Sensitivity of the stability assessment of a deep excavation to the material characterisations and analysis methods
- Authors: Ghadrdan, Mohsen , Shaghaghi, Tahereh , Tolooiyan, Ali
- Date: 2020
- Type: Text , Journal article
- Relation: Geomechanics and Geophysics for Geo-Energy and Geo-Resources Vol. 6, no. 4 (2020), p.
- Full Text: false
- Reviewed:
- Description: Due to the spatial variability of material characterisations in deep and large scale excavations, stability assessment is often a challenging task. Numerous slope stability analysis methods based on a range of assumptions and principles are implemented in commercial software packages to ease the process of stability assessment of non-homogeneous and multi-layered slopes. However, the selection of a suitable method remains crucial as the application of an unrealistic or unsuitable method may lead to catastrophic consequences. Besides material shear strength parameters, and analysis methods, non-strength characterisations such as permeability and creep can affect the result of slope stability analysis significantly. In this study, the sensitivity of the stability assessment of a deep excavation in Australia to material characterisations such as friction angle, cohesion and permeability and creep is investigated by the use of different formulations and assumptions of the Limit Equilibrium Method (LEM) and the Finite Element Method (FEM) as the two most common slope stability methods. The results show that the stability assessment is highly sensitive to the applied method and assumptions. Moreover, the role of material strength and non-strength parameters and the selection of a suitable constitutive model in slope stability assessment is presented. © 2020, Springer Nature Switzerland AG.
Clay mineralogy of central Victorian (Creswick) soils : Clay mineral contents as a possible tool of environmental indicator
- Authors: Sultan, Khawar
- Date: 2006
- Type: Text , Journal article
- Relation: Soil and Sediment Contamination Vol. 15, no. 4 (2006), p. 339-356
- Full Text: false
- Reviewed:
- Description: The clay mineralogy and heavy metal/metalloid (As, Pb and Cu) contents of soils developed on the various rock units in a central highlands environment in Victoria (Creswick, Australia) have been investigated. The clay minerals identified showed an order of abundance as: kaolinite - illite > smectite > mixed-layer (ML) ≈ vermiculite. The soil clay mineralogy did not change systematically with depth (0- 10, 10- 20 and 20- 30 cm) and showed large variations spatially. The high proportion of kaolinite was probably due to the removal of 2:1 phyllosilicates by the formation of 1:1 kaolinite through weathering, which also reduced the cation exchange capacity (CEC) and electrical conductivity (EC, soil: water ratio of 1:5) of soils by aging. Soils were classified as silty loam to loam with a low clay size (≤ 2
- Description: C1
- Description: 2003001961
Comparison of structural stability, carbon fractions and chemistry of krasnozem soils from adjacent forest and pasture areas in south-western Victoria
- Authors: Carter, Martin , Skjemstad, J. O. , MacEwan, Richard
- Date: 2002
- Type: Text , Journal article
- Relation: Australian Journal of Soil Research Vol. 40, no. 2 (2002), p. 283-298
- Full Text: false
- Reviewed:
- Description: Basalt-derived krasnozems are generally well-structured soils; however, there is a concern that intensive agricultural practices may result in an adverse decline in soil organic carbon, organic matter chemistry, and structural quality over time. A study was conducted on loam to silty clay loam krasnozems (Ferrosols) near Ballarat in south-western Victoria to assess changes in soil C, soil structural stability, and C chemistry, at the 0-10 cm soil depth, under 3 paired sites consisting of adjacent long-term forest (Monterey pine or eucalyptus) v. 30 year cropping [3 year pasture-2 year crops (potato and a root crop or grain)]. Soil structural stability was also characterised in the A and B horizons under long-term eucalyptus and several cropped sites. Organic C levels in the A horizons for all the soils were relatively high, ranging from 46 to 89 g/kg. A lower organic C (30%), associated mainly with loss of the sand-sized (> 53 mum) macro-C fraction, and a decrease in exchangeable Ca and Mg was found in the agricultural soils, compared with forest soils. Physically protected C in the <53 μm fraction, as indicated by UV photo-oxidation, was similar among soils. Wet sieving indicated a decline of both C and N concentration in water-stable aggregates and the degree of macro-aggregation under agricultural soils, compared with the forest soils. However, soil structural changes under cropping were mainly related to a decline in the >5 mm sized aggregates, with no deleterious increase in the proportion of 0.10 mm aggregates. Solid state C-13 NMR spectroscopy indicated a decrease in O-alkyl and alkyl C under pasture and cropping compared with forest soils, which was in agreement with the decline in the macro-C fraction. Characterisation of C chemistry following UV photo-oxidation showed that charcoal C (dominant presence of aryl C) accounted for 30% of the total soil organic C, while other functional groups (polysaccharides and alkyl C) were probably protected within micro-aggregates. Based on soil organic C and aggregate stability determinations alone, the implications for soil physical quality, soil loss, and diffuse pollution appear minimal.
