Road, airport and railway consulting services of the soil technical and mechanical laboratory company

The office of consulting engineers of Soil Technical and Mechanical Laboratory Company works with non-destructive pavement evaluation equipment in the field of providing improvement plans, determining the causes of failure, performance indicators and the existing condition of pavements at the network and project level, as well as implementing the road and airport maintenance management system. show With the support of the expansion of the Soil Mechanics and Technical Laboratory throughout the country, in addition to non-destructive equipment, the office of consulting engineers has the possibility of using advanced laboratory and field equipment.

Technical capabilities at the network level

The meaning of the network level is the collection and analysis of data in a set of axes. For example, we can mention the road network of a city or province, the network of highways and arterial roads in the country, or the flight levels of one or more airports. The analysis of the network level examines and calculates the overall condition of the pavement and the budget required to maintain it at the desired level. The most important technical services of the office of consulting engineers at the level of the network are:
- preparation of axles ID card
- assessment of functional and structural characteristics of axles
- separation of axles with structural adequacy from axles with structural weakness
- determination of the type of maintenance operations (preventive, improvement and reconstruction) in the road network
- Segmentation of axes based on functional and structural characteristics
- Determining the axes susceptible to various types of protective operations (fog seal, chip seal, slurry seal, microsurfacing, etc.)
- Implementation of the road pavement management system and airports of the country

Technical capabilities at the project level

Road pavement improvement plan

In this section, the structural adequacy of the pavement is evaluated with the FWD device, and the thickness of the coating required to bear the loads caused by traffic during the pavement design period is calculated. In the road improvement plan, after segmentation of the pavement, the final option in each segment is determined according to the structural condition, unevenness and surface damage, along with destructive tests.

Assessment of pavement surface damage

In this section, pavement surface damage including all kinds of cracks, settlements, deviations, weathering, and unevenness is taken and the PCI index is determined according to the ASTM-D6433 standard on the road and the ASTM D5340 standard in the airport, and the latest version of PAVER software is used to calculate this index. will be In this software, in addition to calculating the PCI index, the percentage of pavement failures caused by loading, weather conditions, and the quality of construction and execution is determined. Based on the importance of the project, the office of laboratory consulting engineers uses the visual or mechanized method to study the surface damage of the pavement. In the visual method, according to the mentioned standards, after segmentation, the surface damage in selected sample units is taken and the PCI index is calculated.

 In the mechanized method, a road surface scanner is used, in which pavement damage is continuously scanned with a LCMS sensor at a speed of up to 100 km/h. This device produces three-dimensional profiles of the pavement surface with a length resolution of 5 mm, a width resolution of 1 mm, and a height resolution of 0.5 mm.

The advantages of mechanized collection of surface damage are:
• Continuous collection of surface damage instead of selected sample units
• Determining the severity of damage mechanized instead of expert judgment
• The possibility of pavement segmentation based on each type of damage after data collection
• Accurate determination of the amount of pavement maintenance operations (Sealing length and area of ​​tarnishing and asphalt grinding)
• The possibility of simultaneous removal of surface damage and roughness index (IRI)
• The possibility of determining the damage index (fatigue crack index, longitudinal crack index, etc.) instead of determining the PCI number

Determining the thickness and depth of pavement layers with GPR device

Using the GPR device, it is possible to non-destructively determine the thickness profile of the pavement layers including asphalt and the sum of the base and sub-base. Also, by examining the data of the GPR device, the depth of the pavement can be examined in terms of the amount of moisture in the foundation and sub-foundation layers and the presence of underground facilities such as pipes and cables.

CBR estimation of pavement granular layers using DCP device

The DCP device has the best performance in pavement and rural roads. By using this device at any point of the pavement after coring from the asphalt layer, the CBR of the granular layers can be estimated. In addition, by examining the changes in the penetration rate of the device in the depth of the pavement, the thickness of the layers with the same resistance can also be determined.

Quality control of bed and soil layers implemented with LWD device

The LWD device determines the yield modulus of the implemented bed, base and sub-base (for use in the AASHTO pavement plan) and by comparing the values ​​obtained at different points of the road axis, the quality of the bed implementation (compaction and stabilization) is also determined. By performing the test on the compacted bed, it is possible to directly use the modulus of elasticity in the pavement design, or compare the results with the values ​​of the initial design and, if necessary, modify the design or increase the bed strength.

