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CONTENTS
Volume 19, Number 6, December30 2019
 

Abstract
In this paper, the geotechnical report of the Northern Fereshteh area in Tabriz is used and the characteristics of shallow foundation of a single pile and compared pile group and geogrid in terms of the settlement of a building foundation on clayey soil. Additionally, impacts of existing variables such as the number of geogrid layers, the length of the pile, and the depth of groundwater level affected by the dynamic load caused by the Taiwan Jiji earthquake via numerical analysis using PLAXIS software are examined. The results of fifty-four models indicated that the construction of a pile group with a diameter of 1 meter and a length of 14 meters significantly diminished the ‏consolidation settlement of the soil in the Northern Fereshteh area, where the settlement value has been triggered by the load inflicted by earthquake. Moreover, the construction of four layers of geogrid at intervals of one meter led to a significant decrease in the settlement. Finally, after reaching a maximum depth, it had no reducing effects on the foundation settlement.

Key Words
shallow foundation; single pile; pile group; geogrid; PLAXIS; consolidation settlement

Address
Mahdi Shariati: 1.) Division of Computational Mathematics and Engineering, Institute for Computational Science,
Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam
2.) Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam

Sadaf Mahmoudi Azar: Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran

Mohammad-Ali Arjomand: Faculty of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran

Hesam Salmani Tehrani: School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran

Mojtaba Daei: Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran

Maryam Safa: Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam


Abstract
Pre-tensioned rock bolts can be classified into fully anchored, lengthening anchored and point anchored bolts based on the bond length of the resin or cement mortar inside the borehole. Bolts in varying anchoring methods may significantly affect the supporting effect of surrounding rock around a tunnel. However, thus far, the theoretical basis of selecting a proper anchoring method has not been thoroughly investigated. Based on this problem, 16 schemes were designed while incorporating the effects of anchoring length, pretension, bolt length, and spacing, and a systematic numerical experiment was performed in this paper. The distribution characteristics of the stress field in the surrounding rock, which corresponded to various anchoring scenarios, were obtained. Furthermore, an analytical approach for computing the active and passive strengthening index of the anchored surrounding rock is presented. A new fully anchoring method with pretension and matching technology are also provided. Then, an isolated loading model of the anchored surrounding rock was constructed. The physical simulation test for the bearing capacity of the model was performed with three schemes. Finally, the strengthening mechanism of varying anchoring methods was validated. The research findings in this paper may provide theoretical guidelines for the design and construction of bolting support in tunnels.

Key Words
rock bolt; pretension; anchoring method; strengthening index; physical simulation test

Address
Hongtao Wang: 1.) School of Civil Engineering, Shandong Jianzhu University, Ji\'nan 250101, Shandong, China
2.) Key Laboratory of Building Structural Retrofitting and Underground Space Engineering (Shandong Jianzhu University),
Ministry of Education, Ji\'nan 250101, Shandong, China

Shucai Li and Qi Wang: Research Center of Geotechnical and Structural Engineering, Shandong University, Ji\'nan 250061, Shandong, China

Dechao Wang: Jinan Rail Transit Group Co., Ltd., Ji\'nan 250101, Shandong, China

Weiteng Li: Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention,
Shandong University of Science and Technology, Qingdao 266000, Shandong, China

Ping Liu, Xiaojing Li and Yunjuan Chen: School of Civil Engineering, Shandong Jianzhu University, Ji\'nan 250101, Shandong, China


Abstract
The reliability of reinforced concrete structures is frequently compromised by the deterioration caused by reinforcement corrosion. Evaluating the effect caused by reinforcement corrosion on structural behaviour of corrosion damaged concrete structures is essential for effective and reliable infrastructure management. In lifecycle management of corrosion affected reinforced concrete structures, it is difficult to correctly assess the lifecycle performance due to the uncertainties associated with structural resistance deterioration. This paper presents a stochastic deterioration modelling approach to evaluate the performance deterioration of corroded concrete structures during their service life. The flexural strength deterioration is analytically predicted on the basis of bond strength evolution caused by reinforcement corrosion, which is examined by the experimental and field data available. An assessment criterion is defined to evaluate the flexural strength deterioration for the time-dependent reliability analysis. The results from the worked examples show that the proposed approach is capable of evaluating the structural reliability of corrosion damaged concrete structures.

