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23 pages, 9902 KiB

Open AccessArticle

A New Method for Predicting Dynamic Pile Head Stiffness Considering Pile–Soil Relative Stiffness Under Long-Term Cyclic Loading Conditions

by Jie Chen, Jiaqing Shu, Shuang Xi, Xiaoqing Gu, Mingxing Zhu and Xiaojuan Li

Buildings 2024, 14(11), 3483; https://doi.org/10.3390/buildings14113483 - 31 Oct 2024

Abstract

Under long-term horizontal cyclic loading, the evolution characteristics of the loading and unloading stiffness of piles are an important representation of pile–soil interaction. However, research in this area is limited, particularly regarding the impact of factors like pile–soil relative stiffness. In this study, [...] Read more.

Under long-term horizontal cyclic loading, the evolution characteristics of the loading and unloading stiffness of piles are an important representation of pile–soil interaction. However, research in this area is limited, particularly regarding the impact of factors like pile–soil relative stiffness. In this study, laboratory tests with a long-term horizontal cyclic loading strategy were conducted to study various factors, including different cyclic amplitude ratios (ζ_b), cyclic load ratios (ζ_c), and pile–soil relative stiffness (T/L) in sandy soil, on dynamic pile head stiffness. The results show that the normalized cumulative displacement increases with the number of cycles and the ratio of T/L but tends to decrease as ζ_c increases. As ζ_b increases, the normalized cyclic loading stiffness also rises, while it has little effect on the normalized cyclic unloading stiffness. On the other hand, as ζ_c or T/L increases, the cyclic loading stiffness increases while the unloading stiffness decreases. Based on these observations, prediction formulas for normalized cumulative displacement and cyclic loading and unloading stiffness were established and confirmed with test results. The findings of this study provide methodological references for establishing models of pile–soil interaction under cyclic loading and for predicting loading and unloading stiffness under different influencing factors. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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21 pages, 15347 KiB

Open AccessArticle

Petrological Characteristics and Physico-Mechanical Properties of Dokhan Volcanics for Decorative Stones and Building Material Applications

by El Saeed R. Lasheen, Mabrouk Sami, Ahmed A. Hegazy, Hasan Arman, Ioan V. Sanislav, Mohamed S. Ahmed and Mohammed A. Rashwan

Buildings 2024, 14(11), 3418; https://doi.org/10.3390/buildings14113418 - 27 Oct 2024

Viewed by 420

Abstract

Wide varieties of igneous rocks are extensively utilized as stones for decoration purposes and as a potential source for building. With the use of petrological (mineralogical and chemical) and physico-mechanical analyses, the current work accurately mapped the Dokhan Volcanics (DV) and utilized them [...] Read more.

Wide varieties of igneous rocks are extensively utilized as stones for decoration purposes and as a potential source for building. With the use of petrological (mineralogical and chemical) and physico-mechanical analyses, the current work accurately mapped the Dokhan Volcanics (DV) and utilized them as decorative stones and their prospective in building materials using Frattini’s test. Field observations indicate that metavolcanics, DV, and monzogranites are the principal rock units exposed in the studied area. The DV rocks are characterized by a dense series of stratified, rhyolitic to andesitic lava interspersed with a few pyroclastics. Andesite, andesite porphyry, dacite, and rhyolite are the primary representatives of the selected DV. The lack of infrequent appearance of mafic units in the current volcanic eruptions indicates that the primary magma is not mantle-derived. This is supported by their Mg# (17.86–33.57). Additionally, the examined DV rocks have Y/Nb ratios above 1.2, suggesting a crustal source. The role of fractionation is interpreted by their variation from andesite passing through dacite to rhyolite, which is indicated by gradual negative distribution groups between silica and TiO₂, Fe₂O₃, CaO, MgO, Co, and Cu from andesite to rhyolitic lava. Additionally, a wide range of widely used DV rocks like Y/Nb, Rb/Zr, and Ba/Nb point to crustal contamination in the rhyolitic rocks. The partial melting of the lower crust can produce andesitic magma, which ascend to higher crustal levels and form lava of calc-alkaline. A portion of this lava may split, settle at shallow crustal depths, and undergo differentiation to create the DV rocks. Based on the results of physico-mechanical properties, the studied samples met the requirements for natural stone to be used as decorative stones, whether as interior or exterior installations. The pozzolanic assessment of the studied rocks revealed their usability as supplementary cementitious materials in the building sector. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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18 pages, 11238 KiB

Open AccessArticle

Study on the Damage Characteristics of Red Sandstone Foundation Under Rainfall Infiltration in the Red-Bed Area of the Sichuan Basin—Taking Zhongjiang County as an Example

by Cong Yu, Wenwu Zhong, Xin Zhang, Tao Li and Zheng Fei

Buildings 2024, 14(11), 3406; https://doi.org/10.3390/buildings14113406 - 26 Oct 2024

Viewed by 339

Abstract

The Sichuan Basin in China is one of the most concentrated areas of red beds in China. In the red-bed area, abundant rainfall can easily cause natural disasters, such as landslides, mudslides, collapses, and subsidence. This has had a great impact on the [...] Read more.

