Consulting services for road, airport and railway
The consulting engineering office of Technical and Soil Mechanics Laboratory, utilizes nondestructive equipment in order to conduct pavement quality evaluations in both project and network levels. The results obtained from these tests can be used in presenting rehabilitation plans and also determining the root causes of pavement distresses and pavement performance indices. All the gathered data is implemented in pavement maintenance management system of roads and airports. Thanks to the nationwide TSML branches, the consulting engineering office is capable of employing advanced and state-of-the-art laboratorial and field equipment across the country.

 {tab title="Network-level Technical Capabilities" alias="Network-level Technical Capabilities"}

A network-level study includes data collection and their analysis over an extensive series of roads such as a province road network, highway road network or airfields of one or several airports. A network-level analysis determines the general condition of pavement as well as the required budget for maintaining it in a desired state. The main network-level technical services provided by Consulting Engineering Office include:
    Preparation of road inventory
    Evaluation of road structural and performance characteristics
    Sectioning road pavements into structurally adequate and the structurally inadequate.
    Determination of road network maintenance strategy (preventative, rehabilitation and reconstruction)
    Road sectioning based on their structural and performance characteristics
    Determining road sections strategies suitable for applying pavement preservation activities such as fog seal, chip seal, slurry seal, microsurfacing…  
    Implementation of road and airport pavement management systems
    Pavement preservation activities

{tab title="Project-level Technical Capabilities" alias="Project-level Technical Capabilities"}

The structural adequacy of pavement is evaluated using FWD. As a result, the overlay thickness for bearing the traffic loads is calculated for the intended pavement lifetime. Following the sectioning of pavement, in order to design a pavement rehabilitation plan, the ultimate recommendation for each section is made according to the structural adequacy of pavement, its roughness, surface distresses and also destructive tests results.

Pavement surface distress evaluation
In order to assess the surface condition, pavement distresses are surveyed and PCI index is determined according to ASTM D-6433 standard (road pavement) and ASTM D-5340 (airport pavement) using the latest version of PAVER. This software can also help in determining the percentage of pavement distresses caused by loading, weather conditions and poor quality of pavement construction. The consulting engineering office is capable of conducting both manual and automatic surveys. In manual method, according to the above-mentioned standards, the surface distresses are collected after sectioning and PCI will be calculated. In automatic method, the LCMS (Laser Crack Measurement System) is utilized to collect surface distress data continuously and at the maximum speed of 96 km/h. This apparatus is able to produce 3D profiles of the pavement which have 5mm longitudinal resolution, 1mm transversal resolution and 0.5mm range resolution.

The advantages of performing an automatic surface distress survey are:
•    Collecting surface distress data continuously instead of rating a few predetermined samples.
•    Determining the severity of distresses automatically so omitting the adverse effects of engineering judgments.
•    Sectioning road pavement with reference to each type of distress
•    Accurate evaluation of the pavement preservation operations required for pavement treatment (the length of sealing, the area of asphalt patching and milling)
•    The simultaneous survey of both surface distresses and the roughness index
•    Determination of distress indices (fatigue cracking index, linear cracking index,…) instead of calculating the PCI.

Determination of Thickness and Depth of Pavement Layers Using Ground Penetrating Radar (GPR)
Thickness profile of pavement layers (asphalt, base and sub-base) can be determined non-destructively using GPR. Furthermore, being sensitive to moisture variations, GPR can measure the depth of damp layers. It can also detect underground utilities such as cables and rebars.

CBR Estimation of unbound Layers Using Dynamic Cone Penetrometer (DCP)
DCP has the best performance on granular layers and rural roads. Using this device, CBR of granular pavement layers can be assessed at each desired point of pavement after asphalt coring. Moreover, the thickness of the layers that have equal strengths, can be determined by analyzing the penetration rate variations.