Evaluation of alternative approaches to rainforest restoration on abandoned pasturelands in tropical north Queensland, Australia
- Authors: Florentine, Singarayer , Westbrooke, Martin
- Date: 2004
- Type: Text , Journal article
- Relation: Land Degradation & Development Vol. 15, no. 1 (Jan-Feb 2004), p. 1-13
- Full Text:
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- Description: The lag time for natural recruitment of tropical rainforest species in abandoned pastureland is very long, therefore artificial restoration techniques have been employed to accelerate natural seedling recruitment. The objectives of this study were to investigate: (1) the success/failure of establishment 502 seedlings belonging to 15 species from 11 families planted approximately ten years ago; and (2) the influence of different restoration techniques on enhancing natural recruitment during this period. The study was conducted in the wet tropical rainforest region of northeast Queensland, Australia as a completely randomized block design involving five treatments with two replicates. In each plot, 63 tropical rainforest seedlings from one or a combination of species were planted randomly. Two control plots were laid out where no seedlings were planted. Survival, height and diameter data were taken on the seedlings ten years after planting. Each 11×17 m2 plot was further divided into 187, 1×1 m2 subplots. Within each subplot all seedlings recruited were located and identified. Canopy cover was estimated using belt transects 1 m apart that ran in an east-west direction across the plots. Within each plot the percentage of grass, and the crown cover were estimated using the Braun-Blanquet cover abundance scale. Survival rate of planted seedlings varied across the treatment plots. The survival rate ranged from 65 to 75 per cent for primary-promoter species, 85 to 100 per cent in middle-phase species and 42 to 57 per cent for mature-phase species. No Pilidiostigma tropicum seedlings survived in any treatment. Fourteen species recruited naturally across the treatment plots. A total of 410 seedlings were naturally recruited from 11 different families in the ten-year-old reforested site. The highest natural recruitment (236 seedlings) occurred in Treatment 3, where Omalanthus novo-guineensis seedlings were planted with eight primary-promoter species, followed by 99 in Treatment 5 where a group of primary-promoters, middle phase species and mature-phase species were planted together, 36 in Treatment 4 (Alphitonia petriei planted with eight primary-promoter species), 10 in Treatment 2 where only Omalanthus novo-guineensis seedlings were planted, and 13 in control plots. Grass cover declined with increasing species diversity and increased canopy cover. The results indicate that the diversity of species used in restoration had a major influence on natural recruitment. Copyright © 2004 John Wiley & Sons, Ltd.
- Description: C1
- Description: 2003000714
Limnology of four saline lakes in western Victoria, Australia : I. Physico-chemical parameters
- Authors: Khan, Tariq
- Date: 2003
- Type: Text , Journal article
- Relation: Limnologica Vol. 33, no. 4 (2003), p. 316-326
- Full Text: false
- Reviewed:
- Description: Major physico-chemical parameters of four saline lakes (Lake Colac, Modewarre, Bolac and Tooliorook), in the volcanic plains of western Victoria (Australia), recorded bi-monthly between November 1999-September 2001 are described. Lakes are permanent, large (surface area range 3.5-29.6 km2) and shallow (mean depth range 1.5-3.9 m). Physico-chemical parameters revealed that lakes were homogenous with few differences between sites within lakes. Of the four lakes, Lake Modewarre had the highest salinity of 8 ppt with weak seasonal fluctuations in salinity in all the lakes. All the lakes were turbid (turbidity range 30-659 NTU), with low light penetration (suspended solids range 23-465 mg 1-1) and low Secchi depth (Secchi depth range 7.7-89 cm). pH of the lakes varied between 8.2-9.3 with low seasonal variations, indicating well buffered waters. Based on nutrient status, lakes were classified as eutrophic to highly eutrophic with higher nutrient concentrations. Nitrogen was limiting in one lake (Lake Colac) and phosphorus in the other three lakes. Meteorological events probably influence the physico-chemical parameters of these lakes strongly.