The Sichuan Basin in China is one of the most concentrated areas of red beds in China. In the red-bed area, abundant rainfall can easily cause natural disasters, such as landslides, mudslides, collapses, and subsidence. This has had a great impact on the safety of people and property and sustainable modernization in the area. Zhongjiang County of Sichuan Province is a typical red-bed area, and red sandstone is one of the main foundation rocks in this area. Under the influence of rainfall, the strength of red sandstone foundation easily decays, causing disasters such as house collapse. Therefore, in order to explore the influence of rainfall on the mechanical properties of red sandstone, this paper takes the red sandstone in Zhongjiang County, Sichuan Province, China, as the research object and conducts acoustic-emission uniaxial compression experiments under different water contents. The strength characteristics, instability precursor characteristics, fracture types, and damage characteristics of red sandstone in different water-bearing states are obtained. The abovementioned results provide a reference for the Zhongjiang County Government to consider the impact of rainfall on the red sandstone foundation during modernization and emergency management. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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22 pages, 8871 KiB

Open AccessArticle

Performance of Monotonic Pile Penetration in Sand: Model Test and DEM Simulation

by Jianxue Feng, Ruiqi Luo, Xiaoyu Dong, Xiaoyong Zhang and Quan Shen

Buildings 2024, 14(10), 3327; https://doi.org/10.3390/buildings14103327 - 21 Oct 2024

Viewed by 411

Abstract

By integrating laboratory tests and three-dimensional discrete element methods, this research extensively explores the macroscopic and microscopic mechanisms of static pile penetration in standard sand. Initially, the mesoscopic parameters of standard sand were established via flexible triaxial compression tests, and a three-dimensional discrete [...] Read more.

By integrating laboratory tests and three-dimensional discrete element methods, this research extensively explores the macroscopic and microscopic mechanisms of static pile penetration in standard sand. Initially, the mesoscopic parameters of standard sand were established via flexible triaxial compression tests, and a three-dimensional discrete element model was created using the particle size magnification technique. The study results confirm the rationality of parameter selection and numerical modeling by comparing penetration resistance and displacement obtained from laboratory model tests and discrete element simulations. Initially, penetration resistance swiftly increases, then stabilizes progressively with increasing depth. The lateral friction resistance grows with penetration depth, especially peaking near the cone tip. Moreover, horizontal stress quickly rises during pile penetration, mainly caused by the pile foundation compressing the adjacent soil particles. Displacement of the foundation particles is primarily focused around the pile side and cone tip, affecting an area roughly twice the pile diameter. Soil particle displacement exhibits a pronounced vertical downward movement, primarily driven by lateral friction. The distribution of force chains among foundation particles indicates that the primary stressed areas are at the pile ends, highlighting stress concentration features. This research offers significant insights into the mechanical behaviors and soil responses during pile foundation penetration. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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26 pages, 44411 KiB

Open AccessArticle

Simulation of Coherent Excavator Operations in Earthmoving Tasks Based on Reinforcement Learning

by Yongyue Liu, Yaowu Wang and Zhenzong Zhou

Buildings 2024, 14(10), 3270; https://doi.org/10.3390/buildings14103270 - 15 Oct 2024

Viewed by 764

Abstract

Earthwork operations are critical to construction projects, with their safety and efficiency influenced by factors such as operator skill and working hours. Pre-construction simulation of these operations is essential for optimizing outcomes, providing key training for operators and improving safety awareness and operational [...] Read more.

Earthwork operations are critical to construction projects, with their safety and efficiency influenced by factors such as operator skill and working hours. Pre-construction simulation of these operations is essential for optimizing outcomes, providing key training for operators and improving safety awareness and operational efficiency. This study introduces a hierarchical cumulative reward mechanism that decomposes complex operational behaviors into simple, fundamental actions. The mechanism prioritizes reward function design elements, including order, size, and form, thus simplifying excavator operation simulation using reinforcement learning (RL) and enhancing policy network reusability. A 3D model of a hydraulic excavator was constructed with six degrees of freedom—comprising the boom, arm, bucket, base, and left/right tracks. The Proximal Policy Optimization (PPO) algorithm was applied to train four basic behaviors: scraping, digging, throwing, and turning back. Motion simulation was successfully achieved using diggable terrain resources. Results demonstrate that the simulated excavator, powered by RL neural networks, can perform coordinated actions and maintain smooth operational performance. This research offers practical implications by rapidly illustrating the full operational process before construction, delivering immersive movies, and enhancing worker safety and operational efficiency. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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16 pages, 4967 KiB

Open AccessArticle

Thermo-Mechanical Coupling Load Transfer Method of Energy Pile Based on Hyperbolic Tangent Model

by Ming Sun, Siyang Wu, Tong Wang, Yunze Xie, Meijuan Xu, Yan Dong, Dongxiao Zhao and Wenbing Wu

Buildings 2024, 14(10), 3190; https://doi.org/10.3390/buildings14103190 - 7 Oct 2024

Viewed by 459

Abstract

By employing the hyperbolic tangent model of load transfer (LT), this paper establishes the thermo-mechanical (TM) coupling load transfer analysis approach for an energy pile (EP). By incorporating the control condition of the unbalance force at the null point, the method for determining [...] Read more.

