Volume 44, Issue 5 (2024)
Special Column: Theory and Technology of Road Engineering in Cold Regions
Progress and Prospects of Road Engineering Disease Treatment Technology in Permafrost Regions
GAO Feng, ZENG Xianzhang, ZHONG Wenhua, HUANG Shengyong, and ZHANG Junhui
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.001
Freeze-thaw disasters are key issues affecting the service performance and operational safety of road projects in permafrost regions.Under the combined influence of warming and humidification of the permafrost environment and engineering thermal effects，the degradation of permafrost is accelerating，exacerbating the risk of road freeze-thaw diseases.Roads in these regions are more frequently maintained and repaired to ensure service performance，with a service life lower than designed.Therefore，deepening the understanding of the disaster mechanism of road geotechnical structures and strengthening the study on engineering disease treatment technology are of great significance in promoting the construction and maintenance of high-quality and high-grade highways in frozen regions.This paper first expounded on typical types of diseases of roads in frozen regions and explored the formation mechanism and evolution mechanism of the diseases based on internal and external factors，such as frozen soil properties，climate and topography，road materials，and structures.Then the current situations and development of disease treatment technology for roads in frozen regions were discussed according to the different treatment principles.Studies have shown that freeze-thaw subsidence，cracking and pitting，and mud pumping are the main diseases on these roads.The causes include frozen soil properties，climate and topography，road materials and structures，and other factors，with subsidence and deformation induced by soaked and softened foundations due to freeze-thaw water particularly significant.Therefore，the line selection should be fully optimized in road planning.According to the different principles of treatment of in-service road diseases，the existing treatment technologies can be divided into three categories：measures of passively cooling subgrade，measures of actively cooling subgrade，and measures of enhancing frozen soil foundation.Among them，the study and application of the former two categories are relatively systematic and comprehensive，and the subsequent focus should be on improving temperature control performance and the combined use of multiple treatment measures.The frozen soil foundation enhancement technology，with good application prospects and promotion value，is currently under exploration and tests，requiring further study in the design method and construction technology.Moreover，as for the disease treatment technology，the performance of in-service roads should be emphasized and the evaluation of the treatment effects should be strengthened.To reduce the risk of road diseases in frozen regions and ensure the safety of plateau transportation，this study points out that the research direction and focus should be an integrated disease treatment technology centered on a comprehensive chain of “foundation enhancement-subgrade temperature control-integrated drainage ”.
Treatment Methods of Unstable Expansive Soil Slope Excavation in Overlying Rock Layer in Alpine Region
SHI Xiaobo, CUI Guangyan, MOU Chao, WEN Ye, XIE Feng, and FU Xiaoyang
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.002
To deeply study the treatment method for instability of highway cutting slope under the condition of expansive soil overlying rock layer in an alpine region，the comprehensive treatment method of unstable slope under this bad geology was put forward based on the unstable slope project of Zhangbei‒Shangyi Expressway.The governance protection structure consisted of a rigid protection system，drainage system，thermal insulation system，flexible protection system，and waterproof system.The rigid protection system was an anti-slide pile setting at the height of 1/3 of the first grade slope，of which parameters were calculated by cutting the slope of the rock layer in the unstable area to reduce the required anti-slide force of the remaining soil.The drainage system consisted of built-in tilting drainage pipes between the rock layer and expansive soil layer，gravel drainage layer outside the expansive soil layer after excavation of soil in unstable area，horizontal drainage pipe in the gravel layer，drainage ditch，intercepting ditch and side ditch of each platform.The thermal insulation system was a backfill soil layer and a cultivated clay layer arranged outside the gravel layer.The flexible protection system was a geogrid in the thermal insulation soil layer.The water-proof system was made of two cloth and one membrane water-proof layers planted under the clay layer on the backfill soil platform，and two cloth and one membrane water-proof layers in the contact area between the gravel layer and the anti-slide pile.The field treatment results show that this method can effectively prevent the slope from instability and failure again.
Review of Snow and Ice Melting Techniques for Road and Bridge in Cold Regions
TANG Liyun, SHAO Haitao, TANG Huaming, QIU Peiyong, DU Xiaoqi, ZHANG Lei, and PENG Hui
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.003
Snow and ice melting of road and bridge surfaces is crucial for traffic safety，but current research on snow and ice melting techniques mainly focuses on engineering effects and technical evaluation，without the analysis and elaboration from the perspective of their mechanisms.To this end，based on the different mechanisms，this study divided snow and ice melting techniques into three types and summarized them：passive deicing，active deicing，and energy utilization deicing.This study systematically evaluated the advantages and disadvantages of traditional deicing methods such as deicing agents and mechanical deicing，analyzed two active deicing techniques，namely inhibitive freezing pavement and phase change material pavement，discussed the environmental-friendly method for road deicing by using phase change materials，and introduced the mechanisms of different energy utilization deicing techniques.This study analyzed the existing road deicing techniques，their actual application effects，and existing problems，to provide foundational support for the research of snow and ice melting on roads and bridges in cold regions.
