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CONTENTS
Volume 33, Number 6, June25 2023
 

Abstract
Wave propagation with high transverse deflection could affect the stability of the ball in its trajectory. For low stiffness balls similar to soccer and volleyball balls, the waves are more noticeable in comparison to other balls like ping-pong ball. On the other hand, the soccer balls are under heavy impact loads from shoots and contacting different objects in the field. The maximum recorded speed of a soccer ball after kicking is the 211 km/hr and the average maximum speed is around 112 km/hr. Therefore, in such speeds the aerodynamic forces become important which are directly related to geometrical shape of the ball. In this regard, the wave propagation in soccer ball is examined in the current study using large deformation shear deformable formulations. Classical relations of stress-strain components are taken into consideration along with minimum total energy principle. The final derived relations were solved by using harmonic differential quadrature method. The results are generally presented ion term of phase velocity as function of different influencing parameters of the materials, geometry and mass of the ball.

Key Words
analytical analysis; contact; football game ball; vibration; wave propagation

Address
Lei Sun and Cancan Wei: Physical Education College of Jilin University, Changchun 130000, Jilin, China
Fei Liu: Department of Public Physical, Changchun Humanities and Sciences College, Changchun 130117, Jilin, China
Lijun Wang: International College, krirk university, Bangkok 10220, Thailand;
Wuchang University of Technology, Wuhan 430000, Hubei, China
Bo Ren: School of Economics and Management Shanghai University of Sport, Shanghai 200438, China

Abstract
The design of foundations based on a deterministic approach may not be safe and reliable occasionally, since soils sometimes show considerable spatial variability, and thus, significant uncertainties in turn affect the estimation of footing bearing capacity. The design of footing on cohesionless stratums on the basis of reliability analysis has not received much attention. This paper performs two-dimensional random finite difference analyses of shallow strip footings on a spatially variable frictional soil considering correlation structure. Friction angle (o) is considered as a log-normally distributed random variable and Monte Carlo Simulation is then performed to determine the statistical response based on the random fields. A new approach reliability-based safety factor is defined based on various reliability levels by considering the coefficient of variation of o and correlation length in both the horizontal and vertical directions. The comparison of the probabilistic safety factor and the conventional one illustrates the limitations of the deterministic safety factor and provides insight into how the heterogeneity of soils properties affects the required safety factor. Results show that the conventional safety factor of 3 can be conservative in some cases, especially for soil with low values of mean o and COVo.

Key Words
footing bearing pressure; Monte Carlo Simulation; probabilistic analysis; reliability assessment; safety factor

Address
Parviz Tafazzoli Moghaddam and Mahmoud Ghazavi: Faculty of Civil Engineering, K.N. Toosi Univ. of Technology, Tehran 19967-15433, Iran
Pezhman Fazeli Dehkordi: Department of Civil Engineering, Shahrekord Branch, Islamic Azad University, Shahrekord 88137-33395, Iran

Abstract
As the structure of broken rock mass is complex, with obvious discontinuity and anisotropy, it is generally necessary to reinforce broken rock mass using grouting in underground construction. The purpose of this study is to experimentally investigate the mechanical properties of broken rock mass after grouting reinforcement with consideration of the characteristics of broken rock mass (i.e., degree of fragmentation and shape) and a range of reinforcement methods such as relative strength ratio between the broken rock mass and cement-based grout stone body (y), and volumetric block proportion (VBP) representing the volumetric ratio of broken rock mass and the overall cement grout-broken rock mass mixture after the reinforcement. The experimental results show that the strength and deformation of the reinforced broken rock mass is largely determined by relative strength ratio (y) and VBP. In addition, the enhancement in compressive strength by grouting is more obvious for broken rock mass with spherical shape under a relatively high strength ratio (e.g., y=2.0), whereas the shape of rock mass has little influence when the strength ratio is low (e.g., y=0.1). Importantly, the results indicate that columnar splitting failure and inclined shear failure are two typical failure modes of broken rock mass with grouting reinforcement.