Subgrade and Granular Layers Quality Control Using LWD
LWD device determines the subgrade resilient modulus (used in AASHTO pavement design) and by comparing obtained values at various road locations, the quality of subgrade implementation (compaction & stabilization) is evaluated. By conducting the test on compacted subgrade, it is viable to either use the obtained resilient modulus directly in pavement design or else, by comparing the results with that of the initial design plan, the plan can be revised.

Evaluation of IRI
Roughness condition has a significant role in riding quality. An RSP (Road Surface Profiler) is used to measure the pavement roughness along the left and right wheel paths so that the IRI (International Roughness Index) and RN (Riding Quality) can be calculated. This index is also useful in testing the newly constructed or overlaid pavements.   
Technical and transportation infrastructure affairs council has regulated an instruction for final and temporary delivery of constructed roads in which IRI index limits are considered as follows:

Determination of superelevation using RSP or LCMS geometric modules
RSP is able to measure geometric parameters of road such as slope, cross slope, radius of curvature and superelevation in horizontal curves. During the repair and maintenance cycles, particularly after implementation of pavement overlay, the superelevation, as an important parameter in providing safety, may change. Hence, measuring this parameter is of utmost importance especially in major roads.

Evaluation of the Surface Friction
The RSP (Road Surface Profiler) or LCMS vehicles are able to measure macro-texture in micron. This parameter plays a significant role in the level of friction produced between pavement and vehicle tires at high speeds. Furthermore, the water drainage of the pavement surface is highly dependent on the macro-texture. RSP measures the macro-texture under the right wheel in terms of MPD. Then, by applying a linear fitting algorithm to this index, it is converted to ETD.

{tab title="Technical Capabilities in Airfield Pavement Design" alias="Technical Capabilities in Airfield Pavement Design"}

Pavement Rehabilitation Design
Airfields pavements including runways, taxiways and aprons are evaluated by carring out destructive and non-destructive testings on the pavements. Based on these evaluations, a pavament rahabilitation plan is proposed.

Determination of CAN/PCN

PCN (Pavement Classification Number) indicates the relative strength of runway, taxiway or airport apron. The values for PCN should be greater than CAN (Aircraft Classification Number) of the airport.  The Consulting Engineering Office is able to determine PCN non-destructively for runway, taxiway and apron by using HWD and GPR.

Determination of Boeing Bump Index of Airfield Runway Pavement
The depreciation rate of aircraft is strongly affected by airfield pavement roughness. Therefore, by calculating the BBI of airfield pavement, the points in which the roughness exceeds the acceptable level, are determined. A rehabilitation plan is required for these points. The vertical acceleration of the cockpit which is directly related to aircraft response to the runway roughness, may be determined using RSP data.

Determination of PrI in airport pavements
According to FAA, airport pavement roughness should be determined in terms of PrI (California Profilograph). This index is calculated by analyzing the measured profile recorded by RSP in Proval for 528ft long sections. With reference to FAA:AC 150/5370-10G for a contractor to get paid, the index should be less than 7in/mi.

Determination of Load Transfer Efficiency of Rigid Pavement Joints
The load transfer rate of joints in concrete pavement (supplied by dowel bars and aggregates interlock) may be evaluated by HWD. LTE poor performance of dowel bars in joints of rigid pavement may lead to some distresses such as pumping, edge cracking and faulting.

{tab title="Equipment" alias="Equipment"}

F/HWD (Falling/ Heavy Weight Deflectometer)
FWD and HWD are quite similar in their mechanism of action. The only significant difference between the two is that, being equipped by greater masses of weights, HWD is able to produce greater stresses so that the simulation of loading stress due to the aircraft landing, would also be viable. Basically, what these devices do, is that they first apply a known amount of stress to the pavement and then record the deflections produced due to the impact. Weather and pavement surface temperatures are automatically measured by the equipment whereas the temperature of asphalt layer depth is measured manually. Based on the project requisites, survey points interval in each route, is selected to be between 3 to 500 meters and geophones are placed with 30 centimeters distance from each other. Next, in a time interval of 1 to 2 minutes, the loading is applied to the pavement at least three times.
Deflection basin, which is the main output of these devices, is analyzed using ELMOD software or AASHTO method; a process through which the elasticity modules of pavement layers are calculated and the required overlay thickness to reach to a structurally sound pavement is calculated.

