Characterisation of permanent deformation of silty sand subgrades from multistage RLT tests

Publisher's full text
Farhad Salour

In thin flexible pavements, unbound aggregate layers and subgrade, contribute largely to the rut formation of the pavement system. Therefore, realistic prediction of surface rutting requires models that can reliably capture the cumulative plastic deformation of pavement unbound materials under repeated loads. Here four models were evaluated to capture the accumulation of permanent deformation of two fine grained subgrade materials.

The models were modified based on the time hardening concept allowing them to be used in a multistage repeated load triaxial (RLT) test procedure, in which a single specimen is exposed to a series of consecutive stress paths of varying magnitudes. The RLT tests were conducted on two non-plastic silty sand subgrade soils with different fines content and at four different moisture contents. The used triaxial testing system was capable of controlling the pore-air and pore-water pressures of the specimen and therefore the permanent deformation tests were carried out with controlled matric suction of the soil samples throughout the test. An effective stress approach was therefore used in the modelling. Using the test data, the model parameters were determined using a parameter optimisation algorithm and the qualities of fits achieved was analysed and compared through goodness-of-fit statistics.

In general, the four permanent deformation models were found to work satisfactorily in capturing the accumulation of the permanent deformation of the tested subgrade materials. It was concluded that the multistage RLT test procedure has the potentials to be used for characterizing the permanent deformation behaviour of subgrade soils. This can considerably reduce the effort and time required for permanent deformation characterization of subgrade materials.

LATEST NEWS


2018-06-13

International Conference on Electric Road Systems starts today

Electric Road Systems (ERS) is a relatively new concept with many initiatives on the way. To learn from each other and stimulate new collaborations the Swedish Research and Innovation Platform for Electric Roads arranged the first international conference...


2018-05-18

Same survey of road users’ attitudes in 50 countries

At the Road Safety on Five Continents Conference, RS5C, one entire session presented a large survey of road users' attitudes in 38 countries. Results show large differences between countries in many areas, both regarding behavior and attitudes. A new survey...


2018-05-17

Good results with alcohol interlock program according to Swedish study

An alcohol interlock program makes it possible for drink driving offenders to continue their everyday lives. In a Swedish study most of the participants were satisfied with the program and experienced improved health. They also reported drinking alcohol more...


2018-05-16

Traffic safety in the spotlight

Today the Conference Road Safety on Five Continents (RS5C) opened in Jeju Island, South Korea. More than 220 participators have come from all over the world to present findings and learn about traffic safety. Dr. Young Tae Kim, Secretary-General of the...


2018-04-17

VTI will develop simulators for ambulance staff

VTI has initiated a pilot study for paramedics with the Centre for Teaching & Research in Disaster Medicine and Traumatology and Linköping University. The aim is to give ambulance staff the opportunity to practice critical medical tasks in a moving vehicle in...


2018-04-12

Unique electrified road opens in Sweden

The world’s first electrified road recharging the batteries of cars and trucks while driving opened in Sweden. The Swedish Minister for Infrastructure, Tomas Eneroth, was at the formal inauguration of the electrified road on April 11, 2018. VTI is one of 22...