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CONTENTS
Volume 35, Number 2, October25 2023
 

Abstract
Ground subsidence in urban areas due to excessive development and degraded underground facilities is a serious problem. Geophysical surveys have been conducted to estimate the distribution and scale of cavities and subsidence. In this study, electrical resistivity tomography (ERT) was performed near an area of road subsidence in an urban area. The subsidence arose due to groundwater leakage that carried soil into a neighboring excavation site. The ERT survey line was located between the main subsidence area and an excavation site. Because ERT data are affected by rapid topographic changes and surrounding structures, the influence of the excavation site on the data was analyzed through field-scale numerical modeling. The effect of an excavation should be considered when interpreting ERT data because it can lead to wrong anomalous results. A method for performing 2D inversion after correcting resistivity data for the effect of the excavation site was proposed. This method was initially tested using a field-scale numerical model that included the excavation site and subsurface anomaly, which was a loosened zone, and was then applied to field data. In addition, ERT data were interpreted using an existing in-house 3D algorithm, which considered the effect of excavation sites. The inversion results demonstrated that conductive anomalies in the loosened zone were greater compared to the inversion that did not consider the effects of excavation.

Key Words
electrical resistivity tomography; excavation; inversion; subsidence

Address
Seo Young Song: Department of Energy and Mineral Resources, Sejong University, 05006 Seoul, Republic of Korea;
Korea Institute of Science and Technology, 02792 Seoul, Republic of Korea
Bitnarae Kim: Department of Energy and Mineral Resources, Sejong University, 05006 Seoul, Republic of Korea;
BRGM, Orléans, France
Ahyun Cho and Juyeon Jeong: Department of Energy and Mineral Resources, Sejong University, 05006 Seoul, Republic of Korea
Dongkweon Lee: His Earth co. ltd., 04540 Seoul, Republic of Korea
Myung Jin Nam: Department of Energy and Mineral Resources, Sejong University, 05006 Seoul, Republic of Korea;
Department of Energy Resources and Geosystems Engineering, Sejong University, 05006 Seoul, Republic of Korea


Abstract
The demand for cement and limestone crushed materials has increased many folds due to the tremendous increase in construction activities in Pakistan during the past few decades. The number of cement production industries has increased correspondingly, and so the rock-blasting operations at the limestone quarry sites. However, the safety procedures warranted at these sites for the blast-induced ground vibrations (BIGV) have not been adequately developed and/or implemented. Proper prediction and monitoring of BIGV are necessary to ensure the safety of structures in the vicinity of these quarry sites. In this paper, an attempt has been made to predict BIGV using artificial neural network (ANN) at three selected limestone quarries of Pakistan. The ANN has been developed in Python using Keras with sequential model and dense layers. The hyper parameters and neurons in each of the activation layers has been optimized using randomized and grid search method. The input parameters for the model include distance, a maximum charge per delay (MCPD), depth of hole, burden, spacing, and number of blast holes, whereas, peak particle velocity (PPV) is taken as the only output parameter. A total of 110 blast vibrations datasets were recorded from three different limestone quarries. The dataset has been divided into 85% for neural network training, and 15% for testing of the network. A five-layer ANN is trained with Rectified Linear Unit (ReLU) activation function, Adam optimization algorithm with a learning rate of 0.001, and batch size of 32 with the topology of 6-32-32-256-1. The blast datasets were utilized to compare the performance of ANN, multivariate regression analysis (MVRA), and empirical predictors. The performance was evaluated using the coefficient of determination (R2), mean absolute error (MAE), mean squared error (MSE), mean absolute percentage error (MAPE), and root mean squared error (RMSE)for predicted and measured PPV. To determine the relative influence of each parameter on the PPV, sensitivity analyses were performed for all input parameters. The analyses reveal that ANN performs superior than MVRA and other empirical predictors, andthat83% PPV is affected by distance and MCPD while hole depth, number of blast holes, burden and spacing contribute for the remaining 17%. This research provides valuable insights into improving safety measures and ensuring the structural integrity of buildings near limestone quarry sites.