Key Words
rock burst; criteria; back-analyses; residual coal pillars; numerical analysis

Address
Pengqi Qiu, Jun Wang, Jianguo Ning, Xuesheng Liu, Shanchao Hu and Qingheng Gu: State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology, Shandong University of Science and Technology, 579 Qianwangang Road, Qingdao, China


Abstract
This study presents an elasto-plastic (EP) solution for drained cavity expansion on the basis of unified strength failure criterion and considers the influence of initial stress state. Because of the influence of initial consolidation of soil mass, the initial stress may be anisotropic in the natural soil mass. In addition, the undrained hypothesis is usually used in the calculation of cavity expansion problem, but most of the cases are in the drained situation in practical engineering. Eventually, the published solution and the presented solution are compared to verify the suitability of the study.

Key Words
elasto-plastic solution; drained cavity expansion; unified strength failure criterion; initial stress state

Address
Chao Li, Jin-feng Zou and Liang Li: School of Civil Engineering, Central South University, Hunan 410075, China

Abstract
Based on the formation characteristics, wellbore parameters and insulated tubing (IT) parameters of the Shengli oilfield, Shandong, China, a geomechanical model is built to predict the temperature distributions of the wellbore and formation. The effects of the IT heat conductivity coefficient (HCC), well depth and IT joint on the temperature distribution of the IT, completion casing, cement sheath, and formation are investigated. Results show the temperature of the formation around the wellbore has an exponentially decreasing relation with the distance to the wellbore. The temperature of the formation around the wellbore has an inverse relation with the IT HCC when the temperatures of the steam and the formation are given. The temperature of the casing outer wall is mainly determined by the steam temperature and IT HCC rather than by the initial formation temperature. The temperature of the casing at the IT joint is much larger than that of the other location. Due to the IT joint having a small size, the effects of the IT joint on the casing temperature distribution are limited to a small area only.

Key Words
energy geomechnics; heavy oil reservoir; thermal recovery; temperature; insulated tubing; heat conductivity coefficient; completion casing

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


Abstract
Geosynthetic reinforced soil method in coarse-grained soils has been widely used in last decades. Two effective factors on soil-geosynthetic interaction are confining stresses and loading rate in clay. In terms of methodology, one pull-out test with four different strain rates, namely 0.75, 1.25, 1.75 and 2.25 mm/min, and three different normal stresses equal to 20, 50 ,and 80 kg have been performed on specimens with dimensions of 30x30x17 cm in the saturated, consolidated condition. The obtained results have demonstrated that activation of geosynthetic strength at contact surface depends on the applied stress. In addition, the increase in normal stress would increase the shear strength at contact surface between clay and geogrid. Moreover, it is concluded that the strain rate increment would increase the shear strength.

Key Words
reinforced soil; saturated and consolidated soil; geosynthetic; strain rate; pull-out test

Address
Maryam Safa: Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam

Amin Maleka: Department of Civil Engineering, Faculty of Engineering, Roudehen Branch, Islamic Azad University, Roudehen, Iran

Mohammad-Ali Arjomand: Faculty of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran

Masoud Khorami: Department of Civil Engineering, Faculty of Engineering, Central Branch, Islamic Azad University, Tehran, Iran

Mahdi Shariati: 1.) Division of Computational Mathematics and Engineering, Institute for Computational Science,
Ton Duc Thang University, Ho Chi Minh City, Vietnam
2.) Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

Abstract
Izmir Bay reserves high amount of residual alluvial deposits generated by Meles River at its stream mouth. These carried sediments with high water content and low bearing capacity are unsuitable in terms of engineering purposes. In-situ soil stabilization with deep soil mixing method is considered to improve properties of soil in this location. This method is widely used especially over Scandinavia, Japan and North America. Basically, the method covers mixing appropriate binder into the soil to improve soil profile according to the engineering needs. For this purpose, soil samples were initially provided from the site, classification tests were performed and optimum ratios of lime and cement binders were determined. Following, specimens representing the in-situ soil conditions were prepared and cured to be able to determine their engineering properties. Unconfined compression tests and vane shear tests were applied to evaluate the stabilization performance of binders on samples with different curing periods. Scanning electron microscope was used to observe time-dependent bonding progress of binders in order to validate the results. Utilization of 4% lime and 4% cement mixture for the long-term performance and 8% lime and 8% cement mixture for short term performance were suggested for the stabilization of Meles Delta soils. Development of CSH and CAH in a gel form as well as CSH crystals were clearly observed on SEM images of treated specimens.

Key Words
soil stabilization; deep soil mixing; lime-cement mixtures

Address
Okan Onal and Cagrihan Sariavci: Dokuz Eylul University, Engineering Faculty, Department of Civil Engineering, Tinaztepe Campus, Buca, Izmir, Turkey


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