Determination of pavement roughness in the form of IRI index

The rough condition of the pavement has a great impact on the quality of road riding. Using the RSP device, the amount of roughness of the pavement along the left and right wheels is calculated in the form of IRI and RN indexes. This index can be used for the delivery of newly constructed or covered roads. The following tables are related to the limits of the IRI index for the temporary and definitive delivery of the country's roads, which was compiled in the Supreme Technical Council of Transportation Infrastructure Affairs and notified by the high authority of the Ministry on 9/6/95 (Notification No. 02/100/27245) .

Determining the dewar in the horizontal arcs of the road using the RSP device

With the help of the RSP device or the road surface scanner, the amount of longitudinal and transverse slopes of the road, the coarse texture of the pavement, as well as the arc radius and the amount of superelevation in horizontal arcs are determined. Since during the maintenance periods, especially when performing asphalt coating, attention may not be paid to maintaining the circumference of the pavement in the arches, therefore, measuring the amount of dewar as an important parameter in ensuring the safety of vehicles, especially on the main roads, is of great importance. Is.

Checking road surface friction

Using the RSP device or the road surface scanner, it is possible to measure the coarse texture of the pavement in terms of microns, which plays an important role in the friction of the pavement at high speeds, as well as water drainage under the wheel of the vehicle. The RSP device measures the coarse texture of the pavement profile in the path of the right wheel of the vehicle and the scanner device measures this index in the entire width of the road.

Technical capabilities in the airport sector

Improvement plan for airport flight agents

In this section, with destructive and non-destructive methods of paving flight surfaces including; Flight runways, creep runways and aprons are evaluated and a suitable improvement plan is presented to serve the flight fleet.

Determining the ACN/PCN index of the airport pavement (Aircraft/Pavement Classification Number)

The PCN index shows the relative resistance of the airport pavement, which should be greater than the ACN index of the aircraft in the fleet of that airport. Using non-destructive equipment such as HWD and GPR, the office of consulting engineers determines the numerical value of this index in the pavement of the runway, crawlway and apron of the airport.

Determining the BBI roughness index in the airport runway pavement

The unevenness of the airport pavement is very effective in the rate of depreciation of the aircraft. Therefore, by determining the BBI index in the airport pavement, it is possible to identify points with roughness higher than the allowed value. Also, the amount of vertical acceleration inside the cockpit, which depends on the roughness of the runway pavement, can also be determined by analyzing the pavement profile.

Determining PrI index in airport runway pavement

According to the FAA, acceptance of the smoothness of the runway surface is done by checking the PrI (California Profilogragh) index. This index is calculated in 528-foot pieces by analyzing the profile measured by the RSP device in the ProVAL software, which according to FAA: AC 150/5370-10G instructions should not exceed 7 in/mi for full payment to the contractor.

Determining the amount of load transfer from joints in concrete pavement (LTE)

The amount of load transfer from joints in concrete pavement (provided by load dowel or aggregate lock and fastener) is evaluated with the help of HWD device. If the dowels do not perform well many times, failures such as pumping, edge breakage and stair-stepping occur in concrete pavement slabs.

Equipment and devices

 Pavement structural evaluation device (F/HWD (Falling/Heavy Weight Deflectometer).

The performance of FWD and HWD devices is completely similar to each other, the only difference is in the possibility of applying more stress by HWD due to its heavier weight, which provides the possibility of simulating the stress caused by the aircraft wheel load on the airport pavement. After applying stress to the pavement, these equipments read and store the drop and rise caused by the impact. The air temperature and asphalt surface are measured and recorded automatically by the device and the depth temperature of the asphalt layer manually by the user. The distance of sampling points on the road axis is between 3 and 500 meters based on the type of evaluation, and geophones are usually placed at a distance of 30 cm from each other. At each point, the device loads at least three times in a period of 1 to 2 minutes. The important output of this device is the curvature of the pavement, which is calculated using ELMOD software or the AASHTO method, the analysis and modulus of elasticity of the layers and the amount of coating needed during the design period for the pavement.

