交通运输工程学报

Hierarchical object method of highway route selection in permafrost region

WANG Shuang-jie, YAN Xiao-min, ZHANG Chi, MENG Liang, YANG Kun

Abstract: In order to design the highway route in permafrost region, the hierarchical object method to protect the permafrost from coarse to fine, from surface to belt, from band to line was proposed based on multi-scale effect theory, and the theory model was constructed. Combined with the display forms of different topographies, landforms, existing projects, structures, and buildings in different scales, the hierarchical division of hierarchical object method was given, and the influence factors of highway route selection in each level were determined. Considering the influence of route node's importance degree, topography and landform in permafrost region, the highway route selection model in the first level was given. The scale classifications of average altitude, average slope, annual average ground temperature, permafrost distribution, talik structure, and existing projects were obtained by using commensurability principle, and then thehighway route selection difficulty degree model in permafrost region was established in the second level. The permafrost hazards caused by permafrost ground temperature, permafrost ice content, permafrost disaster, and vegetation coverage were considered synthetically, and the thermal disturbance among existing projects in permafrost region was also taken into consideration, then the highway route selection reliability model in the third level was established. The permafrost region of Qinghai-Tibet Plateau from Xiushui River to Yamarle River was taken as example, and the route selection was carried out by using hierarchical object method. Analysis result shows that the route plan determined by hierarchical object method can accurately avoid the permafrost region with high disease rate and evade the disturbance among existing projects, and a route plan with low engineering difficulty degree and high engineering reliability is achieved.More>

2016, 16(4): 1-13. doi: 10.19818/j.cnki.1671-1637.2016.04.001

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Highway intelligent route selection method in permafrost region of Qinghai-Tibet Plateau

ZHANG Chi, YANG Kun, WANG Shuang-jie, YANG Hong-zhi, SHAO Guang-jun

Abstract: To solve the problem that traditional highway route selection method can not fully consider the complex geographical environment in the permafrost region of Qinghai-Tibet Plateau, the spatial data analysis technology of geographic information system(GIS)and intelligent evolutionary algorithm were introduced into the highway route selection process in permafrost region. The spatial data mining in the permafrost region of Qinghai-Tibet Plateau was finished by using GIS, the influence of the microtopography of the permafrost region on highway route selection was considered from the continuity degree and development degree of the influence factors of frozen soil diseases, and the risk degree calculation model of frozen soil disease was established. The component GIS was developed by using object-oriented components technology, and then applied in the permafrost region of Qinghai-Tibet Plateau, so the analysis and extraction of complex geographic information in the permafrost region were completed. The route optimization genetic algorithm and the adaptive iterative method were established, and with the aid of particle swarm algorithm, the route optimization model was set up based on the genetic algorithm. A road section of the route corridor of Qinghai-Tibet Plateau between Xidatan and Kunlun Mountains pass was selected as an example, and the highway intelligent route selection was researched, and the final route position scheme was obtained. Analysis result shows that in the experiment based on real environmental data, the optimal scheme with the least of risk degree is obtained after about 60 th iteration, and the risk degree is stable at about 3. 75. So the intelligent route selection method in the permafrost region of Qinghai-Tibet Plateau can combine the risk of all kinds of frozen soil diseases, and specify the area with less impact of frozen soil disease for highway layout. The optimized scheme effectively takes into account the "initiative protecting permafrost, ensuring the stability of roadbed, friendly ecological environment, economic-reasonable layout"requirements, and can be used as the reference method for highway route design in the permafrost region.More>

2016, 16(4): 14-25. doi: 10.19818/j.cnki.1671-1637.2016.04.002

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Automatic detecting method of cement concrete pavement fault

