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CONTENTS
Volume 24, Number 1, January10 2021
 

Abstract
In this study, a new approach using electrical resistivity measurement was proposed to detect grout penetration and to evaluate the grouting performance for such as waterproof efficiency in single rock fracture. For this purpose, an electrical resistivity monitoring system was designed to collect multi-channel data in real time. This was applied to a system for grout injection/penetration using a transparent fracture replica with various aperture sizes and water-cement mix ratio. The electrical resistivity was measured under various grout penetration conditions in real time, which results were directly compared to the visual observation images of grout penetration/distribution. Moreover, the grouting success status after the curing process was evaluated by measuring the electrical resistivity in relation to changes in frequency in fracture cells where grout injection and penetration were completed. Consequently, it was determined that the electrical resistivity monitoring system could be applied effectively to the detection of successful penetration of grouting into a target area and to actual field evaluation of the grouting performance and long-term stability of underground rock structures.

Key Words
electrical resistivity; grout penetration; grouting performance; waterproof efficiency; aperture sizes; water-cement mix ratio

Address
Hangbok Lee: Center for Deep Subsurface Research, Korea Institute of Geoscience and Mineral Resources (KIGAM),
124 Gwahak-ro, Yuseong-gu, Daejeon 34132, Republic of Korea

Tae-Min Oh and Jong-Won Lee: Department of Civil and Environmental Engineering, Pusan National University (PNU),
2 Busandaehak-ro 63beon-gil, Geumjeong-gu, Busan 46241, Republic of Korea


Abstract
Digging well foundation has been widely used in railway bridges due to its good economy and reliability. In other instances, bridges with digging well foundation still have damage risks during earthquakes. However, there is still a lack of knowledge of lateral behavior of digging well foundation considering the soil-foundation interaction. In this study, scaled models of bridge pier-digging well foundation system are constructed for quasi-static test to investigate their lateral behaviors. The failure mechanism and responses of the soil-foundation-pier interaction system are analyzed. The testing results indicate that the digging foundations tend to rotate as a rigid body under cyclic lateral load. Moreover, the depth-width ratio of digging well foundation has a significant influence on the failure mode of the interaction system, especially on the distribution of foundation displacement and the failure of pier. The energy dissipation capacity of the interaction system is discussed by using index of the equivalent viscous damping ratio. The damping varies with the depth-width ratio changing. The equivalent stiffness of soil-digging well foundation-pier interaction system decreases with the increase of loading displacement in a nonlinear manner. The absolute values of the interaction system stiffness are significantly influenced by the depth-width ratio of the foundation.

Key Words
railway bridge; digging well foundation; lateral behavior; soil-foundation interaction; quasi-static test

Address
Yi Wang, Xingchong Chen, Xiyin Zhang, Mingbo Ding, Jinhua Lu, and Huajun Ma: School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou, 730070, China

Abstract
The utilization of buildings can be improved by extending them vertically. However, the added load of the extension might require building foundations to be underpinned; otherwise, the loads on the foundations might exceed their bearing capacity. In this study, a preloading method was presented aiming at transferring partial loads from existing piles to underpinning piles. A pneumatic-type model preloading device was developed and used to carry out centrifuge experiments to evaluate the load–displacement behavior of piles, the pile–soil interaction during preloading, and the additional loading caused by vertical extension. The results showed that the preloading devices effectively transfer load from existing piles to underpinning piles. In the additional loading test of group piles, the load-sharing ratio of a pile increased with its stiffness. The load-sharing ratio of a preloaded micropile was less than that of a non-preloaded micropile as a result of the reduction in axial stiffness caused by preloading before additional loading. Therefore, a slight reduction of the load-sharing capacity of an underpinning pile should be considered if the preloading method is applied. Further, two full scale preloading devices was developed. The devices preload underpinning piles and thereby produce reaction forces on a reaction frame to jack existing piles upward, thus transferring load from the existing piles to the underpinning piles. Specifically, screw-type and hydraulic-jack type devices were developed for the practical application of foundation underpinning during vertical extension, and their operability and load transfer effect verified via full-scale structural experiments.