- Description: C1
- Description: 2003000635
Limnology of four saline lakes in western Victoria, Australia : II. Biological parameters
- Authors: Khan, Tariq
- Date: 2003
- Type: Text , Journal article
- Relation: Limnologica Vol. 33, no. 4 (2003), p. 327-339
- Full Text: false
- Reviewed:
- Description: Major biological parameters of four permanent (Lake Colac, Modewarre, Bolac and Tooliorook), shallow and slightly saline lakes in the volcanic plains of western Victoria, Australia recorded bi-monthly between November 1999-September 2001 are described. Chlorophyll a concentration ranged from 3-29
- Description: C1
- Description: 2003000634
The impact of deforestation and pasture abandonment on soil properties in the wet tropics of Australia
- Authors: Rasiah, Velu , Florentine, Singarayer , Williams, B. L. , Westbrooke, Martin
- Date: 2004
- Type: Text , Journal article
- Relation: Geoderma Vol. 120, no. 1-2 (2004), p. 35-45
- Full Text:
- Reviewed:
- Description: Limited information exists on the changes in soil properties, particularly from the wet tropics of Australia, under long-term abandoned pasture, which was previously grazed and was established on deforested tropical rainforest. This information may be help in successful forest reestablishment. The objectives of this study were to assess the cumulative impact deforestation, grazed and abandoned pasture on selected soil physico-chemical properties from (i) an abandoned pastureland and (ii) a recently planted rainforest (PRF), planted in the abandoned pastureland. The experimental site is a field in the Northeast Queensland (NEQ) wet tropical region of Australia. This site was deforested approximately 70 years ago and brought under unfertilized grazed pasture for 30 years. Subsequently the grazed pastureland was abandoned and remains un-grazed for 40 years. A section of the abandoned pastureland was planted, 10 years ago, with native forest species, involving different combinations in five treatments in a completely randomised block design. A nearby undisturbed rainforest is used as the background against which assessment was carried out. Soil samples from 0- to 15-cm depth were collected in July 2000 and analyzed for nitrate-N, ammonium-N, total N, total soil organic C (SOC) and labile-C, pH (in water and CaCl2), electrical conductivity (EC), exchangeable Ca, Mg, Na, K, and Al, and bulk density. Compared to the rainforest, the N and C concentrations of different forms under abandoned pasture and PRF were significantly less, exclusive of the total N under abandoned pasture. More specifically, the SOC under the abandoned pasture was 37,600 mg/kg compared with 74,800 mg/kg under rainforest and 27,000 mg/kg in the PRF. The exchangeable Al under rainforest was 8.5 c molc/kg compared with 42. 4 to 80.2 c molc/kg under abandoned pasture and PRF. In general exchangeable cations (sum of Ca, Mg, K, and Na) under the rainforest were higher than the abandoned pasture. Soil under the abandoned pasture and PRF are more acidic by 0.5 to 1 units than the rainforest. Higher bulk densities under abandoned pasture and PRF led to 0.03% to 0.07% reductions in total porosities. Though we did not anticipate the soil under the abandoned pasture to recover 100% in 30-40 years, the results indicate that 40 years under abandoned pasture or 30 years of abandoned pasture plus 10 years under PRF was not sufficient to bring about substantial improvement in soil properties comparable to the rainforest. This implies the resiliency of tropical soils, in general, to recover from deforestation and cultivation induced degradation is poor. © 2003 Elsevier B.V. All rights reserved.
- Description: C1
- Description: 2003000713
New records of springtails in New Zealand pasture : How well are our pastoral invertebrates known?