ZHANG Juan, YE Li, LI Wei

Abstract: In order to realize the automatic detection of cement concrete pavement fault, the active optical 3D shape measurement technique was analyzed, area array CCD camera was used to receive the measurement images, the detecting platform of fault was established based on the line laser 3D scanning, and mainly included the power subsystem, the acquisition subsystem of cement road surface image, the external trigger subsystem and the GPS positioning subsystem. The noise filtering threshold was determined according to the noise characteristics of 3Ddetecting data of cement concrete pavement, the open and corrosion operations were implemented for eliminating the isolated points in the data after the mean square deviation filtering. 3D data matrix was divided into homogeneous blocks according to its size, the blocks mean was used to eliminate the incline of data matrix, the inflection point matrix was obtained according to each row inflection point of 3Ddata matrix, and the faulting values were calculated. In order to verify the feasibility and validity of the method, parallel fault, trapezoid fault and cross fault weresimulated and respectively detected three times according to the fault sizes in the laboratory, and the detecting result was compared with the testing result of leveling instrument. The same fault was repeatedly measured 10 times by the leveling instrument and the 3D detecting method to verify the reproducibility of 3D detection method. Experimental result shows that 96% of absolute errors between the measuring values using the 3D detection method and the leveling instrument are less than 1mm, the standard deviation is about 7.8 times larger using the leveling instrument than using the 3Ddetection method, so the 3Ddetection method has higher accuracy, stability and reproducibility and can be used in the automatic detection of concrete joint fault.More>

2016, 16(4): 26-36. doi: 10.19818/j.cnki.1671-1637.2016.04.003

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Mechanical property of polypropylene fiber reinforced concrete under freezing-thawing cycle effect

YAN Wu-jian, NIU Fu-jun, WU Zhi-jian, NIU Fu-hang, LIN Zhan-ju, NING Zuo-jun

Abstract: Through fast freezing-thawing cycle test on four groups of polypropylene fiber reinforced concretes with different mix proportions, the compressive strength, longitudinal wave velocity and dynamic elastic modulus of concrete after different times of freezing-thawing cycleswere obtained, the mechanical property and damage amount characteristics of polypropylene fiber reinforced concrete under freezing-thawing cycle effect were studied, and the effects of material property, material mix proportion and times of freezing-thawing cycles on the mechanical property were analyzed. Analysis result shows that after 200 times of freezing-thawing cycles, the compressive strength loss rates of C30 polypropylene fiber reinforced concrete without air entraining agent, C30 polypropylene fiber reinforced concrete with air entraining agent, C40 polypropylene fiber reinforced concrete without air entraining agent and C40 polypropylene fiber reinforced concrete with air entraining agent are 46. 53%, 49.05%, 34.56%and 37.64%respectively. After 300 times of freezingthawing cycles, the longitudinal wave velocities of four groups of polypropylene fiber reinforced concretes decrease by 8.42%, 6.48%, 16.72%and 11.68%respectively, and the dynamic elastic moduli decrease by 46. 54%, 35.72%, 54.41% and 53.72% respectively. After 150 times of freezing-thawing cycles, the damage amounts of C30 and C40polypropylene fiber reinforced concrete increase rapidly, and the damage amount of C40 polypropylene fiber reinforced concrete is bigger than that of C30 polypropylene fiber reinforced concrete. Under the same times of freezing-thawing cycles, the damage amount of C40 polypropylene fiber reinforced concrete without air entraining agent is biggest. The improving effects on frost resistance property from big to small are C30 polypropylene fiber reinforced concrete with air entraining agent, C30 polypropylene fiber reinforced concrete without air entraining agent, C40 polypropylene fiber reinforced concrete with air entraining agent, C40 polypropylene fiber reinforced concrete without air entraining agent.More>

2016, 16(4): 37-44. doi: 10.19818/j.cnki.1671-1637.2016.04.004

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Cooling effect of thermosyhpon subgrade for Qinghai-Tibet Highway

