Highway Test Research Articles

In Situ Test for Hydraulic Conductivity of Drainable Bases

The development and use of an in situ hydraulic conductivity test for drainable bases under existing pavements is presented. Six highway test sections were constructed by the Ohio Department of Transportation to test the drainage characteristics and durability of four unbound and two stabilized base materials. The in situ test was then used to determine the field hydraulic conductivity of the highway test section bases. This test uses an approach to Darcy's law called the direct velocity technique. A standpipe is placed in a cored hole in the pavement to establish steady-state horizontal flow through the base toward the edge drains. Two probes along a radial flow line measure differential pressure and electrical resistance in the water. An electrolytic solution injected at the standpipe is used to determine the water velocity as the median resistance is noted at each probe. The in situ hydraulic conductivity is calculated by dividing the discharge velocity by the hydraulic gradient. The in situ test provided results that compare favorably with published values from carefully controlled laboratory tests. It proved to work well for high-hydraulic-conductivity drainable bases, and it has the potential to be a valuable tool for condition assessment of bases under existing pavements.

Vision-based mobile robots on highways

Intelligent vehicles are mobile robots on highways. They are expected to improve the safety, efficiency and environmental impacts of the current highway traffic systems. Vision systems will play an important role as sensors for the intelligent vehicles. This paper first compares the vision sensors with other sensing methods from an application point of view and then describes two vision systems, one which we have developed and another which we are developing. Two important features are required for the vision systems applied to intelligent vehicles: three-dimensional (3D) measurement capability and real-time operation. We chose a trinocular stereo vision scheme among a number of 3D vision processing methods because it is suitable for real-time operations with dedicated processor architectures. The trinocular stereo algorithm requires a large number of operations, but all the operations are relatively straightforward and, therefore, they are suitable for custom architecture implementation. The system takes three images simultaneously by using three TV cameras installed on a single horizontal line at the front grill of the test car. Vertical edges are extracted from these images and the spatial offsets (or disparities) among the images are calculated for measuring the distances to the objects. The first version was developed and installed in a car for highway testing. Two custom digital processors were developed: one for edge detection and the other for stereo matching. The test results were encouraging and the architectures based on ASIC (Application Specific Integrated Circuits) are 800 and 550 times more efficient, respectively, compared with conventional microprocessors for edge detection and stereo matching. The second version is currently being developed in order to further reduce the silicon area size. It uses hybrid analog/digital circuit technology while the first version uses only digital circuits. We are developing a hybrid analog/digital array processor chip which includes a large number of processing elements. Each processing element includes a digital memory unit, a data flow control switch unit and an analog arithmetic/logic unit. The analog arithmetic/logic unit reduces the silicon area size significantly compared with the digital one. The data flows among multiple processing elements in the array chip in a form of analog voltage. The data flow is controlled by the data flow switches. The digital memory unit controls the set-up of the data flow control switch and arithmetic/logic units.

The effectiveness of geosynthetic reinforced embankments constructed over weak foundations

A study was undertaken to investigate the effectiveness of using geosynthetic tensile reinforcements for strengthening two highway test embankments, 8·5 and 14·6 m in height, constructed over weak and highly pervious foundations. Both embankments were reinforced with geogrid mats placed near their base and were constructed in two stages. Field instrumentation was installed to monitor the performance of the embankments during construction. The effectiveness of the tensile reinforcements was evaluated by the finite-element method of analysis. Field-measured settlements at the end of the first stage of construction were used to back-calculate the material parameters representative of their foundation materials. The analytical procedure was validated by comparing the predicted versus measured displacements of the embankments in the second stage of construction, and was subsequently used to predict the performance of the embankments without the geogrid inclusion and with reinforcements different from that used in the actual construction. The effectiveness of using tensile reinforcements in such applications is discussed.

GPS Signal Availability in Land Mobile Applications

This paper summarizes the results of a series of direct measurements conducted to characterize the GPS signal environment in land vehicular operations for a variety of highway, city, and railroad situations. The basic instrumentation for these observations consisted of a NAVCORE I (TM) GPS receiver configured to output key measurements to a microcomputer as a data recording device. The results of these tests are presented in tables of the percentages of distance traveled in which one or more and two or more satellite outages were encountered, and in histograms of the outage probabilities as functions of the distance durations of the outages. The equipment was installed both in a van-type vehicle for highway and city street tests, and in a “Hy-Rail” vehicle for operation on railroad tracks.

Quantity of Fines Produced During Crushing, Handling, and Placement of Roadway Aggregates

Abstract A three part test procedure was developed to determine the quantity of fines produced during crushing, handling, and placement of aggregates used as base course in roadway construction. The first test simulates crushing at the aggregate source. It involves processing an aggregate sample of specified gradation through a small laboratory jaw crusher. The second test simulates handling by agitating an aggregate sample of specified gradation at 10% moisture content for 20 min. The modified American Association of State Highway and Transportation Officials (AASHTO) compaction test is used to simulate placement. Following the conduct of each test in the procedure, the fines are measured by washing the aggregate over a 75-µm (No. 200) sieve. At the conclusion of the three part test procedure the fines produced during crushing, handling, and placement are determined by summing the fines determined from each test in the series. The maximum fines produced with the procedure developed were correlated to with the Washington Degradation Test results for samples obtained from six aggregate sources in Alaska. In all cases, a poor correlation was found. Owing to the lack of a large body of well-documented field data, the three part test procedure can only be used at this time to determine the maximum quantity of fines that is likely to be produced for a given crushing, handling, and placement history.

