The influence of pore fluids on shear strength and stress-strain behavior of granular soils

When a dry granular soil is subjected to an external load, the stresses are transferred through mineral to mineral contacts. The shear strength of such a soil is governed by its contact properties. Presence of a thin layer of fluid between mineral to mineral contacts in a saturated soil will alter its contact properties. Therefore any change in the physical properties of pore fluid can logically be reasoned to influence the deformation characteristics of granular soils. To investigate the influence of pore fluid viscosity on shear strength and stress-strain behavior of a soil, a series of consolidated drained triaxial tests were performed on a silty sand. The samples were prepared with four different pore fluids of varying viscosities and tested subjected to different consolidation pressures. Tests were performed with the aid of an automated triaxial testing apparatus. Since the stress-strain behavior of this silty sand can not be normalized, the variation of residual shear strength with critical void ratio was used for the analysis of results. When residual shear strength values were plotted against its critical void ratios, a family of curves that could be identified by their pore fluid viscosities were obtained. For a given critical void ratio, as pore fluid viscosity increased the residual shear strength was found to decrease. To provide a mechanistic explanation to the changes in the strength characteristics due to pore fluid viscosity, a microscopic model was used to study the changes in the contact properties at particle level. The microscopic numerical model TRUBAL, based on the DEM was used in this research to simulate the mechanical behavior of a granular soil subjected to a triaxial stress condition. Since this numerical model was developed to simulate the behavior of a dry granular assembly of spheres, it was modified to incorporate the effects of pore fluid viscosity by using Reynolds equation for hydrodynamic lubrication. The modified TRUBAL program was used to simulate deformation characteristics of saturated granular soils. The modified program was then used in a qualitative study to simulate stress-strain behavior of a granular assembly having different pore-fluid viscosities, subjected to consolidated drained triaxial test conditions. Numerical simulations showed a similar trend as observed in the physical tests

Enhancing Operation of a Sewage Pumping Station for Inter Catchment Wastewater Transfer by Using Deep Learning and Hydraulic Model

This paper presents a novel Inter Catchment Wastewater Transfer (ICWT) method for mitigating sewer overflow. The ICWT aims at balancing the spatial mismatch of sewer flow and treatment capacity of Wastewater Treatment Plant (WWTP), through collaborative operation of sewer system facilities. Using a hydraulic model, the effectiveness of ICWT is investigated in a sewer system in Drammen, Norway. Concerning the whole system performance, we found that the S{\o}ren Lemmich pump station plays a vital role in the ICWT framework. To enhance the operation of this pump station, it is imperative to construct a multi-step ahead water level prediction model. Hence, one of the most promising artificial intelligence techniques, Long Short Term Memory (LSTM), is employed to undertake this task. Experiments demonstrated that LSTM is superior to Gated Recurrent Unit (GRU), Recurrent Neural Network (RNN), Feed-forward Neural Network (FFNN) and Support Vector Regression (SVR)

