Showing papers in "Journal of Chang'an University in 2011"

Rubber asphalt modification mechanism

Abstract: In light of the complexity of rubber asphalt modification mechanism,such means as scanning electron microscopy,infrared spectroscopy,differential thermal analysis,microscopic structure analysis,component analysis were adopted to study the components of the asphalt before and after modifying,and chemical analysis of rubber powder are adopted to study the modification mechanism of asphalt rubber blending system.The results indicate that the swollen rubber powder is mutually-adhered to form a network structure,and the matrix asphalt changes from homogeneous body into a two-phase continuous blending structure system constituted by rubber powder and asphalt;physical swelling dominates the system,accompanied by a little chemical reaction and with the prolongation of time,the chemical reaction becomes more obvious;the swollen rubber powder forms damping effects to improve the viscosity of rubber asphalt.The modification of asphalt comes from two aspects: firstly,the network structure formed by swollen rubber powder;secondly,the modification of the asphalt composition resulting from rubber powder desulphurization degradation.The natural rubber has better performance in modifying asphalt than synthetic rubber.4 tabs,9 figs,12 refs.

Experiment and evaluation on performance of epoxy asphalt waterproof cohesive layer on bridge deck pavement

Abstract: In order to evaluate the performance of epoxy asphalt waterproofing adhesive layer,this paper adopts the shear test and the pull-off test to study the cohesive strength between epoxy asphalt and the basic plane of steel plate or concrete board,as well as the relationship between the strength and the temperature or curing time.Besides,this paper adopts the composite plate to simulate the experiment,then analyzes and compares the shear strength and pull-off strength of different waterproofing cohesive layer with different basic plane plate and asphalt mixture surfacing.The result shows that,epoxy asphalt binder as bridge structure waterproofing adhesive layer,its shear strength and pull-off strength is significantly better than any other type of materials,and its shear strength and pull-out strength to the steel plate are higher than cement plate.It indicates that epoxy asphalt is more suitable for steel bridge deck pavement.At high temperature condition,epoxy asphalt waterproofing adhesive layer has good bonding strength with the upper asphalt mixture structure layer.8 tabs,9 figs,8 refs.

Durability of asphalt mixture in sulfate corrosion environment

Abstract: Few research has been done on the durability of asphalt mixture in the sulfate corrosion environmentIn order to investigate the attenuation law of road performance of asphalt mixture under the action of sulfate corrosive medium,a series of accelerated deterioration tests through dry-wet cycles were carried out in Na2SO4 solution with different mass-ratios including 25%,5% and 10%The results indicate that the attenuation of the performance of asphalt mixture in sulfate solution is more severe than that of being in distilled waterWith the increase of sulfate mass-ratios,the performance of asphalt mixture takes on a decreasing trendBesides,corrosion resistance to sulfate of SMA-13 asphalt mixture is superior to that of AC-13 asphalt mixtureAccording to SEM micro-analysis,it can be indicated that the sulfate solution is easier to invade the interface between asphalt binder and aggregate than distilled water to accelerate water damage along with crystal expansion made in dry environment,this action reduces the interface strength,plays the key role in the the rapid attenuation of the performance of asphalt mixture

Antifreezing and snow melting of MFL modified asphalt concrete

Abstract: In order to solve the problem that the snow or ice on the pavement impacts on the road performance and transportation security in cold areas in northern China,this paper adopted indoor simulating tester for antifreeze pavement to verify the antifreezing capability of MFL modified asphalt concrete and its snow melting function by observing the testing processTwo indicators proposed in the antifreeze test which were defined as attenuation amount weighted average of BPN and attenuation rate weighted average of BPN could describe the antifreezing capability of MFL modified asphalt concrete pavement quantitativelyCompared with ordinary asphalt pavement,the snow on the modified asphalt concrete pavement can be melted more easily,and the adhesion of snow with the surface of road is more weak,so the snow can be cleared easily4 tabs,5 figs,8 refs