Properties and Application of Cement Improved Loess under Low Temperature Environment in Cold Region
LI Xiangyang
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.004
According to the cold climate and low annual average temperature in cold regions of China，the field curing conditions of cement improvement of collapsibility loess under low temperature，room temperature，and medium temperature were simulated at 5 ℃，10 ℃，20 ℃，and 30 ℃，respectively.Based on laboratory experiments，this study analyzed the effects of curing temperature，cement content，and curing age on RCBR，unconfined compressive strength，and dynamic resilience modulus of cement improved loess.The effects of cement content and curing temperature on freeze-thaw durability and erosion resistance of cement improved loess were studied by the freeze-thaw cycle test and dynamic water erosion test.Combined with the laboratory results，the 4% and 5% cement improved loess were applied to fill the upper and lower roadbed of the expressway，with a test of the elastic modulus of the top surface of the roadbed，the dynamic elastic deflection of FWD and the static elastic deflection of Beckman beam in the test section.Finally，the fitting relationships between the elastic modulus of the top surface of the roadbed and the measured bending as well as the dynamic and static bending were established.The results show that the mechanical indexes such as RCBR，unconfined compressive strength，and dynamic resilience modulus of cement improved loess increase continuously with the rise of curing temperature and cement content.After 9 freeze-thaw cycles，the dynamic resilience modulus of cement improved loess tends to be stable.Considering the freeze-resistance，freeze-thaw durability，and economy of cement improved loess，the appropriate cement content is recommended to be 4%‒5%，and the reduction coefficient of dynamic resilience modulus of cement improved loess constructed at 5 and 10 ℃ in cold regions can be 0.80‒0.85 and 0.90‒0.95.The fitting relationship between the measured deflection of BB （LBB） and the measured deflection of FWD （LFWD） is LBB=1.166×LFWD.
Effect of Chloride Ions on Salt Expansion of Salinized Subgrade Fill Soil in Cold Regions
HU Wenzhu, WANG Zhaowei, CAO Yong, ZHANG Jing, and BAI Ruiqiang
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.005
Salinized subgrade fill soil in cold regions typically comprises composite saline soil rich in sodium chloride and sodium sulfate.This study aimed to explore the mechanism of the effect of chloride ion content on salt expansion of the salinized subgrade in cold regions.Based on the calculation theory of the sodium chloride-sodium sulfate-water ternary system solution in the Pitzer ion model and combined with the FREZCHEM model，the study quantitatively analyzed the intrinsic connection between water activity，freezing factor，and supersaturation ratio with temperature and concentration ratio （η=mCl-/mSO2-4）.It investigated the variation patterns of the freezing temperature and crystallization supersaturation ratio of composite saline soil with sodium sulfate content and concentration ratio，revealed the impact mechanism of sodium chloride on the crystallization of sulfate saline soil，and determined the critical concentration ratio for adding sodium chloride to sulfate saline soil to reduce salt expansion.The results show that the FREZCHEM model can be used to analyze composite saline soil ’s freezing and salt crystallization characteristics.The ice formation factor is closely related to temperature and solution concentration，and when it equals 1，the pore solution is in thermodynamic equilibrium.Sodium chloride has a dual role in promoting or inhibiting the crystallization of sodium sulfate.When the concentration of sodium sulfate in the saline soil exceeds 1.0 mol/kg，the salt expansion deformation of sulfate saline soil will be significantly reduced by adding sodium chloride according to a critical concentration ratio greater than 2.5.Meanwhile，the salinization method applied during on-site construction can effectively suppress the salt expansion and deformation of the roadbed in saline cold areas.
Subgrade Engineering
Model Test on Soil Deformation Mechanism and Damage Mode Caused by Mud Leakage from Drilled Piles in Karst Area
JIANG Mingying, CHEN E ’mei, LIU Yongcheng, ZHU Yadong, JIANG Wenkui, and XIE Ruiting
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.006
Pile holes are often drilled through cavities in karst areas，which induces mud leakage and causes hole wall instability，ground collapse，or equipment trapping and hinders smooth construction.It is important to know the collapse mechanism of boreholes due to mud leakage，so as to optimize and determine the construction process of pile holes.In this paper，indoor model tests were used to study the deformation mechanism and damage mode of soil caused by drilling through cavities and mud leakage in pile holes under the conditions of upper clay and lower sandy soil in the karst area，so as to provide an experimental basis for the decision of pile construction plan in karst area.The results show that the mechanical principle of the pile hole drilling through the roof of the cavity and causing the collapse of the upper layer of clay and the lower sand covering layer is that after the pile hole drills through the roof of the karst cavity，the mud quickly goes down and causes the stress of the hole wall to lose balance，and the sand first moves and fills the pile hole due to the single grain structure，which causes the instability and sinking of the upper layer of clay.When the angle between the top surface of the sand and the horizontal surface is about equal to the angle of internal friction，the sand sliding stops.After the sand sliding stops，the upper layer of clay sinks continuously and forms the soil arch.After the soil arch is formed，the ground tends to be stable.The process of ground sinking induced by drilling mud channeling can be divided into three stages：rapid sinking，slow sinking，and stabilization.The whole process takes about one minute.The ground forms a sinking basin.In the project，it is suggested to reinforce the sand on the top of the roof of the karst cavity by grouting to prevent the ground collapse caused by the pile hole drilling through the roof of the karst cavity，and then the safety of the equipment or personnel and smooth construction can be ensured.
