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CONTENTS
Volume 36, Number 3, February10 2024
 

Abstract
Manually mapping fractures in construction stone mines is challenging, time-consuming, and hazardous. In this method, there is no physical access to all points. In contrast, digital image processing offers a safe, cost-effective, and fast alternative, with the capability to map all joints. In this study, two methods of detecting the trace of discontinuities using image processing in construction stone mines are presented. To achieve this, we employ two modified Hough transform algorithms and the degree of neighborhood technique. Initially, we introduced a method for selecting the best edge detector and smoothing algorithms. Subsequently, the Canny detector and median smoother were identified as the most efficient tools. To trace discontinuities using the mentioned methods, common preprocessing steps were initially applied to the image. Following this, each of the two algorithms followed a distinct approach. The Hough transform algorithm was first applied to the image, and the traces were represented through line drawings. Subsequently, the Hough transform results were refined using fuzzy clustering and reduced clustering algorithms, along with a novel algorithm known as the farthest points' algorithm. Additionally, we developed another algorithm, the degree of neighborhood, tailored for detecting discontinuity traces in construction stones. After completing the common preprocessing steps, the thinning operation was performed on the target image, and the degree of neighborhood for lineament pixels was determined. Subsequently, short lines were removed, and the discontinuities were determined based on the degree of neighborhood. In the final step, we connected lines that were previously separated using the method to be described. The comparison of results demonstrates that image processing is a suitable tool for identifying rock mass discontinuity traces. Finally, a comparison of two images from different construction stone mines presented at the end of this study reveals that in images with fewer traces of discontinuities and a softer texture, both algorithms effectively detect the discontinuity traces.

Key Words
building stone mines; degree of neighborhood; hough transform; image processing; rock mass discontinuities

Address
Mojtaba Taghizadeh and Reza Khalou Kakaee: Department of Mining, Petroleum and Geophysics Engineering, Shahrood University of Technology, Shahrood, Iran
Hossein Mirzaee Nasirabad: Department of Mining Engineering, Sahand University of Technology, Tabriz, Iran
Farhan A. Alenizi: Department of Electrical Engineering, College of engineering, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia

Abstract
Determining lateral earth pressure coefficient (EPC) K is a classic problem in geotechnical engineering. It is a key parameter for estimating the stresses in backfilled openings. For backfilled openings with rigid and immobile walls, some suggested using the Jaky's at-rest earth pressure coefficient K0 while other suggested taking the Rankine's active earth pressure coefficient Ka. A single value was proposed for the entire backfilled opening. To better understand the distributions of stresses and K in a backfilled opening, a series of laboratory tests have been conducted. The horizontal and vertical normal stresses at the center and near the wall of the opening were measured. The values of K at the center and near the wall were then calculated with the measured horizontal and vertical normal stresses. The results show that the values of K are close to Ka at the center and close to K0 near the wall. Furthermore, the experimental results show that the horizontal stress is almost the same at the center and near the wall, indicating a uniform distribution from the center to the wall. It can be estimated by analytical solutions using either Ka or K0. The vertical stress is higher near the center than near the wall. Its analytical estimation can only be done by using Ka at the center and K0 near the wall. Finally, the test results were used to calibrate a numerical model of FLAC2D, which was then used to analyze the influence of column size on the stresses and K in the backfilled opening.

Key Words
arching; backfill; earth pressure coefficient; laboratory tests; simultaneous measurement of vertical and horizontal stresses

Address
Jian Zheng: Research Institute on Mines and Environment, Department of Civil, Geological and Mining Engineering
École Polytechnique de Montréal, C.P. 6079, succursale Centre-Ville, Montréal, QC, Canada H3C 3A7;
Department of geotechnical engineering, Tongji University, Shanghai 200092, China
Li Li: Research Institute on Mines and Environment, Department of Civil, Geological and Mining Engineering
École Polytechnique de Montréal, C.P. 6079, succursale Centre-Ville, Montréal, QC, Canada H3C 3A7

Abstract
In recent decades, the protection and vulnerability of civil structures under explosion loads became a critical issue in terms of security, which may cause loss of lives and structural damage. Concrete retaining walls also restrict soils and slopes from displacements; meanwhile, intensive temporary loading may cause massive damage. In the current study, the modified Johnson–Holmquist (also known as J–H2) material model is implemented for concrete materials to model damages into the ABAQUS through user-subroutines to predict the blasting-induced concrete damages and volume strains. For this purpose, a 3D finite-element model of the concrete retaining wall was conducted in coupled Eulerian-Lagrangian simulation. Subsequently, a blast load equal to 500 kg of TNT was considered in three different positions due to UFC 3-340-02. Influences of the critical parameters in smooth blastings, such as distance from a free face, position, and effective blasting time, on concrete damage rate and destroy patterns, are explored. According to the simulation results, the concrete penetration pattern at the same distance is significantly influenced by the density of the progress environment. The result reveals that the progress of waves and the intensity of damages in free-air blasting is entirely different from those that progress in a dense surrounding atmosphere such as soil. Half-damaged elements in air blasts are more than those of embedded explosions, but dense environments such as soil impose much more pressure in a limited zone and cause more destruction in retaining walls.