By employing the hyperbolic tangent model of load transfer (LT), this paper establishes the thermo-mechanical (TM) coupling load transfer analysis approach for an energy pile (EP). By incorporating the control condition of the unbalance force at the null point, the method for determining the null point considering the temperature effect is enhanced. The viability of the presented method is validated through the measured outcomes from model experiments of energy piles. A parametric investigation is conducted to explore the impact of the soil shear strength parameters, upper load, temperature variation, head stiffness, and radial expansion on the axial force, strain, and displacement of the energy pile under thermo-mechanical coupling. The results suggest that the locations of the null point and the maximum axial force are dependent on the constraint boundary conditions of the pile side and the two ends. When the stiffness of the pile top increases, axial stress and displacement increase, while strain decreases. An increase in the drained friction angle leads to an increase in axial stress under thermal-load coupling, but strain and displacement decline. The radial expansion has a negligible influence on the thermo-mechanical interaction between the pile and the soil. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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18 pages, 5989 KiB

Open AccessArticle

Laboratory-Scale Limestone Rock Linear Cutting Tests with a Conical Pick: Predicting Optimal Cutting Conditions from Tool Forces

by Han-eol Kim, Sung-pil Hwang, Wan-kyu Yoo, Woo-seok Kim, Chang-yong Kim and Han-kyu Yoo

Buildings 2024, 14(9), 2772; https://doi.org/10.3390/buildings14092772 - 3 Sep 2024

Viewed by 588

Abstract

This study introduces a simplified method for predicting the optimal cutting conditions to maximize excavation efficiency based on tool forces. A laboratory-scale linear rock-cutting test was conducted using a conical pick on Finike limestone. The tool forces and their ratios were analyzed in [...] Read more.

This study introduces a simplified method for predicting the optimal cutting conditions to maximize excavation efficiency based on tool forces. A laboratory-scale linear rock-cutting test was conducted using a conical pick on Finike limestone. The tool forces and their ratios were analyzed in relation to cutting parameters such as penetration depth and spacing. While the cutting force (FC) and normal force (FN) increased with the penetration depth and spacing, this relationship could not predict the optimal cutting conditions. The ratio of the mean normal force to the mean cutting force (FN_m/FC_m) increased with the penetration depth and the ratio of spacing to penetration depth (s/d). However, even while including this relationship, predicting optimal cutting conditions remained challenging. The ratio of the peak cutting force to the mean cutting force (FC_p/FC_m) reached a maximum value at a specific s/d, which is similar to the relationship between the specific energy (SE) and s/d. The optimal s/d obtained through the SE methodology was found to be between 3 and 5, and FC_p/FC_m reached a maximum at s/d. The error between the optimal s/d and the s/d in which FC_p/FC_m was maximized was less than 5%. Therefore, it was confirmed that the optimal cutting conditions could be predicted through the relationship between FC_p/FC_m and s/d. Additionally, by using the results from previous studies, the optimal cutting conditions obtained from the SE methodology and the proposed methodology were found to agree within a margin of error of 20%. The proposed methodology can be beneficial for the design of cutter heads and the operation of excavation machines. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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19 pages, 27696 KiB

Open AccessArticle

A Real-Time Inverted Velocity Model for Fault Detection in Deep-Buried Hard Rock Tunnels Based on a Microseismic Monitoring System

by Houlin Xie, Bingrui Chen, Qian Liu, Yaxun Xiao, Liu Liu, Xinhao Zhu and Pengxiang Li

Buildings 2024, 14(9), 2663; https://doi.org/10.3390/buildings14092663 - 27 Aug 2024

Viewed by 792

Abstract

Microseismic monitoring is an effective and widely used technology for dynamic fault disaster early warning and prevention in deep-buried hard rock tunnels. However, the insufficient understanding of the distribution of native faults poses a major challenge to yielding precise early warnings of disasters [...] Read more.

