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1.
Impacts on asphalt mixture's high temperature performance with PR series additives added by means of rutting test and Repeated Shear Test (Constant Height) (RSCH) were investigated The analytic results of the two tests show that (1) rutting test is not suitable for the high temperature performance evaluation of asphalt mixture with PR series additives added for the reason of the conflict between dynamic stability and rut depth; (2) the results of RSCH,such as K1,K2,N and γ,show very well consistency which is suitable
for the high temperature performance evaluation of asphalt mixture with PR series additives
added The results of RSCH show that asphalt mixture with PR PLAST S (PRS)
added has the best performance,the PR FLEX MODULE (PRM) one is the next and t
he original one is the worst for the high temperature anti?shear performance 相似文献
2.
To cope with the fatigue cracking occurred to the asphalt mixture on steel deck avement,it is put forward that the fatigue life of asphalt mixture can be improved by reducing the ailure energy of each hysteresis loop of asphalt mixture according to the cumulative dissipated energy and hysteresis loop theory in the principle of viscoelasticity for asphalt mixture Based on this principle,a kind of modified asphalt with high elasticity was developed,and its high and low temperature performances and fatigue performances were also tested The result shows that (1) low temperature deformability of the high?elastic modified asphalt mixture has remarkably improved and low temperature bending strain of girder at -10 ℃ is above 10 000 με; (2) the fatigue life of modified asphalt mixture with high elasticity has greatly improved by 4?point bending beam test compared with common modified asphalt mixture The fatigue life at 1 000 με deformability is about 19 million times which is about 20 times longer than that of ordinary asphalt mixture 相似文献
3.
Mori-Tanaka equivalent inclusion micromechanics theory was employed to investigate the viscoelasticity of asphalt mixture Asphalt mixture was regarded as composites which treated coarse aggregate as a rigid inclusion and the mixture of fine aggregate,filler and binder as viscoelastic matrix The constitutive relations of coarse aggregate inclusion and fine aggregate-filler-binder matrix were converted into elastic problems by Laplace transformation Then the Mori-Tanaka equivalent inclusion and average theory were used to deduce the
viscoelastic performance of asphalt mixture based on that of asphalt mortar in
Laplace space The result shows that (1) coarse aggregate inclusion can enhance
the viscoelastic performance of fine aggregate?filler?binder matrix and viscoelastic constitutive relation of asphalt mixtures can be expressed as the product of an enhancement coefficient of coarse aggregate and the viscoelastic constitutive relation of fine aggregate?filler?binder matrix; (2) the viscoelasticity of the complex asphalt mixture can be predicted from the viscoelasticity of the homogeneous fine aggregate?filler?binder matrix by using the nhancement coefficient; (3) the enhancement coefficient is higher than 10 and it rises with increasing of coarse aggregates' volumetric fraction or Poisson's ratio of fine aggregate-filler-binder matrix but the effect of the former is more important than that of the latter 相似文献
4.
To analyze influencing factors and evaluation method of low-temperature performance of porous asphalt mixture,first,three kinds of modified binder were chosen as original,thin film aging and pressure aging samples for customary index test and bending beam rheometer (BBR) test at -12 ℃ to evaluate low-temperature performance of these modified binders Then,evaluation of the low-temperature anti?cracking performance of different kinds of porous asphalt mixture was made by thermal stress restrained sample test (TSRST) At the sam
e time,the result of abovementioned TSRST were compared with the TSRST result of
samples of the porous asphalt mixtures after long?term aging to evaluate the influence of
aging on low-temperature performance of porous asphalt mixtures The results show that (1) TSRST result of porous asphalt mixtures coincides with creep stiffnesses of BBR test of modified binders; (2) the fracture temperatures of the porous asphalt mixtures increase and their fracture stresses decrease after aging; (3) the fracture stresses of porous asphalt mixtures are just one-third of those of dense?gradation asphalt mixtures while the fracture temperatures almost the same,which indicates that their low?temperature performances are almost the same 相似文献
5.
In the light of semi?rigid material as base course for perpetual asphalt pavement,the bearing capacity and fatigue life of asphalt pavement with semi-rigid base cause and different asphalt layer's thickness were computed with BISAR30 after chosen typical pavement The impact of thickened layer on the stress of the semi?rigid base,the dry shrinkage and temperature shrinkages of the material were analyzed,and its adaptability as base for perpetual pavement was studied The result shows that (1) under the same load,with thickening of the asphalt layer,the compressive stress on the top and the tensile stress at the bottom of the semi?rigid base decrease obviously and the fatigue life of
the base increases substantially; (2)the impact of temperature and humidity on the
semi-rigid base is remarkably weakened,which leads to the fractures,erosion and reflecting cracks of the semi?rigid base to be controlled effectively 相似文献
6.