JIN Long, WANG Shuang-jie, MU Ke, PENG Hui

Abstract: In order to analyze the engineering effect of thermosyphon subgrade in permafrost regions and quantitatively evaluate its cooling effect, the 11 years'observational data were collected from the thermosyphon subgrade test project of Qinghai-Tibet Highway, the ground temperature characteristics, temperature field profiles and freezing-thawing process of thermosyphon subgrade were analyzed, and the horizontal thermal budget near the thermosyphons under the influence of shady-sunny slope effect was evaluated. A threedimensional unsteady coupled air-thermosyphon-foundation computation model was proposed, and the cooling effects of thermosyphon subgrades with different structures, such as one-side vertical type, one-side inclined type, two-side vertical type and two-side inclined type, were investigated. Measured result shows that the monitoring data indicates that the ground temperature of thermosyphon subgrade at sunny side is about-1.5 ℃, 3.0 ℃ lower than thevalue of traditional subgrade, and the lowest ground temperature at shady side can reach to-2. 1 ℃. During 11years'operation of thermosyphon subgrade, the permafrost table at sunny side elevates about 0.95 m, and basically reaches to the level of natural foundation. The mean annual actual powers of thermosyphon subgrades at shady side and sunny side are about 69. 80 and 54.07 W, respectively. During the previous 5years, the thermosyphon presents a larger power. After 6th year, the power gradually decreases, and the thermal state of subgrade tends towards stability. Calculated result shows that after 20 years, the permafrost tables under the two-side vertical and inclined type thermosyphon subgrades are 2.88 and 1.88 mrespectively, the permafrost tables under one-side vertical and inclined type thermosyphon subgrades are 3. 84and3. 46 m, respectively, so, the two-side type thermosyphon subgrade expresses a stronger longterm cooling effect than the one-side type thermosyphon subgrade, similarly, the inclined type thermosyphon subgrade has a stronger cooling effect than the vertical type thermosyphon subgrade. The annual average power of one thermosyphon varies from 47 Wto 56 W, agreeing well with the monitoring data.More>

2016, 16(4): 45-58. doi: 10.19818/j.cnki.1671-1637.2016.04.005

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Applicable effect of thermosyphon subgrades in permafrost regions

LIU Ge, WANG Shuang-jie, JIN Long, DONG Yuan-hong, YUAN Kun

Abstract: In order to investigate the applicable effect of thermosyphon in permafrost regions along Qinghai-Tibet Highway, 8years'observational ground temperature data were collected from Chuma'er River test site, and the effective radius of thermosyphon was evaluated by taking the horizontal temperature gradient as the index. Additionally, to enhance the temperature-adjusted effect of thermosyphon, extend its application scope and meet the using demand of strong heat absorption of widened subgrade, the observational ground temperature data of the subgrade with XPS insulation board and thermosyphons and the subgrade with rock-crushed interlayer and thermosyphons at Beilu River and Anduo test sites were analyzed. Analysis result shows that the effective radius of thermosyphon after 1year's operation is about 2.3 m, and the influencing range gradually increases with the increase of operational time. Within the first 5 years of thermosyphon operation, the ground temperature obviously decreases, the ground temperature's decreasement around the thermosyphon is over 0.5 ℃, and then, the ground temperature slowlydecreases, which results from the decrease of ground-air temperature difference because of the increase of air temperature and the gradual decay of work motivation of thermosyphon. During8 years of thermosyphon operation, the artificial permafrost tables of thermosyphon subgrades are almost unchangeable because of thermosyphons'continuing refrigeration, while the maximum decrease of contemporaneous artificial permafrost table of common subgrade is about 80 cm. Since June for the subgrade with XPS insulation board and thermosyphons, the temperature difference between top and bottom of XPS insulation board gradually increases, and the maximum value is17 ℃, which effectively mitigates the downward transfer of heat in warm seasons. In 2years'adjustment of subgrade with crushed-rock interlayer and thermosyphons, the maximum decrease of ground temperature is 0.51 ℃.More>

2016, 16(4): 59-67. doi: 10.19818/j.cnki.1671-1637.2016.04.006

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Differential settlement of widened subgrade in cold and high-altitude permafrost regions