Back‑Calculation of Subgrade Modulus Based on Genetic Algorithm and Viscoelasticity Theory
DAI Fugui, WANG Xihui, WU Yaguang, and LI Hai
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.007
To improve the applicability of the PFWD detection method for the back-calculation of subgrade modulus，taking the subgrade splicing project of the west loop line in Nairobi as an example，this paper adopted 3D Kelvin viscoelasticity model and quasi-static response analysis to deduce the displacement function of viscoelastic subgrade under long-term fixed loads，and combined the principle of liner superposition of viscoelasticity with genetic algorithm to propose a new method based on multi-population genetic algorithm for the modulus back-calculation of viscoelastic subgrade.Among them，the corresponding program for back-calculation was written by Matlab.The comparison between theoretical derivation and field tests shows that the peak value of vertical displacement on the top of subgrade under PFWD loads lags behind the load peak value.However，selecting only the displacement and load peak value for back-calculation，the traditional method based on the elastic half-space model yields a calculation result 20% larger than the result by the new method.At the same time，the correlation coefficient between the displacement time-history curve calculated by the new method and the real curve is basically greater than 0.9，and compared with the results by other methods，the calculation difference is about 10%.Moreover，with fast convergence speed，good adaptability，and accurate back-calculation results of subgrade modulus，the new method can be the reference for subgrade design and construction quality control.
Pavement Structure and Materials
Correlation between Pavement Distress and Structural Hidden Distress
LIU Xianming, XIA Han, HU Dongping, YAN Chen, YANG Rui, and ZHONG Xinran
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.008
The hidden distress in the pavement structure does great harm to the performance and service life of the road.In this work，based on the statistical idea of pavement distress rate in the Highway Performance Assessment Standards （JTG 5210—2018），an index of characterizing hidden distress in the pavement structure，namely pavement structure distress rate，was proposed.Based on the actual highway inspection project，the pavement distress and the hidden distress in the depth of 1 m below the pavement of a two-way four-lane highway with a length of 38 km were studied.The overall situation of pavement distress and hidden distress and their spatial distribution were analyzed statistically by a pile interval of 100 m.The correlation between pavement distress rate and pavement structure distress rate was further explored.The results show that when the pavement distress is severe，there is a strong correlation between the pavement distress rate and the pavement structure distress rate.When the pavement distress index is low，internal hidden distress will also increase accordingly.At this time，there may be an accompanying relationship between the apparent and hidden distress of the pavement.In addition，with the gradual deepening of the occurrence of hidden distress，the associated pavement distress is more likely to occur.
Review of Evaluation Methods for Mixing Workability of Asphalt Mixture
DONG Fuqiang, ZU Yuanzhe, YU Xin, CHEN Bei, and LIU Lin
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.009
To clarify the evaluation methods an d research status of mixing workability of asphalt mixture， by consulting relevant research literature in China and abroad and analyzing different evaluation methods，indexes，and research findings of the workability of asphalt mixture，the applicability and evaluation effects of different workability evaluation methods were systematically summarized，and the comparative analysis and comprehensive review were made on the main influencing factors of the mixing workability.The results show that in most evaluation methods for the mixing workability of asphalt mixture，corresponding indexes are constructed to quantitatively evaluate the workability by quantifying the resistance or energy consumption in the mixing process.Besides，in some other evaluation methods，workability can be evaluated by taking the compaction volume index or work effectiveness as indirect verification.The material composition and mixing conditions in the mixture directly affect the workability of the asphalt mixture.In addition，the improved workability can not only improve the forming and compaction performance of the mixture but also enhance the quality of road engineering.The improvement and enhancement of the evaluation method for the workability of asphalt mixture and the corresponding evaluation indexes can evaluate the workability of asphalt mixture more accurately and reasonably，which can promote the application of new road engineering technology and reduce energy consumption，pollutants，and carbon emissions.
Research Review of Biomass Ash as Concrete Admixture
MA Bicong, LIANG Jian, and WENG Yiling
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.010
In order to provide a comprehensive overview of research progress in the use of biomass ash as concrete admixture，the physical and chemical properties，mechanism of action，factors affecting the production process of biomass ash，and the effects of biomass ash incorporation on the working properties，mechanical properties，and durability of concrete were studied.The results show that biomass ash has a smaller density and a larger specific surface area than traditional mineral admixture，and the total amount of active components，namely SiO2 + Al2O3 + Fe2O3 （SAF） in most biomass ashes exceeds the requirements of class F volcanic ash （≥70%）.Incorporating biomass ash can effectively improve the mechanical properties and durability of concrete，but it may have a negative impact on the flowability and anti-carbonization performance of concrete.Moreover，the performance of biomass ash is greatly influenced by production processes such as combustion and grinding.To make biomass ash widely used in large-scale engineering in the future，it is necessary to optimize the production process of biomass ash.
Structural Repair and Performance Evaluation of Aged SBS Modified Asphalt
XU Guang, LI Qishi, KUANG Huaping, ZHANG Henglong, ZHOU Ruibo, and CHEN Yanmei
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.011
To rejuvenate the excellent performance of aged styrene-butadiene-styrene （SBS） modified asphalt，colza oil bio-asphalt （COA） and polymethylene polyphenyl isocyanate （PAPI） were used in this study for adjusting the asphalt components and repairing SBS molecular structure，respectively.The above-mentioned dual regeneration mechanism was verified by comparing the effects of different rejuvenation components on the physical and rheological properties，as well as the molecular weight distribution of short-term aged SBS modified asphalt.Moreover，according to the change law of rheological properties of unaged base asphalt and SBS modified asphalt under the effect of dual regeneration agent，the influence of the regeneration agent on the phase angle platform area was excluded.Under the comprehensive consideration of the physical and rheological properties of dual regeneration SBS modified asphalt，the optimal contents of COA and PAPI were determined.The experimental results indicate that the double regeneration agent can not only regulate the asphalt components but also connect the SBS molecular structure，restoring the physical and rheological properties of aged SBS modified asphalt.The optimal ratio of the dual regeneration agent is determined to be 12% COA and 1.25% PAPI.In addition，the fluorescence microscopy test results further verify that PAPI can rebuild the SBS network structure.