Influence of placement temperature on mass concrete temperature stress

Abstract: Based on the analyzing on structure cracking of the temperature stress of mass concrete,the influence on temperature stress during construction of concrete placement temperature was analyzedAccording to the mechanism of mass concrete crack producing and performance of massive concrete temperature stress during construction,using the method of numerical analysis,mass concrete temperature stress and its influence factors were studied when mass concrete's placement temperature changesThe results show that the hydration of cement is accelerated and maximum temperature inside the concrete will occur ahead when mass concrete's placement temperature rises;the first principal stress of structure increases linearly,when placement temperature rises 1 ℃,the first principal stress of structure increases 247%;the mass concrete's cool temperature difference and the temperature difference between inside and outside increase with the increase of placement temperature,and the occurred time of maximum cool temperature difference and the maximum temperature difference between inside and outside will take place in advance with the increase of placement temperature4 figs,11 refs

Setting location of speed limit signs along highway

Abstract: The setting location of speed limit signs is an important factor that affects their valid-ity.This paper studied the setting location of speed limit signs based on driver's visual response,cognitive characteristics.The calculation method of the main parameters during the recognition process was analyzed,a calculation model to determine the minimum pre-distance was established based on the minimum time that drivers required to recognize the speed limit signs and complete deceleration operation,then a maximum pre-distance calculation model was established based on the principle that drivers discover the speed limit signs setting at the entrance of speed limited roads just when the short-term memory about the speed limit information nearly disappeared,to determined the best setting location of speed limit signs.An example was given and verified the practicality of this method.It is found that this method can help to determine the best setting location of speed limit signs,avoid the arbitrary setting based on experience,and improve the validity of roadside speed limit signs.

Movement characteristics of asphalt mixture based on digital image disposal technology

Abstract: In order to analyze the reason of inhomogeneity happened in the process of asphalt mixtures rolling,this paper using digital image processing software,deals with AC-13 type asphalt mixture every 30 s vibration specimens profile,and then gets the charges with time of four aggregates distribution of 13.20 mm,9.50 mm,4.75 mm,2.36 mm.The research results indicate that in the process of AC-13 asphalt mixtures rolling,13.20 mm aggregate movement trend changes with time quite significantly,this aggregate moves reciprocating and periodically in both horizontal and vertical directions,in the test initial stage the vertical movement is more obvious,the effect on asphalt mixture segregation is the greatest.Compared to the 13.20 mm,the 9.50 mm aggregate's,movement trend changing with time intend to mitigate,the whole movement direction is in accord with the one of 13.20 mm,it also has influence on the asphalt mixture of segregation.Compared to the above two grade aggregates,the 4.75 mm and 2.36 mm aggregates' movement trend changing with time is not obvious.Basically their centers of gravity are concentrated in the center position of the profile.This shows that the two aggregates on the whole distribution are much uniform and have little impact on asphalt mixture segregation.

Experimental study on strain monitoring of asphalt concrete using FBG(Fiber Bragg Grating)

Abstract: A packaged FBG strain sensor based on the principle of FBG sensing and characteristics of asphalt concrete pavement was designed for the experimental study on strain monitoring of asphalt concrete.The designed structure of FBG sensor and strain sensing performance was presented.A calibration test for FBG sensor was implemented,its strain sensitivity coefficient of FBG sensor is 1.1 pm/μe,and the fiber grating strain sensing performance would not be changed by packaging technology.The correlation between pressure and axial strain is 0.038 7 μe/N after embedded in SMA-13 asphalt concrete.Sensor static test by ANSYS 11.0 simulation show that sensor strain sensitivity correction factor η is equal to 0.928.FBG strain sensor was used to monitor internal structure of asphalt concrete axial strain.The dynamic test for 5 hours by rutting test show that when increasing the number of rolling,the axial strain can be increased.Monitoring result can reflect the fundamental changes of strain in structural layers of asphalt concrete.The sensor can be used to monitor the strain of asphalt pavement to provide a new method decision-making for pavement maintenance.7 figs,9 refs.