MU Ke, YUAN Kun, JIN Long, DONG Yuan-hong

Abstract: In order to study the influence of heat absorption of widened subgrade surface on underlying permafrost's temperature and settlement in cold and high-altitude permafrost regions, a finite element model computing the differential settlement of widening subgrade based on the thermal-mechanical coupled theory was established and corrected by the monitoring data of practical engineering, the differential settlement distributions under diverse seasons, different filling heights and working conditions at sunny and shady slope sides were studied, and the optimal widened location of subgrade in permafrost regions was determined. Research result shows that the maximum melting depth and settlement of widened subgrade appear in autumn, October is most unfavorable for subgrade settlement, and disease characteristics are remarkable. When the filling height of subgrade is 4 m, the maximum differential settlement of subgrade is16.9cm and 1.1, 1.4, 1.7times larger in October than in July, January and April within 10 years. Within 10 years, when the filling heights of subgrade are 2, 4 and 6 m respectively, thedifferential settlements are 13.2, 16.9 and 18.1 cm respectively, so the differential settlement increases with the increase of filling height. Within 10 years, the maximum rising temperature of subgrade is 1.3 ℃ at sunny slope side and 0.6 ℃ at shady slope side, the maximum differential settlement of subgrade is 16.9cm at sunny slope side and 12.3 cm at shady slope side, so the temperature and settlement of widened subgrade change smaller at shady slope side than at sunny slope side. Even widening subgrade at shady slope side, the differential settlement of subgrade still results in a 2%-3% slope at the top of subgrade, the slope will result in the great additional stress of pavement, so that the diseases of pavement structure occur.More>

2016, 16(4): 68-77. doi: 10.19818/j.cnki.1671-1637.2016.04.007

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Evolution laws and failure characteristics of subgrade deformation in alpine permafrost region

LI Jin-ping, ZHANG Juan, CHEN Jian-bing, ZHU Dong-peng, YUAN Kun

Abstract: In order to further study the evolution process of subgrade deformation failure in permafrost region, the subgrades at section of K6+200 in the high-temperature and ice-rich permafrost region and at section of K8+200 in the low-temperature and ice-rich permafrost region along Mobei Highway were choose as research objects, the temperature and deformation sensors were installed at different positions and different depths of subgrades, and the evolution processes and characteristics of measured temperatures and deformations under different conditions in highlatitude and alpine permafrost region were analyzed. Analysis result shows that in hightemperature and ice-rich permafrost region, an obvious offset of thaw bulb under subgrade is formed after 2years service period. Transverse uneven deformation feature of newly-built widesubgrade is observed obviously, there are two thaw bulbs under subgrade, one obviously offsets to the slope toe of subgrade. The permafrost tables at left slope toe and the center of road obviously decrease by 3-4 m, and the settlement of the original natural surface under subgrade is 4-9 cm after 2 years service period. The permafrost table at shoulder remains stable. In lowtemperature and ice-rich permafrost region, under ensuring a certain height of subgrade, besides the deformation(post-construction settlement)of subgrade soil in early service time, the subgrade deformation caused by permafrost melt is very small, therefore the subgrade stability in low-temperature permafrost region is relatively superior. So, the conclusion further illustrates the causes of serious deformations of subgrade and pavement in high-temperature permafrost region, and offers the reference for the design and disease control of pavement damage resistance in high-latitude and alpine permafrost region. The result further illustrates the failure characteristics and reasons of uneven deformation, such as settlements, longitudinal crack and so on. It is concluded that under ensuring a certain height of subgrade, the subgrade has relatively better stability in low-temperature permafrost region than in high-temperature permafrost region, and this result has great significance for subgrade design and disease control in high-latitude and alpine permafrost region.More>

2016, 16(4): 78-87. doi: 10.19818/j.cnki.1671-1637.2016.04.008

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Impacts of runoff scouring on high-grade highway slope erosion in alpine and high-altitude regions

