Article
Construction & Building Technology
Yali Xu, Panpan Guo, Yixian Wang, Cheng-Wei Zhu, Kang Cheng, Gang Lei
Summary: The research has developed a constitutive model considering the structural effect of loess, with the disturbed function evolving in an exponential form to capture the soil's behavior effectively.
ADVANCES IN CIVIL ENGINEERING
(2021)
Article
Chemistry, Multidisciplinary
Siyuan Shu, Zhishu Yao, Yongjie Xu, Chen Wang, Kun Hu
Summary: This study examined the mechanical properties of red sandstone under different confining pressures and freezing temperatures. The results showed that the stress-strain curves of the rock exhibited four stages and the freezing temperature had an effect on the elastic modulus and peak strength of the rock.
APPLIED SCIENCES-BASEL
(2023)
Article
Geochemistry & Geophysics
Xiuyuan Yang, Zhenlong Ge, Qiang Sun, Weiqiang Zhang
Summary: The brittleness of sandstone increases with the increase in the strain rate, and low temperature and high strain rate conditions are beneficial to the enhancement of sandstone brittleness. On the other hand, high temperature and high strain rate conditions lead to a decrease in sandstone brittleness.
Article
Computer Science, Interdisciplinary Applications
Jakhongirbek Ganiev, Masaki Nakano, Takayuki Sakai
Summary: Reinforcing soils with fibers can increase strength and stability of geo-structures. The study used a constitutive equation to simulate the experimental results and found that an increase in fiber content led to a decrease in initial stiffness and an increase in initial volumetric compression in the reinforced sand, attributed to the lower initial anisotropy caused by fiber inclusions.
COMPUTERS AND GEOTECHNICS
(2022)
Article
Geochemistry & Geophysics
Jessica McBeck, Benoit Cordonnier, Yehuda Ben-Zion, Francois Renard
Summary: The spatial organization of deformation can provide important information about the timing of catastrophic failure in the brittle regime. Recent analyses show that deformation experiences temporary phases of delocalization superposed on an overall trend of localization. X-ray tomography experiments reveal that larger confining pressure promotes more dilation and greater localization of high strain events, while greater amounts of preexisting damage promote delocalization. Importantly, dilative strain may provide more reliable information about the timing of catastrophic failure than shear strain.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2023)
Article
Engineering, Geological
Xin Liang, Shibin Tang, Chun'an Tang, Lihua Hu, Feng Chen
Summary: Water content and distribution significantly affect the mechanical behavior of sandstone, including strength, deformation, and failure patterns. Nonuniform water distribution promotes tensile crack generation, while increasing confining pressure promotes shear crack development. Different water states result in variations in strength and deformation of the sandstone samples, and long-term saturation increases strain-softening.
ROCK MECHANICS AND ROCK ENGINEERING
(2023)
Article
Environmental Sciences
Jessica McBeck, Francois Renard
Summary: This study utilizes machine learning to investigate the relationship between two-dimensional and three-dimensional measurements of fracture networks, by analyzing data from X-ray synchrotron triaxial compression experiments. The models developed provide accurate predictions for the porosity and volume of fractures, but have lower accuracy in predicting tortuosity.
WATER RESOURCES RESEARCH
(2022)
Article
Engineering, Geological
Xiangsheng Chen, Yinping Li, Lihong Tong, Daxin Geng, Zhikai Dong, Peiliang Yang
Summary: Experimental results suggest that the deformation and strength of rocks are heavily influenced by the damage suffered during loading. Traditional constitutive models fail to accurately describe the non-linear deformation behaviors of rocks. To address this limitation, a new elastoplastic damage constitutive model is proposed, taking into account the competition between damage and strain hardening or softening during rock compression. The model is validated through finite element programming and triaxial compression tests. Comparison with experimental data shows that the model effectively captures the stress-strain curves and damage-strain curves of rocks, particularly the phenomenon of softening, hardening, and residual strength. Parametric analysis reveals the impact of confining pressure, scale parameter, and shape parameter on rock damage. The results demonstrate that rock properties significantly affect strength and deformation, which are closely tied to stress-induced damage and strain characteristics.