Parameter optimization of highway optical illusion deceleration markings

Abstract: In order to improve the level of operation security in dangerous road sections,the speed should be slowed down to a safe rangeThe forms and design parameters of the deceleration markings was compared and optimizedBased on the mechanism of optical illusion deceleration markings in dynamic environment,the parameters of the chevron markings were analyzed and the space calculation method was proposedThe different design parameters were combined together to execute the orthogonal experimentThe simulation test and the actual road test were carried out to verify the actual deceleration effectsThe results show that the actual deceleration is effected significantly by the design parameters,and good deceleration effects are subject to reasonable parameters designThe deceleration effects of variable spaced deceleration markings are better than the equal ones

Model to decide optimal timing of asphalt pavement preventive maintenance

Abstract: In order to decide the optimal timing of the aspalt pavement preventive maintenance,a decision model was developed.Through analyzing the change of pavement performance after the maintenance treatment application,the model defined the pavement composite benefit,decided the analysis period and set up the four decision making indexes.An application example shows that the model can reflect the roles of various pavement performance indexes,objectively describe the characteristics of maintenance object;based on the four decision indexes(the composite benefit value,the equal annual cost,the benefit index,and the expected extension of life),the five decision principles can be formed,they are the minimum cost principle,the maximum composite benefit principle,the maximum unit cost benefit principle,the longest service term principle and the comprehensive balance principle;these principles may meet the needs of different decision makers,and the decision precision lies on the data of pavement performance.9 tabs,6 figs,6 refs.

Relationship of academic management and administration in universities from power view

Abstract: The definitions of academic management and administration were presented based on the power view.The intrinsic meanings and characteristics of academic management and administration in universities were analyzed.The development of academic management and administration was disscused with the evolution of universities to reveal their relationship.It was pointed out that the academic management should be superior to administration in universities,the academic management should play a role at decision affairs,the administration should be taken as an executive body.The main problems in Chinese universities are the lose of academic institutions and the violation of academic management laws.

Hydraulic leveling system for asphalt mortar vehicle based on fuzzy PID control strategy

Abstract: The accuracy of metrology equipment can be influenced by levelness when asphalt mortar vehicle is working and need move often.A four-point-leveling system is developed based on key control unit of PLC(programmable logic controller).Some contrast experiment is studied by PID(proportion,integral,derivative) control strategy and fuzzy PID control strategy.The results show that the total leveling time of asphalt mortar vehicle is only 8.5 seconds by fuzzy PID control strategy and total leveling time is 23 seconds by PID control strategy.The fuzzy PID control strategy can improve leveling efficiency and leveling accuracy significantly by changing the value of the proportional valve.The leveling system based on fuzzy PID can improve the metrology accuracy and construction efficiency.

Experimental research of tack coat materials' performance on asphalt pavement

Abstract: Adhesion performance of the materials between asphalt pavement is directly related to the stress of the asphalt pavement,which affects the road life.The hot bitumen,SBS modified bitumen,SBS modified emulsified bitumen are selected to test the adhesion under different temperatures and the spread quantity.The shear strengthen in different temperatures is considered as the assessment indicator.The results show that the shear strengthen of the three kinds of materials will increase with the temperature down,but the changing laws of the three materials with temperature are different,in low quantity of spreading,the modified emulsified bitumen of SBS is better in adhesion performance,and the best spreading is from 0.5 kg/m2 to 0.7 kg/m2.

Compacting mechanism and features of aeolian sands

Abstract: Taking the aeolian sands from Maowusu desert along Shanxi-Inner Mongolia highway as the researched object,this paper analyzes its pellet forms and main characteristics,as well as the method of confirming the biggest dry density.According to the heavy compacting experiment,this paper draws the compacted curve,and receives that the aeolian sands have two compact conditions,dry and wet.In the laboratory and field research,impaction-vibration roller model is used,the compacting features and the compacting mechanism in the impaction-vibration situation are researched.The results show that the moisture content on aeolian sands have little effect on compacting,the impaction-vibration roller has better compacting results than a single vibration and shock roller.4 tabs,7 figs,10 refs.

Process of concrete mixing and its evaluation

Abstract: In order to improve the performance of concrete,the concrete mixing and its evaluation index in the past of 20 years were analyzed.The problem of concrete evaluation indices were presented.Some measures were adopted to promote the performance of concrete.The test result indicate that the microcosmic uniformity of concrete,the interface bonding strength of concrete and its durability can be improved by optimizing parameter of mixer,adopting vibratory stir technology,arranging double row blade organization and using twice stir technology.4 tabs,5 figs,18 refs.

