FACTORS AFFECTING THE SWELLING PRESSURE MEASURED BY THE OEDEMETER METHOD

ABSTRACT: Expansive soils are common in arid and semi-arid climate regions of the world and cause severe problems on civil engineering structures. The Swelling potential of the expansive soil mainly depends upon the properties of soil and environmental factors, and stress conditions. Swelling pressure is a key parameter used in designing structures in and on expansive soil. The swelling pressure of soil is measured in the laboratory using a representative soil samples. The size and the surface friction of the sample ring used in the swelling pressure test have effects on the measured swelling pressure and they have not properly been investigated. In this study, a series of constant volume swelling tests were conducted using an automated consolidation-swell apparatus to evaluate the effect of sample ring size, ring friction, initial dry density, and initial moisture content (IMC). Test results indicate an exponential growing trend of swelling pressure when the dry density is increased. Similarly, high swell pressures are achieved when the IMC is increased for the same dry density. A higher swelling pressure was measured when the friction of the specimen ring was reduced. The measured swelling pressure increases with increasing the height of the sampling ring and it decreases when the ring diameter is increased. Therefore, it is recommended to use a standard sample ring reducing inside wall friction using lubricants when measuring the swelling pressure in the laboratory. Further, the sample ring size, initial density and initial moisture content of soil should be given when reporting swelling pressure of soil

Estimation of Poisson’s Ratio and Variation of Tensile Yield Strength of Composite Clay Balls Used in Pebble Matrix Filtration

Clay balls can be used as an alternative to natural pebbles in pebble matrix filtration, a method for drinking water treatment. These clay balls are subjected to stresses due to self-weight and overburden in water-saturated conditions. Although there are empirical relationships to evaluate tensile yield strength ($T_s$) of clay balls using Poisson’s ratio ($μ$), diameter ($d$) of clay balls, and failure polar force ($F_s$), so far for such calculations the value of Poisson’s ratio has been taken from studies based on clay bricks. However, during ball preparation, if clay is mixed with other raw materials from industry wastes, such as saw dust or alum sludge in order to enhance the pollutant removal properties of the filter media, then the Poisson’s ratio of composite balls would be quite different from that of clay bricks. This paper describes a novel method for estimating Poisson’s ratio of composite clay balls by measuring vertical deformation using LVDTs in a uniaxial compressive strength (UCS) apparatus and lateral deformation using particle image velocimetry (PIV).This research work was carried out with the finance received from Early Career Academic Recruitment and Development (ECARD) Grant from Queensland University of Technology (QUT), Brisbane, Australia

Use of Waste Materials for Sustainable Pavement Industry in Australia: A Review

The demand for fresh materials for the construction and maintenance of pavements is increasing daily with the rapid development of infrastructures. The continuous extraction of natural resources to meet this demand causes environmental, social, and economic dissatisfaction. Recycled materials are the best alternative to replace fresh pavement materials, conversely, to align with the sustainability of the pavement industry. Crumb rubber, reclaimed asphalt pavement, recycled concrete aggregates, crushed bricks, and glass, fly ash, and recycled plastics are viable recycled materials. A progressive trend toward recycled materials is recorded worldwide. However, it needs continuous enforcement to standardize specific criteria to retain a steady demand for their applications in every part of the world. Australia has made significant strides in utilizing recycled materials in the pavement industry under various circumstances. This paper presents an overview of recycled materials, their properties and applications in different layers of flexible pavements in Australia.</p

Factors affecting the swelling pressure measured by the oedemeter method

Expansive soils are common in arid and semi-arid climate regions of the world and cause severe problems on civil engineering structures. The Swelling potential of the expansive soil mainly depends upon the properties of soil and environmental factors,and stress conditions. Swelling pressure is a key parameter used in designing structures in and on expansive soil. The swelling pressure of soil is measured in the laboratory using a representative soil samples. The size and the surface friction of the sample ring used in the swelling pressure test have effects on the measured swelling pressure and they have not properly been investigated. In this study, a series of constant volume swelling tests were conducted using an automated consolidation-swell apparatus to evaluate the effect of sample ring size, ring friction, initial dry density, and initial moisture content (IMC). Test results indicate an exponential growing trend of swelling pressure when the dry density is increased. Similarly, high swell pressures are achieved when the IMC is increased for the same dry density. A higher swelling pressure was measured when the friction of the specimen ring was reduced. The measured swelling pressure increases with increasing the height of the sampling ring and it decreases when the ring diameter is increased. Therefore, it is recommended to use a standard sample ring reducing inside wall friction using lubricants when measuring the swelling pressure in the laboratory. Further, the sample ring size, initial density and initial moisture content of soil should be given when reporting swelling pressure of soil