DAN Yong-ti, HU Lin, WANG Qi, CHEN Rui-hua, GUO Wen

Abstract: In order to expound the erosion laws on high-grade highway slope in alpine and highaltitude regions and provide theoretical basis for the prevention and treatment of water and soil loss for highway slope, subgrade bare slope of Gonghe-Yushu Highway in Qinghai Province was chosen as research object, field runoff scouring experiments were carried out to analyze the erosion laws of sink flow on high-grade highway slope in alpine and high-altitude regions, and protection strategy was expounded. Analysis result shows that runoff produce times with flow rates of 6.0, 10.0, 14.5L·min^-1 respectively advance by 23.83, 107.63, 108.13 scompared to runoff producing time with flow rate of 3. 5L·min^-1. The bigger scouring flow rate is, the shorter runoff producing time is. Total sediment yields with flow rates of 3.5, 6.0, 10.0, 14.5L·min^-1 are14. 65, 20.42, 43.61, 32.20 kg respectively, so the sediment yield first increases then decreases. The relationship between accumulative runoff yield and accumulative sediment yield meets power function form. Scouring flow rate and erosion sediment yield show significant positive correlation. Obviously reducing pavement runoff effectively is the key to decrease highway slope erosion amount, the supporting drainage measures should have the function of collecting and discharging pavement sink flow quickly, masonry protection measures should be reduced in slope protection in alpine and high-altitude regions, and reasonable covering and soil fixing measures should be taken when slope vegetation is in recovery.More>

2016, 16(4): 88-95. doi: 10.19818/j.cnki.1671-1637.2016.04.009

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Characteristics of runoff and sediment yields for highway slope under different vegetation measures in Qinghai-Tibet Plateau

HU Lin, WANG Qi, DAN Yong-ti, CHEN Rui-hua, GUO Wen, LI Zhan-bin

Abstract: In order to explore the erosion law on highway slope with vegetation protection measures and improve highway slope vegetation protection technology in Qinghai-Tibet Plateau, field scouring tests were carried out to study the characteristics of runoff and sediment yields on highway slope in Qinghai-Tibet Plateau under different vegetation protection measures including bare slope, three dimensional network seeding and artificial turfing, and the protection efficiency and sediment interception mechanism under different measures were analyzed. Test result shows that when the scouring flow rates are 3and 8L·min^-1 in Qinghai-Tibet Plateau, the average initial producing times are 225.50 and 163.27 s respectively. There is significant correlation among the initial runoff producing time, the flow rate and the vegetation coverage. The runoffproducing stably time under scouring flow rate of 8L·min^-1 advances by about 2 min compared to the scouring flow rate of 3L·min^-1. The sediment interception effect of vegetation measures mainly embodies in interception of sediment with coarse particles. The slope runoff and sediment yields decrease with the increase of vegetation coverage. The average runoff and sediment interception efficiencies of vegetation measures are 55.7% and 53.5% respectively. The orders of comprehensive protection effects from big to small are three dimensional network seeding with 74% coverage, three dimensional network seeding with 37% coverage, artificial turfing in the middle, artificial turfing at the top, and bare slope. The comprehensive recovery technology of slope vegetation combining turf as frame and three dimensional network seeding is suggested.More>

2016, 16(4): 96-103. doi: 10.19818/j.cnki.1671-1637.2016.04.010

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Early refreezing law of large-diameter cast-in-place piles in permafrost regions

FU Jin, JIANG Yu, PENG Hui, DONG Yuan-hong, YUAN Kun

Abstract: Based on the design and construction of pile foundation concrete in permafrost regions, the early refreezing law of large-diameter cast-in-place pile in permafrost regions was studied. Through pile filed test and numerical simulation model, the hydrate heat of concrete and the permafrost refreezing law around pile were analyzed. Analysis result shows that pile side temperature is above 1 ℃ within 25 d after finishing pouring, and gradually recovers to 0 ℃ in 45 d after finishing pouring. Numerical simulation result shows that the pile temperature decreases to 0 ℃in 60 d after finishing pouring. The soil mass around pile is refrozen to natural state in 200 d after finishing pouring. Every 2 ℃ increase of molding temperature results in 1 ℃ increase of peak temperature at pile side and 0.5 ℃ increase of peak temperature at two times of pile diameters away. For large-diameter pile foundation, the addition of hardening accelerator to pile foundation concrete can be avoided or decreased. It is not necessary to sedulously decrease the molding temperature of mixture. The best construction time of pile foundation is in warm seasons, which can provide a good external condition for concrete curing.More>

2016, 16(4): 104-111. doi: 10.19818/j.cnki.1671-1637.2016.04.011

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Fuzzy expert prediction method for highway diseases in permafrost region