- Authors: Greenslade, Penelope , Boyer, Stéphane , Wratten, Steve
- Date: 2013
- Type: Text , Journal article
- Relation: New Zealand Journal of Agricultural Research Vol. 56, no. 2 (2013), p. 93-101
- Full Text: false
- Reviewed:
- Description: Twenty-four collembolan species are recorded from improved pastures and clovers in New Zealand, of which 17 can be named to species or probable species, the others only to genus. Of the 17 named species, nine have been recorded before from New Zealand but the other eight are new records for the country. All named species are considered as introduced to New Zealand, probably originally from Europe and are unlikely to colonise native habitats. As all named species reported as new records can be abundant at times, this indicates poor knowledge of a major part of New Zealand's agricultural fauna. Collembola are a group of important microarthropod detritivores that make a significant contribution to ecosystem services. The absence so far of quantification of the contribution this and other soil groups make to ecological resilience and function is a serious problem. © 2013 The Royal Society of New Zealand.
- Description: 2003011135
Assessment of error sources in measurements of field pH : Effect of operator experience, test kit differences, and time-of-day
- Authors: Robinson, Nathan , Norng, Sorn , Rees, David , Benke, Kurt , Davey, Michelle
- Date: 2018
- Type: Text , Journal article
- Relation: Communications in Soil Science and Plant Analysis Vol. 49, no. 3 (2018), p. 269-285
- Full Text:
- Reviewed:
- Description: Various methods exist to measure soil pH, and while there is general agreement between the existing published laboratory and field-based methods, the latter are subject to uncertainties including test kit reliability, accuracy, precision, and environmental factors. The contribution of this study is to quantify three uncertainties that affect the conversion between field pH and laboratory pH measurements, namely operator experience, choice of test kit, and the time-of-day for measurement. Soil samples from western Victoria, representing the pH range 4.5–10.0, were used in a randomized complete block design with 10 assessors split into two groups representing experienced and inexperienced users. Statistical analysis of laboratory and field pH was based on using the Maximum Likelihood Functional Relationship (MLFR) to determine if there was any bias between the two methods. Significant differences were found between experienced and inexperienced users, and between test kits. © 2017 Taylor & Francis.
Liberating soil data for profitable agriculture and catchment health in the Corangamite region, Australia
- Authors: Dahlhaus, Peter , Nicholson, Cameron , Ryan, Bret , MacLeod, Andrew , Milne, Robert
- Date: 2018
- Type: Text , Journal article
- Relation: New Zealand Journal of Agricultural Research Vol. 61, no. 3 (2018), p. 333-339
- Full Text: false
- Reviewed:
- Description: Detailed soil data has been collected in the Corangamite region of south-east Australia for over 80 years, as a testament to the productive value of the region’s agricultural soils. Soil science over that period has resulted in soil maps, soil investigation sites and archival materials that provide valuable baseline data for the analysis of trends over time. This legacy data has been brought together with contemporary data in the award-winning Soil Health Knowledge Base, an Internet portal based on spatial data infrastructure that interoperably federates data (open data, research data, industry data, sensor data, legacy data, crowdsourced data … any available data). The portal provides the best available data sources for research and consulting, as well as functions for both the private reward and the public good. The ultimate intent is to provide timely decision support for agricultural enterprises and catchment managers to protect, enhance and restore soil health.