Microseismic monitoring is an effective and widely used technology for dynamic fault disaster early warning and prevention in deep-buried hard rock tunnels. However, the insufficient understanding of the distribution of native faults poses a major challenge to yielding precise early warnings of disasters using an MS (Microseismic Monitoring System). Velocity field inversion is a reliable means to reflect fault information, and there is an urgent need to establish a real-time velocity field inversion method during tunnel excavation. In this paper, a method based on an MS is proposed to achieve the inversion of the velocity field in the monitoring area using microseismic event and excavation blasting data. The velocity field inversion method integrates the reflected wave ray-tracing method based on PSO (Particle Swarm Optimization) theory and FWI (Full-Waveform Inversion) theory. The accuracy of the proposed velocity inversion method was verified by various classic numerical simulation cases. In numerical simulations, the robustness of our method is evident in its ability to identify anomalous structural surfaces and velocity discontinuities ahead of the tunnel face. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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19 pages, 4010 KiB

Open AccessArticle

High-Speed Train-Induced Vibration of Bridge–Soft Soil Systems: Observation and MTF-Based ANSYS Simulation

by Kangming Zhong, Xiaojun Li and Zhenghua Zhou

Buildings 2024, 14(8), 2575; https://doi.org/10.3390/buildings14082575 - 21 Aug 2024

Viewed by 532

Abstract

In this paper, a multi-transmitting formula (MTF) was integrated into ANSYS software through secondary development, enabling dynamic finite element simulation of wave propagation in infinite domains. The numerical reliability and accuracy of the MTF were verified through a plane wave problem involving a [...] Read more.

In this paper, a multi-transmitting formula (MTF) was integrated into ANSYS software through secondary development, enabling dynamic finite element simulation of wave propagation in infinite domains. The numerical reliability and accuracy of the MTF were verified through a plane wave problem involving a homogeneous elastic half-space, as well as 3D scattering and source problems in a three-layered soil site. Additionally, a comparative analysis of various artificial boundaries was conducted to highlight the advantages of the MTF. Field observations of environmental vibrations caused by high-speed railway operations revealed localized amplification of vibrations along the depth direction at the Kunshan segment of the Beijing–Shanghai high-speed railway. Based on these observations, a series of numerical analyses were conducted using the customized ANSYS integrated with the MTF to investigate the underlying causes and mechanisms of this phenomenon, as well as the spatial variation characteristics of foundation vibrations induced by bridge vibrations during high-speed train operations. This study reveals the mechanism by which the combined effect of bridge piles and soft soil layers influences the depth variation in peak ground accelerations during site vibrations. It also demonstrates that the presence of bridge piers and pile foundations effectively reduces vibration intensity in the vicinity of the railway, playing a crucial role in mitigating vibrations induced by high-speed train operations. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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17 pages, 30079 KiB

Open AccessArticle

An Improved Numerical Simulation Method for Rockbolt Fracture and Its Application in Deep Extra-Thick Coal Seam Roadways

by Wenhao Zhang, Shuang Zhao, Bin Zhang, Weimin Gao, Qingwen Zhu, Tingchun Li and Binxu Wang

Buildings 2024, 14(8), 2373; https://doi.org/10.3390/buildings14082373 - 1 Aug 2024

Viewed by 593

Abstract

An improved method for rockbolt fracture is proposed in this paper to determine the exact fracture position of rockbolts simulated using cable structural elements (cableSELs) in FLAC3D. This method employs the total elongation of the free segment of the rockbolt as the fracture [...] Read more.

An improved method for rockbolt fracture is proposed in this paper to determine the exact fracture position of rockbolts simulated using cable structural elements (cableSELs) in FLAC3D. This method employs the total elongation of the free segment of the rockbolt as the fracture criterion. The maximum deformation position is identified by comparing the length of each cableSEL in the free segment, leading to the fracture. The simulation results validated through a rockbolt tensile test closely match actual conditions. The proposed method was used to optimize the roadway support in deep extra-thick coal seams (DECSs). Optimized parameters were obtained by simulating and analyzing different lengths and spacings of rockbolts and anchor cables. The field implementation conducted shows that the optimized deformation and support strength of the roadway meet safety needs. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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16 pages, 6591 KiB

Open AccessArticle

Effect of Drying and Wetting Cycles on the Surface Cracking and Hydro-Mechanical Behavior of Expansive Clays

by Abdullah A. Shaker, Muawia Dafalla, Ahmed M. Al-Mahbashi and Mosleh A. Al-Shamrani

Buildings 2024, 14(7), 1908; https://doi.org/10.3390/buildings14071908 - 22 Jun 2024

Cited by 2 | Viewed by 788

Abstract

Expansive clays present serious issues in a variety of engineering applications, including roadways, light buildings, and infrastructure, because of their notable volume changes with varying moisture content. Tough weather conditions can lead to drying and shrinking, which alters expansive clays’ hydro-mechanical properties and [...] Read more.