Compaction Characteristics of Granular Material and its Structural Mechanical Behavior Considering Orthotropy
HUANG You, ZHANG Yunbao, LIU Zhaohui, PAN Yu, LIU Zebin, and FANG Ronghai
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.012
The orthotropy of granular materials is closely related to the compaction process and has a significant impact on the mechanical behavior of pavement structures.In this study，in order to study the effect of the compaction process on the orthotropy of granular materials，different compaction methods and compaction energies were employed to compact granular materials for pavement into specimens，and improved dynamic resilient mechanical tests were conducted.Orthotropic coefficients （α2） of typical granular materials were obtained，and the finite element method was used to conduct mechanical analysis of asphalt pavement structures considering the orthotropy of granular materials.The results show that the dry density of specimens by gyratory compaction is slightly higher than that of specimens by impact compaction.Increasing compaction energy will increase the dry density and orthotropy of granular materials.Under low compaction energy，the orthotropy of granular materials by gyratory compaction is more significant，while under high compaction energy，the orthotropy of granular materials by impact compaction is more significant.The orthotropy of granular materials has a significant impact on the critical responses of asphalt pavement structures.Ignoring the orthotropy of granular materials will underestimate the risk of pavement structure damage.Moreover，considering the orthotropy of granular materials in pavement structure calculation can improve the tensile stress at the bottom of the granular material base and better reflect the actual situation.
Effect of Basalt Fiber on Strength of Cement‑Stabilized Macadam Base
SHU Hongbo, TANG Zhengguang, ZHANG Yanhong, BU Xilian, and LIANG Dong
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.013
To study the performance of basalt fiber in improving the poor angularity of the crushed cobble base，based on the orthogonal test，this paper determined that the optimal dosage of basalt fiber in the cement-stabilized crushed cobble was 1 kg/m3 （15 mm） + 2 kg/m3 （25 mm）.Besides，unconfined compressive strength and splitting strength tests were carried out on mixtures under three working conditions including the cement-stabilized crushed cobble，cement-stabilized crushed cobble with the optimal dosage of basalt fiber，and cement-stabilized macadam （limestone machine-crushed stone ）.The results show that influenced by the aggregate angularity，the strength of the cement-stabilized macadam （limestone machine-crushed stone ） mixture is better than that of the cement-stabilized crushed cobble mixture.For the cement-stabilized crushed cobble with the optimal dosage of basalt fiber，with the increase in curing age，its strength increases rapidly.Compared with the cement-stabilized crushed cobble without a dosage of fiber，its compressive strength is decreased by 0.08% on the seventh day and increased by 3.9%，17.1%，and 28.3% on the fourteenth day，the twenty-eighth day，and the sixtieth day respectively，and its splitting strength is increased by 4.3%，10.2%，19.0%，and 28.7% on the seventh day，the fourteenth day，the twenty-eighth day，and the sixtieth day，respectively.On the forty-fifth day，the strength of the cement-stabilized crushed cobble with a dosage of fiber reaches the strength of the cement-stabilized macadam （limestone machine-crushed stone ）.
Bridge Engineering & Tunnel Engineering
Vessel Collision Force and Anti‑Collision Performance of Long‑Span Beam‑Arch Composite Rigid Frame Bridge
ZHANG Wenming, WANG Zhiwei, and LAI Yaping
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.014
Beam-arch composite rigid frame bridge is a new bridge type，and it has few vessel collision studies.By taking the Lijia Jialing River Bridge as the engineering background，the standard value of vessel collision force and anti-collision performance of the long-span beam-arch composite rigid frame bridge were studied.After determining the representative vessel type and vessel collision calculation conditions，the vessel-bridge collision processes of the single-pier models under various calculation scenarios were simulated by using ANSYS/LS-DYNA nonlinear finite element transient dynamic software.The simulation results of collision forces were compared with the results of several empirical formulas.Finally，the full bridge model and the ultimate bearing capacity of the checked section were used，and the ultimate anti-collision force of the piers was obtained.Then，the anti-collision performance of the pier was evaluated.The results show that the vessel collision forces have a strong nonlinear fluctuation feature；the time when the maximum collision depth occurs lags behind the time when the maximum collision force occurs；the system energy during the vessel-bridge collision is mainly converted from the vessel kinetic energy to the internal energy of the local deformation of the bow.The results of different empirical formulas of vessel collision force vary greatly，and the dynamic simulation values are recommended.The checking results of the ultimate anti-collision force show that the anti-collision performance of the main piers of the Lijia Jialing River Bridge meets the requirements.
Installation and Connection Mode of Stiffening Beam Segment of Steel Truss Suspension Bridge
CHEN Changsong and WU Junjie
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.015
During the construction of long-span steel truss suspension bridges，the main girder can be connected in segment-by-segment articulated connection method and rigid-articulated connection combination method.Taking a Yangtze River Highway Bridge in Hubei Province as an example，this paper established the plane calculation model of the full bridge using the Bridge Design and Construction Monitoring System BDCMS to simulate the above two connection methods of the main girder in construction.From the comprehensive analysis of chord member internal forces and line shape of the stiffening beam，this paper finds that the rigid-articulated connection combination method is more appropriate in the construction.In addition，this paper researched the opening width of the temporary hinge through simulation calculation to obtain the optimal conversion time of articulated and rigid connections.