Improving the information content in soil pH maps: a case study
- Authors: Robinson, Nathan , Benke, Kurt , Norng, Sorn , Kitching, Matt , Crawford, Deborah
- Date: 2017
- Type: Text , Journal article
- Relation: European Journal of Soil Science Vol. 68, no. 5 (2017), p. 592-604
- Full Text: false
- Reviewed:
- Description: Uncertainties associated with legacy data contribute to the spatial uncertainty of predictions for soil properties such as pH. Examples of potential sources of error in maps of soil pH include temporal variation and changes in land use over time. Prediction of soil pH can be improved with a linear mixed model (LMM) to analyse factors that contribute to uncertainty. Probabilities from conditional simulations in combination with agronomic critical thresholds for acid-sensitive species can be used to identify areas that are likely, or very likely, to be below these critical thresholds for plant production. Because of rapid changes in farming systems and management practices, there is a need to be vigilant in monitoring changes in soil acidification. This is because soil acidification is an important factor in primary production and soil sustainability. In this research, legacy data from south-western Victoria (Australia) were used with model-based geostatistics to produce a map of soil pH that accommodates a variety of error sources, such as the time of sampling, seasonal variation, differences in analytical method, effects of changes in land use and variable soil sample depth in legacy data. Spatial covariates that are representative of soil-forming factors were used to improve predictions. To transform spatial prediction and estimates of error in soil pH into more informative and usable maps with more information content, simulations from the conditional distribution were used to compute the probability of a soil's pH being less than critical agronomic production thresholds at each of the prediction locations. These probabilities were mapped to reveal areas of potential risk. Highlights: Can maps of soil pH be improved by accounting for temporal variation and change in land use? First example of taking account of temporal variability in sampling for pH in spatial models. Key factors for uncertainty in spatial prediction include time of sampling and sample depth. Accuracy improved by accounting for additional sources of error combined with conditional simulations. © 2017 British Society of Soil Science
Conformational effects of adsorbed polymer on the swelling behavior of engineered clay minerals
- Authors: Kim, Sungho , Motyka, Michael , Palomino, Angelica , Podraza, Nikolas
- Date: 2012
- Type: Text , Journal article
- Relation: Clays and Clay Minerals Vol. 60, no. 4 (2012), p. 363-373
- Full Text: false
- Reviewed:
- Description: The conformational behavior of polymers in clay-polymer nanocomposites (CPN) is not fully understood because of the many factors involved. The purpose of the present study was to investigate the conformational behavior of a polymer at the micro- and meso-scales in order to predict the behavior of tunable CPN. The study used a pH-responsive polymer, polyacrylamide, which has time-dependent hydrolysis response properties, to examine micro-scale conformational behavior of the polymer adsorbed on representative clay-mineral surfaces, SiO2 and Al2O3. A nanocomposite and a microcomposite were used to link meso-scale CPN behavior to micro-scale polymer conformation. The conformational behavior was characterized using in situ, real-time spectroscopic ellipsometry. The contracted coil conformation of polyacrylamide was observed at pH = 3, while extended conformation was observed at pH = 11.5 on both SiO2 and Al2O3 surfaces. At pH = 11.5, the polymer conformation changed from expanded coil to extended conformation over time. The polymer conformation changed more rapidly with the Al2O3 surface due to mineral dissolution at pH = 3 and 11.5. Swelling tests were conducted as functions of pH and time to link the micro-scale phenomena to meso-scale CPN behavior. The results indicated that the swelling potential of CPN corresponded to the conformation of adsorbed polyacrylamide, which varied with pH and time. The swelling potential of CPN was maximized at pH = 11.5 and decreased with decreasing pH, corresponding to the observed micro-scale conformational behavior.
New records of springtails in New Zealand pasture: how well are our pastoral invertebrates known?
- Authors: Greenslade, Penelope , Boyer, Stéphane , Wratten , Steve
- Date: 2013
- Type: Text , Journal article
- Relation: New Zealand Journal of Agricultural Research Vol. 56, no. 2 (2013), p. 93-101
- Full Text: false
- Reviewed:
- Description: Twenty-four collembolan species are recorded from improved pastures and clovers in New Zealand, of which 17 can be named to species or probable species, the others only to genus. Of the 17 named species, nine have been recorded before from New Zealand but the other eight are new records for the country. All named species are considered as introduced to New Zealand, probably originally from Europe and are unlikely to colonise native habitats. As all named species reported as new records can be abundant at times, this indicates poor knowledge of a major part of New Zealand's agricultural fauna. Collembola are a group of important microarthropod detritivores that make a significant contribution to ecosystem services. The absence so far of quantification of the contribution this and other soil groups make to ecological resilience and function is a serious problem.
Development of pedotransfer functions by machine learning for prediction of soil electrical conductivity and organic carbon content
- Authors: Benke, Kurt , Norng, Sorn , Robinson, Nathan , Chia, K. , Rees, David , Hopley, J.
- Date: 2020
- Type: Text , Journal article
- Relation: Geoderma Vol. 366, no. (2020), p.
