Practical approach to predict the shear strength of fibre-reinforced clay

yesCarpet waste fibres have a higher volume to weight ratios and once discarded into landfills, these fibres occupy a larger volume than other materials of similar weight. This research evaluates the efficiency of two types of carpet waste fibre as sustainable soil reinforcing materials to improve the shear strength of clay. A series of consolidated undrained (CU) triaxial compression tests were carried out to study the shear strength of reinforced clays with 1%, to 5% carpet waste fibres. The results indicated that carpet waste fibres improve the effective shear stress ratio and deviator stress of the host soil significantly. Addition of 1%, 3% and 5% carpet fibres could improve the effective stress ratio of the unreinforced soil by 17.6%, 53.5% and 70.6%, respectively at an initial effective consolidation stress of 200 kPa. In this study, a nonlinear regression model was developed based on a modified form of the hyperbolic model to predict the relationship between effective shear stress ratio, deviator stress and axial strain of fibre-reinforced soil samples with various fibre contents when subjected to various initial effective consolidation stresses. The proposed model was validated using the published experimental data, with predictions using this model found to be in excellent agreement

Assessment of lime treatment of expansive clays with different mineralogy at low and high temperatures

YesThis paper examines the impacts of clay mineralogy on the effectiveness of lime stabilisation at different temperatures. A comprehensive experimental programme was conducted to track down the evolution of lime-clay reactions and their durations through monitoring the evolution of strength gain at predetermined times using the Unconfined Compressive Strength (UCS) test. The study examined clays with different mineralogy compositions comprising Na+ Bentonite and Ball (Kaolinite) clay. Four different clays were tested including 100% bentonite, 100% Ball clay and two clay mixtures with ratios of 1:1 and 1:3 by mass of bentonite to Ball clay. All clays were treated using a range of lime content up to 25% and cured for a period of time up to 672 h at two different temperatures of 20 and 40 °C. The results showed that the continuity of the fast phase (stage 1) of strength gain was dependent on the availability of lime in particular at the higher temperature. Whereas, for the same lime content, the duration of the fast phase and the kinetic of strength gain were significantly related to the clay mineralogy and curing temperature. Except for the initial strength gain at 0 h curing time, the lime-treated Ball clay specimens at 20 °C appeared to show no strength gain throughout the curing period that extended up to 672 h. However, when curing occurred at 40 °C, the no strength gain stage only lasted for 72 h after which a gradual increase in the strength was observed over the remaining curing period of time. The addition of Bentonite to Ball clay succeeded in kicking off the strength gain after a short period of curing time at both curing temperatures

The effects of lime content and environmental temperature on the mechanical and hydraulic properties of extremely high plastic clays

YesThis paper focuses on monitoring the evolution of lime-clay reactions using geotechnical parameters as a function of lime content and environmental temperature. Lime contents of 5, 7, 9, 11 and 13% by dry weight of expansive clay powder were added to prepare lime-clay specimens. The specimens were prepared at the same dry unit weight of 12.16 kN/m3 and moisture content of 40% except for tests aimed at the determination of dry unit weight as a function of mellowing period. Prepared specimens were mellowed or cured at two different ambient temperatures of 20 °C and 40 °C. Results attained from Unconfined Compressive Strength and permeability tests were employed to assess the impact of lime content on the mechanical and hydraulic properties of lime treated expansive clays. The results revealed that at the beginning, the rate of strength gain is remarkably fast for a particular period of time which is dependent on lime content. Furthermore, the strength gain on specimens cured at 40 °C is 8 times higher than that observed on specimens cured at 20 °C which highlights significant effect for the environmental temperature on accelerating the chemical reactions. Reduced dry unit weight due to increased resistance to compactability is observable with increasing lime content and higher environmental temperature. Accelerated pozzolanic reaction at higher environmental temperature resulted in permeability coefficient of specimens mellowed for 24 h at 40 °C to be higher than those mellowed at 20 °C. The results also highlighted that the permeability coefficient would be relatively stable when expansive clays were treated with small amounts of lime e.g. 5%

Factors affecting consumers’ willingness to buy private label brands (PLBs): Applied study on hypermarkets

Purpose - The aim of this research is to investigate the factors affecting consumers’ willingness to buy private label brands (PLBs). The relationships among store image, familiarity with PLBs, consumers’ perceptions of PLB quality, risk, price consciousness and attitude towards PLBs are examined. Finally, the relationship between attitude towards, and willingness to buy PLB is explored. Design/methodology/approach - Self-administered questionnaire was distributed to shoppers at Carrefour operating in Cairo, Egypt. The data obtained from 265 respondents were examined using structural equation modelling (analysis of moment structures) version 22, which empirically test the hypothesised relations established in the research conceptual model. Findings - With the exception of perceived risk, the results suggest that all consumers’ perceptual and attitudinal factors affect directly or indirectly consumers’ willingness to buy PLB. Research limitations/implications - This study is limited to international hypermarket/supermarket operating in Egypt. So the findings should be exercised with cautious while attempting to generalise the research results. Practical implications - Retail managers should focus on the enhancement of both store image and familiarity with PLBs to leverage consumers’ perceptions with respect to PLBs quality and risk to achieve differentiation and to increase sales. Originality/value - This is one of the few studies that investigate the role of familiarity with PLBs in a developing context. In doing so, it proposes that familiarity with PLBs directly affects consumers’ perceived quality and perceived risk, while it indirectly influences consumers’ willingness to buy PLBs

The Impact of moisture and clay content on the unconfined compressive strength of lime treated highly reactive clays