Seismic Responses of Cable‑Sta yed Bridge Considering Ponding Effect under Near‑Fa ult Ground Motions
LYU Long, YU Deen, YUAN Yuhang, and YANG Huaiyu
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.016
To study the influence of the pon ding e ffect on seismic responses of the cable-stayed bridge under near-fault ground motions，taking a double-tower cable-stayed bridge as the engineering background，this paper analyzed the ponding response of the main bridge and the main beam of the approach bridge of the cable-stayed bridge under near-fault ground motions and the influence of the ponding response on the structural seismic response.Besides，the influence of viscous dampers and elastic cables on the ponding effect of the cable-stayed bridge under near-fault ground motions was studied，which was compared with the seismic response of the cable-stayed bridge under far-fault ground motions to discuss the influence of the ponding effect on the seismic mitigation rate of the cable-stayed bridge.The results show that compared with non-pulse ground motions，under near-fault pulse-type ground motions， the main bridge and approach bridge of the cable-stayed bridge are more likely to collide within the pulse period，and the influence of the ponding effect on the seismic response of the cable-stayed bridge is more significant.When viscous dampers and elastic cables are installed，the main bridge and approach bridge still collide within the pulse period，but the ponding response decreases.Besides，the influence of the ponding effect on seismic responses of the cable-stayed bridge under pulse-type ground m otions is significantly reduced，and the ponding effect should be considered when the seismic mitigation rate of the cable-stayed bridge under pulse-type ground motion is analyzed.
Multi‑Dimensional and Multi‑Point Random Seismic Response Analysis of Long‑Span Cable‑Stayed Bridges at Different Sites
SHI Yi, LU Lu, FAN Shuli, SHEN Meng, ZUO Chunyuan, SUN Xinguo, and CAO Feifei
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.017
To study the random seismic response of long-span cable-stayed bridges at different sites，the site transfer function was used to evaluate the influence of different site conditions on ground motion propagation.By considering the traveling wave effect and the coherence effect，the multi-point power spectrum under different site conditions was generated.By using the pseudo excitation method for solving the absolute displacement，the seismic responses of cable-stayed bridges under uniform excitation and multi-dimensional and multi-point excitation at different sites were compared.A long-span cable-stayed bridge was selected as an example，and Ansys finite element software was used to analyze the random seismic response of the bridge.By considering the influence of site conditions on the seismic power spectrum，the random responses of the bridge under different excitation modes were calculated，and the power spectrum of each element of the bridge was extracted.The extreme root mean square of the power spectrum response was calculated.The results show that the amplification effect of soft soil on the random response of the bridge is about three times that of hard soil，and the amplification effect of multi-point excitation on the random response of the bridge is about 1.5 times that of uniform excitation.Therefore，the site effect has a great influence on the random seismic response of long-span cable-stayed bridges，and its influence cannot be ignored in bridge design.
Experimental Study on Influence of Stress Ratio on Fatigue Life of High Strength Steel Wire
ZENG Yi, YAN Donghuang, XU Hongsheng, and YANG Ying
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.018
To clarify the influence of stress ratio on the fatigue life of high strength steel wire and verify the applicability of the fracture mechanics model to evaluate the fatigue life of steel wire，based on the assumption of equating wire corrosion pits to notches，fatigue tests were carried out on steel wire samples with different prefabricated notch depths at different stress ratios，and a fatigue life empirical equation considering the stress ratio effect was established.The results show that the fatigue life of the steel wire samples is significantly influenced by the stress ratio，which decreases with the increase in the stress ratio.The increase in both prefabricated notch depth and stress ratio will lead to a decrease in the fatigue strength of the steel wire samples.The fatigue life of the steel wire samples is predicted by the fracture mechanics model considering the stress ratio effect，and the predicted values are within the error band of ± 2.0 times.The fracture mechanics model has certain applicability for predicting the fatigue life of notched steel wires at different stress ratios.
Rigid Domain Optimization of Steel Truss Joint with Reference to Multi‑Scale Model
LIU Gaocheng, LIU Jian, DONG Chuangwen, and LI Chuanxi
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.019
The rigidity enhancement effect of the integral gusset plate is often simulated in the calculation of an integral nodal steel truss bridge by using a beam element with a rigid arm to improve the calculation accuracy.By taking Zhongshan Lianshwan Bridge as the engineering background，an optimization method based on a multi-scale truss model for nodal rigid domain simulation was proposed and verified.Five consecutive standard sections were selected as the study objects，and the beam element model with rigid arm and the multi-scale model of gusset plate substructure were established by using Ansys.The same boundary and loading conditions were applied.The deflection of the main truss of the multi-scale model was used as the target deflection，and the deflection of the main truss of the beam element model with a rigid arm was fitted to the target deflection by changing the length of the nodal rigid arm.The length of the nodal rigid arm was substituted into the whole bridge model for subsequent calculations after the deflection was fitted，which optimized the length of the nodal rigid arm.The three models before and after optimization were calculated and analyzed for the construction process and bridge state.The comparison between the finite element calculation results and the measured data shows that the theoretical deflection after optimizing the nodal rigid domain is always in good agreement with the measured data，and under the maximum cantilever condition，the theoretical maximum deflection of the nodal domain is only 26.6% of the rigid domain，while the theoretical maximum deflection without considering the influence of the rigid domain is 124.1% of the measured value.The error is smaller than that under the overestimated rigidity，which indicates that the optimized model simulates the actual rigidity of the bridge better，while the error caused by the inaccurate simulation of the nodal rigidity enhancement effect may be larger than the error of ignoring the rigid domain.
