1,721,056 research outputs found
Effects of fines on the cyclic liquefaction behaviour in unsaturated, well-graded materials
No full textThe liquefaction of cargoes of metallic ores during maritime transportation is believed to have caused a number of ships to capsize during the past 30 years. To minimise the risk of liquefaction, shipping standards specify a transportable moisture limit (TML), which is the maximum moisture content for ore cargoes to be loaded onto a ship. However, the mechanics leading to the liquefaction of these cargoes is not well understood. This study uses an unsaturated soil mechanics perspective to understand the cyclic liquefaction behaviour of partially saturated materials, similar in grading to iron ore fines, a metallic ore that is known to liquefy during shipping transportation. Iron ore fines are transported at relatively low densities and have variable gradings containing a wide range of particle sizes and fines contents. Therefore, the effects of the degree of saturation and the fines content on the cyclic liquefaction behaviour of well-graded materials have been investigated by performing unsaturated, compression-only cyclic triaxial tests on samples prepared with four different gradings containing particle sizes from 9.5 mm to 2 μm with fines (<75 μm) contents of 18%, 28%, 40% and 60%. The trends in the data are discussed and used to develop a simple method that can conservatively estimate the number of cycles that samples with different degrees of saturation and fines contents are able to resist. The use of this method to describe the liquefaction behaviour of cargoes containing iron ore fines, in practice, is discussed
Critical state interpretation of effects of fines in silty sands
No full textThe effect of the fines content in silty sands on the location of the critical state line (CSL) has been investigated by performing standard drained and undrained triaxial tests on reconstituted samples containing Sydney sand, feldspar fines and mixtures of the two at 20, 40 and 60% fines content. In the e-log p′ plane, CSLs of silt–sand mixtures shifted parallel to one another. The transitional fines content of silt–sand mixtures was 40%. Transitional soil behaviour was also observed in silt–sand samples that contained 40 and 60% fines as densely and loosely prepared samples with these fines contents failed on two different and parallel CSLs
Transitional behaviour in asphalt derived aggregate specimens
No full textA Critical State Soil Mechanics approach has been taken to understand the interactions between the different aggregates and bitumen present in an asphalt mix. A series of conventional drained triaxial tests have been performed on samples of the aggregate used in Dense Asphaltic Concrete (DAC). These aggregate samples contained no bitumen and were prepared at two densities. The dense aggregate samples had a void ratio equivalent to the asphalt (DAC) samples where the bitumen was assumed to be part of the void space. The loose aggregate samples were prepared at a void ratio that was as loose as physically possible. The behaviour of the aggregate samples was compared to the asphalt samples when loaded continuously at a rate of 0.3% strain/hour. It has been found that at these slow rates of loading, the aggregates control the behaviour of the asphalt and the 5% bitumen content had little effect. Transitional soil behaviour of the aggregates was also observed as the dense and loose aggregate samples did not approach a unique critical state line when sheared to failure. The microstructure of the particle arrangements in the dense and loose aggregate samples was also observed under optical microscopes. Different particle arrangements were characteristic of the dense and loose samples. More bulky grain-to grain contacts were evident in the dense aggregate samples as the fines in the loose aggregate samples tended to flock together and form bridges between the bulky grains. As a result of this transitional soil behaviour, it was difficult to define Critical State Soil Mechanics parameters for DAC as required for advanced numerical modeling. This difficulty was also a consequence of the challenges in performing triaxial tests on the dense aggregate material
Reply to the discussion by Noor on “Effect of fines on liquefaction behaviour in well-graded materials”
Full text linkN/AThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Effects of fines on liquefaction behaviour in well-graded materials
No full textThis study uses a critical state soil mechanics perspective to understand the mechanics behind the liquefaction of metallic ores during transport by ship. These metallic ores are transported at relatively low densities and have variable gradings containing a wide range of particle sizes and fines contents. The effect of the fines content on the location of the critical state line (CSL) and the cyclic liquefaction behaviour of well-graded materials was investigated by performing saturated, standard drained and undrained monotonic and compression-only cyclic triaxial tests. Samples were prepared at four different gradings containing particle sizes from 9.5 mm to 2 μm with fines (<75 μm) contents of 18%, 28%, 40%, and 60%. In the e versus log plane, where e is void ratio and is mean effective stress, the CSLs shifted upwards approximately parallel to one another as the fines content was increased. Transitional soil behaviour was observed in samples containing 28%, 40%, and 60% fines. A sample’s cyclic resistance to liquefaction depended on a combination of its density and state parameter, which were both related to the fines content. Samples with the same densities were more resistant to cyclic failure if they contained higher fines contents. The state parameter provided a useful prediction for general behavioural trends of all fines contents studied
Investigating the use of Boyle's Law to relate pore air pressures and volume changes in unsaturated triaxial samples
No full textMeasuring the volume changes of unsaturated triaxial soil samples is one of the main challenges when performing unsaturated triaxial tests. Under fully undrained conditions, Boyle's Law can be used to calculate the sample's volume changes caused by the compression of air, as Boyle's Law relates changes in volume to changes in pore air pressures within the sample. This method has been used to calculate the volumetric strains and pore air pressures in unsaturated samples tested under cyclic loading conditions. However, the volume changes calculated from using Boyle's Law and the increases in pore air pressures, have not been compared with the actual measured volume changes of unsaturated samples. This study presents the pore pressures and compares the measured and predicted volumetric strains calculated from using Boyle's Law, in unsaturated triaxial samples that were tested cyclically. In some cases, using Boyle's Law was found to be similar to the volume changes estimated from direct measurement, but sometimes the method did not appear to work. Reasons for the discrepancies will also be discussed
Creating the future:tourism, hospitality and events education in a post-industrial, post-disciplinary world
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