YesThis study aims to provide a thorough evaluation for the changes in the microstructure and evolution of strength of highly reactive clays that were treated with 7 % lime over a period of curing time as a function of the mixing moisture content. Three series of testing were carried out on specimens with 100 %, 85 % and 75 % of bentonite content and prepared with different moisture content of 10, 20, 30 and 40 % above the corresponding optimum moisture content. Specimens of 100 % bentonite were treated with 7 % of lime, compacted to achieve a predetermined dry unit weight and cured at temperatures of 20 OC and 40 OC for up to 28 days whereas the specimens with 85 % and 75 % of bentonite content were prepared by the addition of sand and were cured at 20 oC for up to 7 days. Unconfined Compressive Strength tests and Scanning Electron Microscopy were conducted to observe the strength and the microstructural changes resulting from increasing mixing moisture content. California Bearing Ratio and Resilient Modulus were correspondingly determined based on correlations with the Unconfined Compressive Strength. The failure pattern was also studied to better understand the ultimate behaviour of lime stabilised clays. The results revealed that the strength of treated bentonite increased with the increase in the moisture content up to 30 % above the corresponding optimum moisture content and with increasing the curing time and temperature. Nevertheless, substituting bentonite with sand on the specimen resulted in a significant reduction on the attained strength. Furthermore, the results of California Bearing Ratio and Resilient Modulus showed that values for both parameters are significantly enhanced with lime treatment. The microstructural analysis provided visual evidence to the improved strength in which the pozzolanic reaction was found to be significantly affected by the amount of moisture in the mixture. The results suggested that compacting lime treated expansive clays with moisture content moderately higher than the optimum moisture content would result in a significant enhancement to the attained strength over the period of curing

Analysis of unreinforced and reinforced shallow piled embankments subject to cyclic loading

YesReinforced piled embankment technique is becoming increasingly utilised for the construction over soft grounds due to its efficiency on reducing potential settlement, speed of construction and associated cost. Most of previous studies focused on developing understanding for the behaviour of thick embankments that are loaded with a static surcharge load. Data for the behaviour of shallow piled embankments under cyclic loadings are scarce. In this study, an experimental programme was undertaken using a fully instrumented testing rig to generate data and improve our understanding for the behaviour of unreinforced and reinforced shallow piled embankments subject to monotonic and cyclic loadings that were applied over a predetermined area of the embankment. The experimental results showed that collapse of soil arching is imminent and occurs during the first few cycles of load. However, regain of strength and recovery of the arching effect was observable during further stages of cyclic loadings due to densification of the embankment material and deformation of the soft subsoil. Inclusion of reinforcement layers was found to enhance the performance of load transfer mechanisms by concentrating stresses on pile caps. The results clearly showed a significant reduction in surface settlement, soft subsoil settlement and heaving with increasing the number of reinforcement layers

Analysis of sequential active and passive arching in granular soils

YesArching in soils has received great attention due to its significance on the soil–underground structure interaction. The state of stress on underground structures as a result of cycles of active and passive arching was neither explored nor systematically assessed. In the present study, comprehensive investigation was carried out to examine: i. the effects of displacement direction to induce active or passive arching, ii. the behaviour of subsequent arching, iii. the effect of magnitude of initial displacement on the formation of arching and iv. the influence of soil height on sequential active and passive arching. The results showed that alternating the displacement of the underground inclusion exacerbated the formation of active and passive arching leading to a substantial reduction in shear resistance and stress redistribution. It is noted that sequentially alternating displacement of the underground inclusion was detrimental to the formation of full active and passive arches irrespective of the burial height

Numerical behaviour of buried flexible pipes in geogrid-reinforced soil under cyclic loading

YesThree-dimensional finite element models were executed and validated to investigate the performance of buried flexible high-density Polyethylene (HDPE) pipes, in unreinforced and multi-geogrid-reinforced sand beds, while varying pipe burial depth, number of geogrid-layers, and magnitude of applied cyclic loading. Geogrid-layers were simulated considering their geometrical thickness and apertures, where an elasto-plastic constitutive model represented its behaviour. Soil-geogrid load transfer mechanisms due to interlocked soil in-between the apertures of the geogrid-layer were modelled. In unreinforced and reinforced cases, pipe burial depth increase contributed to decreasing deformations of the footing and pipe, and the crown pressure until reaching an optimum value of pipe burial depth. On the contrary, the geogrid-layers strain increased with increasing pipe burial depth. A flexible slab was formed due to the inclusion of two-geogrid-layers, leading to an increase in the strain in the lower geogrid-layer, despite its lower deformation. Inclusion of more than two geogrid-layers formed a heavily reinforced system of higher stiffness, and consequently, strain distribution in the geogrid-layers varied, where the upper layer experienced the maximum strain. In heavily reinforced systems, increasing the amplitude of cyclic loading resulted in a strain redistribution process in the reinforced zone, where the second layer experienced the maximum strain

Acoustical properties of novel sound absorbers made from recycled granulates

YesThis study investigates the acoustic performance of materials made using various amounts of bio-binder (cis-1,4-polyisoprene). The filler used in making these materials was from recycled tyres which consist of nylon 6,6 fibres bonded to rubber grains known as tyre shred residue (TSR). The materials have shown high acoustical performance especially at low binder levels, due mainly to the open porosity of the tested samples. The paper begins with a discussion of materials made using recycled granulates. The macroscopic properties (e.g. flow resistivity, porosity, tortuosity, etc.) that control the acoustical behaviour of these materials are then defined as are methods for their measurements. The acoustical characterisation of porous media is considered next, followed by discussion of the acoustic performance of the materials. The characteristics of these novel materials are illustrated through experimental and theoretical models involving sound absorption and transmission