A Method for Predicting Rain-induced Instability of an Individual Slope

Awareness to avoid losses and casualties due to rain-induced landslide is increasing in regions that routinely experience heavy rainfall. Improvements in early warning systems against rain-induced landslide such as prediction modelling using rainfall records, is urgently needed in vulnerable regions. The existing warning systems have been applied using stability chart development and real-time displacement measurement on slope surfaces. However, there are still some drawbacks such as: ignorance of rain-induced instability mechanism, mislead prediction due to the probabilistic prediction and short time for evacuation. In this research, a real-time predictive method was proposed to alleviate the drawbacks mentioned above. A case-study soil slope in Indonesia that failed in 2010 during rainfall was used to verify the proposed predictive method. Using the results from the field and laboratory characterizations, numerical analyses can be applied to develop a model of unsaturated residual soils slope with deep cracks and subject to rainwater infiltration. Real-time rainfall measurement in the slope and the prediction of future rainfall are needed. By coupling transient seepage and stability analysis, the variation of safety factor of the slope with time were provided as a basis to develop method for the real-time prediction of the rain-induced instability of slopes. This study shows the proposed prediction method has the potential to be used in an early warning system against landslide hazard, since the FOS value and the timing of the end-result of the prediction can be provided before the actual failure of the case study slope

Impact resistance and evaluation of retained strength on geotextiles

Over the last few decades, geotextiles have progressively been incorporated into geotechnical applications,\ud especially in the field of coastal engineering. Geotextile materials often act as separator and a filter\ud layer between rocks laid above and subgrade beneath. This versatile material has gradually substituted\ud traditional granular materials because of its ease of installation, consistent quality and labour costefficiency.\ud However, geotextiles often suffer damage during installation due to high dynamic bulk\ud loading of rock placement. This can degrade geotextiles' mechanical strength. The properties considered\ud in this paper include the impact resistance and retained strength of geotextiles. In general, the greater\ud the impact energy applied to geotextiles, the greater the potential for damage. Results highlight the\ud inadequacy of using index derived values as an indicator to determine geotextile performance on site\ud because test results shows that geotextiles (staple fibre (SF) and continuous filament (CF)) with better\ud mechanical properties did not outperform lower mechanical strength materials. The toughest CF product\ud with a CBR index value of 9696N shows inferior impact resistance compared to SF product with the least\ud CBR strength (2719N) given the same impact energy of 9.02 kJ. Test results also indicated that the\ud reduction of strength for CF materials were much greater (between 20 and 50%) compared to SF materials\ud (between 0 and 5%) when subjected to the same impact energy of 4.52 kJ

Assessment of recycled concrete aggregate for road base and sub-base

Population increase and economic developments can lead to construction as well as demolition of infrastructures such\ud as buildings, bridges, roads, etc and used concrete is the main waste product of them. Recycling of waste concrete to\ud obtain the recycled concrete aggregates (RCA) for base and/or sub-base materials in road construction is a foremost\ud application to be promoted to gain economical and sustainable benefits. As the mortar, bricks, glass and asphalt present in different constituents in RCA, it exhibits inconsistent properties and performance. In this study, six different types of RCA samples were subjected classification tests such as particle size distribution, plasticity, compaction test and California Bearing Ratio (CBR). Results were compared with those of the standard road materials used in Queensland, Australia and found that ‘RM1-100/RM3-0’ and ‘RM1-80/RM3-20’ samples are sitting in the margin of the minimum required specifications of base materials while others are lower than that

Field performance of in-service cast iron gas reticulation pipe buried in reactive clay

Field instrumentation of an in-service cast iron gas pipe buried in a residential area is detailed in this paper. The aim of the study was to monitor the long-term pipe behavior to understand the mechanisms of pipe bending in relation to ground movement as a result of seasonal fluctuation of soil moisture content. Field data showed that variation of soil temperature, suction, and moisture content are closely related to the prevailing climate. Change of soil temperature is generally related to the ambient air temperature, with a variation of approximately −3°C per meter depth from the ground surface in summer (decrease with depth) and winter (increase with depth). Seasonal cyclic variation in moisture content was observed with maxima in February and March, and a minimum around September. The pipe top was under tensile strain during summer and subsequently subjected to compressive strain as soil swelling occurred as a result of increase in moisture content. The study suggests that downward pipe bending occurs in summer because of soil shrinkage, while upward pipe bending occurs in winter when the soil swells