ROCK MECHANICS AND ROCK ENGINEERING
(2023)
Article
Energy & Fuels
Quanqi Zhu, Diyuan Li, Wenjian Wang
Summary: Permeability, a fundamental index related to rock damage, was studied through dynamic triaxial compression tests on sandstone under various conditions. Results showed that peak stress, strain, plasticity, damage, and permeability increase with higher incident energy. Only peak stress increases with higher confining pressure.
GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES
(2021)
Article
Engineering, Environmental
Shuai Liu, Gengshe Yang, Xihao Dong, Yanjun Shen, Hui Liu
Summary: The energy characteristics and damage laws of frozen sandstone during mine freezing are studied through triaxial compression and synchronous acoustic emission tests. The results show that the performance of frozen sandstone under peak stress is influenced by negative temperature and confining pressure, and the damage variables can be defined using AECE.
JOURNAL OF COLD REGIONS ENGINEERING
(2022)
Article
Engineering, Geological
Xiao Ma, Wenbao Dong, Dawei Hu, Hui Zhou
Summary: In this study, true triaxial compression tests were conducted on granite specimens at different temperatures and under different intermediate principal stresses. The influences of temperature on crack initiation stress, crack damage stress, and peak strength of granite were analyzed. The failure characteristics of granite specimens under high temperature and true triaxial stress were investigated, and a Mogi-Coulomb failure criterion with temperature-dependent coefficients was proposed. This study provides new insights into the mechanical properties of rock under high temperature and true triaxial compression.
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES
(2023)
Article
Energy & Fuels
Jing Wu, Yani Lu, Kaibin Wang, Yang Cai, Cong Xiao
Summary: Triaxial compression tests were conducted on sandstone specimens in cold regions to study the combined effects of freeze-thaw cycles and chemical corrosion. The increase in freeze-thaw cycles led to the deterioration of mechanical properties, especially under the action of strong acid solution. Confining pressure also played an important role in the rock mechanical properties.
GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES
(2023)
Article
Engineering, Mechanical
Zhi-Jin Dong, Sheng-Qi Yang, Bo-Wen Sun, Wen-Ling Tian, Yan-Hua Huang
Summary: In this study, a three-dimensional grain-based model was used to simulate the triaxial compression of fissured granite specimens under different confining pressures. The results showed that fissured granite has smaller mechanical properties compared to intact granite, and the mechanical properties increase with the increase of fracture angle. As axial stress increases, cracks emerge from the crack apices and propagate towards the ends of the specimen. The main cracks occur at the interfacial locations where large relative displacements occur between the particles. The distribution of cracks is influenced by both the confining pressure and the fissure angle.
THEORETICAL AND APPLIED FRACTURE MECHANICS
(2022)
Article
Energy & Fuels
Lulin Kong, Jie Wu, Haige Wang, Xiangchao Shi, Leiyu Gao, Xiao Zhuo, Shuai Chen
Summary: Accurate evaluation of the mechanical properties of rocks is crucial for large-scale projects. Experimental studies on sandstone and granite samples of 10-25 mm show that the elastic modulus of both rocks decreases significantly with increasing size. The uniaxial compressive strength, however, has different trends with sandstone increasing by approximately 12% and granite decreasing by 35% as the size increases.
FRONTIERS IN ENERGY RESEARCH
(2023)
Article
Mechanics
Qiang Liu, Yanlin Zhao, Jian Liao, Tao Tan, Xiaguang Wang, Yang Li, Zhe Tan
Summary: This study investigates the mechanical properties of saturated sandstone through hydro-mechanical coupling experiments. A damage constitutive model is established and verified. The results show that the strength and elasticity modulus of sandstone are positively correlated with confining pressure and negatively correlated with pore pressure. The model parameters have non-linear relationships with confining pressure. Additionally, pore pressure and confining pressure significantly affect damage variables.
