作者：
Zhao, Chengwei;Huang, Tuo;Gao, Xinglong;Li, Yahui;Lu, Li
期刊：
Materials,2024年17(5):1027- ISSN：1996-1944
通讯作者：
Tuo Huang
作者机构：
[Gao, Xinglong; Lu, Li; Li, Yahui] School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Changsha 410114, China;Author to whom correspondence should be addressed.;[Zhao, Chengwei] Guangxi Transportation Science Engineering Construction Co., Ltd., Nanning 530007, China;[Huang, Tuo] School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Changsha 410114, China<&wdkj&>Author to whom correspondence should be addressed.
通讯机构：
[Tuo Huang] S;School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Changsha 410114, China<&wdkj&>Author to whom correspondence should be addressed.
摘要：
Cement-stabilized macadam materials are widely utilized as semi-rigid base materials in road construction. However, conventional cement-stabilized macadam (CCSM) bases often develop shrinkage cracks during early construction and maintenance due to variations in humidity and temperature. Shrinkage cracks can subsequently result in reflective cracks in the asphalt pavement, significantly reducing the overall service life of the road. This study systematically evaluates the shrinkage and mechanical properties of large-size cement-stabilized macadam (LSCSM). Initially, the mix proportion for LSCSM is determined using the Bailey method. Subsequently, an experimental design based on the response surface method is implemented to comprehensively investigate various properties, including unconfined compressive strength, compressive rebound modulus, flexural strength, and the durability aspects of early drying shrinkage and temperature shrinkage through laboratory experiments. Further, the performance differences between CCSM and LSCSM are analyzed comparatively. The findings reveal that the compressive strength of LSCSM surpasses that of CCSM, albeit with comparatively lower compressive rebound modulus and flexural strength. LSCSM demonstrates a unique blend of characteristics, exhibiting traits of both semi-rigid and flexible materials. Furthermore, LSCSM exhibits favorable crack resistance properties, as evidenced by lower dry shrinkage strain, average dry and temperature shrinkage coefficient compared to CCSM. The proposed LSCSM in this study effectively reduces cement dosage and enhances the crack resistance performance of base materials.
摘要：
High-temperature hazards of asphalt pavement and pollution from car exhaust are two major problems that need to be solved in road construction. In this paper, a multifunctional composite coating has been prepared from the perspective of reducing road temperature and car exhaust degradation. The principle of heat-reflecting coating is used to reduce the road surface temperature. At the same time, the TiO2 aqueous solution with photocatalytic degradation effect is added to the heat-reflective coating material to achieve the purpose of degrading automobile exhaust degradation, creating a new type of multifunctional coating that has both cooling and exhaust degradation effects. In addition, by changing the amount of carbon black, a multi-functional coating with the best coloring is selected, so that it has better functionality and has the most suitable shade for the road surface. Finally, the cooling effect and the exhaust gas reduction effect are examined through indoor and outdoor tests and the slip resistance of the coating is tested using the pendulum method. The results show that the functional coating group has a certain ability of cooling and exhaust gas degradation compared to the normal control group without coating. For the functional coating group with different carbon black content, the functional coating (G2) with 0.9% carbon black content has the strongest overall functionality. The cooling and exhaust gas reduction effects proved to be the best. The surface cooling rate is 5.4 degrees C, while the internal cooling rate is 4.3 degrees C. The cumulative degradation efficiency of CO and NO is found to be 27.77%, and 73.75%, respectively.