Confronted with accidents in a shallow?buried weak tunnel using the bench excavation method,such as great subsidence and cracks in the ground surface as well as those in the preliminary support,a double downside drifts construction method was presented The drifts were used to detect geological conditions and reinforce the lower parts of the tunnel Its construction procedures and load transiting mechanism were then described Its Construction behavior was also studied by numerical simulation using software MIDAS The results show that (1) double-side drifts can improve tunnel load,the key construction step is arch ring excavation and core soil is good to keep tunnel steady; (2) weak parts mainly l
ocate at wall foot of drifts,wall foot and crown foot of tunnel,and the connections; (3) reinforcement of soil under the drifts has no apparent effect on improving rock deformation and support load Advice on construction was proposed that main parts to be reinforced are drifts (its foot depth,connection parts with tunnel,and its corners) and core soil should be kept if rock is unsteady and needs reinforcing 相似文献
7.
In order to study the fatigue behavior of RC beams strengthened with High Performance Ferrocement Laminates (HPFL) under overloading conditions,static and fatigue experiments were conducted on two control beams and nine strengthened beams The failure mode,fatigue life,deflection and material strain under overloading conditions were analyzed The result shows that (1) fatigue failure of the beams subjected to overload starts with steel rupture at the bottom and the fatigue life is only between 327 000 and 668 000 while fatigue
life of strengthened beams is greater than two million times in case of not overload
ing; (2) compared with the control specimen,the fatigue life of strengthened beams is obvio
usly extended and increased with the increase of steel mesh consumption; (3) after the same number of cycles,the deflections,the strains of concrete and steels of four strengthened beams are lower than those of the control specimen Debonding at the interface of HPFL and concrete is not observed because of shear pins planted at the end of the beams 相似文献
8.
he prestressed concrete skewed box girder with transversely segmental construction was brought out on the basis of the need in the engineering,both model experiments and FE analysis of the presented construction and the beam box with integral construction were carried out With the analysis of the obtained data by mathematical statistics,comparison of table and graph,and the corresponding FE analysis,the difference of mechanical performances of both constructions was analyzed under various experimental loading cases The results
show that (1) the deflection of the presented construction is about 53% larger than that of the beam box with integral construction,the longitudinal strain is 135% larger than that of the latter,and the longitudinal strain of the cast concrete is 59% as large as that of the same area at the beam box with integral construction before concrete cracking; (2) there exists stress redistribution in the cross-section of presented construction,which can restrain the tensional distortion of the wet?joint,and the value of the stress cannot be computed by the current FE program 相似文献
9.
The effect of damaged transverse connection of diaphragm beams on the bearing capacity of prefabricated concrete T?beam bridges was studied through model experiment and finite element analysis On the basis of standard drawing of 16 m T?beam bridge,a refabricated concrete T?beam bridge model on the scale of 1 to 4 was designed by using of welding steel plate The impacts of different condition on transverse load distribution were discussed The result shows that (1) flange connection has little impact on the transverse load distribution when the diaphragm beams are connected reliably; (2) the damage of transverse connections has much influence on the transverse load distribution of adjacent girders but it has little effect on the girders apart from them; (3) if a certain transverse connection is damaged entirely except for that of the end diaphragm beams,the load distribution would not degenerate to the conditions determined by the flange connection because of the advantageous effects of the other diaphragm beams; (4) only when the bilateral diaphragms of one beam are damaged at the same time,the lateral load distribution will degenerate to the conditions determined by the flange connection 相似文献
10.
The GIL chamber in the utility tunnel under Tanxinpei Road in Wuhan is an ultra long closed structure. Heat exhaust ventilation is the controlling problem in engineering design for the project, especially the heat transfer between the tunnel and the surrounding soil in the long term. A one dimensional model for the GIL chamber is established by using the IDA tunnel simulation software to analyze the short term and long term heat exhaust, respectively. The short term heat exhaust is analyzed for the typical climate of summer/winter/transitional seasons and the long term analysis is carried out under the seasonal changes in 1 year/ 10 years/ 30 years. The short term analysis results indicate that the slope of the utility tunnel and the temperature gradient lead to lower ventilation efficiency in certain areas. The long term analysis results show that the air temperature in the GIL chamber and the wall temperature rise most pronouncedly during the first 5-6 years of operation and remain stable for the remaining time within 30 years. It also is found that around 10%-40% of the heat is released to the surrounding soil. A three dimensional model of the GIL chamber is established using the fluid mechanics based program, OpenFOAM, for 3D simulation. The effects of cables and brackets on the temperature and velocity fields in the chamber are analyzed. The effect of non uniformity of velocity distribution and the stack effect on the temperature distribution in the GIL chamber are revealed. The results can provide some reference for the design and specification revision of heat exhaust ventilation for similar utility tunnels in the future. 相似文献
11.