WANG Shuang-jie, XIONG Li, ZHANG Chi, MU Ke, JIN Long

Abstract: To predict the disease sections of newly-built highway in permafrost region and assist the decision-makers to carry on the reasonable design at design stage, a highway disease prediction method in permafrost region was proposed based on fuzzy expert system. The disease degree was used as analysis index, a road section of the Qinghai-Tibet Highway was selected as research object, and the influence factors of road disease were qualitative analyzed. The disease degrees of Qinghai-Tibet Highway were divided into 3levels according to actual disease data. Combined with the years of disease data of annual average ground temperature, ice content and frozen-heave factor of Qinghai-Tibet Highway, the fuzzy expert system for identifying disease sections in permafrost region was built. A variety of influence factors were used as input variables, and the disease degrees of the 10 equidistance road sections in permafrost region were calculated by using the Fuzzy Logic Toolbox of MATLAB. The calculated disease degree and the actual disease degree were compared and analyzed by using SPSS software. Analysis result showsthat the road disease degree increases with the increase of annual average ground temperature, ice content and frozen-heave factor, the relevance between the calculated disease degree and the actual disease degree is 0.751, so, the application of fuzzy expert system in the prediction of highway diseases in permafrost region has a beneficial effect.More>

2016, 16(4): 112-121. doi: 10.19818/j.cnki.1671-1637.2016.04.012

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Evaluation on snow calamity along Qinghai-Tibet Highway corridor based on multi-source remote sensing data

YU Hui, ZHANG Ling-mei, WANG Zuo, LU Xun, ZHAO Li-ting

Abstract: Based on the multi-source remote sensing data, the spatial distribution characteristic of the snow cover along the Qinghai-Tibet Highway corridor was surveyed, and the snow calamity was evaluated for key road sections. Terrain and mountain snow cover characteristics were fully considered, the cloud-removing of daily snow cover was finished by jointly using of types of cloud-removing processes and steps. The annual average snow cover days were statistically counted by the data of cloud-removed MODIS daily snow cover area. The highway snow cover information within a large scale was extracted and used to determine the key snow cover sections along the entire road. Taking the advantage of high spatial resolution of Landsat images, the snow area and snow-free area of key sections were identified by using normalized difference snow index threshold method, the spatial distribution information of snow cover of key sections along the highway was effectively extracted, which would contribute to more accurate observation and evaluation on highway snow calamity. Based on the temporal-spatial information of images, theground surface temperature information under cloud cover was rebuilt, and the representative questions were analyzed and verified. Using the reconstructed MODIS daily ground surface temperature, annual average ground surface temperature was computed, the snow calamity information in the key snow cover road sections along the Qinghai-Tibet Highway corridor were determined and extracted. Analysis result indicates that evaluation method is able to effectively monitor and extract the snow cover distribution along the Qinghai-Tibet Highway corridor, and the key snow cover regions are Kunlun Mountains, Wudaoliang, Fenghuo Mountain and Tanggula Mountains, part of road sections have large amount of snow accumulation and are subject to road icing.More>

2016, 16(4): 122-132. doi: 10.19818/j.cnki.1671-1637.2016.04.013

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Service performance prediction model of tunnel structure in alpine freezing-thawing environment

WANG Zhu, DONG Zhang-song, HAN Chang-ling, LI Yan

Abstract: In order to analyze the influence of alpine freezing-thawing environment with large temperature difference on the long-term service performance of highway tunnel lining structure, the temperature variation law of Jiangluling Tunnel portal was obtained by field test method, the calculation formula for the mechanical property deterioration of lining concrete in freezingthawing environment was obtained based on indoor freezing-thawing cycle test, and the load structure method was used to establish the spatial and temporal prediction model of service performance for lining structure in alpine freezing-thawing environment. Research result shows that after the insulation layer with the thickness of 5cm and the thermal conductivity of 0. 03W·(m·℃)^-1 is laid, the number of equivalent indoor freezing-thawing cycles for Jiangluling Tunnel in one year decreases from 8to 0.32. When there is no insulation layer and concrete is saturated, 5, 10, 15, 20 years later, the safety coefficients of arch foot section respectively decrease by 0.6%, 23.7%, 41.1%, 69.8% compared to the original service time. After 20 years of service, the safety coefficient of second lining cannot meet structure load requirement. After the insulation layerwith the thickness of 5cm and the thermal conductivity of 0.03W·(m·℃)^-1is laid, the safety coefficient of second lining still meet the load requirement after 100 years of service. The severe degree of freezing-thawing cycles has significant influence on the long-term service performance of lining structure, and the insulation layer can effectively improve the freezing-thawing environment of concrete.More>

