Ashis Kumar Bera

Effect of design and operating parameters on gas hold-up in Pachuca (air-agitated) tanks

Abstract Gas hold-up is a crucial parameter for liquid circulation as well as particle suspension in Pachuca tanks. These tanks, used as leaching vessels in hydrometallurgical industries, are air-agitated slurry reactors, cylindrical in cross-section with a conical bottom and usually equipped with a full-length central draught tube. In spite of the widely varying designs and operating parameters of Pachuca tanks, little attention has been paid hitherto to the gas hold-up in these tanks. Extensive experiments on gas hold-up in laboratory-scale Pachuca tanks have now been performed. The effects of such design and operating parameters as tank height to tank diameter ratio (H t/D t), draught-tube diameter to tank diameter ratio (D d/D t), cone angle, superficial gas velocity, particle size and concentration were examined. It was found that gas hold-up in the draught tube increased with an increase in superficial gas velocity, but decreased with increase in H t/D t and D d/D t ratios, cone angle of conical bottom and tank diameter. It was also observed that gas hold-up increased in the presence of fine particles and decreased in the presence of coarser particles. A correlation–as a function of design and operating parameters, as well as the scale of the tank–has been developed as a first attempt to quantify the gas hold-up in Pachuca tanks.

Regression model for prediction of optimum moisture content and maximum dry unit weight of fine grained soil

Abstract In the present paper, log linear regression models have been developed to estimate the maximum dry unit weight and optimum moisture content of fine grained soil. The parameters such as compaction energy, specific gravity, liquid limit, and grain size (grain size, corresponding to 50% finer particles) are showing the significant contribution for both the models for predicting the maximum dry unit weight as well as optimum moisture content of fine grained soil. All possible regression techniques have been performed for predicting the best models. The above models are useful within the range of 318.10 - to 10832.10 kJ/m3, 2.60 to 2.80, 30.81 - to 213.27%, and 0.0008 - to 0.019 mm for compaction energy, specific gravity, liquid limit, and grain size (Grain size, corresponding to 50% finer particles) respectively.

Compaction characteristics of fine grained soil and rice husk ash mixture

Abstract This study presents the compaction characteristics of fine grained soil and rice husk ash (RHA) mixture. Three types of fine grained soils viz., montmorillonite clay, kaolinite clay, and one local soil has been used in the present study. From the compaction tests results it is observed that with increase in RHA content (0–30%) maximum dry density (MDD) decreases and also optimum moisture content (OMC) increases irrespective of types of fine grained soil. Based on the experimental data, a number of linear regression models have been developed to estimate MDD and also OMC of fine grained soil and RHA mixture. Empirical models also presented to estimate dry density in terms of water content of dry side of optimum or water content of wet side of optimum, compaction energy, RHA content, and also specific gravity of fine grained soil and RHA mixture. The above models may be useful for the field engineers within the range of compaction energy from 300 kJ m−3 to 2700 kJ m−3, RHA content from 0%–30%, specific gravity of fine grained soil and RHA mixture from 2⋅311–2⋅750, and OMC for soil from 16⋅8%–37⋅0%.

Uplift capacity of model bell shaped anchor embedded in sand

Abstract This paper presents the details of a series of model tests conducted to investigate the influence of relative density (Dr) of sand, the ratio of embedment depth (H) of anchor to diameter (D) of bell of anchor, diameter (D) of bell of anchor, and types of sand on uplift capacity of bell shaped anchor embedded in sand. From the experimental results, it has been found that uplift capacity of anchors increases with increases in relative density of sand and also H/D ratio. In the present investigation, the bell diameter of the anchors is kept as 125·0, 187·5, 250·0 and 312·5 mm. Three types of sand were used as foundation medium. From the experimental results, it is observed that sand with more fines exhibits lower values of ultimate uplift capacity of anchors. Based on the experimental data obtained in the present investigations, breakout factor (Fq) was calculated. From the calculated breakout factor (Fq), it is observed that the breakout factor (Fq) depends on relative density and H/D ratio. An empirical model has been developed to predict breakout factor (Fq) in terms of H/D ratio and relative density (Dr).

Influence of Granulated Blast Furnace Slag Contents on California Bearing Ratio Value of Clay GBFS Mixture

Nowadays it is common practices to strengthening the soft subgrade by using waste materials. Granulated blast furnace slag (GBFS), an industrial waste may be used to stabilize soft clay sub-grade. In the present study, an attempt has been made to evaluate the effect of GBFS contents on California bearing ratio (CBR) value of clayey soil GBFS mixture. Three types of clayey soil and one types of GBFS has been used in the present investigation. Soaked CBR test has been performed with varying GBFS content (0–50%) for above three types of soil. From the experimental outcomes it has been found that with increase in GBFS content the soaked CBR values increases and reaches a maximum value at certain GBFS content after that it decreases. The optimum value of GBFS content is 30% irrespective of types of soil when it has been compacted at OMC and MDD of the respective mixture. Based on the experimental data a nonlinear power model has been developed to predict the CBR value of soil GBFS mixture in terms of GBFS content and CBR value of the respective soil alone.

Field and Numerical Investigation on Time-Dependent Behavior of Jute Geotextile (JGT) Reinforced Rural Road

A rural road section reinforced with Jute Geotextiles (JGT) sandwiched between thin sand layers has been constructed to study the strength improvement of subgrade soil. In this present investigation, an attempt also has been made to develop a three-dimensional (3D) finite element (FE) model of the JGT reinforced and unreinforced rural road sections using general purpose FE software ABAQUS. Numerical simulation of time-dependent behavior for JGT reinforced rural road has been carried out using the data obtained from field investigation at regular time interval. In this present investigation, subgrade soil has been modeled using Mohr–Coulomb plasticity model, whereas JGT has been assumed as membrane type of material. From FE analysis, pavement responses under traffic loading such as rut depth, maximum tensile strain developed at JGT, and vertical compressive strain developed at the top of subgrade soil has been evaluated. From the field investigation, it has been found that the subgrade California bearing ratio (CBR) value is increased with increase in time under study. It has been found that the reinforced rural road sections are performing well in terms of rut depth than the unreinforced section.

Influence of Fly Ash Content on Compaction Characteristics of Fly Ash Clay Mixture

In the present paper, a series of compaction tests have been performed to investigate the effect of fly ash content on compaction characteristics of fly ash clay mixture. Three types of fly ash and three types of clay have been used in this investigation. From the test results, it is observed that with the increase in fly ash content (0 to 25%) in the fly ash clay mixture, the value of maximum dry density decreases irrespective of type of soil, type of fly ash and type of compaction method. Fly ash content also influences significantly the optimum moisture content of fly ash clay mixture. Based on the present experimental data, a number of linear regression models have been developed to estimate the values of optimum moisture content and maximum dry density of fly ash clay mixture.