (NF) was used to develop a design guideline for lightweight foamed soils.

Key Words
dredged soil; foam; lightweight soil; normalized factor; waste fishing net

Address
Jinung Do: Department of Ocean Civil Engineering, Gyeongsang National University, 2-13 Tongyeonghaean-ro,
Tongyeong 53064, Republic of Korea

Abstract
This paper presents a thermoelastic analysis of variable thickness plates made of functionally graded materials (FGM) subjected to mechanical and thermal loads. The thermal load is applied to the plate as a temperature difference between the top and bottom surfaces. Temperature distribution in the plate is obtained using the steady-state heat equation. Except for Poisson's ratio, all mechanical properties of the plate are assumed to vary linearly along the thickness direction based on the volume fractions of ceramic and metal. The plate is resting on an elastic foundation modeled based on the Winkler foundation model. The governing equations are derived based on the third-order shear deformation theory (TSDT) and are solved numerically for various boundary conditions using the differential quadrature method (DQM). The effects of various parameters on the stress distribution and deflection of the plate are investigated such as the value of thermal and mechanical loads, volume fractions of ceramic and metal, and the stiffness coefficients of the foundation.

Key Words
differential quadrature method; functionally graded material; thermoelastic analysis; third-order shear deformation theory

Address
Majid Amiri, Abbas Loghman and Mohammad Arefi: Department of Solid Mechanic, Faculty of Mechanical Engineering, University of Kashan, Kashan 87317-51167, Iran

Abstract
Dams are inevitably planned to be built on thick overburden with high permeability and deformability. The connection part between concrete cut-off wall in overburden and earth core in dam body is not only a key part of the anti-seepage system, but also a weak position. Large uneven settlement will be aroused at the concoction part. However, the interaction behavior and the scope of the connection part cannot be determined effectively. In this paper, numerical analysis of a high earth core dam built on thick overburden was carried out with large deformation FE method. The mechanical behavior of the connection part was detail studied. It can be drawn that there is little differences in dam integral deformation for different analysis method, but big differences were found at the connection part. The large deformation analysis method can reasonably describe the process that concrete wall penetrates into soil. The high plasticity clay has stronger ability to adapt to large uneven deformation which can reduce stress level, and stress state of concrete wall is also improved. The scope of high plasticity clay zone in the connection part can be determined according to stress level of soils and penetration depth of concrete wall.

Key Words
connection part; earth core dam; large deformation numerical analysis; mechanical behavior; thick overburden

Address
Xiang Yu: School of Water Conservancy Engineering, Zhengzhou University, Zhengzhou, 450001, China;
National Local Joint Engineering Laboratory of Major Infrastructure Testing and Rehabilitation Technology, Zhengzhou 450001, China;
The State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, 116024, China
Gan Wang: School of Water Conservancy Engineering, Zhengzhou University, Zhengzhou, 450001, China
2National Local Joint Engineering Laboratory of Major Infrastructure Testing and Rehabilitation Technology, Zhengzhou
Yuke Wang and Xueming Du: School of Water Conservancy Engineering, Zhengzhou University, Zhengzhou, 450001, China;
National Local Joint Engineering Laboratory of Major Infrastructure Testing and Rehabilitation Technology, Zhengzhou 450001, China
Yongqian Qu: The State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, 116024, China

Abstract
In order to explore the stable anchoring conditions of coal side under the mining disturbance of soft section coal pillar in Wangcun Coal Mine of Chenghe Mining Area, the distribution model of the anchoring support pressure at the coal pillar side was established, using the strain-softening characteristics of the coal to study the distribution law of anchoring coal side support pressure. The analytical solution for the reinforcement anchorage stress in the coal pillar side was derived with the inelastic state mechanical model. The results show that the deformation angle of the roadway side and roof increases with the roof subsidence due to the mining influence at the adjacent working face, the plastic deformation zone extends to the depth of the coal side, and the increase of anchorage stress can effectively control the roof subsidence and further deterioration of plastic zone. The roadway height and the peak support pressure have a certain influence on the anchorage stress, the required anchorage stress of the coal side rises with the roadway height and the peak support pressure. The required anchorage stress of the coal pillar side decreases as the cohesion between the coal seam and the roof and floor and the anchor length increases. Then, applied the research result to Wangcun coal mine in Chenghe mining area, the design of anchor cable reinforcement support was proposed for the section of coal pillars side that has been anchored and deformed, which achieved great results and effectively controlled the convergence and deformation of the side, providing a safety guarantee for the roadway excavation and mining.

Key Words
anchor cable reinforcement; elastic-plasticity; peak support pressure; section coal pillar

Address
Ang Li and Bingnan Ji: School of Architecture and Civil Engineering, Xi'an University of Science and Technology, Xi'an, Shaanxi 710054, China
Haifeng Zhou: School of Architecture and Civil Engineering, Xi'an University of Science and Technology, Xi'an, Shaanxi 710054, China;
Shenhua Shendong Coal Group Co., Ltd., Yulin, Shaanxi 719315 China
Feng Wang: Shaanxi Coal Chemical Industry Group Chenghe Mines Co., Ltd, Weinan, Shaanxi 715200, China
Yingjie Liu: Research Institute of Emergency Science, China Coal Research Institute, Beijing 100013, China
Pengfei Mu, Jian Yang, Ganggang Xu and Chunhu Zhao: Xi'an Research Institute of China Coal Technology & Engineering Group Corp, Xi'an, Shaanxi 710077, China



Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2022 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-2-736-6800 (SCS, EAS, WAS, ANR) +82-42-828-7995 (GAE, SEM, SSS, CAC) Fax : +82-2-736-6801, Email: info@techno-press.com