SELF-ASSEMBLED AND FLOW INDUCED NANO-STRUCTURES IN POLYMER NANOCOMPOSITES

Distribution of nanoparticles (NPs) in polymers and role of NPs in modifying the structure of the polymeric matrices were studied using X-ray diffraction, neutron scattering, neutron reflectivity and atomic force microscopy techniques. Dispersion of NPs in polymers is challenging due to the aggregation tendency of NPs and inherent mixing challenges of polymer. Several strategies were used to control the NP distribution in polymers, including \u27smart blending\u27 and tailoring the interactions of the polymers. In smart blending chaotic flow fields were used to disperse and orient montmorillonite NPs in homopolymer melt of polyamide 6 (PA6). The roles of duration of chaotic advection on the melt (N) and NP concentration on polymer chain orientation and crystalline morphology were investigated. The major crystalline form of PA6 changed from a stable α form to a meta-stable, which is defined as a state with local stability to small perturbations in the system, γ form upon addition of NPs. This crystalline transformation is enhanced with increasing N for lower NP concentrations. At higher NP concentrations, polymer chain packing is mainly controlled by the surface forces of NPs. In these nanocomposites the polymer chains orient perpendicular to the NP surface as well as to the extrusion direction. Upon annealing and stretching, the fraction of the stable crystalline form increases and the polymer chains orientate parallel to the NP surface. Using small angle neutron scattering we were able to show that in blended films amorphous and crystalline domains form stacks where water uptake of amorphous domains is significantly higher than the crystalline ones. A second approach included tailoring interaction of polymer and NPs. For this purpose we used block copolymers. Block copolymer can be used as a template to disperse NPs into specific domains of the matrix polymer. Using fluorinated segments affects many of the polymer properties. The first stage of this study investigates the effects of fluorine on a model diblock copolymer, polytrifluoro propyl methylsiloxane-b-polystyrene, in solution. We found that this polymer forms assemblies with different shapes ranging from spherical to elliptical micelles in solutions. These micelles exhibit unique temperature stability and associated into micelles at small volume fractions of the fluorinated block compared to the diblock copolymer micelles in lower segregation limit. As the temperature increases the micelles dissociate into free chains to form unimolecular micelles. In the second phase of the study, copolymer templates were used to control the dispersion of NPs in thin polymer films. A semi-fluorinated random copolymer, biphenyl perfluorocyclobutyl, was used as a matrix polymer. Fluorinated blocks segregated toward the lower surface energy air/polymer interface while the hydrogen rich blocks moved to the substrate/polymer interface due to differences in surface energies of the fluorinated and protonated blocks. This segregation results in multi layer thin films with alternative fluorine rich and hydrogen rich layers. The dimensions of the NPs and the combine size of the fluorinated and protonated blocks were about the same. NPs migrate to internal surface induced interfaces in contrast to block copolymer in the lower segregation limit where NPs were segregated to the external interfaces due to translational and conformational entropic contributions. Modifying the NPs with a single matrix polymer chain further reduced the tendency of the NPs to migrate to the external interfaces and induced layering at the center of the film. The different distributions of NPs in the polymer affected the distribution of water molecules, which are absorbed from saturated vapor, in polymer films. We found that the amount of solvent penetration in thin films is governed by the density of NPs at the air/polymer interface

Approbation of the texture analysis imaging technique in the wastewater treatment plant

publishedVersio

DeepCSO: Forecasting of Combined Sewer Overflow at a Citywide Level using Multi-task Deep Learning

Combined Sewer Overflow (CSO) is a major problem to be addressed by many cities. Understanding the behavior of sewer system through proper urban hydrological models is an effective method of enhancing sewer system management. Conventional deterministic methods, which heavily rely on physical principles, is inappropriate for real-time purpose due to their expensive computation. On the other hand, data-driven methods have gained huge interests, but most studies only focus on modeling a single component of the sewer system and supply information at a very abstract level. In this paper, we proposed the DeepCSO model, which aims at forecasting CSO events from multiple CSO structures simultaneously in near real time at a citywide level. The proposed model provided an intermediate methodology that combines the flexibility of data-driven methods and the rich information contained in deterministic methods while avoiding the drawbacks of these two methods. A comparison of the results demonstrated that the deep learning based multi-task model is superior to the traditional methods

Effects Of Some Herbicides On Soil Nitrifiers and Nitrification

The herbicides Ioxynil, Bromoxynil, NPH 1320. Totril, Dieamba, Tricamba, Trifluralin, Oxadiazon, Legurame, M and B 9057 and M and B 9555 were tested for their effects on the process of nitrification in soil as well as in pure cultures. An improved version of the perfusion apparatus was developed and the perfusion technique was used as the principal experimental method in the soil studies in which the effects of different herbicides on the rates of nitrification in soils previously enriched with nltrifiers and in fresh soils continuously perfused with the herbicides were estimated. These estimates were made use of in the assessment of the degree of toxicities of the herbicides under consideration, on the metabolic rates per cell of nitrifiers and on their degree of proliferation in soil. An attempt was also made to study the possible differential effects of these herbicides on the two main groups of chemoautotrophic soil nitrifiers and the results obtained revealed that the metabolic activities of Nitrosomonas populations in soil were much less sensitive to the lower concentrations of many of the herbicides tested when compared with the sensitivities shown by the Nitrobacter populations, of the same soils, to the toxic effects of the same herbicides. But the rates of metabolic activities of Nitrosomonas populations were found to be the factor limiting the overall rates of the nitrification process in soils treated with the higher concentrations of most of these herbicides. The nitrification experiments carried out with cell suspensions of pure cultures of Nitrosomonas Euronaea and Nitrobacter Winogradski indicated that the herbicides exerted differential effects on the metabolic activities of these two organisms even in artificial media. The only other method used in studying the effects of herbicides on soil nitrification involved the measurement of the rates of oxygen uptake by samples of enriched soil treated with known concentrations of herbicides, making use of the conventional Warburg respirometrie technique. The qualitative effects of most of the herbicides on the activities of nitrifiers, grown in artificial media and in the natural medium of soil, were found to be essentially similar although the concentrations effective in causing these toxicities in pure cultures were much less than the concentrations needed to cause similar levels of toxicities in soil media. <p