The large testing platform for immersed tunnel is established to analyze the distribution laws of the temperature field and its influencing factors when a tunnel fire breaks out. Meanwhile, the combination method of physical testing (1∶1 full scale fire test) and numerical calculation FDS are applied. Some conclusions are drawn as follows: (1) Longitudinal wind speed within limits can decrease the maximum temperature of tunnel crown top effectively when fire breaks out in tunnel. (2) The maximum temperature of tunnel crown top and fire behavior are related to fire types obviously. (3) The high temperature resistance safe position of the tunnel equipment is below 3.5 m of tunnel sidewall in case of fire source heat quantity of 50 MW. (4) The fire maximum temperature is positively related to heat release rate (HRR) and longitudinal wind speed. 相似文献
12.
According to the features of high?liquid?limit foundation in southwest mountainous area and the characteristics of geogrid reinforced cushion,geogrid reinforced cushion was used to reinforce high?liquid foundation By using the elastic?plastic finite element analysis method,the mechanisms of the geogrid reinforced cushion were studied The results show that geogrid reinforced cushion can greatly reduce loading and deformation and improve the high?liquid foundation stability In addition,the effect of factors such as location,lay
ers,stiffness,etc of geogrids on reinforcement and the regularity were discussed Compari
son of centrifugal model test result with numerical calculation result indicates that the error is negligible between them,which shows that (1) constitutive relationship,calculation model and calculation parameters are reasonable; (2) numerical simulation reflects deformation behavior of high?liquid foundation improvement effectively and the results of numerical analysis are re
liable 相似文献
13.
Stresses of pavement with flexible base of LSAM-30,ATPB-30 and AC-30I at the most adverse point under the function of traffic load and temperature load as well as the coupling of them were calculated and compared by finite element method. The result indicates that flexible bases of LSAM?30 and ATPB?30 are more effective in the prevention of reflection crack Because of the great volume of coarse aggregate and large maximum nominal particle?size,the LSAM-30 thermal conductivity is greater,and the temperature shrinking coefficient is lower as well as the modulus of resilience,which could reduce the emperature gradient among the structure layers effectively and then minish the thermal stress At the
same time,the adequate flexibility performance of the LSAM may also absorb strain energy at the crack of the semi?rigid subbase sufficiently As a result,itpresented preferable reflection crack resistance A case study was conducted to do comparative analysis of anti?cracking performance of LSAM-30,ATPB-30 and AC-30I flexible bases A long?term follow?up observation of test roads with the three bases shows that the pavement with LSMA base is in good condition and no sign of crack found while pavements with ATPB?30 and AC?30I flexible bases have varying degrees of crack LSMA flexible base has an obvious performance of anti-crack 相似文献
14.
《中国汽车(英文版)》1994,(2)
A new laboratory in China Automotive Technology and Research Center (CATARC), which was designed to test the automotive lighting & signalling equipment and field of vision, is going to be put into operation. The official ceremony will be held in the near future. 相似文献
15.