Key Words
CEL simulation; concrete damage; explosive blasting; Johnson-Holmquist; retaining wall

Address
Javad Tahamtan, Iman Najjarbashi and Abdullah Hossaini: Department of civil engineering, sanjesh parsian advanced skills Institute, Mashhad, Iran
Majid Gholhaki and Hamid Pirmoghan: Department of Civil Engineering, Semnan University, Semnan, Iran

Abstract
Tailings are waste materials of mining operations, consisting of a mixture of clay, silt, sand with a high content of unrecoverable metals, process water, and chemical reagents. They are usually discharged as slurry into the storage area retained by dams or earth embankments. Poor knowledge of the hydro-mechanical behaviour of tailings has often resulted in a high rate of failures in which static liquefaction has been widely recognized as one of the major causes of dam collapse. Many studies have dealt with the static liquefaction of coarse soils in saturated conditions. This research provides an extension to the case of silty tailings in unsaturated conditions. The static liquefaction resistance was evaluated in terms of stress-strain behavior by means of monotonic triaxial tests. Its dependency on the preparation method, the volumetric water content, the void ratio, and the degree of saturation was studied and compared with literature data. The static liquefaction response was proved to be dependent mainly on the preparation technique and degree of saturation that, in turn, controls the excess of pore pressure whose leading role is investigated by means of the relationship between the -B Skempton parameter and the degree of saturation. A preliminary interpretation of the static liquefaction response of Stava tailings is also provided within the Critical State framework.

Key Words
CSL; degree of saturation; preparation technique; static liquefaction; suction; unsaturated soil; void ratio

Address
Gianluca Bella: Pini Group SA, Via Besso 7, Lugano, Switzerland
Guido Musso: Politecnico di Torino, C.so Duca degli Abruzzi 24, Torino, Italy

Abstract
The undrained shear strength is widely acknowledged as a fundamental mechanical property of soil and is considered a critical engineering parameter. In recent years, researchers have employed various methodologies to evaluate the shear strength of soil under undrained conditions. These methods encompass both numerical analyses and empirical techniques, such as the cone penetration test (CPT), to gain insights into the properties and behavior of soil. However, several of these methods rely on correlation assumptions, which can lead to inconsistent accuracy and precision. The study involved the development of innovative methods using extreme gradient boosting (XGB) to predict the pile set-up component "A" based on two distinct data sets. The first data set includes average modified cone point bearing capacity (qt), average wall friction (fs), and effective vertical stress (ovo), while the second data set comprises plasticity index (PI), soil undrained shear cohesion (𝑆𝑢), and the over consolidation ratio (OCR). These data sets were utilized to develop XGBoost-based methods for predicting the pile set-up component "A". To optimize the internal hyperparameters of the XGBoost model, four optimization algorithms were employed: Particle Swarm Optimization (PSO), Social Spider Optimization (SSO), Arithmetic Optimization Algorithm (AOA), and Sine Cosine Optimization Algorithm (SCOA). The results from the first data set indicate that the XGBoost model optimized using the Arithmetic Optimization Algorithm (XGB- AOA) achieved the highest accuracy, with R2 values of 0.9962 for the training part and 0.9807 for the testing part. The performance of the developed models was further evaluated using the RMSE, MAE, and VAF indices. The results revealed that the XGBoost model optimized using XGBoost-AoA outperformed other models in terms of accuracy, with RMSE, MAE, and VAF values of 0.0078, 0.0015, and 99.6189 for the training part and 0.0141, 0.0112, and 98.0394 for the testing part, respectively. These findings suggest that XGBoost-AoA is the most accurate model for predicting the pile set-up component.