Article
Engineering, Civil
Tara Radvand, Vahab Toufigh
Summary: This study investigates the impact of Guar gum as an environmentally friendly additive on the mechanical properties of concrete. The results indicate that replacing up to 0.8% of cement with Guar gum can enhance the compressive and tensile strengths of concrete, while an increase in water to cement ratio has a negative effect on the mechanical properties. Additionally, the scanning electron microscope analysis reveals changes in the morphological characteristics of concrete due to the formation of Guar gum strings.
EUROPEAN JOURNAL OF ENVIRONMENTAL AND CIVIL ENGINEERING
(2022)
Article
Construction & Building Technology
Vahab Toufigh, Alireza Jafari
Summary: Geopolymer concrete is an eco-friendly alternative to traditional concrete, but the lack of standard mix design is a major obstacle to its use in the construction industry. This study proposes a comprehensive model for predicting the compressive strength of fly ash-based geopolymer concrete, highlighting the importance of chemical compositions on the strength. The model can estimate the compressive strength of low calcium FAGC with acceptable accuracy, saving time and money in practical applications.
CONSTRUCTION AND BUILDING MATERIALS
(2021)
Article
Construction & Building Technology
Morteza Azizmohammadi, Vahab Toufigh, Mohsen Ghaemian
Summary: The study investigates the mechanical characteristics and permeability of the interface layer of RCC by considering key parameters such as water-to-cementitious materials ratio, water-to-cementitious ratio of bedding mortar, and time interval between layers. Various tests and analysis were conducted to determine the impact of these parameters on the strength and permeability properties of RCC, leading to the achievement of optimal mix design. The joint condition of the RCC layer is affected by the age of the joint and bedding layer, and increasing the cement content of bedding mortar can improve shear and tensile strengths while reducing permeability.
JOURNAL OF MATERIALS IN CIVIL ENGINEERING
(2021)
Article
Engineering, Environmental
Vahab Toufigh, Mohammad Hossein Karamian, Saeid Ghasemalizadeh
Summary: This study focused on stabilizing rammed earth material using geopolymerization technique with fly ash and granulated blast furnace slag. It was found that increasing the GBFS to binder ratio and alkali activator molarity improved properties like modulus of elasticity, compressive strength, and energy absorption, while higher clay content had a negative impact on compressive strength and modulus of elasticity but increased energy absorption. The numerical model accurately predicted the behavior of stabilized rammed earth material and independent data sets.
BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT
(2021)
Article
Construction & Building Technology
Ghasem Pachideh, Vahab Toufigh
Summary: This article studied the mechanical properties of self-compacting lightweight concretes containing different fibers at high temperatures, finding that steel fibers and metal springs improve compressive strength, while polypropylene fibers enhance tensile strength. However, the flexural strength of all specimens was significantly reduced at 700 degrees C.
STRUCTURAL CONCRETE
(2022)
Article
Construction & Building Technology
Vahab Toufigh, Ghasem Pachideh
Summary: This study evaluated the effects of various pozzolans as partial replacements for cement in concrete under elevated temperatures. The specimens containing zeolite and granulated blast furnace slag showed better compressive strength and performance against heat. Additionally, XRD tests revealed that specimens with silica fume and GBFS had less grain size reduction with increasing temperature.
STRUCTURAL CONCRETE
(2022)
Article
Construction & Building Technology
Iman Ranjbar, Vahab Toufigh, Mehrdad Boroushaki
Summary: This article presents an efficient deep learning technique using a combination of convolutional neural network (CNN) and genetic algorithm (GA) for predicting the compressive strength of high-performance concrete (HPC). Six different CNN architectures were considered and the optimal number of filters in each convolutional layer was determined using GA. The results show that all proposed CNN models are capable of accurately predicting the compressive strength of HPC.