Key Words
artificial neural network; blast-induced ground vibrations; grid search method; peak particle velocity; randomized and sensitivity analysis

Address
Salman Ihsan and Shahab Saqib: Department of Mining Engineering, University of Engineering and Technology, Lahore 54890, Pakistan
Hafiz Muhammad Awais Rashid: Department of Geological Engineering, University of Engineering and Technology, Lahore 54890, Pakistan
Fawad S. Niazi: Department of Civil and Mechanical Engineering, Purdue University, Fort Wayne, 2101 E. Coliseum Blvd., Fort Wayne, IN 46805, USA
Mohsin Usman Qureshi: Faculty of Engineering, Sohar University, Oman

Abstract
Sand columns in clayey soil are considered one of the most economical and environmentally-friendly soil-improving techniques. It improves the shear strength parameters, reduces the settlement, and increases the bearing capacity of clayey soils. The aim of this paper is to study the effect of grain shape in sand columns on their performance in improving the mechanical properties of clayey soils. An intensive series of consolidated-drained triaxial tests were performed on clay specimens only and clay specimens with sand columns. The parameters examined during the experimental work were grain shape in sand columns (angular, rounded, sub-rounded) and effective confining pressure (50 kPa, 100 kPa, 200 kPa). The results indicated that there is a significant improvement in the deviatoric stress and stiffness values of specimens with sand columns. Improving deviatoric stress values in the use of angular sand grains was found to be higher than those in the use of sub-rounded and rounded sand grains. A 187%, 159%, and 153% increment in deviatoric stress values were observed for the sand columns with angular, sub-rounded, and rounded grain shapes, respectively. The specimens were observed to be more contractive as the sand column was installed, and as the angularity of grains in the sand column was increased. Sand column installation improves significantly the angle of internal friction, and the effective angle of internal friction increases as the angularity of the sand grains increases.

Key Words
grain shape; local strain measurements; sand column; triaxial test

Address
Zuheir Karabash: Department of Dams and Water Resources Engineering, University of Mosul, Mosul, Iraq
Ali Firat Cabalar: Department of Civil Engineering, University of Gaziantep, Gaziantep, Turkey

Abstract
This paper presents stability evaluation of unlined tunnels with semi-circular arch and straight sides (SASS) driven in non-homogeneous and anisotropic undrained clay. Numerical analysis has been conducted based on lower bound finite element limit analysis with second order cone programming under plane strain condition. The solutions will be used for the assessment of stability of unlined semi-circular arch tunnels and tunnels in which semi-circular roof is supported over rectangular/square sections. The stability charts have been generated in terms of a non-dimensional factor considering linear variation in undrained anisotropic strength for normally consolidated and lightly over consolidated clay with depth, and constant undrained anisotropic strength for heavily over-consolidated clay across the depth. The effect of normalized surcharge pressure on ground surface, non-homogeneity and anisotropy of clay, tunnel cover to width ratio and height to width ratio of tunnel on the stability factor and associated zone of shear failure at yielding have been examined and discussed. The geometry of tunnel in terms of shape and size, and non-homogeneity and anisotropy in undrained strength of clay has been observed to influence significantly the stability of unlined SASS tunnels.

Key Words
anisotropy; clay; non-homogeneous; stability; unlined tunnels

Address
Bibhash Kumar: Department of Civil Engineering, National Institute of Technology Uttarakhand 246174, India
Jagdish P. Sahoo: Department of Civil Engineering, Indian Institute of Technology Kanpur 208016, India

Abstract
This study investigates the uplift capacity of a single vertical belled pile buried at shallow depth in dry sand. The laboratory model experiments are conducted with different pile-tip angles and relative densities. In addition, image and FEM analyses are performed to observe the failure surface of the belled pile for different pile-tip angles and relative densities. Accordingly, the uplift capacity and failure angle in the failure surface of the belled pile were found to depend on the belled piletip angle and relative density. A predictive model for the uplift capacity of the belled pile was proposed considering the relative density and belled pile-tip angle based on a previous limit equilibrium equation. To validate the applicability of the proposed model, the values calculated using the proposed and previous models were compared to those obtained through a laboratory model experiment. The proposed model had the best agreement with the laboratory model experiment.

Key Words
belled pile; FEM analysis; image analysis; model experiment;shallow depth; uplift capacity

Address
Jung-goo Kang and Gyeongo Kang: Department of Civil Engineering, Gwangju University, 277 Hyodeck-ro, Nam-gu, Gwangju, 61743, Republic of Korea
Young-sang Kim: Department of Civil Engineering, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju, 61186, Republic of Korea

Abstract
The primary objective of this study is to examine the influence of geometry on the stability characteristics of cylindrical microstructures. This investigation entails a stability analysis of a bi-directional functionally graded (BD-FG) cylindrical imperfect concrete beam, focusing on the impact of geometry. Both the first-order shear deformation beam theory and the modified coupled stress theory are employed to explore the buckling and dynamic behaviors of the structure. The cylinder-shaped imperfect beam is constructed using a porosity-dependent functionally graded (FG) concrete material, wherein diverse porosity voids and material distributions are incorporated along the radial axis of the beam. The radius functions are considered in both uniform and nonuniform variations, reflecting their alterations along the length of the beam. The combination of these characteristics leads to the creation of BD-FG configurations. In order to enable the assessment of stability using energy principles, a numerical technique is utilized to formulate the equations for partial derivatives (PDEs).