摘要：
Recycled rubber materials represent an environmentally sustainable option as asphalt modifiers. This research delves into the modification effects of Styrene Butadiene Rubber (SBR) asphalt at varying SBR content levels, employing a blend of molecular simulation techniques and laboratory experimentation. A comprehensive molecular model of SBR-modified asphalt is established, and molecular dynamics simulations are executed to scrutinize the thermodynamic attributes, dipole moments, mechanical characteristics, and adhesion properties inherent to SBR asphalt. The outcomes of this inquiry reveal that SBR exhibits notable compatibility with a majority of asphalt molecules, as evidenced by their dipole moments. The introduction of SBR into the asphalt matrix results in the adsorption of a substantial quantity of lightweight components, fostering the formation of a cross-linked network that bolsters the asphalt's resilience against external deformation forces. Furthermore, in terms of adhesion work, asphalt demonstrates heightened affinity with alkaline aggregates, and SBR serves to augment van der Waals interactions at the asphalt-aggregate interface, thereby amplifying interfacial bonding strength. However, when the content of SBR reaches 30%, some SBR molecules will be aggregated in the asphalt, which will lead to phase separation and affect the stability of the colloid. Therefore, it is recommended that the content of SBR should be limited to about 20% in practical engineering applications. In this work, the modification mechanism of SBR was analyzed at the molecular scale and verified experimentally, and the results provide a theoretical basis for the rational use of recycled SBR powder in asphalt applications.
作者：
Zhao, Wensheng;Fang, Guotao;Qin, Xiao;Mao, Jie
期刊：
REVIEWS ON ADVANCED MATERIALS SCIENCE,2024年63(1) ISSN：1606-5131
通讯作者：
Qin, X
作者机构：
[Zhao, Wensheng] Changsha Univ Sci & Technol, Natl Engn Res Ctr Highway Maintenance Technol, Changsha 410114, Peoples R China.;[Qin, Xiao; Qin, X] Foshan Univ, Sch Transportat & Civil Engn & Architecture, Foshan 528000, Peoples R China.;[Zhao, Wensheng] Changsha Univ Sci & Technol, Sch Traff & Transportat Engn, Changsha 410114, Peoples R China.;[Fang, Guotao] Guangzhou HuaHui Traff Technol Co Ltd, Guangzhou 510335, Peoples R China.;[Mao, Jie] Guangdong GuanYue Highway & Bridge Co Ltd, Engn Dept, Guangzhou 511450, Peoples R China.
通讯机构：
[Qin, X ] F;Foshan Univ, Sch Transportat & Civil Engn & Architecture, Foshan 528000, Peoples R China.
关键词：
asphalt;UV aging;characterization
摘要：
To clarify the effect and mechanism of hindered amine light stabilizer (HALS) on the UV aging behavior of asphalt binder, T622-HALS was selected as the modifier for UV aging resistance of asphalt. The physicochemical properties and microstructure of T622 light stabilizer were comprehensively analyzed. The light stabilizer-modified asphalt was prepared and placed in the UV radiation chamber for UV aging treatment. Scanning electron microscope and atomic force microscope were used to analyze the microscopic morphology evolution of light stabilizer-modified asphalt induced by UV radiation. The thermal properties and functional group composition changes in light stabilizer-modified asphalt during UV aging were studied by using the thermogravimetric and infrared spectroscopy combined testing system. The decay laws of the physical and rheological performances of light stabilizer-modified asphalt were studied during UV aging process, and the effect of light stabilizer on the UV aging behavior of asphalt binder was clarified. The research results indicated that HALSs could alleviate the microcracks and roughness change on the surface of asphalt and reduce the content of functional groups such as carbonyl and sulfoxide in asphalt. Furthermore, HALS could reduce the value difference of physical and rheological properties of asphalt before and after UV aging, significantly improving the UV aging resistance of asphalt binder.
摘要：
The accuracy of the data is crucial to the real-time prediction of autonomous driving. Due to factors such as weather and the accuracy of data collection equipment, there frequently exist noises in the data collected in real time. Therefore, it is necessary to perform analysis on acquired kinematic features related to driving behavior prediction. This study proposes a novel deep learning framework to explore influences of data noises on lane-changing intention prediction. Kinematic features including the longitudinal distance difference, velocity and acceleration, lateral velocity and acceleration of the vehicles are first extracted from the HighD. Then, the anti-interference performance of deep learning models such as transformer is tested. By comparing dataset with and without noises, we develop an evaluation method containing several predictive performance metrics and statistical measures. The results show that: (1) the longitudinal acceleration of the vehicle has the lowest sensitivity to noise, and the lateral velocity has the weakest anti-interference and the highest sensitivity. (2) The Bi-LSTM model with multi-head attention mechanism performs well in reducing the sensitivity of longitudinal acceleration and prediction accuracy. This study provides valuable information for data acquisition and model selection of real-time driving intention prediction.
