MLS10 Test System
achieves a balance between the factors which enable APT to be optimized
 

 

  
 

 

Technical Aspects of the Full Scale APT MLS10

 

The MLS10 is based on the third scale load simulator, MMLS3 produced by MLS Test Systems Pty Ltd in Stellenbosch, South Africa . The operating principle of the two devices is very much the same. The machine structure is a space frame approximately 10m long, 3m high and 2.4m wide. The MLS10 has four wheel bogies, each fitted with two 295/65 R22.5 (940mm diameter) or similar tyres. The maximum load on each set of dual wheels is 6 tons (60 kN) at maximum speed. The system is designed to enable the bogies to travel at up to a maximum speed of 7.2 m/s (26 km/hr), when 7 200 axle loads are being applied per hour. The maximumload can be increased when the speed is reduced. Load control is semi-automatic with the load applied hydraulically.

 
The operating dead load of the machine, including ballast weights is approximately 27 tons. Lateral movement of the device for simulating wander can be applied. Tyre contact pressures is variable within the guidelines provided by the tyre manufacturer's specification
 

Each bogie has 12 sets of guide wheels. Each wheel set consists of two wheels, the inner one being a 250mm diameter flanged steel wheel to apply the load. The outer one is also a 250mm diameter steel wheel linking the bogie chain.

 
     
MLS10 in factory  

Loading MLS10 in Stellenbosch for transit to Mozambique
 

Provision has been made to get access to the pavement under the machine for the purpose of testing, measurements and, diagnostic inspection. There are primarily two options that can be used. Firstly by either pulling the machine off the test section on its transport wheels; or by jacking it up high enough to be able to work underneath it. Long distance transport of the machine is by low bed trailer by road or rail.
 
 
 
  Calibration of Load Wheels at Komatipoort Weigh Station  
Measurement of Surface Deflection During Trafficking Using Insturmented Benkalman Beam
 

Environmental conditions during testing are important. Trafficking can be done at ambient conditions or with the pavement at temperatures of -10C to 70C as per the APT performance specification. However, the conditioning of the pavement has to be done by auxiliary systems. The surrounding environmental conditions during testing have a profound effect on the efficiency and effectiveness of the auxiliary environmental systems. Different methods have been developed to cater for the various scenarios with different MLS testing devices.

 
Heating can be applied to the pavement by means of heated airflow across the pavement surface. Generally the MMLS3 is used for artificially heated and low temperature trafficking tests. Wet trafficking can be applied with the MMLS3 and full-scale MLS'.
 

The composition of a MLS test system should preferably comprise the following:

-MLS10 with profilometer and a data collection system

-A seismic testing tool such as the PSPA

-A MMLS3 with

    • a temperature chamber
    • a water heating unit
    • a heated air unit
    • a core test bed
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A system such as the above could be delivered within six months after receipt of a firm order. Depending on the research requirements a unit also capable of freezing the pavement could be included. It is worth noting that full-scale APT users are now utilizing the MMLS3 for prescreening tests and exploratory investigations.

 
Extensive reporting is available on studies that were conducted with the MLS Test System. Some details are contained in the MMLS3 Bibliography.
 
Trafficking of a test section in Manhica, Mozambique
 
3D Schematic of the MLS10
 
 

Comparison of MMLS3 and MLS10 APT Machine Parameters

 

 
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