Type classification on natural disasters of highway

Abstract: In order to develop prevention measures of natural disasters to highway,this paper studied highway's characteristics and its safe requirements,to highway adopted systematic theory and analytic approach to divide the natural disasters of highway into two types: geological hazard and meteorological disasterAccording to disaster causes,scale,failure modes and location,the common types of highway hazard were further divided,for example,collapse,landslide,debris flow,subgrade settlement and subgrade collapse,storm or floodIt is pointed out that the hazard type classification is the basis of disaster prevention and mitigation,such as hazard management6 tabs,2 figs,10 refs

Analysis on driving fatigue before and after lunch based on indices of physiology and psychology

Abstract: In order to analyze the variation of the driver fatigue characteristics,6 drivers were selected to carry out driving simulation experiments,and the indices of physiology and psychology,such as body temperature,heart rate variability,depth perception,speed perception,were recorded at the same time.And the results of self-evaluation about fatigue were gotten by questionnaire,and the driving fatigue characteristics changes of drivers before and after lunch were analyzed.The analysis results of physiological indices show that heart rate variability(HRV) index of drivers tends to increase after lunch about 1~1.5 hours,then decreased to normal levels;body temperature will decrease to a low level after lunch and then return to normal;PERCLOS index value increase occur on all drivers,of which 67% PERCLOS value increases dramatically obvious.Changes in indices of psychological characteristics show that,after lunch,the driver's cognitive abilities decrease,mainly reflected in decrease of ability in depth perception,reaction time and speed perception,these will affect the drivers' getting road environmental information,thereby increasing insecurity of driving behavior.4 tabs,4 figs,11 refs.

Emission characteristics of harmful gas from engineering machinery under tunnel construction in plateau regions

Abstract: In pleatu regions,the engineering machinery has more harmful emission such as CO and HCIn order to provide scientific basis for ventilation design and pollution control of the tunnels in plateau,based on the construction of Guanjiao tunnel,the harmful gas from the loaders,excavators and dump vehicles was tested,the emission characteristics of harmful gas from engineering machinery under tunnel construction in plateau regions was studied by the way of polynomial fittingThe results show that the harmful gas such as CO and HC from engineering machinery in plateau regions varies by the way of index,it grows with the increase of rotating velocity of engineering machineryWhen excess air ratio reduces,emission goes upWhen excess air ratio increases,emission falls

Grade division system of existing tunnel's freeze injury based on event tree theory

Abstract: In order to provide management measure for freeze injury of tunnel,based on the event tree theory,taking the occurrence of freeze injury to the tunnel as the initial fault event,the development of the tunnel's freeze injury,such as the lining peeling and breaking,water overflowing and freezing on the pavements,and water leakage and freezing of the lining,as the subsequent events,the inner link of every hidden danger was analyzed,the losses and rectification costs were estimated,the freeze injury degree of existing tunnel was divided into five grades,a general table was designed on the expansion and evolution of the freeze injury in highway tunnel at cold regions,then,a grade division system of highway tunnel's freeze injury was established.An example of a highway tunnel is given to verify the practicality of this system.It is found that an effective guide for the treatment work of tunnel 's freeze injury is provided by this system,the freeze injury degree which is judged by experience is avoided,and the validity and scientificity of providing management measure for freeze injury tunnel is improved.

Test and numerical simulation on subgrade temperature field of cement concrete pavement structure

Abstract: The distribution and change of subgrade temperature is critical to the stability of cement concrete pavement in seasonal frost region.Based on the infield test datum of subgrade temperature filed in Jixi-Nahe highway of Heilongjiang Province,the changing law of subgrade temperature is analyzed,and the model is established.The numerical simulation is carried out under the first boundary situation(additional layer theory) and the second,third boundary situation.The results show that the internal temperature change of subgrade lagged is behind the outer climate temperature.The numerical simulation of temperature with the second,third boundary situation is superior to the first boundary situation at accuracy,which is near to the infield test datum.Along the subgrade depth,the temperature difference between the calculation under the first boundary situation and the test is the most,when the site is near to the subgrade surface,and tends to be small little by little when the site is far away the surface.However the difference between the second,third boundary situation is consistent to the infield test data,and can be applied for predicting the subgrade temperature field.1 tab,6 figs,10 refs.