Design and Simulation of Anti‑Collision System on Independent Pile with External Composite
LIAO Yuanyuan, LIU Yu, ZHU Lu, FANG Hai, ZHANG Jinrui, and HAN Juan
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.020
The precise calculation of the ship-bridge collision force is necessary for the assessment of the structural safety of the bridge and the design of an effective anti-collision system.Taking the ship-bridge issue in Furong Bridge in Xiangtan City，this paper compared the collision forces from different angles and in different locations calculated through the finite element software Ansys/LS-DYNA with the results calculated through the empirical formula，thereby determining the fortification collision forces of the bridge piers.Based on the weak anti-collision ability of the bridge double-limb thin-walled pier，the paper designed and implemented a new anti-collision system combined with composite and concrete-filled steel independent piles.The comparison between collision forces on the pier and independent pile with and without anti-collision devices shows that，with the anti-collision system，transverse and longitudinal collision forces under typical unfavorable conditions have a sharp decrease，which verifies the effectiveness of the system.
Influence of High Temperature on Large Cantilever Construction Control of Wide Extradosed Cable‑Stayed Bridge
ZHU Haojie, ZHANG Xiedong, LI Yong, LIN Yuan, and WU Di
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.021
In order to investigate the influence of temperature gradient on the construction of wide extradosed cable-stayed bridges in the large cantilever construction stage at high temperatures，the solar radiation and thermal boundary conditions of wide equal-height box girder were theoretically calculated，and the thermal analysis finite element model of the wide equal-height box girder was established by Abaqus.The cross-section temperature of the box girder was measured by intelligent string sensors and an infrared thermometer.The temperature gradient and its distribution of wide equal-height box girder from sunrise to sunset on a certain day in summer were calculated.The finite element model of the construction stage was established by Midas Civil，and the influence of positive temperature gradient on the main beam alignment and stress under control conditions of a large cantilever was analyzed.The results show that the results of the thermal analysis finite element model are in good agreement with the measured temperature results.The temperature gradient effect at the side and middle web of the wide equal-height box girder is the most significant.During the noon period at high temperatures，the vertical temperature gradient and the range of action at the top of the side and middle web of the wide equal-height box girder are higher than the specified value of the General Specifications for Design of Highway Bridges and Culverts （JTG D 60—2015）.The positive temperature gradient causes the main beam to deflect，and as the cantilever increases，the deflection effect of the main beam is more significant.Compared with no temperature gradient，the deflection of the cantilever end of the main beam increases by 36.08 mm after the maximum cantilever segment pouring，and the deflection of the cantilever end of the tail-cable tensioning main beam increases by 40.23 mm.The positive temperature gradient makes the compressive stress on the roof of the main beam increase significantly.
Method of Solving Initial Construction Cable Force of Completed Cable‑Stayed Bridge
XU Yufeng, CHEN Si, XIE Yunfei, and ZHU Mengyang
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.022
To solve the initial construction cable forces of a completed cable-stayed bridge，a method that combines unstressed cable length and forward-iteration is proposed.Firstly，the unstressed length of each cable is calculated according to the completed bridge state.Then，the initial cable forces are obtained by using the unstressed cable length for the forward analysis.The initial construction cable forces are adjusted by difference iteration.Finally，the initial construction cable forces are fine-tuned according to the deformation of the pylon deformation to obtain the bridge completion state that satisfies the deviation requirements.The proposed method is employed in a cable-stayed bridge with a known completion state to calculate the initial construction cable forces.The example shows that the calculation workload can be reduced by this method.The deviation of this completed state from target meets engineering accuracy requirements.
Impact Resistance of ECC Pipe Piles Based on LS‑DYNA
ZENG Qingyou, YE Chenfeng, LIU Junjun, FENG Kai, CHENG Peiyuan, and CHEN Weihong
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.023
To study the impact resistance of Engineering Cementitious Composite （ECC） pipe piles，this paper used ANSYS/LS-DYNA to simulate the impact of a vertical drop hammer on the pipe piles.The HJC constitutive model of ECC was established based on key parameters obtained from static tension and compression tests and dynamic compression tests.The correctness of the finite element model was verified by split Hopkinson Pressure Bar （SHPB） tests.The parametric analysis conducted on the pipe pile models compounded with different hammer mass and impact velocity yielded dynamic responses including the displacement，time-history curve of energy，and effective plastic strain diagrams of the pipe piles under various impact energies.The results show that under the action of vertical impact，the maximum residual deformation of ECC pipe piles is only 66.0% of that of high-strength concrete （HC） pipe piles，and the minimum residual deformation is only 13.7% of that；in addition，the proportion of deformation energy released by ECC pipe piles is 6.26 times that of HC pipe piles on average.These results show that ECC pipe piles have better damage resistance and elastic recovery ability than HC pipe piles.
