Experimental Study on Early Age Characteristics of Lime-GGBS-Treated Gypseous Clays under Wet–Dry Cycles

Gypseous soils are capable of presenting ground construction challenges to civil and geotechnical engineers due to their unpredictable deformation characteristics. These undesirable responses are sometimes caused by environmental changes in moisture content due to temperature variations, fluctuation of underground water table, surface water, and gypsum content. Hence, the adoption of effective and economical means of stabilising gypseous soils is imperative. This study’s focus is on the early age strength and microstructural characteristics of gypseous soils treated with lime and GGBS. Treated and untreated gypseous soils with 5%, 15%, and 25% gypsum content were subjected to wet–dry cycles while investigating unconfined compressive strength (UCS), water absorption, pH, microstructural changes, and swell. The analysis of the results shows that at zero cycle, the UCS of the untreated gypseous soils increases from 0.62 to 0.79 MPa and swell decreases from 69 to 23%, respectively, as gypsum content increases. However, upon subjection to wet–dry cycles, the UCS reduced from 0.16 to 0.08 MPa at the end of the sixth cycle due to dissolution of gypsum within the soil pores which reduced the strength. The result also shows that gypsum content increases water absorption and reduces the pH of the untreated gypseous soils because of the neutral pH of gypsum. Furthermore, lime-GGBS-treated gypseous soils maintained a higher pH after six wet–dry cycles compared to untreated gypseous soils due to the high pH of lime and the increase in calcium content which improved bonding. In addition, microstructural analysis using SEM indicated early age precipitation of cementitious compounds (CSH) for increasing strength of lime-GGBS-treated gypseous soils compared to untreated gypseous soils.

An Extension of Taylor’s φ-Circle Method and Some Stability Charts for Submerged Slopes

Taylor’s φ-circle method is a classical method for slope stability calculation, which has analytical solutions. Taylor derived equations in two cases separately, namely, (i) the outlet of the critical failure surface is at the slope toe and (ii) the outlet of the failure surfaces is not at the slope toe. The method is only appropriate for two conditions (without underground water table in slopes or totally submerged slopes). In this study, a general equation that unifies the equations of the two cases is proposed and partially submerged condition is introduced. The critical failure surfaces corresponding to the minimum factor of safety are determined using the computer program proposed by the authors. The general expression of the safety factor of slopes under the following four conditions is derived, namely, (i) partly submerged, (ii) completely submerged, (iii) water sudden drawdown, and (iv) water slow drawdown. The corresponding charts for practical use are available.

Extraction, characterization and biological activity of citrus flavonoids

Citrus is one of the largest and most popular fruit crops commercially grown across the globe. It is not only important in terms of economy but is also popular for its nutritional benefits to human and farm animals. Citrus is available in several varieties, all with attractive colors. It is consumed either fresh or in processed form. After processing, approximately 50% of the fruit remains unconsumed and discarded as waste. The latter includes fruit pith residue, peels and seeds. Direct disposal of these wastes to the environment causes serious problems as these contain bioactive compounds. Release of these bioactive compounds to the open landfills cause bad odor and spread of diseases, and disposal to water bodies or seepage to the underground water table deteriorates water quality and harms aquatic life. In this regard, a number of research are being focused on the development of better reuse methods to obtain value-added phytochemicals as well as for safe disposal. The important phytochemicals obtained from citrus include essential oils, flavonoids, citric acid, pectin, etc., which have now become popular topics in industrial research, food and synthetic chemistry. The present article reviews recent advances in exploring the effects of flavonoids obtained from citrus wastes, the extraction procedure and their usage in view of various health benefits.

Evolution of Secondary Deformations Captured by Satellite Radar Interferometry: Case Study of an Abandoned Coal Basin in SW Poland

The issue of monitoring surface motions in post-mining areas in Europe is important due to the fact that a significant number of post-mining areas lie in highly-urbanized and densely-populated regions. Examples can be found in: Belgium, the Czech Republic, France, Germany, the Netherlands, Spain, the United Kingdom, as well as the subject of this study, the Polish Walbrzych Hard Coal Basin. Studies of abandoned coal fields show that surface deformations in post-mining areas occur even several dozen years after the end of underground coal extraction, posing a threat to new development of these areas. In the case of the Walbrzych area, fragmentary, geodetic measurements indicate activity of the surface in the post-mining period (from 1995 onward). In this work, we aimed at determining the evolution of surface deformations in time during the first 15 years after the end of mining, i.e., the 1995–2010 period using ERS 1/2 and Envisat satellite radar data. Satellite radar data from European Space Agency missions are the only source of information on historical surface movements and provide spatial coverage of the entirety of the coal fields. In addition, we attempted to analyze the relationship of the ground deformations with hydrogeological changes and geological and mining data. Three distinct stages of ground movements were identified in the study. The ground motions (LOS (Line Of Sight)) determined with the PSInSAR (Persistent Scatterer Interferometry) method indicate uplift of the surface of up to +8 mm/a in the first period (until 2002). The extent and rate of this motion was congruent with the process of underground water table restoration in separate water basins associated with three neighboring coal fields. In the second period, after the stabilization of the underground water table, the surface remained active, as indicated by local subsidence (up to −5 mm/a) and uplift (up to +5 mm/a) zones. We hypothesize that this surface activity is the result of ground reaction disturbed by long-term shallow and deep mining. The third stage is characterized by gradual stabilization and decreasing deformations of the surface. The results accentuate the complexity of ground motion processes in post-mining areas, the advantages of the satellite radar technique for historical studies, and provide information for authorities responsible for new development of such areas, e.g., regarding potential flood zones caused by restoration of groundwater table in subsided areas.