- Full Text:
- Reviewed:
- Description: The pedotransfer function is a mathematical model used to convert direct soil measurements into known and unknown soil properties. It provides information for modelling and simulation in soil research, hydrology, environmental science and climate change impacts, including investigating the carbon cycle and the exchange of carbon between soils and the atmosphere to support carbon farming. In particular, the pedotransfer function can provide input parameters for landscape design, soil quality assessment and economic optimisation. The objective of the study was to investigate the feasibility of using a generalised pedotransfer function derived with a machine learning method to predict soil electrical conductivity (EC) and soil organic carbon content (OC) for different regional locations in the state of Victoria, Australia. This strategy supports a unified approach to the interpolation and population of a single regional soils database, in contrast to a range of pedotransfer functions derived from local databases with measurement sets that may have limited transferability. The pedotransfer function generation was based on a machine learning algorithm incorporating the Generalized Linear Mixed Model with interactions and nested terms, with Residual Maximum Likelihood estimation, and a predictor-frequency ranking system with step-wise reduction of predictors to evaluate the predictive errors in reduced models. The source of the data was the Victorian Soil Information System (VSIS), which is a database administered for soil information and mapping purposes. The database contains soil measurements and information from locations across Victoria and is a repository of historical data, including monitoring studies. In total, data from 93 projects were available for inputs to modelling and analysis, with 5158 samples used to derive predictors for EC and 1954 samples used to derive predictors for OC. Over 500 models were tested by systematically reducing the number of predictors from the full model. Five-fold cross-validation was used for estimation of model mean-squared prediction error (MSPE) and mean-absolute percentage error (MAPE). The results were statistically significant with only a gradual reduction in error for the top-ranked 50 models. The prediction errors (MSPE and MAPE) of the top ranked model for EC are 0.686 and 0.635, and 0.413 and 0.474 for OC respectively. The four most frequently occurring predictors both for EC and OC prediction across the full set of models were found to be soil depth, pH, particle size distribution and geomorphological mapping unit. The possible advantages and disadvantages of this approach were discussed with respect to other machine learning approaches. © 2020 Elsevier B.V.
Stress–strain relationship of sandstone under confining pressure with repetitive impact
- Authors: Wang, Shiming , Xiong, Xianrui , Liu, Yunsi , Zhou, Jian , Khandelwal, Manoj
- Date: 2021
- Type: Text , Journal article
- Relation: Geomechanics and Geophysics for Geo-Energy and Geo-Resources Vol. 7, no. 2 (2021), p.
- Full Text:
- Reviewed:
- Description: Abstract: A series of triaxial repetitive impact tests were conducted on a 50-mm-diameter split Hopkinson pressure bar testing device to reveal the characteristics of dynamic stress–strain of sandstone under confining pressure, and the confining pressure in this study was set as 5 and 10 MPa. The results showed that sandstone is very sensitive to confining pressure and strain rate. As the confining pressure and strain rate increases, the dynamic strength, critical strain and absorbed energy also increases, however with the increases in number of impacts, they decrease. With impact numbers increases, the stress–strain curve of sandstone gradually transits from a Class I to a Class II. The dynamic statistical damage constitutive model used in the paper can describe the dynamic response of sandstone under confining pressure with repetitive impact. Various influencing factors, such as material characteristics, confining pressure, strain rate and damage on the dynamic mechanical behavior of sandstone are also fully considered in the model. The damage curve changes from concave to convex as the F/ F increase. When the F/ F exceed 0.5, the damage curve appears convex, and the damage is obvious. By comparing with the variation of the reflected wave waveform with the impact numbers, it is found that damage evolution law of the rock under confining pressure with the impact numbers is similar to that of the reflected wave waveform with the impact numbers, can reflect the damage degree of the rock specimen without other auxiliary equipment, which has been verified. Article Highlights: The stress-strain curve of sandstone under confining pressure with repeated impact changes from Class I to Class II, and it will become less obvious as the confining pressure increases.The constitutive model used in the article can well describe the dynamic mechanical properties, strain rate effect and its turning point of rock under confining pressure with repeated impact.The damage curve changes from concave to convex, and the damage evolution law is similar to that of the reflected wave waveform with the impact numbers. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Manoj Khandelwal” is provided in this record**