Key Words
foundation underpinning; preloading device; centrifuge experiment; full-scale experiment; load-sharing ratio

Address
Chengcan Wang: 1.) Department of Civil and Environmental Engineering, Korea University of Science and Technology,
217, Gajong-Ro, Yuseong- Gu, Daejeon-Si, Republic of Korea
2.) Department of Infrastructure Safety Research, Korea Institute of Civil Engineering and Building Technology,
283, Goyangdae-Ro, Ilsanseo-Gu, Goyang-Si, Republic of Korea

Jin-Tae Han and Seokjung Kim: Department of Infrastructure Safety Research, Korea Institute of Civil Engineering and Building Technology, 283, Goyangdae-Ro, Ilsanseo-Gu, Goyang-Si, Republic of Korea

Young-Eun Jang: Innovative SMR System Development Division, Korea Atomic Energy Research Institute, 111, Daedeok-daero, 989beon-Gil, Yuseong-Gu, Daejeon, Republic of Korea

Abstract
Peatland is distributed in China widely, and organic matters in soil frequently induce problems in the construction and maintenance of highway engineering due to the high permeability and compressibility. In this paper, a selected site of Dali-Lijiang expressway was surveyed in China. A numerical model was built to predict the settlement of the foundation of the selected section employing the soft soil creep (SSC) model in PLAXIS 8.2. The model was subsequently verified by the result of field observance. Consequently, the parameters of 17 types of soils from different regions in China with organic contents varying from 1.1–74.9% were assigned to the numerical model to study the settlement characteristics. The calculated results showed that the duration of primary consolidation and proportion of primary settlement in the total settlement decreased with increasing organic content. Two empirical equations, for total consolidation settlement and secondary settlement, were proposed using multiple linear regression based on the calculated results from the numerical models. The analysis results of the significances of certain soil parameters demonstrated that the natural compression index, secondary compression index, cohesion and friction angle have significant linear relevance with both the total settlement and secondary settlement, while the initial coefficient of permeability exerts significant influence on the secondary settlement only.

Key Words
foundation; soft soil creep model; secondary settlement; organic content; expressway embankment

Address
Ruiling Feng, Liyang Wang, Kang Wei and Jiacheng Zhao: School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China

Abstract
The effects of initial soil fabric and aspect ratio (AR) on the small-strain stiffness (G0) of granular soils are studied by employing discrete element method (DEM) numerical analysis. Elongated clumps composed of subspheres were adopted, and the G0 values were obtained by DEM simulations of drained triaxial tests under different densities and initial confining pressure (p0). The DEM simulations indicate that the initial soil fabric has an insignificant effect on G0. The effect of the AR on G0 is related to the initial density. Namely, for dense specimens, G0 first increases with increasing AR, reaching a plateau value when the AR ≥1.5. However, for loose specimens, G0 gradually increases as the AR increases. Microscopic examination reveals that G0 uniquely depends on the coordination number of the particles (CN-particle) rather than the subspheres (CN-sphere) at the particulate level for the effects of initial soil fabric and AR. Finally, Poisson's ratio v0 is also determined by CN-particle. In addition, based on data in literature and this study, v0 can be fitted as v0 = 5.920(G0/( p0)1/3)-0.99, which can be used to predict v0 of granular soils based on the measured G0.

Key Words
inherent anisotropy; aspect ratio; small-strain stiffness; Poisson's ratio; granular soils; DEM

Address
Jian Gong: 1.) College of Civil Engineering and Architecture, Guangxi University, Guangxi, China
2.) School of Civil Engineering, Central South University, Hunan, China

Liang Li, Lianheng Zhao, Jinfeng Zou and Zhihong Nie: School of Civil Engineering, Central South University, Hunan, China

Abstract
The influence of ground motions on the seismic response of utility tunnels was investigated. A series of small-scale shaking table model tests were carried out under uniform excitation in the transverse direction. Different peak accelerations of EL-Centro and Taft earthquake waves were applied. The acceleration responses, earth pressure, seismic strain, bending moment and structure deformations were measured and discussed. The results showed that the types of earthquake waves had significant influences on the soil-structure acceleration responses. However, the amplitude of the soil acceleration along the depth showed consistent variation regardless of the types of earthquake waves and tunnels. The horizontal soil pressure near the top and bottom slabs showed obviously larger values than those at other depths. In general, the strain response in the outer surface was more significant than that on the inner surface, and the peak strain in the end section of the model was larger than that in the middle section. Moreover, the bending moment at the corner points was much larger than that at middle point, and the bending moment was greatly affected by both input accelerations and seismic wave types. The opposite direction of shear deformation on the top and bottom slabs presented a rotation trend of the model structure.