Properties of geopolymer pervious concrete made with GGBS

Pervious concrete is a light weight concrete containing voids in the range of 14 to 31%. The usage of pervious concretes has been in- creased due to its merits on pollution control and environmental considerations. The pervious concretes are also used to reduce the storm water runoff and recharges the underground water table. Eventhough the pervious concrete has lot of merits, it also has consider- able demerits related to strength issues. In order to achieve the strength high cement content mixes may be incorporated which is not a viable solution. In this paper, geopolymer technology has been used to develop pervious concrete. Geopolymer pervious concrete is pro- duced using GGBS as raw material and sodium hydroxide and sodium silicate as activator solution. Five mixes have been developed with varying GGBS content of 450, 460, 470, 480 and 490 kg/m3. The cement to aggregate ratio is fixed at 1:3 for all the mixtures and the water cement ratio is kept constant at 0.3. The compressive strength revealed that strength of around 20 MPa was attained for all the mixtures and strength increases with respect to the increase in GGBS content. There was not significant changes in the permeability property since the aggregate cement ratio is maintained for all the mixtures.

Combination of line sampling and important sampling for reliability assessment of buried pipelines

In this article, a novel approach for estimating the time-dependent reliability of a buried pipe under the impact of internal and external stresses by combining line sampling and important sampling is proposed. The stresses are analysed given the severe effect of corrosion on the performance of underground pipeline. The effect of corrosion during the design life of buried pipe decreases the capability of the pipe wall to sustain the stresses that occur internally or externally. Herein, the failure conditions of total axial stress and the ovality–stress due to point load in conjunction with the adverse effect of corrosion are examined using the proposed computational framework. The quantification of pipe failure due to these stresses is usually challenging because of the imprecision in the determination of the structural parameters. Therefore, the approach is used to capture and evaluate the influence of randomness behaviour of the parameters of pipe and soil in estimating the structural reliability. The proposed method can be applied to any structural engineering problems. In this study, a buried pipe under a roadway is examined and the effect of the underground water table on the performance of buried pipe over time is investigated. The outcome shows that a continuous increase in underground water table can aggravate the likelihood of the buried pipeline to fail. A parametric and sensitivity assessment of corrosion parameters shows their significant contribution to the probability of failure.

The issues of drainage of discussed mines in the Katowice conurbation, Poland

The Katowice conurbation is situated in the Upper-Silesian Coal Basin, in a region which had high rate of water inflow in the pre-mining period. In order to make deposits of mineral resources accessible, it was, and still is, necessary provide mines with a draining system, which now reaches as deep as 1200 m. The area of the depression sink which was thus created is about 1200 km2. Currently, all metal ore mines within the conurbation, as well as part of coal mines, have been closed down, but water which flows into them is still pumped out due to the legal obligation to protect neighbouring operating mines. After the operation and drainage of mines cease, water coming to abandoned excavations will begin restoring static reserves in the orogen, which, depending on hydrological conditions, will take between several and a few dozen years. As the level of underground water rises, the process of subsidence of old shallow mining excavations will intensify, and many depressions may appear in highly urbanized areas. In areas of mining subsidence, the underground water-table will be close to the surface, causing flooding of basements and building foundations, and the deepest subsidence basins will probably be completely flooded. Current location of operating mines on the northern and southern sides of the conurbation with the central belt of drained excavations is unfavourable for its sustainable development. A solution, which would make it possible for the conurbation to grow, would be to close down and flood the mines on the northern side as soon as their mining concessions expire, which will be in early 2020s. Then, the area would regain its original stability within a decade and all kinds of construction activities could be carried out there. That, however, requires authorities of municipalities to object to the extension of concessions for mines, which may be impossible to obtain due to fears of social discontent resulting from miners - residents of those municipalities - being made redundant.

Development and operation of a muon detection system under extremely high humidity environment for monitoring underground water table

In order to investigate the complex nature of landslides triggered by rainfall, dynamic muon radiography of the motion of the underground water table is planned in a drainage tunnel drilled underneath an estimated fault plane. However, the humidity inside the tunnel is almost 100%. In order to suppress moisture effects, a scintillation counter with Cockcroft–Walton photomultipler tubes (CW-MPT) was developed and tested at the observation site located in Shizuoka Prefecture, Japan. The counter was stably operated for 38 days without gain degrading. Based on the result, we constructed a muon detection system with CW-PMTs at the same site and started operation runs. In this work, the data from borehole-based water gauge measurements of the underground water levels were analyzed and discussed. It was confirmed that the comparison between muon and borehole data would be useful.

Development and operation of a muon detection system under extremely high humidity environment for monitoring underground water table

In order to investigate the complex nature of the landslides triggered by rainfall, dynamic muon radiography of the motion of the underground water table is performed in a the drainage tunnel drilled underneath an the estimated fault plane. However, the humidity inside the tunnel is almost 100%. In order to suppress the moisture effect, a scintillation counter with Cockcroft-Wwalton photomultipler tubes (CW-MPT) was developed and tested at the observation site. The counter was stably operated for 38 days without gain degrading. Based on the result, we constructed a muon detection system with CW-PMTs at the same site and started operation runs. In this work, the data from borehole-based measurement of the underground water levels were analyzed and discussed. It was confirmed that the comparison between muon and borehole data would be useful.