STRUCTURAL CONCRETE
(2022)
Article
Engineering, Geological
Vahab Toufigh, Saeid Ghasemalizadeh, MohammadHossein Karamian
Summary: This study investigates the utilization of alkali-activated granular blast furnace slag (GBFS) and fly ash (FA) for stabilizing rammed earth materials and assessing their mechanical and durability properties. The results reveal the influence of clay content, binder composition, and NaOH molarity on the compressive strength and acid resistance of the materials. An increase in NaOH molarity and GBFS content in the binder enhances the compressive strength, while the clay content negatively affects it. The optimal binder composition can be determined using numerical optimization methods to maximize compressive strength and minimize strength reduction after acid exposure.
INTERNATIONAL JOURNAL OF GEOMECHANICS
(2022)
Article
Forestry
Soheil Palizi, Vahab Toufigh
Summary: This study proposes three empirical models using gene expression programming (GEP) to predict the bond strength between timber and fiber-reinforced polymer (FRP) under various environmental conditions. The models consider the strength reduction in different environments and are trained and validated using data from previous studies.
EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS
(2022)
Article
Green & Sustainable Science & Technology
Mohammad Rahmati, Vahab Toufigh
Summary: Studying the mechanical performance of concrete after exposure to high temperatures is crucial for the damage assessment and fire safety applications in buildings. However, accurately predicting the compressive strength of geopolymer concrete (GPC) at high temperatures is a challenging task. In this study, artificial neural network (ANN) and support vector regression (SVR) models were developed and compared to predict the compressive strength of GPC at temperatures ranging from 100°C to 1000°C. Results show that SVR outperformed ANN, and sodium silicate and curing time were identified as the most influential factors on the residual compressive strength of GPC at high temperatures. The findings demonstrate that machine learning approaches can effectively enhance the monitoring of GPC after exposure to high temperatures.
JOURNAL OF CLEANER PRODUCTION
(2022)
Article
Engineering, Multidisciplinary
Moein Ramezanpour Kami, Vahab Toufigh
Summary: In this paper, the bond between carbon-fiber reinforced polymer (CFRP) and timber was investigated using linear and nonlinear ultrasonic methods. Artificial neural network models were developed to quantitatively predict important bond characteristics based on ultrasonic response signals and physical parameters.
STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL
(2023)
Article
Construction & Building Technology
Soheil Palizi, Vahab Toufigh
Summary: Recent studies have shown that alkali-activated slag-based concrete, when combined with activators, can be a potential construction material. This paper focuses on investigating the effect of elevated temperatures on the properties of this cementless concrete. Various tests were conducted, including nondestructive evaluations such as visual inspections and ultrasonic pulse velocity measurements, as well as destructive tests to determine post-fire mechanical properties. The results showed that exposing slag-based concrete samples to temperatures below 500°C can enhance their compressive strength, with a reduction in strength of 22% to 59% at 700°C, which is an improvement compared to normal concrete. Regression-based models were also proposed to predict destructive measurements based on nondestructive evaluations, yielding accurate predictions.
CONSTRUCTION AND BUILDING MATERIALS
(2023)
Article
Engineering, Multidisciplinary
Vahab Toufigh, Iman Ranjbar
Summary: This study proposes an unsupervised anomaly detection-based framework using ultrasonic response signals for distributed damage detection in concrete. A deep fully connected auto-encoder is utilized to reconstruct the ultrasonic response signals, showing high prediction error for damaged specimens. Time-domain and frequency-domain features are defined to measure the reconstruction error of the auto-encoder. The Isolation Forest algorithm is implemented for anomaly detection. The framework achieves a high prediction accuracy for damaged and intact stages.
STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL
(2023)
Article
Acoustics
Mohammad Rahmati, Vahab Toufigh, Kaveh Keyvan
Summary: This study proposes the evaluation of crack healing in geopolymer concrete (GPC) using different linear and nonlinear ultrasonic techniques. The results indicate that the phase-space analysis of ultrasound can successfully represent the healing progress inside the GPC beam, and the fractal dimension can be used as a healing index.
Article
Acoustics
Pooria Khademi, Vahab Toufigh
Summary: In this study, the bond strength of concrete layers was estimated based on vital ultrasound parameters using convolutional neural network (CNN) and multilayer perceptron (MLP). The results showed that attenuation was the most sensitive parameter to bond strength variation.