Comparative Study of Different Ventilation Methods during Tunnel Construction
YUE Kun, BAO Xiaohua, AO Xiang, LIU Kuan, WU Han, LI Tao, and SHEN Jun
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.024
The continuous improvement of tunnel construction technology brings a rapid increase in the speed and mileage of tunnel excavation，during which ventilation is a main problem affecting construction efficiency and safety.Taking the Zhuhai Xingye Express （West Line ） tunnel project as an example，this paper studied the influences of forced ventilation，exhaust ventilation，and hybrid ventilation on the dilution and discharge of harmful gas CO near the tunnel face and the wind speed in the tunnel.The results show that hybrid ventilation performs better in CO dilution，while exhaust ventilation has higher CO emission efficiency with a lower wind speed near the working face.Therefore，although forced ventilation is slightly weaker in terms of CO dilution and discharge efficiency，it is still demanded in tunnel construction when maintaining a certain air volume near the working face is considered.
Treatment and Measurement of Water Inrush during Highway Tunnel Construction
WANG C haojie, FENG Zhihua, and FAN Haobo
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.025
As a special geological condition of highway tunnels，water inrush will cause difficulties in engineering construction technology and management.Unnecessary disputes and management difficulties will emerge when different construction units hold different views about the treatment measures of water inrush，which leads to distributed provisions in the specification and a long treatment period.In view of key problems about the water inrush during highway tunnel construction，including water inrush treatment concept，investigation and estimation，measurement and pricing，and on-site confirmation，this paper systematically sorted out the current regulations and other guiding documents and investigated the treatment methods of tunnel water inrush and reverse slope pumping in China ’s highway and railway industries.Besides，based on the existing practical experience，this paper pointed out important issues including reasonable labor division that should be considered by development units，investigation and design units，supervision units，and construction units，which can provide a useful reference for the construction management of water inrush treatment in highway tunnels in the future.
Stability of Excavation Face of Double‑Mode Shield in Earth Pressure Mode Crossing Fault Zone of Pearl River
TONG Bin, ZHANG Bin, ZHU Hanbiao, and WANG Shuying
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.026
In view of the stability of the excavation face of the double-mode shield crossing the fault zone of the Pearl River，the project of the section from Hongshengsha Station to Yufengwei Station of the second phase of Guangzhou Metro Line Seven was studied.Through numerical simulations conducted to analyze the whole area and the local high-risk area of the shield crossing the fault zone of the Pearl River，this paper explored the construction risk of the shield crossing process.Besides，this paper analyzed the influence of different support stresses and grouting pressures on the stability of the excavation face and ground deformation，and finally，the tunneling parameters analysis was used to evaluate the rationality of numerical simulation.The results show that ① when the tunnel excavation surface is distributed with soft soil above and hard soil below，large ground settlement is prone to occur during the shield tunneling process.When it is distributed with hard soil above and soft soil below，large ground uplift is prone to occur；② The excavation face is likely to become unstable in the weak local stratum when the shield passes through the composite stratum.The soil mass in the weak stratum deforms towards the inside of the tunnel when the support stress is less than the static earth pressure in the weak stratum，and the deformation increases with the reduction of the support stress ratio；③ The grouting pressure does not affect the stability of the excavation face but is inversely proportional to the ground settlement.Greater grouting pressure indicates lighter ground settlement，and the shield tunneling verifies the correctness of the numerical simulation results.
Smart Road and Intelligent Transportation
Intelligent Recognition Technology of Highway Cracks Based on Semantic Segmentation
GAO Liang, RAO Faqiang, YANG Zhongmin, DAI Zongsheng, and SUN Hao
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.027
Real-time detection and timely treatment of highway cracks are crucially fundamental for vehicle safety.Rapid identification and comparison of cracks is a new method for monitoring the development and changes of geological disasters especially when they induce cracks.Therefore，this study proposed an intelligent recognition method of highway cracks based on semantic segmentation，establishing a model with dataset，neural network，calculation parameters，and evaluation indicators to rapidly identify the cracks.The results show that，firstly，when the neural network Attention U-net built in this study semantically segments highway cracks，the binary cross loss function value and accuracy rate reach 0.008 7 and 0.998 4，respectively.Secondly，compared with traditional algorithms，the semantic segmentation method shows higher accuracy，reliability，and superiority in intelligent recognition of highway cracks，with a Dice similarity coefficient of 0.978.Thirdly，the semantic segmentation method has better robustness and generalization ability to deal with brightness and noise.
Deformation Measurement and Safety Warning of Highway Bridges Based on Machine Vision
SU Ziyue, DU Wenkang, and LEI Dong
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.028
The structural safety of highway bridges plays a crucial role in traffic safety operations and regional economic development.Due to the rapid increase and complex changes in traffic loads，the demand for real-time monitoring of bridge ’s structural deformation and safety conditions has been increasingly prominent.However，the structural health monitoring system，dominated by contact sensors，has limitations such as difficult installation and construction，complicated maintenance and replacement，and the need to interrupt traffic.To this end，a non-contact deformation measurement system based on machine vision was proposed.Template matching and feature point recognition methods were utilized to achieve recognition of structural surface markings and displacement extraction of key positions.The accuracy and stability of visual methods were tested through laboratory and on-site experiments.In addition，a corresponding finite element model was built for the actual operation status of the bridge structure，and the multi-level warning threshold was set through the dynamic and static mechanical experiments to further determine the safety status of the structure.The experimental results show as follows.① The displacement measurement error of the established visual deformation measurement system is within 5%，and the error of vibration frequency is within 1%；② Measurement techniques based on template matching and feature point recognition can recognize the inherent features of structures，and meet the needs of long-term deformation monitoring；③ Through finite element analysis under multiple working conditions，warning thresholds can be set for long-term displacement monitoring of structures.
