Pavement Engineering - Science topic

Thanks Greg Stephenson

In the original research for the "Mechanistic-Empirical Pavement Design Guide" (MEPDG), delivered under NCHRP Project 1-37A, there is a detailed discussion of how they considered lateral wander in road traffic. Perhaps you can start your review from there. The original documents appear temporarily unavailable; let me know if you don't find them online.

I recommend looking into resources from organizations like the International Road Assessment Programme (iRAP), the American Association of State Highway and Transportation Officials (AASHTO), and academic journals related to transportation engineering and road safety. These sources should provide valuable insights into wheel wander analysis within lanes.

G'day

We have design processes that assign various percentages of heavy traffic to the outer lane but tend to err on the conservative side and adopt 90% to 100% of the heavy vehicles in the outer lane. We wouldn't design the inner and outer lanes for different traffic as part of new construction partly for uniform construction practices across the road. We also worry about the discontinuities in the base layers acting as potential points for water/seepage to accumulate, so we prefer uniform layers across the road.

However, in resurfacing or rehabilitation projects, if the outer lane needs reconstruction and the inner lane is still sound, we might do a deeper mill and fill on the outer lane than the inner lane. In that case there is no point strengthening the inner lane if it is performing.

Again if we are widening a road and adding an outer lane, that is likely to be designed for the full heavy vehicle traffic which probably results in the thicker pavement than the original lane which now becomes the inner lane. Dealing with the interface and ensuring a new full depth AC outer lane doesn't act as a dam in the pavement means that there might be a need for subsoil drains along this interface.

Regards

Hello,

The moving concentrated forces of wheel load can be applied in ABAQUS using cyclic dynamic force. Find attached the paper on similar moving load analysis of a bridge beam subjected to moving wheel load for your reference..ok all the best..

yes what are the topics u will be discussing

Greetings there,

To be laconic, I think if u can go through it, it might help.

Jason Wen-chieh Cheng Thank you, I will check it out.

Gracias. ¿Me pueden enviar el enlace web? No entiendo español tan bien para buscar el sitio web del instituto.

Did you consider old cobblestone from another, previously demolished roads? For this kind of low-traffic volume and low speed roads around historical sections of the city we often use old (e.g. granite) elements. Personally I think that cobblestone pavements (old or new) are more enviromental friendly than asphalt pavements mainly because life cycle of this surface will exceed asphalt one. You can surely find granite pavements older than 100 years and they rarely need any extended rehabilitation treatment. Ofc I'm talking about low speed and low traffic volume roads. Cobblestone also helps to reduce car speed without any additional dedicated solutions.

Agreed @Amjad Albayati

To model pavements with three layers (one rigid and one flexible) in Canada, it is necessary to collect this information from the design offices responsible for diagnosing and prospecting pavements affected by deterioration.

Cohesionless soils when sheared at low confining stress will dilate and generate negative pore pressures. The particles are interlocked but at some point of continued axial stain they must lift to ride across one another. The perfect example can be seen in the direct shear device with vertical axial stain measurements. Taught in basic soil mechanics. At high confining stress soil is contractive. Dense soil is dilative and loose soil is contractive and depsnds on confining stress.

As I see it you have frequency data for each category. From the frequency for each vehicle category you can calculate the total number of single tandem or tridem axles and multiply that with the number for each axle load from the respective column in your attachment. And repeat that for every category.

can you send me the BS EN 16659:2015 standard , please Rufus Adjetey

Here are some impacts of long term flooding pertinent to structural distresses:

1. Reduction in structural strength

2. Increased deflections

3. Loss of sub-grade strength

4. Increase in roughness, rutting, and fatigue cracking

5. Potholes

6. Swelling

7. Joint deterioration

The underlying layers play a critical role. If fundamental drainage is an issue, then it would be convenient to either provide dense surface and drainage layers or a proper drainage system. Another solution could be the provision of gap-graded asphalt or porous asphalt / concrete in top surface course, followed by a concrete base course, and subsequent dense layers. Furthermore, utilize additive materials that reduce the pavement's susceptibility to moisture.

Attached are a few studies for your reference:

http://onlinepubs.trb.org/Onlinepubs/trr/1987/1121/1121-009.pdf

You can calculate the stresses and strains induced by your representative truck loads and at the different temperatures using any existing free software (Kenlayer, ELSYM 5, Bisar), then use the failure model (Fatigue, rutting) to calculate the damage using Excel or any other spreadsheet software. Of course, the MEPDG software uses models to find the temperature at different depths, etc. For your case just use uniform temperatures. The same applies to the water content of the subgrade soil and untreated base materials.