摘要：
This study addressed the complex problems of selecting a constitutive model to objectively characterize asphalt mixtures and accurately determine their viscoelastic properties, which are influenced by numerous variables. Inaccuracies in model or parameter determination can result in significant discrepancies between the calculated and measured results of the pavement’s structural dynamic response. To address this, the research utilized the physical engineering principles of asphalt pavement structure to perform dynamic modulus tests on three types of high-content rubberized asphalt mixtures (HCRAM) within the surface layer. The research aimed to investigate the influencing factors of the dynamic modulus and establish a comprehensive master curve. This study also critically evaluated the capabilities of three viscoelastic models—the three-parameter solid model, the classical Maxwell model, and the classical Kelvin model—in depicting the dynamic modulus of HCRAM. The findings indicated a negative correlation between the dynamic modulus of the asphalt mixture and temperature, while a positive association exists between the loading frequency and temperature, with the impact of the loading frequency diminishing as the temperature increases. Notably, the three-parameter solid model was identified as the most accurate in describing the viscoelastic properties of the HCRAM. Furthermore, the dynamic response calculations revealed that most indexes in the surface layer’s dynamic response are highest when evaluated using the three-parameter viscoelastic model, underscoring its potential to enhance the pavement performance’s predictive accuracy. This research provides valuable insights into optimizing the material performance and guiding the pavement design and maintenance strategies.
摘要：
Recommendation systems have been effectively utilized in various fields, but their internal decision-making methods are still largely unknown. This opaque decision-making method can greatly affect users’ trust in the recommendation system. Therefore, finding a way to explain the reasons for model decisions has become an urgent task. Previous studies often used LSTM and other models to generate recommendation explanations and explain the reasons for recommendations in text form. However, traditional methods cannot effectively use the ID information of users and items, and the text generated is highly repetitive. To solve this problem, this paper uses the method of prompt learning combined with a graph encoder to design a recommendation explanation generation model. In order to narrow the semantic gap between the ID information of users and items and natural language and capture high-level interaction information, this paper designs a graph encoder based on user similarity to learn the interactive semantic information of user and item IDs, and to construct a continuous prompt. Then, the discrete prompt composed of discrete features of users and items is combined with the continuous prompt to construct a hybrid prompt to input into the pre-trained model to generate the recommended explanation. This paper experiments on three publicly available datasets and compares them with several state-of-the-art methods to demonstrate the personalization and text quality of the generated explanations.
作者机构：
[Haishan Fan; Fan Gu; Junhui Zhang; Junhui Peng] School of Traffic and Transportation Engineering, Changsha University of Science & Technology, Changsha, Hunan, China;[Jianlong Zheng] National Engineering Research Center of Highway Maintenance Technology, Changsha University of Science & Technology, Changsha, Hunan, China
通讯机构：
[Fan Gu] S;School of Traffic and Transportation Engineering, Changsha University of Science & Technology, Changsha, Hunan, China
摘要：
This study aimed to develop a method to determine nonlinear viscoelastic properties of subgrade soil using the light weight deflectometer (LWD) test. Firstly, a constitutive model was developed to accurately characterize the nonlinear viscoelastic behavior of subgrade soil. A User-Defined Material Subroutine (UMAT) was coded to define this constitutive model in ABAQUS, which was verified by the virtual triaxial test analysis. Secondly, a numerical model was developed to simulate the LWD test, which considered the true LWD load pattern and the constitutive nature of subgrade soil. The sensitivity analysis demonstrated that the viscoelastic parameters significantly affected the deflection-time history curves. Subsequently, a batch calculation program was developed via MATLAB and ABAQUS to automatically compute the dynamic responses of subgrade in the LWD test. A total of 42,057 groups of subgrade deflection data were calculated under the LWD load, covering a wide range of nonlinear viscoelastic parameters. Finally, two machine-learning approaches (i.e., artificial neural network [ANN] and convolutional neural network [CNN]) were proposed to backcalculate these viscoelastic parameters of soil from the LWD load–deflection-time history data. The results showed that the CNN approach was much more accurate than the ANN approach for the backcalculation of the nonlinear viscoelastic properties of subgrade.