Key Words
broken rock mass; compressive strength; degree of fragment; failure modes; grouting reinforcement; volumetric block proportion

Address
Yanxu Guo, Qingsong Zhang, Rentai Liu and Xin Chen: Geotechnical and Structural Engineering Research Center, Shandong University, Jinan 250061, China
Hongbo Wang: College of Civil Engineering and Architecture, Shandong University of Science and Technology, Qingdao 266590, China
Wenxin Li: Key Laboratory of Mining Disaster Prevention and Control, Shandong University of Science and Technology, Qingdao 266590, China
Lihai Zhang: Department of Infrastructure Engineering, The University of Melbourne, VIC 3010, Australia

Abstract
The prediction and achievement of a proper rock fragmentation size is the main challenge of blasting operations in surface mines. This is because an optimum size distribution can optimize the overall mine/plant economics. To this end, this study attempts to develop four improved artificial intelligence models to predict rock fragmentation through cascaded forward neural network (CFNN) and radial basis function neural network (RBFNN) models. In this regards, the CFNN was trained by the Levenberg-Marquardt algorithm (LMA) and Conjugate gradient backpropagation (CGP). Further, the RBFNN was optimized by the Dragonfly Algorithm (DA) and teaching-learning-based optimization (TLBO). For developing the models, the database required was collected from the Midouk copper mine, Iran. After modeling, the statistical functions were computed to check the accuracy of the models, and the root mean square errors (RMSEs) of CFNN-LMA, CFNN-CGP, RBFNN-DA, and RBFNN-TLBO were obtained as 1.0656, 1.9698, 2.2235, and 1.6216, respectively. Accordingly, CFNN-LMA, with the lowest RMSE, was determined as the model with the best prediction results among the four examined in this study.

Key Words
blasting; cascaded forward neural network; fragmentation; prediction models; radial basis function neural network

Address
Xiaohua Ding: School of Mines, China University of Mining and Technology, Xuzhou 221116, China;
State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou 221116, China
Moein Bahadori: Faculty of Engineering, University of Gonabad, Khorasan-e-Razavi, Iran
Mahdi Hasanipanah and Rini Asnida Abdullah: Department of Geotechnics and Transportation, Faculty of Civil Engineering, Universiti Teknologi Malaysia,
Skudai 81310, Johor Bahru, Malaysia

Abstract
The interlayers, either softer or stiffer than the surrounding layers, are usually overlooked during field investigation due to the small thickness. They may be neglected through the analysis process for simplicity. However, they may significantly affect the dynamic behavior of the soil-foundation system. In this study, a series of 3D finite-element Direct-solution steady-state harmonic analyses were carried out using ABAQUS/CAE software to investigate the impacts of interlayers on the dynamic response of a cast in place pile group subjected to horizontal harmonic load. The experimental data of a 3X2 pile group testing was used to verify the numerical modeling. The effects of thickness, depth, and shear modulus of the interlayers on the dynamic response of the pile group are investigated. The simulations were conducted on both stiff and soft soils. It was found that the soft interlayers affect the frequency-amplitude curve of the system only in frequencies higher than 70% of the resonant frequency of the base soil. While, the effect of stiff interlayer in soft base soil started at frequency of 35% of the resonant frequency of the base soil. Also, it was observed that a shallow stiff interlayer increased the resonant amplitude by 11%, while a deep one only increased the resonant frequency by 7%. Moreover, a shallow soft interlayer increased the resonant frequency by 20% in soft base soils, whereas, it had an effect as low as 6% on resonant amplitude. Also, the results showed that deep soft interlayers increased the resonant amplitude by 17 to 20% in both soft and stiff base soils due to a reduction in lateral support of the piles. In the cases of deep thick, soft interlayers, the resonant frequency reduced significantly, i.e., 16 to 20%. It was found that the stiff interlayers were most effective on the amplitude and frequency of the pile group.