The total length of the 2nd stage water transfer project in the northern area of Xinjiang of China is 540 km. The project consists of three tunnels, namely Xi Er (XE) Tunnel, Ka Shuang (KS) Tunnel and Shuang San (SS)〖HJ6.5mm〗 Tunnel, with lengths of 139.04 km, 283.27 km and 92.15 km respectively. All of these three tunnels have deep cover and are super long tunnels, and 95.6% of the total length of these three tunnels is constructed by TBMs. KS Tunnel is the longest water tunnel built or under construction in the world. In the paper, the trial TBM boring scheme and schedule of the water transfer project are introduced; the geological conditions revealed are statistically analyzed; and main project difficulties, i.e. durability of key equipment in long distance driving, passing through fault and fracture zones, water inrush, single head ventilation and transportation in long distance tunneling, anti slope drainage, and rock breaking efficiency and boring efficiency, are put forward. The adaptability of the TBMs used is analyzed from the aspects of adaptability to different surrounding rocks, adaptability to bad geological conditions and countermeasures, long distance ventilation and belt conveyor mucking and countermeasures, and TBM boring stability (such as equipment availability, boring time proportion, system malfunction and operation time). The following conclusions are obtained: (1) Accurate geological survey is the precondition of efficient tunneling. (2) The open type TBM can better adapt to Grade Ⅱ and Ⅲ of surrounding rocks, jointed and fractured zones and small faults; the adaptability of the TBMs used to the large scale fault fracture zones and water rich strata in this project is poor, and it needs to be improved in aspects of TBM equipment, supporting and construction technology. (3) The average availability of the TBM equipment in the trial boring stage is 89.9%, however, the malfunction rate of some ancillary equipment is high, particularly oil leakages occur to the main bearing seals; in order to achieve long distance tunneling, it is necessary to further improve the reliability and durability of the TBM equipment. (4) The average net boring efficiency in the trial boring stage is 296%, and TBM1 in Section Ⅱ of SS Tunnel achieves up to 45.2 % net boring efficiency; and highest monthly progress rate is 1 280 m, which created the highest record of the open type TBM boring in China. (5) TBM need to make great efforts to achieve 90% of the equipment system′s availability and over 40% of the tunneling efficiency. 相似文献
16.
Targeted to the issue of lacking of systematic design standards for thermal insulation and drainage facilities of railway tunnels in cold regions, the authors propose the method of design division of railway tunnels in cold regions based on the division of cold regions, the current technical status of thermal insulation and drainage in tunnels, and the investigation on some tunnel freezing damage cases in northeastern China and the northern part of North China. Through analyzing the application conditions of the thermal insulation and drainage facilities and combining the measured temperatures in the operating tunnels and drainage facilities, the authors propose the suggested length for the thermal insulation and drainage facilities of tunnels in cold regions in different divisions. The results show that: (1)railway tunnels in cold regions may be classified into 5 divisions based on annual average temperature and average temperature in the coldest month; (2)the elevated thermal insulation ditch only adapts to the cold regions with a higher temperature; (3)an effective measure for thermal insulation and drainage in cold regions is to embed ditches into structures within a certain range from the portal; (4)the ditches may be arranged in structures for the trunk section of long tunnels equipped with thermal insulation measures; (5)for the tunnels with the necessary conditions available, the double spur grade and a steep gradient in the longitudinal slope may be applied, which is beneficial to improving drainage conditions and preventing the ditch from freezing. 相似文献
17.
As a great romantic novelist in America in 19th century,Hawthorne was outstanding in handling the application of symbolism.The Scarlet Letter is Hawthorne's most important symbolic novel,which stands as the best work of Hawthorne and one of the indubitable masterpieces of American literature.This thesis aims at the exploration of the usage of the symbolism in the novel.It mainly discusses the deep symbolic significance of the scarlet letter "A" and the little pearl.The scarlet letter is the central symbol of the novel.Its symbolic meaning changes from 'adultery' to 'able',even 'angelic' in the novel.It also examines the symbolic meanings of little Pearl and some typical natural surroundings such as the jail,the forest,the rosebush and so on. 相似文献
18.
MARKET The Chinese auto market is perhaps the only miracle land at a time of global recession. The financial crisis is extending and sales in the main countries allow no optimism. May still found sliding figures in the previous month:in the US it was 34 percent down 相似文献
19.
Four methods of erecting steel stiffening truss girder of suspension bridge,including the deck lifting gantry crane method,the cable-mounted crane method,the cantilever erection method with derrick crane and the incremental launching method,were studied Based on construction conditions of the bridge,according to the optimal combination of various factors such as construction safety,quality,period,environmental protection and economic performance,etc,the cantilever erection method with derrick crane was recommended for the bridge. On this basis,three categories of connection in cantilever erection methods,including the all hinged method,the successive fully splicing method and the successive splicing with temporary erection hinge method,were studied The successive splicing with temporary erection hinge method was recommended in the bridge with consideration of the requirements of construction safety,quality and time limit In addition,the traction method of hangers at the top end during cantilever erection was studied Finally,the erection method of three key
stages,including the first segment near the pylon,the standard segment,as well as the closure segment of steel stiffening truss girde,r was studied. The cantilever erection method with derrick crane provides a new way for design and construction of long-span suspension bridge with steel stiffening truss girder in the western area of China 相似文献
20.
《中国汽车(英文版)》1997,(3)
Intelligent Transport System (ITS), a sys-tematic integration of modern hi-techs, such as computer technologies, communication technolo-gies, etc., is an important development trend in the field of communication & transportation sys-tem in the 21st century. The Chinese govern- 相似文献