Source parameters of the 1949 magnitude 7.1 south Puget Sound, Washington, earthquake as determined from long-period body waves and strong ground motions

AbstractTeleseismic P, SH, and SV first motions and SH to SV amplitude ratios recorded at eight teleseismic receivers from the 1949 magnitude 7.1 Olympia, Washington, earthquake in combination with data from three stations at regional distances were utilized in a grid testing routine to constrain focal mechanism. Identification of the pP phase places the event at 54 km depth. Distinct pulses, assumed to be source effects, are observed in the far-field waveforms. Analysis of these pulses for directivity made possible discrimination between the fault and auxiliary planes. The plane taken to represent the fault surface strikes east-west ± 15°, dips 45° ± 15° to the north, and has nearly pure left-lateral slip. The preferred source model has an eastward propagation of 40 km. Surface reflections of successive source pulses suggest an upward component of propagation of 5 km. Bounds on the earthquake location and rupture of the 13 April event were determined using depth and source mechanism constraints from the teleseismic study and characteristics of local strong ground motion recordings. The 9-sec S-instrument trigger time seen in the Seattle acceleration recordings places the event at least 60 km from Seattle. Strong motion velocity at the Olympia Highway Test Laboratory is characterized by an impulsive and rectilinear S wave. The low amplitude of the vertical component of initial S motion suggests that either the epicenter is within 5 km of the Olympia Highway Test Laboratory for a pure incident SV wave or located along an azimuth of N159° if the wave is SH. The combined constraint of minimum distance from Seattle and the S polarization angle implied by the teleseismic data focal mechanism places the initiation of rupture 5 to 10 km north to north-northwest of the Olympia Highway Test Laboratory at 47.13°N, 122.95°W. This is approximately 20 km west of previously determined epicenters. The T axis, gently dipping to the southeast, supports other evidence that the Juan de Fuca plate dips to the southeast in a zone between segments of the plate north and south of the event's location. The fault plane's slip is taken to indicate that subduction is still active beneath Washington and that motion of the two segments is probably independent.

Natural Rubber Compounds for Truck Tires

Abstract An 80 NR/20 BR truck tread compound containing a semi-EV cure system and modified with a 6.0 phr level of stearic acid has been shown to exhibit excellent resistance to reversion when compared to a similar compound containing a normal 2.0 phr level of stearic acid. Improvements in the retention of laboratory abrasion resistance, heat generation, and most physical properties have been identified on test pieces subjected to typical truck retread overcure conditions. In highway fleet testing trials of 1100 × 22.5 truck retreads fitted to both third and fourth drive axles of tipper trucks, the modified compound displayed a 42% improvement in treadwear performance over the normal compound in the lower severity third axle positions while performance in the higher severity fourth axle positions was inferior by 20%. In comparison to a 55 SBR/45 BR truck tread, both NR compounds displayed superior wear performance on the fourth axles while some further adjustments of the modified compound are required to match the synthetic compound on the third axles. The reversal of wear performances for all compounds between third and fourth axles is due to the different abrasion mechanisms encountered. Laboratory abrasion rankings do not correlate with wear performances of compounds on the fourth drive axle of trucks, but they do correlate with wear performances on third drive axles. Despite the reversion characteristics of the normal semi-EV compound, no significant adverse effect on treadwear performance was evident at the start of tire life. The low heat generation of the modified compound in laboratory tests is confirmed in actual tire testing. Advantages in rolling resistance characteristics are also evident for the modified compound. Current studies at MRPRA suggest that further modifications of cure system design, in combination with the optimization of NR/BR ratios and mixing methods, will potentially provide NR dominant truck tread compounds which will exhibit superior wear performance in both the higher and lower abrasion severities encountered in heavy-duty truck tire service conditions.

Cyclic loading triaxial testing of crushed rubble and lava

This paper describes a laboratory investigation into the suitability of crushed rubble as a substitute for conventional road base materials. The rubble investigated was a mixture of crushed concrete and crushed bricks, whilst lava from the Eifel was chosen as a reference material. Standard highway engineering tests (Proctor, CBR) and durability tests (Los Angeles Abrasion, Slake Durability and the standardized Dutch crushing test) were performed to provide reference date with every-day engineering practice. Cyclic loading triaxial tests were performed on both materials. The resilient moduli were determined at various levels of confining stress and the cyclic deviator stress. The susceptibility to plastic strain development (rutting) of both materials was determined in triaxial tests with up to 106 load applications. The degradation of the materials in the plastic strain tests was determined through sieve analyses prior to and after the tests.