期刊：
Bulletin of Engineering Geology and the Environment,2024年83(1):1-13 ISSN：1435-9529
通讯作者：
Lan, T
作者机构：
[Gao, Q. F.; Zhang, R.] Changsha Univ Sci & Technol, Sch Traff & Transportat Engn, 960 Wanjiali South Rd, Changsha 410114, Peoples R China.;[Lan, T.; Lan, T] Hunan Univ Sci & Technol, Sch Civil Engn, 2 Taoyuan Rd, Xiangtan 411201, Peoples R China.;[Zheng, J. L.] Changsha Univ Sci & Technol, Natl Engn Res Ctr Highway Maintenance Technol, 960 Wanjiali South Rd, Changsha 410114, Peoples R China.
通讯机构：
[Lan, T ] H;Hunan Univ Sci & Technol, Sch Civil Engn, 2 Taoyuan Rd, Xiangtan 411201, Peoples R China.
关键词：
Road engineering;Reinforced slope;Geogrid;Expansive soil;Field testing and monitoring
摘要：
The aim of this study is to better understand the long-term stability and reinforcement mechanism of expansive soil cut slopes repaired by geogrid reinforcement. A expansive soil slope repaired by geogrid was monitored for two years without interruption. The monitored results demonstrate that the water content of the reinforced expansive soil slope is gradually stabilized in two years after the treatment. The variation trend of geogrid strains is consistent with that of lateral earth pressures in the slope. The geogrid strain decreases with a decrease in earth pressure. When the earth pressure is stable, the geogrid strain approaches the initial value. The geogrid reinforcement is able to inhibit crack development, limit soil deformation and release soil swelling pressure, thus maintaining the long-term stability of expansive soil slope.
摘要：
Currently, the research on the mechanical properties of rubber-modified asphalt mixtures primarily focuses on small-scale investigations, with insufficient exploration into the performance of rubber particles and their relationship with the mechanism and properties of modified asphalt mixtures. Limited studies have been conducted on large-scale rubber modification in asphalt mixtures. Due to frequent use and subsequent high damage to existing asphalt pavements, incorporating rubber-modified asphalt mixtures can partially alleviate premature deterioration. Dynamic modulus tests were conducted using MTS equipment under unconfined conditions to investigate the viscoelastic behavior of rubber-modified asphalt mixtures with high rubber content and elucidate the influence of rubber particle content on the elastic deformation and recovery capability. The dynamic mechanical properties of the mixtures were determined at different loading rates, temperatures, and types of rubber-modified asphalt mixtures. Based on the test data, variations in the dynamic modulus, phase angle, storage modulus, loss modulus, loss factor, and rut factor of the rubber-modified asphalt mixtures under different loading frequencies, temperatures, and types were analyzed. The results demonstrate the pronounced viscoelastic behavior of rubber-modified asphalt mixtures. The mixtures exhibit enhanced elasticity at low temperatures and high frequencies, while their viscosity becomes more prominent at high temperatures and low frequencies. Under constant test temperatures, an increase in load loading frequency leads to a higher dynamic modulus; conversely, a decrease in dynamic modulus is observed with increasing test temperatures. The dynamic modulus of ARHM-25 at a frequency of 10 Hz is found to be 12.99 times higher at 15 degrees C compared to that at 60 degrees C, while at 30 degrees C, the dynamic modulus at 25 Hz is observed to be 2.72 times greater than that at 0.1 Hz. Furthermore, the rutting resistance factors of the asphalt mixtures increase with loading frequency but decrease with temperature. The rutting factor for ARHM-13 at a frequency of 10 Hz is found to be 22.98 times higher at 15 degrees C compared to that at 60 degrees C, while at a temperature of 30 degrees C, the rutting factor for this material is observed to be 3.09 times greater at a frequency of 25 Hz than at 0.1 Hz. These findings suggest that rutting is most likely when vehicles drive at low speeds in hot weather conditions.