Keith Govo You may use this title for your thesis, "Feasibility of designing a bypass route by congestion assesment at [location]"

Quite a number, but as stated by Amara, look out for the AASHTO incorporated model.

Soil properties, gradation curve, compaction curve and soil type are all important factors in deciding! However, previous work done in this field suggest that plus-minus 2 of the OMC would be safe.

As per AASHTO T-193 if the curves start concave upwards they should be corrected by extending the linear portion of the curve until it intersects the x-axis (penetration) and use the intersection as the new origin of the axis.

"Besides providing load distribution in post-construction stage and working platform in the construction stage, sub-base can also serve as a drainage layer to remove water coming from the pavement.

For thick layers of road pavement, it is likely that the water leakage from pavement is insignificant and therefore the sub-base layer mainly serves to support the traffic stresses. However, for thin pavement layers, water penetration is quite substantial and therefore sub-base may also act as a drainage layer to remove these water."

Check out the following links:

Note that the last links provide significant information regrading the optimum moisture content and dry density for granular materials.

Try to contact The University of Nottingham. They have a specialised centre for Highways and pavement research, called Nottingham Transportation Engineering Centre, which provides such services.

You can refer to AASHTO T 193.

Any pavement design method would have to consider 4 parameters:

1- traffic loads; 2- Environmental conditions ; 3- pavement materials' properties; and 4- Properties of the supporting subgrade.

Therefore, for the subgrade, early design method rely on the CBR test to get its bearing capacity. Then, AASHTO with its major experimental road test performed in the late 50s, switched from using CBR to resilient modulus for characterizing the subgrade. The resilient modulus is a weighted average based on the climatic conditions during the whole year. Therefore, for those who still use CBR as a Test and wanted to use the AASHTO statistical method needed a way to correlate between the two properties and many equations came out. With its recent mechanistic-empirical pavement design guide, AASHTO still uses the resilient modulus property, but use more complex equations that relate this property with moisture content and stress conditions.

In short, simple design method use simple easy to get properties, but people attack these methods because of their simplicity. More complex methods (such as the new AASHTO design guide) use sophisticated models in order to simulate the real conditions, but the average user finds himself/herself trying to input properties that are not easy to get and in most case use default values.

So now depending on which school you want to be, you can use simple design method or use more complex methods that are supposed to achieve more reliable designs. Of course, if you work in an engineering firm, the choice on which method to use comes from the client and not you.

Ansys, Abaqus and plaxis

This programs used to make finite element and used to know the stress and deflection on the pavement

Vibration compaction tests include vibrating table test and vibrating hammer test.each method will give different results though dry unit weight and water contents are the same for a given granular soil.

However it has been suggested that impact factor be used and its result must be considered.

There is no index for correction for vibratory compaction.

you can try to use MMA Colplastic material, this is thermosetting with 2 component product

The University of Nottingham. They have a specialised centre for Highways and pavement research. It is the UK's foremost university-based research organisation in highway engineering.

Yes it is possible not because of the physical properties but because every system can be configured and calibrated into doing what you want. Try and find the route. Good luck 

There is a number of software for that. In addition to those already cited, there is also ELSYM5, it is old, but still very common.

If you like to generate nice graphics with color gradients have a look for "finite elements analysis" software, like Ansys (paid).

The main reason for obtaining different material properties for different specimen size is the variation in the sate of stress and strain within the test specimen.

Theoretically, when you apply a uniaxial compression on cylindrical specimens, the material close to a free surface is not confined can deform laterally and there is a plastic deformation in this region. As the diameter decreases, the vertical normal stress through the diameter varies less, and it approaches the state of plane stress. As the specimen diameter increases, the material inside the specimen away from the free surface becomes laterally combined by the surrounding material, and it approaches the state of plane strain where it experiences elastic deformation. Therefore, the specimens with smaller diameter tend to be more ductile, while those with large diameters tend to be more brittle. This means that the larger diameter of your specimens might theoretically lead to higher values of the stiffness modulus and shorter fatigue life.

However, the research has shown that values of the complex stiffness modulus from uniaxial compression test are mostly not influenced by the specimen size. You should also pay attention that different void distribution of gyratory compacted specimens depending on the specimen preparetoin (cored/uncored) could have a certain influence.

For more details please refer to the listed references. Please be fre to contact me for an further discussion.

ASTM and AASHTO grooving tools make different groove shapes. A groove made with the ASTM tool has faces which form an angle of approximately 45°, while a groove made with the AASHTO tool form faces under the angle of 60°. The ASTM groove tool also shapes the top surface of the soil cake.