Key Words
utility tunnels; seismic response; shaking table tests; earthquake waves; transverse excitation

Address
Chenglong Wang, Xuanming Ding, Zhixiong Chen, Li Feng and Liang Han: 1.)College of Civil Engineering, Chongqing University, Chongqing, 400045, China
2.)Key Laboratory of New Technology for Construction of Cities in Mountain Area, Ministry of Education, Chongqing, 400045, China


Abstract
Uniaxial compression tests were conducted on sandstone-CGFB composite samples with different interface angles, and their strength, acoustic emission (AE), and failure characteristics were investigated. Three macro-failure patterns were identified: the splitting failure accompanied by local spalling failure in CGFB (Type-I), the mixed failure with small sliding failure along with the interface and Type-I failure (Type-II), and the sliding failure along with the interface (Type-III). With an increase of interface angle β measured horizontally, the macro-failure pattern changed from Type-I to Type-II, and then to Type-III, and the uniaxial compressive strength and elastic modulus generally decreased. Due to the small sliding failure along with the interface in the composite sample with β of 45° , AE events underwent fluctuations in peak values at the later post-peak failure stage. The composite samples with β of 60° occurred Type-III failure before the completion of initial compaction stage, and the post-peak stress-time curve initially exhibited a slow decrease, followed by a steep linear drop with peaks in AE events.

Key Words
rock-cemented coal gangue-fly ash backfill bi-materials; interface angle; strength characteristics; failure mechanism; uniaxial loading

Address
Da W. Yin: 1.) State Key Laboratory of Mine Disaster Prevention and Control, Shandong University of Science and Technology, Qingdao 266590, China
2.) Key Laboratory of Safety and High-efficiency Coal Mining, Ministry of Education, Anhui University of Science and Technology, Huainan 232001, China

Shao J. Chen and Ning Jiang: State Key Laboratory of Mine Disaster Prevention and Control, Shandong University of Science and Technology, Qingdao 266590, China

Xi Z. Sun: College of Civil Engineering and Architecture, Linyi University, Linyi 276000, China


Abstract
This paper concerns with forced dynamic response of thick functionally graded (FG) beam resting on viscoelastic foundation including porosity impacts. The dynamic point load is proposed to be triangle point loads in time domain. In current analysis the beam is assumed to be thick, therefore, the two-dimensional plane stress constitutive equation is proposed to govern the stress-strain relationship through the thickness. The porosity and void included in constituent is described by three different distribution models through the beam thickness. The governing equations are obtained by using Lagrange's equations and solved by finite element method. In frame of finite element analysis, twelve-node 2D plane element is exploited to discretize the space domain of beam. In the solution of the dynamic problem, Newmark average acceleration method is used. In the numerical results, effects of porosity coefficient, porosity distribution and foundation parameters on the dynamic responses of functionally graded viscoelastic beam are presented and discussed. The current model is efficient in many applications used porous FGM, such as aerospace, nuclear, power plane sheller, and marine structures.

Key Words
dynamic response; functionally graded beam; porosity; viscoelastic foundation; numerical finite element method

Address
Ali Alnujaie: Department of Mechanical Engineering, Faculty of Engineering, Jazan University, P. O. Box 45142, Jazan, Kingdom of Saudi Arabia

Şeref D. Akbas: Department of Civil Engineering, Bursa Technical University, 16330, Bursa, Turkey

Mohamed A. Eltaher: 1.) Department of Mechanical Engineering, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah, Saudi Arabia
2.) Department of Mechanical Design & Production, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt

Amr Assie: 1.) Department of Mechanical Engineering, Faculty of Engineering, Jazan University, P. O. Box 45142, Jazan, Kingdom of Saudi Arabia
2.) Department of Mechanical Design & Production, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt


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