Highway test to use sulfur in pavement

RETURN TO ISSUEPREVNewsNEXTHighway test to use sulfur in pavementCite this: Chem. Eng. News 1977, 55, 47, 7Publication Date (Print):November 21, 1977Publication History Published online7 November 2010Published inissue 21 November 1977https://doi.org/10.1021/cen-v055n047.p007bCopyright © 1977 American Chemical SocietyArticle Views2Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (256 KB) SUBJECTS:Sulfur Get e-Alerts

Reduced truck fuel consumption through aerodynamic design

Full-scale fuel consumption and drag tests were performed on a conventional cab-over-engine tractor-trailer combination and a version of the same vehicle with significant forebody modifications. The modified configuration had greatly increased radii on all front corners and edges of the tractor and a smooth fairing of the modified tractor top and sides extending to the trailer. Concurrent highway testing of the two configurations showed that the modified design used 20% to 24% less fuel than the baseline configuration at 88.5 km/hr (55 mph) with near-calm wind conditions. Coastdown test results showed that the modified configuration reduced the drag coefficient by 0.43 from the baseline value of 1.17 at 88.5 km/hr (55 mph) in calm wind conditions.

Testing of Tire Treadwear under Laboratory and under Service Conditions

Abstract Four different laboratory machines for the evaluation of tire treadwear have been described which used concrete, steel, and tungsten carbide abrasion surfaces at variable speed and slip, but none has satisfactorily replaced highway testing. Predominant sources of wear on passenger tires appear to be cutting and frictional fatigue, the rates of which are influenced differently by temperature and load. Thus, seasonal or climatic, topographical, and geographical effects are evidenced. Treadwear cannot be expressed solely as a property of the tire since it is the resultant of the interaction of the tire with multivariate environmental conditions.

Some Recent Findings In Flexible Pavement Research

This paper is based on sponsored research done by the Texas Transportation Institute on Texas highways. The results reported include: (1) The development of an empirical equation for estimating load-induced deflections from the thickness and laboratory-determined strength of the materials used in a highway pavement, and (2) the use of the equation, together with deflections observed on 323 highway test sections, to evaluate the regional effect in Texas. With a surprisingly large regional effect determined, the net result of the research was an equation for deflections that contained: (1) a Field Compression Coefficient for each layer dependent on both laboratory strength and regional effect, and (2) a Depth Coefficient for each layer dependent upon the thickness of the layer and its position in the structure. The equation presumably could be used in the design of flexible pavements in Texas if deflection criteria were made a part of the design procedure, and if the underlying causes of the regional effect were known.

Laboratory Testing of Tread-Stock Abrasion Resistance at Constant Transmitted Power. I. Comparison of Road and Laboratory Data at Various Severities

Abstract Laboratory abrasion data were obtained on various tread vulcanizates over a large range of severities, including the region equivalent to the low severity encountered on straight, smooth California highways. The constant transmitted power principle was used as a severity criterion for comparison of abrasion of different tread vulcanizates. Load, wheel angular velocity, and ambient temperature were held about equal to those prevalent during road tests. These data were compared with road tests on the same vulcanizates, conducted on tires tested on courses varying from low to high severity. The laboratory data and the California low severity test data show a high degree of correlation for BR vs SBR (50 HAF) over the entire range of severities tested. The loss rate-severity plots for BR and SBR show a crossover point, with the BR showing the higher abrasion resistance at the higher severities. The BR shows a substantially higher abrasion resistance than the SBR on the Texas straight highway course. This is in opposition to the California data, which shows a substantially lower abrasion resistance of the BR compared to SBR on the straight highway course. The abrasion rates for BR and SBR in Texas, California, and laboratory tests are consistent if the severity of the Texas course is assumed to be equivalent to a linear combination of at least two California or laboratory severities. A plausible cause of the difference between California and Texas results is the difference in pavement surface texture. This viewpoint is shown to be consistent with abrasion patterns observed on tires in the California and Texas straight highway tests. The laboratory data and California test data on NR relative to SBR are consistent at the high severities, and for laboratory data extrapolated into the low severities from the high severity data. However, the actual laboratory data taken at low severities are more erratic and show consistently higher loss rates than those observed in the California freeway test. It is postulated that this may be the result of increased susceptibility to thermal oxidative degradation of the NR surface, caused by relatively longer exposure in the laboratory than on the road at a given severity. The investigation described in this paper lends a great deal of encouragement to the usefulness of laboratory abrasion testing for the screening of treadstock vulcanizates. The ability to obtain abrasion results under carefully controlled conditions of transmitted power, temperature, load and wheel angular velocity allows results to be investigated confidently as a function of conditions in the instrument, or of the polymeric properties. These investiagtions can be quite fruitful in eventual understanding of the polymer behavior or of the mechanism of abrasion. An important observation has also been the large variations in tire test results on different courses of assumed equal severities. Thus, the laboratory abrasion test can also assume the position of a guide to more effective road tests.