Dear Onyelowe;

1- This papar shows relationship between durability and unconfined compressive strength for fly ash.

DOI: 10.1061/(ASCE)0899-1561(2006)18:1(18)

2- In this paper, the resistance of loss in strength [durability] was determined as a ratio of the Unconfined Compressive Strength [UCS] after curing.

3- In the following paper, the results of conducted CBR tests are shown as durability Effect of stabilized soil.

You can find some simplified relations in the sources below. if you can be more precise, I would try to give you a more complete answer.

Al-Omari, B., Darter, M.I., 1994. Relationships between International Roughness Index and Present Serviceability Rating. Transportation Research Record, 1435, 130–136.

Carey Jr, W.N., Huckins, H.C., Leathers, R.C., 1962. Slope Variance as a Measure of Roughness and the Chloe Profilometer. Highway Research Board Special Report, 73, 126–137.

Sun, L., 2001. Developing Spectrum-Based Models for International Roughness Index and Present Serviceability Index. Journal of Transportation Engineering, 127 (6), 463–470.

Walker, R.S., Fernando, E., 2002. Evaluation of Ride Equation using Current Profiler Systems and New Sensor Technology. The University of Texas at Arlington.

Plate bearing test. Applying the concepts described in Yoder's textbook for pavement design. Good resource

You can use BISAR or Overstress to calculate pavement displacement.

ABBAS 

You can simulate the pavement as a plate elements with the corresponding material properties. The supporting layer can be simulated as a semi finite layer with the corresponding material properties. The interface between the pavement and the underneath layer is simulated by a linkage elements in the horizontal and vertical elements with appropriate stiffnesses. 

Depending on the type of tests (fatigue, modulus) you carry out in your country the French method would be fine.

Dear Nithin..it depend into large extent on testing temperature due to the rheological properties of asphalt..anywhy..you can consider low limit of stress when testing on high temperature say over 40 degree Celsius otherwise when testing at low temperature you can pickup high stress level,,but you should remember that the testing loading cycles better to be more than 1000 repetitions to get good statistical relationship..regards   

Thank you Ayyanna Habal.

I came through this document and it helped me a lot.  

Dear Dr. Ullah:

I will scan some relevant pages for you and send them

This suggestion is untested for this type sampling for your purpose, but worked well for sampling water in irrigation study.  Plastic pipe with porous ceramic cups epoxied at one end, two hole stopper at other end with long and short tubes used in plastic pipe, short one for evacuating or pulling a suction and after water enters and accumulates, use pressure on the short tube to push water into long tube and out for collection.  In this type of installation, perhaps gravity could be used to deliver water if pipe installed from side of road with a grade for delivery.  I would try to use bentonite clay to seal up hole if necessary if it is not a tight fit (Note: Do not get bentonite on the ceramic cup (or anything else basically, wear gloves, eye and other protection) as it could seal ceramic cup and limit sampling.  Bentonite expands when moistened, and wont wash out of clothes and probably has some other hazards to review if using.). I dont know that this sampling approach would work, but relatively inexpensive to make and install, just use the same size soil corer and pipe, ceramic cup for a tight fit.  You may need to pull the vacuum on the pipe before the storm to ensure sample is taken.  If the sampler will not hold a vacuum, you may need to pull the vacuum after the storm or look into running such as a peristaltic vacuum pump to provide a continuous vacuum.  When removing sampler from road after done, use bentonite or other suitable fill, compacted in layers to refill hole. 

If you use the pipe installed on an gradient for delivery of water, even if the ceramic cup becomes cracked or smashed, the void may still be able to collect some water to provide a sample.  I would pick a place to sample along road where if the road surface is damaged for some reason, it is not going to create an accident or excessively damage the road. 

Thank you all for your answers

Dear all

Thank you very much to give me a hand, the AASHTO R68-15 section 3.2.2 and AI MS-2(7th) section7.2.4 both metioned the correlation procedure, it is really confused me. 

When performing automated operation, I agree with yours' opinion. it is due to many varaibles exists in the manual procedure.  

Thanks yours' help indeed

Dear Sadeq

for every laboratory testing, there is a degree of significance, as you are testing asphalt concrete specimens, 0.95 significance is sufficient for your purposes, the standard deviation of test results from the mean value should be within -+ 5%.

Hai,

      I am doing a project on crack growth simulation. May we could discuss about your project

1. Is there relationship between asphalt roughness and SAR backscattering coefficients?

A. Obviously. But results will be severely biased by car traffic, off-road infrastructure (road signs, poles, ads), trees (remember all RS radars are backscattering radars), buildings, hills and mountains, etc.