2016, 16(4): 133-140. doi: 10.19818/j.cnki.1671-1637.2016.04.014

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Calculation method of thawing circle for highway tunnel in permafrost regions

YAO Hong-zhi, ZHANG Xiao-xu, DONG Zhang-song

Abstract: In order to obtain the temperature field of surrounding rock and the development law of thawing circle for highway tunnel in permafrost regions, the calculation method of thawing circle for surrounding rock was established, the calculated values and measured values of thawing circle depth and surrounding rock temperature were compared, and the finite element method was adopted to analyze the influence of support on the thawing circle. Analysis result shows that the average error of surrounding rock temperature is no more than 0.6℃, the error of thawing circle depth is no more than 10%, so the calculated value has better accordance with the measured value. When the time of operating shotcrete delays 1 d, the thawing circle depth increases by10 cm. When the thickness of shotcrete increases by 5cm, the thawing circle depth increases by about 10 cm. The thawing circle depth with molding temperature of 15 ℃ for the first molding concrete increases by about 10 cm compared to the molding temperature of 5 ℃. When the thickness of insulation board increases from 5cm to 20 cm, the thawing circle depth decreases by2/3. The insulation board and the hydration heat of secondary molding concrete have big influence on the thawing circle depth. The thawing circle depth with wind speed of 3. 0m·s^-1 in hole decreases by 10-20 cm compared to wind speed of 1.0 m·s^-1 in hole. 30, 60, 90, 120 d after shotcrete being operated, the thawing circle depths at air temperature of 8 ℃ in hole are1. 25, 1. 31, 1. 35, 1. 40 times of thawing circle depths at air temperature of 2 ℃ in hole respectively. Obviously, air temperature in hole should be controlled at 3 ℃-5 ℃, the support should be operated as early as possible after surrounding rock excavation, and low heat or medium heat cement should be used to decrease the hydration heat released by concrete.More>

2016, 16(4): 141-150. doi: 10.19818/j.cnki.1671-1637.2016.04.015

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Fatigue characteristics of driver in Qinghai-Tibet Plateau based on electrocardiogram analysis

LIU Jian-bei, MA Xiao-long, ZHANG Zhi-wei, GUO Zhong-yin, LIU Ben-min

Abstract: In order to obtain the fatigue characteristics of driver in plateau environment, three test sites with different altitudes and 20 d rivers were selected to do simulation tests, heart rate change of driver and driving behaviors were recorded in test process, the changing rate of heartbeat interval was regarded as the evaluation index to do fatigue research and verify its rationality, receiver operating characteristic(ROC)curve was used to determine the fatigue time point, and binary Logit model of driver fatigue was built. Analysis result shows that when the altitudes are 3 500, 4 200 and 4 600 m respectively, the average heartbeat intervals of driver are 0.759, 0.746 and 0. 615 srespectively. The fatigue time points of large vehicle and small vehicle drivers at the altitude of 4 600 m respectively advance by 20. 8 and 8.4 min compared with altitude of 3 500 m. The higher the altitude is, the earlier the fatigue time point comes. Every one unit increases of time length and change rate of heartbeat interval result in 1.215 and 1.139 times of fatigue happening ratio respectively. The fatigue happening ratio of large vehicle driver is 14. 6% of fatigue happening ratio of small vehicle driver, so large vehicle driver shows stronger fatigueresistance ability.More>

2016, 16(4): 151-158. doi: 10.19818/j.cnki.1671-1637.2016.04.016

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