Numerical simulation of support action of systematic anchorage bolts in shallow-buried loess tunnel

Abstract: In order to study the actional function of systematic anchorage bolts in shallow-buried loess tunnel,this paper taking Liujiaping 5# tunnel of Wubao—Zizhou freeway as an example,two-dimensional plane models with systematic anchorage bolts and without systematic anchorage bolts were established by using the finite element analysis software MIDAS/GTS.In the process of numerical analysis,the displacement amounts were simulated during the six excavation stages and the stage before secondary lining construction,and the numerical simulating results were compared with the ones of measuring.The results show that the displacement of the model with systematic bolts is bigger than that of the model without systematic bolts during the construction of shallow-buried loess tunnel,because the rock bolts are constructed after steel arch.Construct-ing the anchorage blots,not only the stability of soil mass is broke,but also the best time of constructing shotcrete and steel support is delayed.Moreover,both the two modes have almost the same settlement in the tunnel arch crown and horizontal convergence during in-situ test.Through comprehensive analysis,it is found that the role of systematic anchorage bolts is not obvious in shallow-buried loess tunnel and can be eliminated.

Deformation analysis on reinforced embankment taking into account of creep of geogrid

Abstract: In order to clear the reinforced structures' deformation law caused by creep of geosynthetics,the reinforced embankments under different working conditions were analyzed with finite difference method.The deformation of reinforced embankment caused by the creep of geogrid was presented.Three aspects,such as the settlement distribution on the top of the embankment,horizontal displacement of the embankment caused by the creep of geogrid,and geogrid strain were analyzed.The results show that the settlement distribution on the top of the embankment,the horizontal displacement of embankment,the geogrid strain have positively proportional relations with the height of embankment,and have inverse proportion relations with slop rate and elastic modulus of geogrid.3 tabs,6 figs,10 refs.

Design of tanker sensor node based on WSN and improvement of TinyOS tasks scheduling

Abstract: For real-time monitoring of temperature,humidity,car body posture,carriage pressure,inlet and outlet mouths oil leaks and other security information while driving oil tank truck,the wireless network node of monitoring tanker security information was designed with ultra-low power of ATmega1281 microcontrollers and AT86RF230 RF modules.To resolve the problem of TinyOS FCFS scheduling strategy which not able to give strong real-time tasks timely response and low message treatment,a multi-task queue scheduling strategy is proposed,which uses grading scheduling for real-time tasks and priority tasks and sets dynamic priority and task overtime interrupts.The algorithm can meet the system's response of real-time and high-priority tasks,make low-priority tasks in appropriate within the time to get scheduling opportunity.The TinyOS test result indicates that the tanker sensor node can realize the real-time monitoring within the 3% increasing of power consumption.3 tabs,14 figs,9 refs.

Analysis and application of energy saving principle in mechanical products design

Abstract: To find out and verify the basic energy-saving principles of machinery design,based on energy analysis methods,the potential energy changing-rate,the kinetic energy changing-rate,the output force consumed power and the useless power,which are all represented by some periodic functions,are individually and synthetically analyzed.The causes of input power high-matching and the failure of full-utilization are extracted,and the basic energy-saving principles are presented and proven theoretically.In order to ensure that the consuming energy can be utilized at the most degree,all types of the energy and the power should be constant or varied in the minimum range,the system energy and the system power should be kept constant or varied in the minimum range.It is demonstrated from the real engineering application results that the proposed principles are effective,and generally suitable to be used in energy-saving electro-mechanics machinery design.3 figs,7 refs.