Unfortunately, I don't have the pdf file. You can try to request the full text through the link provided above.

The attached file implemented the stat-of-the-art optimization algorithms in excel and you can use it.

For granular layers, the elastic modulus based on the recoverable strain under repeated loads is used. This is the resilient modulus Mr. for granular materials, this modulus is determined by the repeated load triaxial test. For asphalt mixtures, indirect tensile tests can be used. It is worth noting however, that most advanced pavement analysis tools rely on the dynamic modulus. The dynamic modulus test provides a better characterization of HMA than the resilient modulus test because it provides full characterization of the mix over temperature and loading frequencies

If you are following AASHTO there is an equation 

which described in a graph

this site is summarizing this method

http://www.pavementinteractive.org/article/1993-aashto-flexible-pavement-structural-design/  

Ebrahim,

Here is the procedure of increasing water content after compaction:

-Find an appropriate mold (maybe plastic pipe for cylinder or wood made for cubic)

-Start with an initial water content which matches with saturation ratio and  dry density target .

- Compact your sample till calculated height (still you are not on your targeted water content)

- Calculate target water content on the wet side of optimum density and matches with saturation ratio-dry density and pour half of it on the top. let it be isolated for 1-3 days depending on your soil type. ours was cohesive clay and we kept it for 2.5 days.

- Reverse the sample and pour other half of water on the bottom. Keep it isolated for the same time.

- Now your sample is almost homogeneous in water content percentages. 

-Run a water content test from top, bottom and middle of every sample after you ran your test as a report.

* you may see some error according to change in height, expansion, non homogeneous distribution and ...  You have to verify them with measuring height after reaching water content as well as water content tests.

Dear Mr. Sangsefidi:

your question is too general in its essence and tries to be all embracing. Climate, parent material etc. have such a strong impact as the hydraulic regime and the geomorphology. You ask about opinions on chemical reactions and refer to physical processes leading to mechanical performance.

What is it all about? Be more focused, please.

Harald G. Dill

Dear Ebrahim:

Look at the formula for the thickness of the diffuse electric double layer in the Gouy-Chapman theory. The charge of the ion is in the denominator . Therefore the thickness of the diffusion layer decreases with increasing ionic charge.

Regards.

Fe+3 should increase the soil strength as it acts as a binding material.  Fe+2 is soluble, so it will actually have the opposite effect on soil strength.

You can't really determine the equivalent without testing. The range of rheological properties for a given Pen grade is much wider than PG. Based on my limited experience with Pen 40/50, its HTPG could be 70 or perhaps 76. To run your MSCR you may try 64 or 70 as your base temperature. But, if you want to go to the trouble of doing the MSCR, why don't you just determine the HTPG as well. You have to do RTFO aging and make DSR samples, you might as well make a few extra samples and run the HT PG on both age and unaged as well. You need to do that and find the S grade and then see if it satisfies H or not. Read the following short article: 

You might find help, at least on the methodology, in this study of accidents on all types of roadways (not just highways), their geometry and detailed surface conditions (ch 9, enclosed).

If you want more details, you have to look at the final table in the detailed paper, enclosed also. The last variables in the list (Groups 13 and 14) are all surface quality variables. But the source of the data, the French technical road services, forced us to hide the detailed results for eight variables (A...H) in that section. They were afraid of lawsuits, as were occurring in Germany at the time, based on the idea that better surfaces increase speed and perhaps accident risk or severity.

Hoping this helps. Marc Gaudry

Hello

I Do not finished....I'm Sorry. I´ll Try to do another hing in my research. I´ll try to model whit DEM. Thanks for your answer. 

Dear Ravi,

Thank you for your response.

I totally agree with you, but I am seeking for a method to accelerate the aggregate deterioration due to the presence of water. In the other word, I want to simulate the effect of water on aggregate during pavement life.

for example, the effect wetting and drying, freezing and thawing and etc. 

Thank you.

Dear Ebrahim,

Like Harith said,

I think it depends on your design loads, base on that, you can calculate and choose which materials and gradation that fulfill your needs. For example, according to AASHTO, soil classified as A-1-b, A-2-5, A-3, A-2-6 with CBR test result from 20-50 described in "Good criteria" for base and subbase, but even so, sometimes that is not what we need, maybe our pavement design needs already fulfilled by the use of soil in the medium criteria, because materials selection also related to our cost, so we have to choose wisely.