Expansive clays present serious issues in a variety of engineering applications, including roadways, light buildings, and infrastructure, because of their notable volume changes with varying moisture content. Tough weather conditions can lead to drying and shrinking, which alters expansive clays’ hydro-mechanical properties and results in cracking. The hydro-mechanical behavior of Al-Ghatt expansive clay and the impact of wetting and drying cycles on the formation of surface cracks are addressed in this investigation. For four cycles of wetting and drying and three vertical stress levels, i.e., 50 kPa, 100 kPa, and 200 kPa, were investigated. The sizes and patterns of cracks were observed and classified. A simplified classification based on main track and secondary branch tracks is introduced. The vertical strain measure at each cycle, which showed swell and shrinkage, was plotted. The hydromechanical behavior of the clay, which corresponds to three levels of overburden stress as indicated by its swell potential and hydraulic conductivity was observed. It was found that at low overburden stresses of 50 kPa, the shrinkage is high and drops with increasing the number of cycles. Al-Ghatt clay’s tendency to crack is significantly reduced or eliminated by the 200 kPa overburden pressure. The results of this work can be used to calculate the depth of a foundation and the amount of partial soil replacement that is needed. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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36 pages, 12070 KiB

Open AccessArticle

The Simplified Method of Head Stiffness Considering Semi-Rigid Behaviors of Deep Foundations in OWT Systems

by Wei Li, Xiaojuan Li, Tengfei Wang, Qian Yin and Mingxing Zhu

Buildings 2024, 14(6), 1803; https://doi.org/10.3390/buildings14061803 - 14 Jun 2024

Viewed by 639

Abstract

Simplified methods of static free head stiffness of the semi-rigid foundation under lateral loads were limited to flexible or rigid behavior by the critical length of piles. This would lead to errors when predicting the static or dynamic performance of their upper structures [...] Read more.

Simplified methods of static free head stiffness of the semi-rigid foundation under lateral loads were limited to flexible or rigid behavior by the critical length of piles. This would lead to errors when predicting the static or dynamic performance of their upper structures in OWT Systems. This paper presents a comprehensive analysis of the head static stiffness of the semi-rigid pile without considering the critical length. Firstly, case studies using the energy-based variational method encompassing nearly twenty thousand cases were conducted. These cases involved different types of foundations, including steel pipe piles and concrete caissons, in three types of soil: homogeneous soil, linearly inhomogeneous soil, and heterogeneous soil. Through the analysis of these cases, a series of polynomial equations of three kinds of head static stiffness, containing the relative stiffness of the pile and soil, the slenderness ratio, and Poisson’s ratio, were developed to capture the semi-rigid behavior of the foundations. Furthermore, the lateral deflection, the rotation for concrete caissons in the bridge projects, and several natural frequencies of three cases about the OWT system considering the SSI effect were carried out. the error of high-order frequency of the OWT system reached 13% after considering the semi-rigid effect of the foundation. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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22 pages, 6639 KiB

Open AccessArticle

Experimental Study on the Horizontal Bearing Characteristic of a Strip-Walled Underground Diaphragm Wall

by Guoqing Du, Shuang Xi, Chen Ling, Weian Shi, Xiaojuan Li, Mingxing Zhu and Shouguo Li

Buildings 2024, 14(6), 1637; https://doi.org/10.3390/buildings14061637 - 3 Jun 2024

Viewed by 359

Abstract

Researching and developing a new type of diaphragm wall foundation can solve the probl em that the traditional diaphragm wall structure may not meet the high standards of safety and stability of underground structures in some specific engineering environments. This paper focuses on [...] Read more.

Researching and developing a new type of diaphragm wall foundation can solve the probl em that the traditional diaphragm wall structure may not meet the high standards of safety and stability of underground structures in some specific engineering environments. This paper focuses on the horizontal bearing characteristic of a new form of foundation, a strip-walled underground diaphragm wall, through a series of model tests. In the tests, nine plexiglass models with different section sizes, wall spacings and wall heights, as well as loading strategies (horizontal loads along and against the wall in the model), were conducted. The influence of the above factors on the horizontal bearing performance of the foundation and the soil resistance distribution around the wall was studied. The results show that when the horizontal load applied along the wall is greater than 50 N, the growth rate of total displacement at the top of the wall gradually decreases; when a horizontal load is applied against the wall, with a uniform change in wall height, the optimal wall spacing is 11 cm. When the same displacement occurs, the bearing performance of the model under the former loading strategy is generally 10% higher than that under the later loading strategy. In addition, the depth where the maximum bending moment along the wall occurred gradually moves downward with the increase in horizontal load, and the increase in wall spacing and wall height has a positive effect on the horizontal bearing characteristic. With the application of load, the maximum bending moment of the wall will gradually decrease along the depth. The increase in wall spacing and wall height can improve the overall flexural stiffness and horizontal bearing performance of the foundation. Lastly, the group wall effect coefficient, β, is put forward, and a simplified formula for calculating the horizontal bearing capacity of a strip wall foundation is proposed. In the formula, β is negatively correlated with the buried depth of the wall and positively correlated with the distance between the walls, and its coefficient is greater than 1. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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20 pages, 9165 KiB

Open AccessArticle

Analysis of the Effect of Loading Rate on Mechanical Properties of Fissured Rock Materials and Acoustic Emission Characteristic Parameters

by Guokun Liu, Wenxi Wang, Xiaohua Li, Wei Chen, Yu Zhou, Yuanzeng Wang and Sheng Ren

Buildings 2024, 14(6), 1579; https://doi.org/10.3390/buildings14061579 - 30 May 2024

Cited by 1 | Viewed by 564

Abstract

In nature, rock masses often exhibit fissures, and varying external forces lead to different rates of loading on fissured rock masses. By studying the influence of the loading rate on the mechanical properties of fractured rock mass and AE characteristic parameters, it can [...] Read more.

