Journal of Geotechnical and Geoenvironmental Engineering, May 1, 1999
Two discussions of a paper with the aforementioned title by J.A.R. Ortigao, T.R.R. Loures, C. Nog... more Two discussions of a paper with the aforementioned title by J.A.R. Ortigao, T.R.R. Loures, C. Nogueira, and L.S. Alves, published in this journal (Volume 123, Number 9, September 1997), are presented. The first discusser has observed shallow or surficial failures in similar materials and thus argues about the possibility of slips caused by seepage parallel to the slope. The second two discussers add information on the site geology and on characteristics of the porous clay, concluding that this clay did not have a predominant effect in the observed slips. They then raise the issues of matrix suction and anisotropy. Discussions are followed by closure from the authors.
This paper presents results obtained by using a tensiometer designed in the Soil Mechanics Labora... more This paper presents results obtained by using a tensiometer designed in the Soil Mechanics Laboratory of COPPE/UFRJ and several other instruments. This new instrument measures suctions with values of more than 100 kPa. In more typical tensiometers, the cavitation of the system hinders the measurement of suctions with values over 100 kPa. Ridley and Burland (1993) designed a new model of tensiometer to measure suctions of more than 100 kPa. This paper presents an updated model of a tensiometer, using a variation of the equipment used by Ridley and Burland (1993). The updated model worked extremely well and cost little to build. The equipment used allows suctions to be measured relatively quickly and as previously stated is economical to produce (about 300 US$). To date, the range of suctions that can be measured reaches 350 kPa with no difficulty. The tests were carried out in a mini-lysimeter under laboratory conditions. The equipment used included a ceramic stone of 15 m.c.a., pressure sensor, de-aerated water and a special acrylic tube specifically designed for this instrument. The results were compared with two simple automated tensiometer and equivalent tensiometers. In general very comprehensive results were obtained.
This paper is a study of the correlation between the humidity, density and matrix suction of non-... more This paper is a study of the correlation between the humidity, density and matrix suction of non-plastic soil taken from a region located near the city of Rio de Janeiro. The study was conducted through laboratory tests, using minilysimeters and equipment that indirectly measured the humidity through soil suction: in effect, an automated tensiometer, an equivalence tensiometer (EQ2), a TDR and a specially adapted system, which measures the suction in situ, using filter paper. The electronic instruments were connected to a data logger and placed in three mini-lysimeters. Cycles of wetting and drying of the confined material were simulated. The soil was characterised. This characterisation enabled the determination of physical indexes, density, plasticity, grain size, porosity, and the characteristic curve of water retention, using the Richards pressure pan (cooker) test. The results obtained by the instruments, humidity and matrix suction, were compared with the characteristic curve. Overall, the equipment was satisfactory. The low presence of clay in this soil, around 7%, and its associated high porosity, were factors in limiting water retention. The equilibrium time of the soil humidity and the filter paper, obtained at intervals of fifteen days, presented better results than the weekly intervals (seven days). The equivalence tensiometer EQ2 compared to the filter paper presented quite efficient results for high suction values.
This work sought to analyse the main difficulties in implementing and maintaining the selective w... more This work sought to analyse the main difficulties in implementing and maintaining the selective waste collection in a Brazilian metropolis with more than one million inhabitants. Therefore, a qualitative method was used through in-depth interviews with 18 professionals working in the area of selective collection. The interviews were recorded and the data submitted to content analysis. The results showed the following difficulties: lack of management by the government, low efficiency and limited coverage; poor separation of waste at source; distortions in the selective collection logistics chain and in the distribution of waste by cooperatives; high informality, precarious work and low pay for waste collectors; the presence of middlemen and corruption in the system; and idle capacity of cooperatives and public organs. It was concluded that to overcome the difficulties in the selective collection and for it to be more effective, there is a need to improve the management of the process by the government with greater transparency and integration between the various actors involved, education of the population, better working conditions and remuneration for waste collectors.