So it depends on your design calculation, with that needs, which materials acceptable to support it, what gradation and etc.

Hope that could help...

Dear Hossein,

The report that Tatjana sent is good. But, please note the comments made by Luis and Sinnappoo. The correlations will be very much dependent on the level of maintenance and rehabilitations. For example the IRI in the wheelpath picks up mainly the distresses such as corrugation, depression (short lengths), bumps and sags, potholes. But, not the low and moderate ravelling, bleeding, carackings (unless they are severe enough to contribute to roughness), etc, So, the correlations as commented by others can best be used as a rough estimate. Because, they depend on the class of the road, level of maintenance, environment, etc. that could be very different from a country to anither. Therefore, You can't use the ones from the Washington DC area to your locality of Zanjan.

Regards,

Dear Hossein Mohammadi,

I suggest a paper link which is useful for your research work.

See Paper No. 590 “Pavement Deterioration Modeling for Low Volume Roads” by

Vandana Tare, H.S. Goliya, Atul Bhatore and Kundan Meshram, Journal Of The

Indian Roads Congress Volume 73-4, pp. 67.

Many studies suggested that Discrete Element Method (DEM) via PFC2D and PFC3D software (Itasca) could be used to to simulate deformation and fracture in different materials, even in asphalt mixes. The discrete element algorithm models a continuum as a system of distinct, interacting, and general-shaped particles subjected to laws of motion and deformation, which are bonded together. When the maximum stress in a contact bond is reached, the bond is broken and a separation of these particles (cracks) can be observed. 

PFC software is a little tricky and not that user friendly, especially if you are going to use your own model to simulate asphalt mixes responses.

Good luck.

Please find attached a good article regarding your question above. hope it will help.

Surface deflection, as like as stress/strain, is a pavement response which may be considered to be dependent upon various internal and external factors. Internal factors, i.e. material specifications and characteristics, are those which are usually selected to produce different types of asphalt mixture, and base/subbase courses; while the external factors, e.g. loading frequency, aging condition, temperature, etc., are related to different traffic and/or environmental conditions to which the pavement may be exposed.

I think you can define another term namely "inter-particle areas" instead of "inter-particle distances". In other words, if you can use the image processing method on your photos, you may calculate the net area surrounded by the particles. The mentioned area, which is an indication of air void content, decreases as the compaction effort increases for constant mix characteristics. Finally, if you can correlate the air void content as well as the compaction degree, both of which may be determined by the direct measurements, to the newly defined "inter-particle areas", it is possible to develop predictive models. It must be noted that the method of compaction may have a significant effect on the distribution of air voids within the specimen depth/height. So, you have to calculate the average of "inter-particle areas" determined for different slices.

I support the good answer stated by dear Rawand. To complete the mentioned explanation, it may be noted that the primary factor which is used in the existing literature to determine the PSI may be considered to be longitudinal roughness. Thus, some researchers have not used the other factors, e.g. cracking, patching, etc., in their correlations. Therefore, PSI may be determined solely by the use of pavement roughness, especially for the rural pavements, with a high degree of accuracy.

Professor Cong: I totally agree with your comment about the lack of  ductility of these types of binders.  That was actually confirmed through laboratory testing.  Aging does not seem to be a problem though according to the RTFO aging protocol. I could not find sound literature about such types of binders to compare my data with.

The Purple sample was a PAV aged VG 20 grade binder without any modification. 

Assuming you are asking what issues are unique to hot weather seals...... most sealing binders, in order to be able to wet the stone at normal temperatures, have low softening points – at least compared to asphalt binders. If not sealed during the hottest weather, the bitumen can then go soft when very hot. This is a high risk during the first summer when the volatiles escape – but soften the bitumen beforehand. My message is: do not seal in hot weather environments except during the hottest weather, and never seal in the coolest weather when cutter is required to wet the stone.  Also pick the most high-temperature resistant bitumen you can without adversely impacting your ability to wet the stone during construction.  I have numerous papers on sealing airport pavements which all address this issues.

You can benefit from the Texas Transportation Institute report FHWA/TX-09/0-5627-1. A good reference.  Check pages 75-77 in particular which talk about the British Pendulum testing. You might be able to download it from the following link:

Dear scholar, Thank you so much to initiate this discussion. This is an interesting discussion to follow. Thank you Mr Kundan Meshram for your information as well.

Dear Khalid

I am interested in asphalt stabilization of gypseous soil and had published many papers on the subject, kindly inform me if this is matching your problem so I will send you my work.

Thx Yavuz

If you could pls give me some more details about the same.

Regards,

Vinayak