In nature, rock masses often exhibit fissures, and varying external forces lead to different rates of loading on fissured rock masses. By studying the influence of the loading rate on the mechanical properties of fractured rock mass and AE characteristic parameters, it can provide a theoretical basis for the safety and stability prediction of engineering rock mass. To investigate the influence of loading rates on fissured rock masses, this study utilizes surrogate rock specimens resembling actual rock bodies and prefabricates two fissures. By conducting uniaxial compression acoustic emission tests at different loading rates, the study explores changes in their mechanical properties and acoustic emission characteristic parameters. Research findings indicate the following: (1) Prefabricated fissures adversely affect the stability of specimens, resulting in lower strength compared to intact specimens. Under the same fissure inclination angle, peak strength, elastic modulus, and loading rate exhibit a positive correlation. When the fissure inclination angle varies from 0° to 60° under the same loading rate, the peak strength of specimens generally follows a “V”-shaped trend, decreasing initially and then increasing, with the minimum peak strength observed at α = 30°. (2) Prefabricated fissure specimens primarily develop tensile cracks during loading, gradually transitioning to shear cracks, ultimately leading to shear failure. (3) The variation patterns of AE (acoustic emission) characteristic parameters under the influence of loading rate differ: AE event count, AE energy, and cumulative AE energy show a positive correlation with loading rate, while cumulative AE event count gradually decreases with increasing loading rate. (4) AE characteristic parameters exhibit good correlation with the stress–strain curve and can be divided into four stages. The changes in AE characteristic parameters correspond to the changes in the stress–strain curve. With increasing loading rate, AE signals in the first three stages gradually stabilize, focusing more on the fourth stage, namely the post-peak stage, where the specimens typically experience maximum AE signals accompanying final failure. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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25 pages, 6373 KiB

Open AccessArticle

The Shear Effect of Large-Diameter Piles under Different Lateral Loading Levels: The Transfer Matrix Method

by Jing Liu, Mingxing Zhu, Xiaojuan Li, Chen Ling, Tengfei Wang and Xuan Li

Buildings 2024, 14(5), 1448; https://doi.org/10.3390/buildings14051448 - 16 May 2024

Viewed by 826

Abstract

In various analytical models, modeling the behavior of large-diameter monopiles and piles can be challenging due to these foundations with huge body sizes carrying mechanisms of lateral loads to the surrounding soils. In this paper, the transfer matrix method with the Timoshenko beam [...] Read more.

In various analytical models, modeling the behavior of large-diameter monopiles and piles can be challenging due to these foundations with huge body sizes carrying mechanisms of lateral loads to the surrounding soils. In this paper, the transfer matrix method with the Timoshenko beam theory was used to modify the shear rotation of pile sections under different loading stages, including serviceability limit stages and the ultimate loading stage. In this transfer matrix method, a large-diameter pile is considered according to the Timoshenko beam theory, and the recurring variables in the matrix equation are replaced with constants to simplify the calculation steps. Two model test cases were used to verify the accuracy of the method. Then, a series of comparisons between the Timoshenko beam and the Euler–Bernoulli beam theories, with the relative pile–soil stiffness being equal to 0.15, 0.45, and 0.75, was conducted to investigate the differences in pile response after considering the shear deformation. The results show that the effect of shear deformation of large-diameter piles changes with different loading levels. The values of the pile deformation based on the Timoshenko beam theory divided by those of that based on the Euler–Bernoulli beam theory were in the range of 1.0 to 1.10, and they increased slightly with increasing loads, reaching their maximum value, and then rapidly decreased to 1.0 when close to the ultimate lateral load; the maximum value was influenced by the relative pile–soil stiffness. Furthermore, the ratio of the shear rotation of the pile section to the slope of the deflection curve was in the range of 1.0 to 1.10; these also showed similar but more moderate trends compared with the values of pile deformation based on the Timoshenko beam theory divided by those of that based on the Euler–Bernoulli beam theory. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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25 pages, 10760 KiB

Open AccessArticle

Model Test Study on the Vertical Uplift Bearing Characteristics of Soil Continuous Solidified Pile Group Foundations

by Tao Sun, Fakai Yang, Xinzhuang Cui, Zhaochao Huang, Xianzhou Lyu, Ruijin Ma, Yujun Chang, Shengmei Liu, Chen Wang, Zhiyuan Lin and Xiaoning Zhang

Buildings 2024, 14(3), 849; https://doi.org/10.3390/buildings14030849 - 21 Mar 2024

Viewed by 977

Abstract

To solve the problem of the high bearing capacity of structures in deep and weak soil layers, we invented a new type of pile group foundation in which the soil was continuously solidified between piles (hereinafter referred to as the SCS pile group [...] Read more.