摘要：
The asphalt mixture splitting test is one of the most important methods for measuring asphalt's tensile properties. To characterize the limitations of the traditional splitting test and the influence of the specimen size and loading conditions on the accuracy of the test, the factors affecting the strength of the splitting test were analyzed to reveal the splitting failure state and establish a unified representation model between the splitting and direct tensile tests. Initially, the moment of specimen cracking was taken as a key indicator, combined with image processing technology, to establish a set of criteria to judge the splitting test. Subsequently, standardized splitting tests were conducted and compared to tests of different specimen sizes and loading methods. Based on the octahedral strength theory, the stress points before and after the improved test were compared to the existing failure criteria. Direct tensile and splitting tests were conducted at different rates, and a unified strength-rate function model was established, realizing the unified representation of direct tensile and splitting tests. The research results indicate that the standardized splitting test is prone to the phenomenon wherein the specimen end face cracks before the center, affecting the accuracy of the test and potentially leading to redundant material strength evaluations. Using a loading method with a "35 mm specimen thickness" and a "0.3 mm rubber gasket + 12.7 mm arc-shaped batten" can essentially achieve the test hypothesis of "cracking at the center first", resulting in less discrete outcomes and closer alignment to the three-dimensional stress failure state. The tensile and splitting strengths are both power function relationships with the rate as the independent variable, establishing a unified function model of the tensile and failure strengths. The research provides a more reliable testing method and calculation model for asphalt pavement structure design, and it also provides an effective basis for the improvement of splitting tests on materials such as concrete and rock.
期刊：
Journal of Materials in Civil Engineering,2024年36(2):04023543 ISSN：0899-1561
通讯作者：
Dong, HW
作者机构：
[Huang, Tuo; Qin, Haoyun; Wang, Zhaoyang; Liu, Hongfu] Changsha Univ Sci & Technol, Changsha 410114, Peoples R China.;[Cao, Zhonglu; Dong, HW; Dong, Hongwu] China Commun Construct Co CCCC First Harbor Engn, Tianjin Port Engn Inst Co Ltd, 1002 Dagu South Rd, Tianjin 300222, Peoples R China.;[Cao, Zhonglu; Dong, HW; Dong, Hongwu] China Commun Construct Co CCCC First Harbor Engn, Tianjin 300461, Peoples R China.
通讯机构：
[Dong, HW ] C;China Commun Construct Co CCCC First Harbor Engn, Tianjin Port Engn Inst Co Ltd, 1002 Dagu South Rd, Tianjin 300222, Peoples R China.;China Commun Construct Co CCCC First Harbor Engn, Tianjin 300461, Peoples R China.
摘要：
To objectively characterize the time-temperature-stress equivalence of viscoelastic properties of asphalt mixture, the triaxial compressive creep test was carried out on an AC-13 asphalt mixture under the conditions of different temperatures and stress states in this paper and the nonlinear variation law of creep deformation was obtained. According to the characteristics of similar creep curves and the principle of time-temperature equivalence, two methods were used to shift the creep compliance under different confining pressure, temperature, and axial stress conditions, and the change of temperature and stress shift factors with confining pressure were obtained; in addition, the creep compliance principal curve was fitted by the Prony series and its principal surface was established. On this basis, the multiple stress creep recovery test under different confining pressures was conducted to measure the parameters of Schapery’s nonlinear viscoelastic model and their variation law with the triaxial stress ratio was obtained, which accurately characterized the synergistic effect of confining pressure and axial stress.
期刊：
World Electric Vehicle Journal,2024年15(1):3- ISSN：2032-6653
通讯作者：
Chenhui Liu
作者机构：
[Qinglu Ma] School of Traffic and Transportation, Chongqing Jiaotong University, Chongqing 400074, China;[Meiling Su; Xuerui Hou] College of Civil Engineering, Hunan University, Changsha 410082, China;Research Institute of Hunan University in Chongqing, Chongqing 401120, China;Key Laboratory of Highway Engineering of Ministry of Education, Changsha University of Science & Technology, Changsha 410114, China;Author to whom correspondence should be addressed.