The laser crack measurement system, uses laser line projectors, high speed cameras and advanced optics to undertake automated measurement of road surface conditions and geometry by acquiring high resolution 3D profiles of the road. The survey can be performed at speeds up to 100 km/h covering 3.7 m lane width. Longitudinal resolution of 3D profiles can be set as high as 1-5 mm (adjustable); lateral resolution is 1 mm and range resolution is 0.5 mm. The surface is surveyed continuously and the data is recorded in 5-10 m length sections.
The capabilities of this unique 3D vision technology in identifying pavement surface distresses are as follows:
1-    Different types of cracks (longitudinal, transversal and alligator), their associated intensities (low, medium, high) and their extents (length or area)
2- Surface macro-texture in 1 m length intervals or higher (adjustable). The output can be calculated in terms of MTD according to ASTM-E965 or in terms of MPD according to ASTM-E1845-01.
3- Road surface raveling and porosity indices.
4- Rutting of the surface which is calculated according to ASTM-E1703 and determination of rutting width and depth in 1 m length intervals or higher (adjustable).
5- Potholes area and depth.
6- IRI of the wheel paths in 1 m length intervals or higher (adjustable).
7- Slope and cross fall in 1 m length intervals or higher (adjustable).
8- The geographical coordinates of each section.
9- Lane marks perimeter and area.
10- Drop-off and curb position and height.
11- Automated lane position detection to avoid surveying defects outside the lane.

Road Surface Profiler (RSP)

Pavement roughness, as the main factor in generation of dynamic loads due to vehicle movement, can expedite deterioration of pavement as well as wear and tear of vehicles. By using RSP, the pavement roughness of the wheel path area is determined in terms of IRI. Furthermore, this device is able to measure the geometrical characteristics of the road including the slope, cross-slope and radius of curvature. Macro-texture (in terms of MPD) and rutting, are yet the other parameters that can be measured by an RSP.

GPR (Ground Penetrating Radar)
GPR is a non-destructive equipment used for evaluating depth of pavement layers. It is capable of producing profiles of layer thickness measurements along the road. Furthermore, it can be used to locate underground utilities.
Ground penetrating radar is a geophysical technique that uses electromagnetic wave to image the underlying pavement layers. When the radar is moving along a line an amplitude-time trace is produced for each point and by sorting these point alongside each other, an underground profile is yielded.  Applications of GPR include:
•    Quality control and evaluation of road, airport and railway (determining layer thickness, measuring wet content, detecting voids, …)
•    Detecting urban utilities (pipes, cables, sewage system, voids, aqueduct, …)
•    Engineering geology studies (detecting layers susceptible to  landslide and water saturated regions, determination the depth of bedrock and faults, …)
•    Environmental studies (studying the pollution spreading pattern in underground waters)

LWD (Light Weight Deflectometer)
The LWD device is able to nondestructively determine resilient modulus of granular layers (subgrade, sub-base, and base) in a short time. This device is especially useful in quality control of pavement layer construction and also in determination of resilient modulus. An important advantage of LWD is its ability to conduct large number of tests on the field in a short period of time.

Dynamic Cone Penetrometer
The in-situ strengths of subgrade, sub-base and base layers of pavement are measured by Dynamic Cone Penetrometer (DCP). Its mechanism is such that an 8-kilogram mass is dropped from a height of 575 millimeters. The number of blows versus the amount of penetration by cone are recorded. As a result, the penetration rate (mm/blow) is calculated. In existing pavements, the strength of sub-layers can be measured by DCP after coring the asphalt pavement layer.

Pavement Assessment Projects at Network Level

 

Pavement Evaluation Projects at Project Level

Airport Projects

Miscellaneous Projects

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