To solve the problem of the high bearing capacity of structures in deep and weak soil layers, we invented a new type of pile group foundation in which the soil was continuously solidified between piles (hereinafter referred to as the SCS pile group foundation). Considering the two key factors of pile spacing and CSM depth, the antipulling load characteristics of SCS pile group foundations in dry sand were studied via indoor half-model tests and numerical simulations. The results showed that the ultimate uplift capacity of the SCS pile group foundation with a 2D–6D CSM depth was about 2–3 times that of the traditional pile group. When the stiffness of the CSM is so large that its effect can be ignored, the greater the pile spacing is, the greater the ultimate uplift capacity is. For the same pile spacing, the greater the depth of the CSM is, the greater the ultimate uplift bearing capacity is. When the CSM depth is greater than 10D, the uplift effect of the CSM can be effectively exerted, and the antipulling advantage of the SCS pile group foundation can be fully utilized. This study provided a reference for the antipulling design of SCS pile foundations. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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12 pages, 2778 KiB

Open AccessArticle

Application of a Hot Melt Recoverable Anchor Cable in Foundation Pit Support

by Shian Liu, Gang Liu, Hua Ji and Xueying Liu

Buildings 2024, 14(2), 393; https://doi.org/10.3390/buildings14020393 - 1 Feb 2024

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Abstract

With the continuous development of the social economy, the depth of foundation pit excavation of proposed construction projects in various places gradually increases, which is closer to the building red line, and the surrounding environment is relatively complex; therefore, there are few supporting [...] Read more.

With the continuous development of the social economy, the depth of foundation pit excavation of proposed construction projects in various places gradually increases, which is closer to the building red line, and the surrounding environment is relatively complex; therefore, there are few supporting schemes for foundation pit selection. Based on the Vanke B-6 plot of a real estate development project, the project has close neighboring buildings. If we use a normal anchor cable, underground cut line problems are possible, and so we choose the hot melt-type recoverable anchor; with three element dispersion pressure, the anchor cable can minimize broken sections of brush slope excavation and has advantages of a simplified construction process and good seismic performance. Except for the cable barrel, the other parts and all steel strands can be recycled, and recycled parts can be reused. The recyclable bolt (cable) overcomes the disadvantages of the conventional bolt (cable) as a temporary support, such as pollution of the underground environment, encroachment on the underground space of adjacent buildings, and becoming an underground obstacle in follow-up projects. It accords with the characteristics of the times of environmental protection and sustainable development, and has achieved good economic and social benefits. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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13 pages, 3224 KiB

Open AccessArticle

Study on Thermodynamic Properties of Spiral Tube-Encapsulated Phase-Change Material Energy Pile

by Ming Liu, Peng Zhang, Zhiyu Yang, Zhen Zhu, Xiaozheng Liu and Chuntang Ma

Buildings 2024, 14(1), 188; https://doi.org/10.3390/buildings14010188 - 11 Jan 2024

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Abstract

Based on the research status of phase-change material (PCM) energy piles, this paper proposes a new type of PCM energy pile-spiral tube-encapsulated PCM energy pile. In order to study the related properties of the energy pile, this study designed and processed the relevant [...] Read more.

Based on the research status of phase-change material (PCM) energy piles, this paper proposes a new type of PCM energy pile-spiral tube-encapsulated PCM energy pile. In order to study the related properties of the energy pile, this study designed and processed the relevant test equipment and built an indoor scale model experimental system. The thermodynamic performance of the spiral tube-encapsulated phase-change energy pile under summer conditions was studied by the test system. Through the indoor scale model test, it is found that compared with the traditional energy pile, the spiral tube-encapsulated PCM energy pile improves the heat exchange capacity of the unit pile body in the early and middle stages of operation, and reduces the surface temperature of the pile body and the heating rate of the surface temperature of the pile body. The upward displacement of the energy pile top is reduced. The heat exchange capacity of the unit pile depth is increased by 6.52 W/m, the maximum pile surface temperature difference is 0.62 °C, and the maximum pile top displacement difference is 0.005 mm. In addition, the total heat transfer of the spiral tube-encapsulated PCM energy pile during the whole operation period is 3.38% higher than that of the traditional energy pile. However, during the whole operation period, the surface stress value of the spiral tube encapsulated PCM energy pile is higher than that of the traditional energy pile. The maximum difference between the two is 9.84 kPa and the maximum difference is 10.8%. The difference between the two is finally stabilized at 1.4 kPa with an increase in time, and the final difference is only 8.8%. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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24 pages, 15867 KiB