Key Words
arithmetic optimization algorithm; cone penetration test; extreme gradient boosting model; particle swarm optimization; pile set-up parameter A; social spider optimization

Address
Xigang Du, Ximeng Ma and Chenxi Dong: Department of Transportation Engineering, Hebei University of Water Resources and Electric Engineering, Hebei Cangzhou,061000
Mehrdad Sattari Nikkhoo: Department of Civil Engineering, University of Mohaghegh Ardabili, Ardabil, Iran

Abstract
Shored Mechanically Stabilized Earth (SMSE) walls are types of soil retaining structures that increase soil stability under static and dynamic loads. The damage caused by an earthquake can be determined by evaluating the probabilistic seismic response of SMSE walls. This study aimed to assess the seismic performance of SMSE walls and provide fragility curves for evaluating failure levels. The generated fragility curves can help to improve the seismic performance of these walls through assessing and controlling variables like backfill surface settlement, lateral deformation of facing, and permanent relocation of the wall. A parametric study was performed based on a non-linear elastoplastic constitutive model known as the hardening soil model with small-strain stiffness, HSsmall. The analyses were conducted using PLAXIS 2D, a Finite Element Method (FEM) program, under plane-strain conditions to study the effect of the number of geogrid layers and the axial stiffness of geogrids on the performance of SMSE walls. In this study, three areas of damage (minor, moderate, and severe) were observed and, in all cases, the wall has not completely entered the stage of destruction. For the base model (Model A), at the highest ground acceleration coefficient (1 g), in the moderate damage state, the fragility probability was 76%. These values were 62%, and 54%, respectively, by increasing the number of geogrids (Model B) and increasing the geogrid stiffness (Model C). Meanwhile, the fragility values were 99%, 98%, and 97%, respectively in the case of minor damage. Notably, the probability of complete destruction was zero percent in all models.

Key Words
dynamic analysis; fragility curves; numerical method; seismic performance; Shored Mechanically Stabilized Earth (SMSE) wall

Address
Sheida Ilbagitaher: Department of Civil Engineering, University of Science and Culture, Tehran, Iran
Hamid Alielahi: Department of Civil Engineering, Zanjan Branch, Islamic Azad University, Zanjan, Iran

Abstract
Understanding the post-liquefaction shear behavior is crucial for predicting and assessing the damage, such as lateral flow, caused by liquefaction. Most studies have focused on the behavior until liquefaction occurs. In this study, we performed undrained multi-stage tests on clean sand, sand-silt mixtures, and silty soils to investigate post-liquefaction shear strain based on soil compressibility. The results confirmed that it is necessary to consider the soil compressibility and the shape of soil particles to understand the post-liquefaction shear strain characteristics. Based on this, an index reflecting soil compressibility and particle shape was derived, and the results showed a high correlation with post-liquefaction small resistance characteristic regardless of soil type and fine particle content.

Key Words
compressibility; density index; lateral spreading; liquefaction; shear strain

Address
Jongkwan Kim and Jin-Tae Han: Department of Geotechnical Engineering Research, Korea Institute of Civil Engineering and Building Technology,
283 Goyang-daero, Ilsan-seogu, Goyang-si, 10223, Republic of Korea
Mintaek Yoo: Department of Civil & Environmental Eng., Gachon University,
1342 Seongnam-daero, Seongnam-si 13120, Republic of Korea

Abstract
Seismic records are composed of mainshock and a series of aftershocks which often result in the incremental damage to underground structures and bring great challenges to the rescue of post-disaster and the repair of post-earthquake. In this paper, the repetition method was used to construct the mainshock-aftershocks sequence which was used as the input ground motion for the analysis of dynamic time history. Based on the Daikai station, the two-dimensional finite element model of soil-station was established to explore the failure process of station under different seismic precautionary intensities, and the concept of incremental damage of station was introduced to quantitatively analyze the damage condition of structure under the action of mainshock and two aftershocks. An arc rubber bearing was proposed for the shock absorption. With the arc rubber bearing, the mode of the traditional column end connection was changed from "fixed connection" to "hinged joint", and the ductility of the structure was significantly improved. The results show that the damage condition of the subway station is closely related to the magnitude of the mainshock. When the magnitude of the mainshock is low, the incremental damage to the structure caused by the subsequent aftershocks is little. When the magnitude of the mainshock is high, the subsequent aftershocks will cause serious incremental damage to the structure, and may even lead to the collapse of the station. The arc rubber bearing can reduce the damage to the station. The results can offer a reference for the seismic design of subway stations under the action of mainshock-aftershocks.

Key Words
collapse damage; earthquake resistance of underground structure; mainshock-aftershocks sequence; shock absorption; seismic precautionary intensity

Address
Zhen-Dong Cui, Wen-Xiang Yan and Su-Yang Wang: State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering,
China University of Mining and Technology, Xuzhou, Jiangsu 221116, P.R. China

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