Journal of Geotechnical and Geoenvironmental Engineering, May 1, 1999
Two discussions of a paper with the aforementioned title by J.A.R. Ortigao, T.R.R. Loures, C. Nog... more Two discussions of a paper with the aforementioned title by J.A.R. Ortigao, T.R.R. Loures, C. Nogueira, and L.S. Alves, published in this journal (Volume 123, Number 9, September 1997), are presented. The first discusser has observed shallow or surficial failures in similar materials and thus argues about the possibility of slips caused by seepage parallel to the slope. The second two discussers add information on the site geology and on characteristics of the porous clay, concluding that this clay did not have a predominant effect in the observed slips. They then raise the issues of matrix suction and anisotropy. Discussions are followed by closure from the authors.
This paper presents results obtained by using a tensiometer designed in the Soil Mechanics Labora... more This paper presents results obtained by using a tensiometer designed in the Soil Mechanics Laboratory of COPPE/UFRJ and several other instruments. This new instrument measures suctions with values of more than 100 kPa. In more typical tensiometers, the cavitation of the system hinders the measurement of suctions with values over 100 kPa. Ridley and Burland (1993) designed a new model of tensiometer to measure suctions of more than 100 kPa. This paper presents an updated model of a tensiometer, using a variation of the equipment used by Ridley and Burland (1993). The updated model worked extremely well and cost little to build. The equipment used allows suctions to be measured relatively quickly and as previously stated is economical to produce (about 300 US$). To date, the range of suctions that can be measured reaches 350 kPa with no difficulty. The tests were carried out in a mini-lysimeter under laboratory conditions. The equipment used included a ceramic stone of 15 m.c.a., pressure sensor, de-aerated water and a special acrylic tube specifically designed for this instrument. The results were compared with two simple automated tensiometer and equivalent tensiometers. In general very comprehensive results were obtained.
This paper is a study of the correlation between the humidity, density and matrix suction of non-... more This paper is a study of the correlation between the humidity, density and matrix suction of non-plastic soil taken from a region located near the city of Rio de Janeiro. The study was conducted through laboratory tests, using minilysimeters and equipment that indirectly measured the humidity through soil suction: in effect, an automated tensiometer, an equivalence tensiometer (EQ2), a TDR and a specially adapted system, which measures the suction in situ, using filter paper. The electronic instruments were connected to a data logger and placed in three mini-lysimeters. Cycles of wetting and drying of the confined material were simulated. The soil was characterised. This characterisation enabled the determination of physical indexes, density, plasticity, grain size, porosity, and the characteristic curve of water retention, using the Richards pressure pan (cooker) test. The results obtained by the instruments, humidity and matrix suction, were compared with the characteristic curve. Overall, the equipment was satisfactory. The low presence of clay in this soil, around 7%, and its associated high porosity, were factors in limiting water retention. The equilibrium time of the soil humidity and the filter paper, obtained at intervals of fifteen days, presented better results than the weekly intervals (seven days). The equivalence tensiometer EQ2 compared to the filter paper presented quite efficient results for high suction values.
This work sought to analyse the main difficulties in implementing and maintaining the selective w... more This work sought to analyse the main difficulties in implementing and maintaining the selective waste collection in a Brazilian metropolis with more than one million inhabitants. Therefore, a qualitative method was used through in-depth interviews with 18 professionals working in the area of selective collection. The interviews were recorded and the data submitted to content analysis. The results showed the following difficulties: lack of management by the government, low efficiency and limited coverage; poor separation of waste at source; distortions in the selective collection logistics chain and in the distribution of waste by cooperatives; high informality, precarious work and low pay for waste collectors; the presence of middlemen and corruption in the system; and idle capacity of cooperatives and public organs. It was concluded that to overcome the difficulties in the selective collection and for it to be more effective, there is a need to improve the management of the process by the government with greater transparency and integration between the various actors involved, education of the population, better working conditions and remuneration for waste collectors.
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