Key Words
ABAQUS/CAE; dynamic response; interlayer; pile group; resonant amplitude; resonant frequency

Address
Masoud Oulapour, Sam Esfandiari and Mohammad M. Olapour: Department of Civil Engineering, Faculty of Civil Engineering and Architecture, Shahid Chamran University of Ahvaz, Ahvaz, Iran

Abstract
The instability and failure of engineered rock masses are influenced by crack initiation and propagation. Uniaxial compression and acoustic emission (AE) experiments were conducted on cracked sandstone. The effect of the crack's dip on the crack initiation was investigated using fracture mechanics. The crack propagation was investigated based on stress-strain curves, AE multi-parameter characteristics, and failure modes. The results show that the crack initiation occurs at the tip of the pre-fabricated crack, and the crack initiation angle increases from 0 to 70 as the dip angle increases from 0 to 90. The fracture strength kcr is derived varies in a U-shaped pattern as B increased, and the superior crack angle Bm is between 36.2 and 36.6 and is influenced by the properties of the rock and the crack surface. Low-strength, large-scale tensile cracks form during the crack initiation in the cracked sandstone, corresponding to the start of the AE energy, the first decrease in the b-value, and a low r-value. When macroscopic surface cracks form in the cracked sandstone, high-strength, large-scale shear cracks form, resulting in a rapid increase in the AE energy, a second decrease in the b-value and an abrupt increase in the r-value. This research has significant theoretical implications for rock failure mechanisms and establishment of damage indicators in underground engineering.

Key Words
acoustic emission; fracture mechanics; meso-crack evolution; pre-fabricated cracked sandstone; uniaxial compression

Address
Bing Sun, Haowei Yang and Junwei Fan: School of Civil Engineering, University of South China, Hengyang, Hunan 421001, PR China
Sheng Zeng: School of Resources Environment and Safety Engineering, University of South China, Hengyang, Hunan 421001, PR China
Yu Yin: School of Resources Environment and Safety Engineering, University of South China, Hengyang, Hunan 421001, PR China;
Sinosteel Maanshan General Institute of Mining Research Co., Ltd., Maanshan, Anhui 243000, PR China

Abstract
Soil properties make it attractive as a building material due to its mechanical strength, aesthetically appearance, plasticity, and low cost. However, it is frequently necessary to improve and stabilize the soil mechanical properties with binders. Soil-cement is applied for purposes ranging from housing to dams, roads and foundations. Unconfined compression strength (UCS) and split tensile strength (CD) are essential mechanical parameters for ascertaining the aptitude of soil-cement for a given application. However, quantifying these parameters requires specimen preparation, testing, and several weeks. Methodologies that allowed accurate estimation of mechanical parameters in shorter time would represent an important advance in order to ensure shorter deliverable timeline and reduce the amount of laboratory work. In this work, an extensive campaign of UCS and CD tests was carried out in a sandy soil from the Leiria region (Portugal). Then, using the machine learning tool Neural Pattern Recognition of the MATLAB software, a prediction of these two parameters based on six input parameters was made. The results, especially those obtained with resource to a Bayesian regularization-backpropagation algorithm, are frankly positive, with a forecast success percentage over 90% and very low root mean square error (RMSE).

Key Words
artificial neural networks; compression; flexural; mechanical properties; soil-cement

Address
Luís Pereira, Luís Godinho and Fernando G. Branco:University of Coimbra, ISISE, ARISE, Department of Civil Engineering, Coimbra, Portugal

Abstract
The volume changes associated with moisture or suction variation in expansive soils are of geotechnical and geoenvironmental design concern. These changes can impact the performance of infrastructure projects and lightweight structures. Assessment of unsaturated function for these materials leads to better interpretation and understanding, as well as providing accurate and economic design. In this study, expansive soils from different regions of Saudi Arabia were studied for their basic properties including gradation, plasticity and shrinkage, swelling, and consolidation characteristics. The unsaturated soil functions of saturated water content, air-entry values, and residual states were determined by conducting the tests for the entire soil water characteristic curves (SWCC) using different techniques. An attempt has been made to provide a prediction model for unsaturated properties based on the basic properties of these soils. Once the profile of SWCC has been predicted the time and cost for many tests can be saved. These predictions can be utilized in practice for the application of unsaturated soil mechanics on geotechnical and geoenvironmental projects.

Key Words
expansive soils; index properties; prediction model; soil-water characteristic curve; unsaturated soil properties

Address
Ahmed M. Al-Mahbashi, Muawia Dafalla and Mosleh Al-Shamrani: Bugshan Research Chair in Expansive Soils, Dept. of Civil Engineering, College of Engineering,
King Saud Univ., Riyadh 11421, Saudi Arabia

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