Modelling of water resources: water balance, water use and water security

This paper presents three interacting models that facilitate the establishment of water management policies targeting sustainable and equitable use of water. For a given sub-basin, the water balance model attempts to establish the balance of water flows across the system boundary. Considering the whole system, the inflows have to balance the outflows. However, the water use model, set inside the system, allows for water within the system to be used many times over, thus increasing water availability. The water security model defines a multi-dimensional metric for water security depending on the water use model. The model structure allows for compatibility across boundaries, enabling construction of a composite mode for a basin, and hence a model for the country considering trans-basin exchanges

Development of a Novel Tread Compound using Rice Husk Ash for Non-Marking Solid Tyres

Rice husk is an agro waste that is not used in valuable ways especially in Sri Lanka other than as an alternative energy source. The conventionally burnt rice husk contains about 80-90% silica. Thus, these rice husk ash (RHA) could be a good replacement for commercially used silica filler in non-marking tread compounds. This study dedicated to research on possibility of using RHA and amorphous silica extracted from RHA as filler in non-marking tread compounds. The ash color RHA was obtained from conventionally burnt of rice husk at high temperature (550 C-700 C). The sodium silicate slurry was obtained by dissolving RHA in sodium hydroxide, heated above 140° C and stirred for 4 hrs. The slurry was filtered and filtrate was used to produce silica gel using sulphuric acid. This reaction was taken place at temperature 80° C-90° C range. The addition of sulphuric acid was done very slowly until medium become acidic. This was observed by using litmus papers. Then gel was allowed to age for overnight and formed silica gel was filtered and allowed to dry. The formed silica was purified by dissolving in hydrochloric acid, filtered it and residue was washed thoroughly with distilled water to remove metallic ions and sulphate impurities. The white color silica was obtained. Conventionally burnt RHA was blended with commercially used silica filler with different ratios and then formulated a tread compound. The controlled sample was made using commercially used silica filler. Another set of tread compound with same amount of filler loadings was prepared by adding Poly Ethylene Glycol as a coupling agent. MDR test for rheological properties, tensile and tearing tests, hardness and SPG tests, heat build-up test, abrasion and resilience tests were carried out for all the samples. Even though, rice husk ash contains high silica percentage the sample with 100% replacement of commercial silica with RHA showed worst mechanical properties, which improved with decreasing the RHA content. However, significant improvements in mechanical properties were observed when amorphous silica extracted from RHA was used. The characterization of extracted silica confirms that the presence of impurities such as metals and metal oxides. Thus, further improvements are being carrying out with further purification and modification of extracted silica.Keywords: Silica, Rice husk, Rice husk ash, Non-marking solid tyre, Tread compoun

Eight-year retrospective study of young adults in a diabetes transition clinic

The transition of people from paediatric to adult diabetes services is associated with worsening glycaemia and increased diabetes-related hospitalisation. This study compared the clinical characteristics of those with and without mental health conditions among attenders at a diabetes young adult clinic diabetes before and after changes in service delivery. Retrospective audit of 200 people with diabetes attending a Sydney public hospital over eight years corresponding to the period before (2012–2016) and after (2017–2018) restructuring of a clinic for young adults aged 16–25 years. Characteristics of those with and without mental health conditions (depression, anxiety, diabetes related distress, eating disorders), were compared. Among clinic attenders (type 1 diabetes n = 184, 83.2%), 40.5% (n = 89) had a mental health condition particularly, depression (n = 57, 64%), which was higher among Indigenous than non-Indigenous people (5.6% vs. 0.8%, p = 0.031) but similar between diabetes type. Over eight years, those with, compared with those without a mental health condition had higher haemoglobin A1c (HbA1c) at the last visit (9.4% (79 mmol/mol) vs. 8.7% (71 mmol/mol), p = 0.027), the proportion with diabetic ketoacidosis (DKA 60.7% vs. 42.7%, p = 0.009), smoking (38.4 vs. 13.6%, p = 0.009), retinopathy (9.0 vs. 2.3%, p = 0.025), multiple DKAs (28.4 vs. 16.0%, p = 0.031) were significantly higher. Having a mental health condition was associated with 2.02 (95% confidence intervals 1.1–3.7) fold increased risk of HbA1c ≥9.0% (75 mmol/mol). Changes to the clinic were not associated with improvements in mental health condition (39.0% vs. 32.4%, p = 0.096). In conclusion, we found that mental health conditions, particularly depression, are common in this population and are associated with diabetes complications. Diabetes type and clinic changes did not affect the reported mental health conditions. Additional strategies including having an in-house psychologist are required to reduce complication risks among those with mental health conditions