Key Words
buckling analysis; concrete beam; functionally graded material; nonlinear analysis; porous material; truncated conical tube

Address
Ying Yang: College of Universal Quality Education, Wuchang University of Technology, Wuhan 430223, Hubei, China
Yike Mao: Department of Physical Education, Wuhan University of Technology, Wuhan 430076, Hubei, China

Abstract
The nodular diaphragm wall (NDW) is a novel type of foundation with favorable engineering characteristics, which has already been utilized in high-rise buildings and high-speed railways. Compared to traditional diaphragm walls, the NDW offers significantly improved vertical bearing capacity due to the presence of nodular parts while reducing construction time and excavation work. Despite its potential, research on the vertical bearing characteristics of NDW requires further study, and the investigation and visualization of its displacement pattern and failure mode are scant. Meanwhile, the measurement of the force component acting on the nodular parts remains challenging. In this paper, the vertical bearing characteristics of NDW are studied in detail through the indoor model test, and the displacement and failure mode of the foundation is analyzed using particle image velocimetry (PIV) technology. The principles and methods for monitoring the force acting on the nodular parts are described in detail. The research results show that the nodular part plays an essential role in the bearing capacity of the NDW, and its maximum load-bearing ratio can reach 30.92%. The existence of the bottom nodular part contributes more to the bearing capacity of the foundation compared to the middle nodular part, and the use of both middle and bottom nodular parts increases the bearing capacity of the foundation by about 9~12% compared to a single nodular part of the NDW. The increase in the number of nodular parts cannot produce a simple superposition effect on the resistance born by the nodular parts since the nodular parts have an insignificant influence on the exertion and distribution of the skin friction of NDW. The existence of the nodular part changes the displacement field of the soil around NDW and increases the displacement influence range of the foundation to a certain extent. For NDWs with three different nodal arrangements, the failure modes of the foundations appear to be local shear failures. Overall, this study provides valuable insights into the performance and behavior of NDWs, which will aid in their effective utilization and further research in the field.

Key Words
model test; nodular diaphragm wall; nodular part; PIV technology; vertical bearing behavior

Address
Jiujiang Wu: Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province,
Southwest University of Science and Technology, No.59, Qinglong Avenue, Mianyang, The People's Republic of China;
Department of Civil and Environmental Engineering, Western University, London N6A 5B9, Canada
Longjun Pu, Hui Shang and Haodong Hu: Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province,
Southwest University of Science and Technology, No.59, Qinglong Avenue, Mianyang, The People's Republic of China
Yi Zhang: Shanghai Horizon Construction Development Co., Ltd., No.1815 Huiwang Road, Shanghai, The People's Republic of China
Lijuan Wang: State Key Laboratory of GeoHazrd Prevention and GeoEnvironment Protection, Chengdu University of Technology, No.1, East 3rd Road, Erxianqiao, Chengdu, The People's Republic of China


Abstract
This paper presents numerical investigations into the particle crushing effect on the shear properties of gravel under direct shear condition. A novel particle crushing model was developed based on the octahedral shear stress criterion and fragment replacement method. A series of direct shear tests were carried out on unbreakable particles and breakable particles with different strengths. The evolutions of the particle crushing, shear strength, volumetric strain behavior, and contact force fabric during shearing were analyzed. It was observed that the number of crushed particles increased with the increase of the shear displacement and axial pressure and decreased with the particle strength increasing. Moreover, the shear strength and volume dilatancy were obviously decreased with particle crushing. The shear displacement of particles starting to crush was close to that corresponding to the peak shear stress got. Besides, the shear-hardening behavior was obviously affected by the number of crushed particles. A microanalysis showed that due to particle crushing, the contact forces and anisotropy decreased. The mechanism of the particle crushing effect on the shear strength was further clarified in terms of the particle friction and interlock.

Key Words
granular materials; ground improvement; numerical analyses; rock fills; shear strength

Address
Xi Li: National Engineering Research Center of Highway Maintenance Technology, Changsha University of Science and Technology,
Changsha, Hunan 410114, China;
2School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114, China;
Ecole des Ponts ParisTech, Laboratoire Navier/CERMES, 6 et avenue Blaise Pascal, 77455 Marne La Vallée cedex 2, France
Yayan Liu: School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114, China
Guoping Qian: National Engineering Research Center of Highway Maintenance Technology, Changsha University of Science and Technology,
Changsha, Hunan 410114, China;
School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114, China
Xueqing Liu: Shanghai Zhuxin Real Estate Broker Co., Ltd., Shanghai 201418, China
Hao Wang and Guoqing Yin: Ecole des Ponts ParisTech, Laboratoire Navier/CERMES, 6 et 8 avenue Blaise Pascal, 77455 Marne La Vallée cedex 2, France


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