Roadside safeguard technique of rural highway in mountainous area

Abstract: There are many influence factors on the roadside safety of mountainous rural highway,but no specific safety evaluation and safety measuresTo resolve these problems,an on-site roadside safety investigation was done in Xianyang areaThe investigating datum were analyzed with experts' markings,analytic hierarchy process and grey theory evaluation methodResults show that: the influence factors on roadside safety are traffic volume and compositions,roadside features and road alignmentThe evaluation indicators of roadside safety were put forward which contain horizontal curve variable,vertical curve variable,AHT(average hourly traffic)during daytime,motor proportion,numbers of roadside accident,casualties of roadside accident,fill rate of roadside recover distance,depth of roadside,closeness and lateral separation of discrete obstaclesThe roadside hazard should be classified into three levels which are class Ⅰ,Ⅱand Ⅲ,and different safeguard measures should be defined to suit for different hazards5 tabs,8 figs,10 refs

Influence of intermediate principal stress on asphalt mixture strength in positive temperature

Abstract: Both strength theory of Mohr-Coulomb and testing methods,which are used to value the strength of asphalt mixture in specification,do not include intermediate principal stressMechanical study corresponding to closed tri-axial test is carried outThe rest shows that maximum shear stress in tri-axial extrusion stress state is more than the counterparts in tri-axial compression stress stateThe result is attributed to the difference of intermediate principal stress in two different stress statesIn order to study the influence of intermediate principal stress on asphalt mixture strength,the characteristics of testing method,which is related to intermediate principal stress's influence on asphalt mixture strength,is considered,and testing device for plain strain is designed,and the asphalt mixture strength in different condition is tested on the base of orthogonal test,which includes three factors,such as temperature,loading velocity and intermediate principal stressWhen both interaction of different factors and temperature difference are considered,the orthogonal test design significance analysis shows that intermediate principal stress has the most obvious influence on asphalt mixture strength,the followed factors are temperature and loading velocity6 tabs,2 figs,11 refs

Combined multiple vehicle types stochastic dynamic traffic assignment and signal optimization

Abstract: The combined problems of multiple vehicle types stochastic dynamic traffic assignment and traffic signal optimization were studied.A combined model on multiple vehicle types stochastic dynamic traffic assignment and traffic signal optimization in saturated networks was presented.The model is formulated as a generalized bi-level programming problem.The upper level optimizes signal settings,while the lower level represents a multiple vehicle types stochastic dynamic traffic assignment,which sets network traffic flow.Meanwhile,the model applied a physical-queue dynamic network model with multiple vehicle types,which considers the impact of physical-queue on the network conditions in saturated networks and interactions between multiple types sharing the same road infrastructure.The solution of traffic signal and traffic assignment was optimized by using genetic algorithm.Simulation result shows that the total travel time can be minimized in considering multiple vehicle types stochastic user route choice behavior,the optimal signal control strategies and the corresponding optimal path flow are achieved,and the optimization settings of traffic signal and optimization of network traffic flow can be realized.

Emergence and its conditions in China individualization——review of correlated theories of individualization

Abstract: Through reviewing the correlated theory of individualization's,this paper investigates the concepts and features of individualization,and believes that China is now undergoing the transconform-ation of individualization.This paper then researches the social conditions of individualizations emergence from two perspectives,points out the limitations in the above-mentioned two perspectives,and attempts to find a new road to remedy these limitations,that is: to examine the situation of individualization in the changes of relationship and types of gift exchange.This paper proves the process of Chinese and West individualization which YAN Yun-xiang has pointed out.The author finally believes that as there exist differences is social situations of China and West,China probably may go to a different individualized road from West.

Control of designing indices for asphalt pavement with different types of base

Abstract: Based on the reconstruction and extension project of Xitong expressway,the fatigue and breakage forms of semi-rigid asphalt pavement,compound base asphalt pavement and flexible base asphalt pavement were analyzed and the corresponding design parameter system was established separatelyThe sensibility of the materials parameter as the mechanical responses was analyzed using Shell designing software Bisar30,which verified the rationality of pavement de-signing indices from the point of stress balanceThe results show that taking flexible strain and surface shear stress as designing indices for flexible pavement could keep the modulus value of semi-rigid base in proper rangeTaking flexible stress of base and shear stress of base as designing indices for semi-rigid pavement and compound pavement could constraint the modulus value of semi-rigid baseThe introduction of shearing stress is particularly necessary for asphalt pavement design because it can seriously affect material parameters and help optimize both the structure and material design