Road surface scanner equipped with LCMS (Laser Cracking Measurement System

This device, which is equipped with LCMS (Laser Crack Measurement System) sensor , uses a linear laser projector and high-speed cameras to produce three-dimensional profiles of the pavement surface with a length resolution of 5 mm, a width resolution of 1 mm, and a height resolution of 0.5 mm. he does. This device picks up the mentioned profiles in one lane at a speed of 100 km/h.

By using the data analysis software of the scanner device, all types of pavement surface damage are automatically identified and reported separately. In this way, the opinion of the expert in determining the type, severity and amount of damage is removed and the results of this method will be comparable in all axes. The main outputs of the scanner are as follows.

• Determining the type (longitudinal, transverse and lizard skin), intensity (based on crack width) and extent of cracks (length or area)
• Determining the macrotexture of the pavement
• Determining the pavement gravel index ( Raveling )
• Determining the severity and extent of pavement rutting
• Identifying holes and determining their area and depth
• Determining the roughness index ( IRI ) along the wheel path
• Obtaining the geometric characteristics of the track (longitudinal slope, transverse slope, arc radius)
• Recording the spatial characteristics of the data (kilometer and GPS coordinates )
• Detection of pavement markings ( Lane marking )
• Imaging every 10 meters of the road surface and surrounding area

 RSP (Road Surface Profiler).

The roughness of the pavement, which causes the dynamic loads caused by the movement of vehicles and accelerates the process of pavement damage and wear and tear of vehicles, can be determined by using the RSP device. In addition to evaluating the roughness, this device is able to determine the geometric characteristics of the track, including longitudinal slope, transverse slope, arc radius in the crossing line. The coarse texture of the pavement surface ( MPD or ETD ) and rutting are other parameters that are measured with this device. Also, by using the camera installed in front of the RSP device , it is possible to take pictures of every 10 meters of the road surface and the surrounding environment.

Ground Penetrating Radar (GPR).

 The GPR device is one of the non-destructive equipments for depth evaluation of pavement layers. This device is able to measure the thickness of pavement layers in the form of a continuous profile along the road axis. Also, this device is used to identify the location of underground facilities and to diagnose damage in the depth of pavement layers.

The ground penetrating radar method is one of the new methods in geophysics, which is based on the emission of electromagnetic waves into the earth and the recording of return waves .  When the radar system is moved along a line, a time-domain trace is created for each point, and by placing these traces together, a profile of the subsurface (radargram) along with existing complications and layers is obtained. The uses of this device are as follows:

• Quality control and assessment of roads, runways and railways (determining the thickness of layers, detecting damage in depth, determining the amount of moisture, detecting holes, etc.),
• Identifying the location of urban facilities (pipes, cables, sewers, aqueducts, pits, etc.),
• Engineering geological studies (identification of drift-prone layers, determination of bedrock depth, faults, loose and water-saturated areas...),
• Environmental studies (examination of the spread of pollution in underground water, etc.),
• Geological studies (underground water level, identification of saturated layers, karst ranges, etc.).

Light Weight Deflectometer (LWD).

 By using this device, it is possible to measure the modulus of elasticity of granular pavement layers (pavement base, sub-base and base) in a short period of time and without disturbing. This device is especially used to control the quality of the substrate during implementation and to determine its yield modulus. One of the important advantages of this device is the ability to perform a large number of tests in the shortest time and at the project site.

Dynamic Cone Penetrometer (DCP).

 The DCP device is suitable for estimating the resistance (CBR) of the foundation, sub-base and pavement layers. The working mechanism of the DCP device is based on measuring the penetration rate of a steel cone in the soil layer under the effect of an 8 kg weight falling from a height of 575 mm. The number of times the weight falls against the penetration of the cone is recorded for each test and the penetration rate (mm/blow) is calculated. In the existing pavements, it is possible to determine the resistance of the layers below it by taking a core from the asphalt layer with the DCP device.

Completed projects

Pavement evaluation projects at the network level

Road sector projects

Projects of the airport sector

Special projects

Research Activities