Open AccessArticle

Study on the Stability of Accumulation Using a Slope Shaking Table Test during Earthquake Action

by Jianmin Xu, Yuyue Jia, Junwei Liu, Mohsen Saleh Asheghabadi and Yulin Wang

Buildings 2024, 14(1), 2; https://doi.org/10.3390/buildings14010002 - 19 Dec 2023

Viewed by 1103

Abstract

To examine the effects of different peak accelerations on the stability of the accumulation slope and the effectiveness of anti-slide piles under seismic loads, this paper used the Fanlingqian landslide as the main research object and combined it with digital image correlation (DIC) [...] Read more.

To examine the effects of different peak accelerations on the stability of the accumulation slope and the effectiveness of anti-slide piles under seismic loads, this paper used the Fanlingqian landslide as the main research object and combined it with digital image correlation (DIC) technology in order to carry out a shaking table test. Then, the acceleration response, displacement field, strain field, the bending moment distribution of the 0.05–0.3 g ground motion accumulation slope, and the anti-slide pile reinforcement were studied. The results of the test show the following: the amplification coefficient of the measuring points A1–A6 of the accumulation slope reaches the maximum at a peak acceleration of 0.2 g, and its values are between 1.25 and 1.3, respectively. Finally, it shows a decreasing trend at a peak acceleration of 0.3 g, and its corresponding values are, respectively, between 1.1 and 1.2. In the anti-slip pile reinforcement test, due to the obstruction of the anti-slip pile, the damping of the soil around the pile increases. As the peak value of the seismic wave input increases, the amplification factor shows an overall decreasing trend. A1–A6 correspond to a peak acceleration of 0.3 g. The amplification factors are all close to 1. During different peak accelerations, the accumulation slope mainly experienced the earthquake-induced stage, tensile failure stage, creeping deformation stage, and overall instability stage. In the anti-slide pile reinforcement test, under the same conditions, the slope mainly experienced the earthquake-induced stage, tensile failure stage, lower sliding surface formation stage, and soil shedding stage in front of the pile. At the same time, the displacement and strain fields of each stage of the two groups of tests are compared, and it is found that the displacement and strain values of the accumulation slope test are greater than those of the anti-slide pile reinforcement test, and the horizontal displacement difference at the top of the slope is the most significant, reaching 2.3 times at the maximum. The bending moment of the anti-slide pile first increases and then decreases with the increase in acceleration, the reverse bending point of the pile appears at 5 times the pile diameter below the soil surface, and the maximum bending moment of the middle pile, corresponding to a peak acceleration of 0.05–0.3 g, is between 7.5 N·m and 47 N·m, respectively, while the maximum bending moment of the outer pile is between 6.5 N·m and 52 N·m, respectively. It is important to apply DIC image processing technology to the monitoring of landslide structure and the evaluation of slope stability in practical engineering. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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18 pages, 9949 KiB

Open AccessArticle

A Cost-Effective System for Indoor Three-Dimensional Occupant Positioning and Trajectory Reconstruction

by Xiaomei Zhao, Shuo Li, Zhan Zhao and Honggang Li

Buildings 2023, 13(11), 2832; https://doi.org/10.3390/buildings13112832 - 11 Nov 2023

Viewed by 943

Abstract

Accurate indoor occupancy information extraction plays a crucial role in building energy conservation. Vision-based methods are popularly used for occupancy information extraction because of their high accuracy. However, previous vision-based methods either only provide 2D occupancy information or require expensive equipment. In this [...] Read more.

Accurate indoor occupancy information extraction plays a crucial role in building energy conservation. Vision-based methods are popularly used for occupancy information extraction because of their high accuracy. However, previous vision-based methods either only provide 2D occupancy information or require expensive equipment. In this paper, we propose a cost-effective indoor occupancy information extraction system that estimates occupant positions and trajectories in 3D using a single RGB camera. The proposed system provides an inverse proportional model to estimate the distance between a human head and the camera according to pixel-heights of human heads, eliminating the dependence on expensive depth sensors. The 3D position coordinates of human heads are calculated based on the above model. The proposed system also associates the 3D position coordinates of human heads with human tracking results by assigning the 3D coordinates of human heads to the corresponding human IDs from a tracking module, obtaining the 3D trajectory of each person. Experimental results demonstrate that the proposed system successfully calculates accurate 3D positions and trajectories of indoor occupants with only one surveillance camera. In conclusion, the proposed system is a low-cost and high-accuracy indoor occupancy information extraction system that has high potential in reducing building energy consumption. Full article

(This article belongs to the Special Issue Research on Rock Mechanics and Rock Engineering, Geotechnical Engineering and Mining Sciences in Construction)

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