Swell-shrink Cycles of Lime Stabilized Expansive Subgrade

AbstractSubgrades of expansive nature are one of the main causes of damage to road network in Australia. Consequently, lime stabilization has been widely used to reduce the swell- shrink potential of these types of soils and thus reduce the associated damage. After stabilization and compaction, the subgrade will naturally be exposed to cycles of full swell and or partial shrinkage due to climatic cycles. This paper investigates this behaviour for lime stabilized compacted expansive soil from weathered Quaternary Volcanic geological deposits located in Western Victoria; Australia. These soils were stabilized with varying percentages of hydrated lime (2, 3, 4, 6 and 8 percent) and the swell-shrink paths of both untreated and treated soils were studied. Test specimens were compacted at optimum moisture content and maximum dry density. The samples were subjected to full swell-shrink cycles under a surcharge of 25kPa to reach structural stabilization and to simulate the impact of climatic wetting and drying cycles. Vertical deformation and swell-shrink cycle relationships for untreated and treated samples were obtained and analyzed. The results of lime stabilization indicate that equilibrium is reached after three cycles for both untreated and treated samples. In addition, results suggest that maximum deformation occurs in the second swelling cycle. Vertical deformation of untreated sample was reduced to a third after adding 2 percent lime and reduced to a sixth after adding 3 percent lime. The gradient of swelling and shrinkage path reduced to about a sixth and third when it is treated with 2 and 3 percent, respectively. The treated samples reached maximum swelling at a higher degree of saturation than the untreated sample

A prediction model for the loading-wetting volumetric behavior of unsaturated granular materials

Geotechnical structures made of granular material tend to be unsaturated during their service life. However, there is presently a lack of sufficient research and studies on their volumetric behavior under unsaturated conditions. In this study, loading and wetting induced volumetric behavior of granular materials in the unsaturated state was studied within a moisture content-based framework. Recycled crushed brick (CB) and excavation waste rock (WR) were the granular materials used in this research to promote sustainable construction. Several loading, unloading, and wetting state paths were investigated with respect to virgin compaction surfaces (VCS) developed using groups of compaction curves. The obtained experimental data was utilized to develop a constitutive model capable of predicting wetting-induced volume changes of granular materials in a net stress range of 100–4000 kPa and gravimetric moisture content range of 3.6% for WR, and 7.5% for CB to saturation. The model was verified by undertaking several independent state paths on independent materials and comparing the experimental responses with those predicted using the model. The proposed model is featured with simplicity in acquiring the model input parameters with the aim of filling the existing gap between the theoretical and real-life application of unsaturated soil mechanics. An application of the model can be the basis for the prediction of the settlement of a granular geotechnical structure that is being externally loaded and is subject to changes in moisture content due to climatic effects

Editorial: the importance of environmental geotechnics

Abstract not available

Green roads and footpaths using recycled construction and demolition materials (STEM Blitz May 2015)

A summary of recent research in geotechnical engineering on construction and demolition materials in pavements and footpaths. Recorded on 8 May 2015

Comparison of degree of improvement assessed by observational methods using field instrumentation

The Changi East Reclamation Project in Singapore necessitated land reclamation of the foreshore for the future airport facilities. Ground improvement works in the project comprises the installation of prefabricated vertical drains and the subsequent placement of sand surcharge to accelerate the consolidation of the underlying soft marine clay. In such ground improvement projects in soft soil, the degree of improvement attained by the marine clay has to be ascertained to confirm whether the soil has achieved the required degree of consolidation to enable surcharge removal. This analysis can be carried out by means of observational methods for which continuous records of ground behaviour can be monitored from the date of instrument installation. A research case study Vertical Drains Area and an adjacent untreated Control Area were fully instrumented and monitored to compare the degree of consolidation of the treated and untreated areas close to the surcharge removal period. Instruments installed, monitored and analysed in the case study area include settlement plates, deep settlement gauges, pneumatic piezometers, electric piezometers and water-standpipes

Laboratory testing of reclaimed asphalt pavement: crushed rock for footpath applications

As recycling continues to grow by means of utilizing waste materials in today’s world, more markets must be established for products containing recycled materials. Currently in the state of Victoria in Australia, 200,000 tonnes of waste asphalt is stockpiled annually and these stockpiles are growing. The use of reclaimed asphalt pavement in applications such as footpaths bases is an effective way of utilising them and would also significantly minimise the need for quarry based virgin materials. This paper primarily focuses on the applicability of reclaimed asphalt pavement blended with recycled crushed rock as a base material in footpaths. Reclaimed asphalt pavement (RAP) is classified as a Construction & Demolition waste material. It is obtained when asphalt is removed from rehabilitated roadways. Maximum particle sizes of 20 to 40 mm are the commonly used sized recycled RAP aggregates in construction activities. This paper discusses the results of reclaimed asphalt pavement when used in blends with recycled crushed rock for footpath base applications. The results of the laboratory tests undertaken in this research have shown overall that the incorporation of up to 50% 'reclaimed asphalt pavement' in footpath bases has 'low to minimal effect' on the physical and mechanical properties of the original material. As such, the reclaimed asphalt pavement blends with recycled crushed rock were demonstrated to satisfactorily meet the local government council requirements

Ground improvement of road over rail approach embankments

Abstract not available

Statnamic load testing of an instrumented borepile

Abstract not available