通讯机构：
[Chenhui Liu] C;College of Civil Engineering, Hunan University, Changsha 410082, China<&wdkj&>Research Institute of Hunan University in Chongqing, Chongqing 401120, China<&wdkj&>Key Laboratory of Highway Engineering of Ministry of Education, Changsha University of Science & Technology, Changsha 410114, China<&wdkj&>Author to whom correspondence should be addressed.
关键词：
traffic safety;electric vehicles;traffic accidents;accident size;ordered logit model
摘要：
With the great increase of electric vehicles (EVs) in the past decade, EV-involved traffic accidents have also been increasing quickly in many countries, bringing many new traffic safety challenges. Norway has the largest EV penetration rate in the world. Using the EV accident data from Norway in 2020 and 2021, this study aims to investigate the features of EV safety comprehensively. Firstly, a descriptive analysis is conducted. It has been found that rear-end collisions are the major collision type of EVs, and EVs are very likely to collide with pedestrians/cyclists. In addition, in terms of roadway type, EV accidents mainly occur on medium- and low-speed roads; in terms of environment, they mainly occur in good visibility conditions and dry road surface conditions. Then, a regression analysis is conducted to identify the key factors affecting the accident size, which is the number of traffic units involved in an accident and taken as the accident severity surrogate here. Since EV accidents are divided into four categories in order of accident size, the ordered logit model is adopted. It divides a multi-categorical dependent variable into multiple binary data points in order and calculates the probability of the dependent variable falling into each category with the logit model, respectively. The estimation results indicate that time of day, speed limit, and presence of medians have statistically significant impacts on the EV accident size. Finally, some countermeasures to prevent EV accidents are proposed based on the research results.
关键词：
Asphalt mixture;Mesoscopic analysis;Skeleton evolution;Aggregate contact;Particle movement;Discrete element method
摘要：
The aggregate skeleton is the intrinsic core of asphalt mixtures for load transfer, which is quite different under various gradations. For evaluating the loading characteristics of the aggregate skeleton, this research combined the 3D blue -ray scanning technology and discrete element method (DEM) to establish the numerical models of different graded asphalt mixtures considering the real aggregate morphology. A linear parallel bond model was used to simulate the adhesion effect of asphalt, and the uniaxial compression numerical simulation was verified by indoor tests. In addition, the contact force, contact number, anisotropy, and rotation angle were used to evaluate the aggregate skeleton evolution under uniaxial compression loading. Furthermore, the contribution of each grade aggregate in the gradation to the skeleton structure was analyzed. Results show that the average contact force is higher in large -size aggregates above 9.5 mm, which exhibit greater load transfer efficiency. Moreover, 4.75-9.5 mm size aggregates combine the functions of bearing and filling, and its role is significantly affected by the gradation. It is also found that the internal skeleton structure can be optimized and adjusted under stress. The contact numbers of different graded mixtures follow a close decrease, and the strong contacts are mostly provided by coarse aggregates above 4.75 mm. The anisotropy development of aggregate skeleton contact force is induced by the stress, and the deviator fabric of asphalt mixtures show a good linear positive correlation with the uniaxial compressive strength (UCS). Besides, fine aggregates exhibit greater cumulative rotation angle and instability effect, it is feasible to detect asphalt mixture deformation by the rotation angle of particles.