Overall Design Concept of Municipal Reconstruction of Cross‑City Expressway
FU Yuankun and ZHANG Yu
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.029
The municipal reconstruction of the cross-city expressway is of great significance in enlarging the urban framework，refining the spatial pattern，and promoting the integrated development of clusters.However，China’s expressways seldom undergo municipal reconstruction，with less synergy formed with cities.Therefore，taking one case described above in Hebei Province as an example，this article proposed the overall design concept of integrating with the city from urban space，road networks，municipal facilities，urban ecology，cultural landscape，and other perspectives after analyzing problems in urban space，traffic，industry，landscape and urban quality in existing cross-city expressways. In addition，this paper studied and optimized the municipal reconstruction plan.Holding a theme of “municipalization ”，the plan eliminated the fragmentation of urban space by expressways and strengthened the integration of expressways and cities.
Road Maintenance and Environmental Protection
Development Trend on Raw Materials Market of Ready‑Mixed Concrete under Green Construction
DING Hu, DING Qingjun, LIN Haojun, and ZHANG Zhen
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.030
In the face of resource depletion，high energy consumption in production，high carbon emissions，and serious pollution brought by traditional pumpcrete raw materials，a variety of new raw materials have been gradually developed and promoted to conform with the green construction promoted by China ’s civil engineering industry，witnessing a stable increase in quality，output，and social recognition.High-quality natural river sand and pebbles are in short supply at the origin，and they can be explored in old silted river channels.Gravel and manufactured sand produced using large particle size natural pebbles，limestone，construction waste，and others as raw materials will become new substitutes.In the transformation and upgrading of production enterprises which tend to build factories in areas with transportation convenience，raw materials including cement，fly ash，and granulated blast furnace slag powder will cause uneven supply in plains，hills，mountains，and other terrains.Therefore，it is required to use local materials according to the situation in the construction site.Polycarboxylic set retarding superplasticizer，though already popularized in the market for its high efficiency，low cost，high compatibility，and convenience in construction，still needs to be more compatible with manufactured sand and other materials.The compensation shrinkage of concrete by calcium and magnesium expansion agents should be synchronized with concrete shrinkage to control shrinkage cracks and avoid structural cracking.In the preparation of pumpcrete，the investigation at the height of the life cycle of buildings，the improvement of the performance of various raw materials，and the utilization of the combination effects of raw materials are all necessary.
Post‑Evaluation Method for Decision‑Making and Implementation of Highway Maintenance Projects Based on AHP‑DEMATEL
YU Wei, YANG Na, and LI Jue
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.031
Addressing the current lack of post-evaluation management systems related to highways，particularly highway maintenance，this paper proposed a post-evaluation method for the decision-making and implementation of highway maintenance projects based on the combination of analytic hierarchy process （AHP） and decision-making trial and evaluation laboratory （DEMATEL ）.After building a post-evaluation model for the decision-making and implementation of highway maintenance projects and designing the evaluation process，this paper calculated key factors influencing the post-evaluation of the decision-making and implementation of highway maintenance projects and their respective comprehensive weights.The research results indicate that decision-making can possess higher accuracy and efficiency under the above calculation method，providing a reference for project planning.
Foreign Highway
Lessons Learned from 60 Years of Pavement Trials in Continental Climate Regions of Canada and Future Perspective
WANG Di, LI Jingxiao, REN Xueyuan, ZHANG Fan, and YUAN Dongdong
Date posted: 10-28-2024
DOI: https://doi.org/10.14048/j.issn.1671-2579.2024.05.032
During the early 1960 s，Canadian road authorities began using stiffer asphalt to address the issue of early rutting in the wheel track zone of asphalt pavements，which was caused by the growing traffic volumes.Pavements constructed with stiffer asphalt commonly exhibit evenly spaced transverse cracks due to the significant internal stresses caused by low temperatures and the inadequate resistance of the asphalt to cracking under such conditions.Research conducted on asphalt pavements with cracks caused by low temperatures has verified the significant impact of asphalt ’s consistency，temperature sensitivity，phase uniformity，and durability.In order to tackle the difficulties presented by the utilization of modified asphalt in the current asphalt performance evaluation system，the Canadian asphalt pavement test section during the 1990 s was used to examine and assess the dependability of the U.S.Superpave ™ specification.The results reveal that blown asphalt exhibits inadequate durability，while polymer modifiers only improve the durability of soft asphalt.In the early 21st century，the Ontario municipality commissioned studies on asphalt pavement test sections to enhance the current asphalt performance test specifications.These studies mainly considered the occurrences of phase separation，phase transformation，and thermally reversible aging （gelation） of asphalt，as well as the impact of polymers and fibers on the durability of asphalt.The results find that using different types of colloids （sol，gel，and sol-gel ） in the same Superpave level can result in asphalt pavements with benefit/cost ratios varying by up to 2‒3 times.By assessing and choosing the appropriate type of asphalt，such as Alberta oil sand asphalt （sol），the service life of asphalt pavements can be prolonged.Compared with polymer-modified asphalt with high content，more oxidized recycled asphalt，or asphalt with higher wax content （gel），Alberta oil sand asphalt has lower wax content.The service life of asphalt pavements can be further improved by incorporating small quantities of polymer or fiber modification.Improved test specifications for asphalt cement will help save costs and meet the maintenance needs of 25 million km of asphalt pavements under global climate change.On the basis of summarizing the research of asphalt pavement trials in Canada in the past 60 years，new prospects and suggestions on the future research content and key technical problems of pavements in cold areas are put forward，which can provide a reference for future research.