关键词：
Asphalt pavement;Photocatalytic coating;Nanometer titanium dioxide;Quantum dot;Tail gas degradation
摘要：
To address the escalating issue of vehicular exhaust pollution, the application of photocatalyst materials on road surfaces for rapid degradation of exhaust gas has gained significant attention in pavement engineering. However, poor visible light response and low separation efficiency of photogenerated charge carriers limit the practical application of nanometer titanium dioxide (nano-TiO2) photocatalyst on road surfaces. In this study, tungsten oxide (WO3) and tungsten sulfide (WS2) quantum dots (QDs) were introduced into graphene oxide (GO)/TiO2 nanocomposites through a sol-gel process to form ternary heterojunction structures. Characterization results revealed that the QDs modified GO/TiO2 composites exhibited enhanced light absorption, electrical conductivity and surface area. Photocatalytic degradation tests of model vehicle exhaust pollutants showed that the GO/WS2 QDs/TiO2 and GO/WO3 QDs/TiO2 coatings achieved over 70 % degradation rate of nitrogen oxides within 120 min under visible light irradiation, outperforming bare TiO2 and binary GO/TiO2. Mechanism studies suggested that the ternary heterojunction facilitated efficient separation of photogenerated charge carriers at multi-phase interfaces. Additionally, the photocatalytic coating demonstrated good durability after simulated traffic loading, maintaining a 60 % degradation rate of nitrogen oxides even after 20,000 rolling cycles. This work provides a promising solution for sustainable environmental remediation on road surfaces.
摘要：
Modification of fly ash geopolymer with steel slag: Preparation of steel slag-fly ash geopolymer paste using steel slag andvarying dosages of NaOH-Na2SiO3 as variables. The study aims to investigate the workability, strength, and strengthening mechanismof this paste material, as well as to assess its mechanical properties and water stability in stabilized gravel. The results showed thatincorporating steel slag could decrease the fluidity and setting time of fly ash geopolymer while increasing its strength. When the steelslag and activator was 30% and 18%, respectively, the compressive strength at 7 and 28 days was the highest, reaching 19.3 and 24.9MPa, respectively. The strength of geopolymer-stabilized gravel was equivalent to that of cement-stabilized gravel. When thegeopolymer content is modified to 6%, the unconfined compressive strength at 7 and 28 days is 5.2 and 6.1 MPa, respectively. After28 days of curing, the water stability has significantly improved, with a water stability coefficient exceeding 0.9. The addition of steelslag can enhance the reactivity of the reaction system, facilitate the formation of C-(A)-S-H gel, increase the bonding strength, and fillthe internal pores, resulting in a 23.3% reduction in porosity, a denser structure, and improved strength.
摘要：
Internal erosion refers to the movement of fine particles within soil framework due to subsurface water seepage. Existing criteria for assessing internal erosion usually are based on static loading, and the effect of cyclic load is not considered. Additionally, there are limited studies to examine the particle -size distribution and origin of eroded fine particles. This study presents an experimental investigation that examines the impact of cyclic loading on internal stability through a series of seepage tests. The composition and origin of lost particles are quantitatively studied using particle staining and image recognition techniques. With increasing hydraulic gradient, particle erosion progresses from top layer to bottom layer, with a gradual increase in the maximum particle size of eroded particles from each layer. After significant loss of particles, the specimens reach a state of transient equilibrium, resulting in a gradual slowdown of both particle loss rate and average flow velocity. The results indicate that cyclic loading promotes massive particle loss and causes erosion failure of specimens that are considered stable according to existing criteria. The reason is that under cyclic loading, local hydraulic gradients is oscillating, and a larger than average hydraulic gradient may occur, which is responsible for the internal instability. The analysis suggests that existing criteria can provide a reasonable assessment of the relative stabilities of specimens under static loads but fail to capture the stabilities under cyclic loading conditions.
摘要：
Improved depth is of fundamental importance for earth-filled foundations with dynamic compaction (DC) and is closely relevant to the mechanical characteristics of earth fillers under impact load. This study carried out numerical DC tests on fine-grained soil to estimate the improved depth more easily and accurately. The filler's multiscale responses, including crater depth and porosity, were evaluated. Results showed that a heavier tamper weight with a lower drop distance was relatively more efficient in densifying soil fillers, although the tamping energy (MH1.0) and tamping momentum (MH0.5) were the same; however, contrary results were observed under the same value of MH0.2. In addition, three different combinations of M and H led to similar soil responses under the same value of MH0.3, which is thus recommended as the new index to estimate the improved depth and densification efficiency of DC. A mechanistic analysis found that M contributes more than H to compact soil fillers, which can be quantified by contribution ratio alpha. Moreover, large-scale field DC tests confirmed the findings.
