Bottom Ash Columns Research Articles

Experimental and 3D numerical analysis of embankment on soft soil improved with cement bottom ash columns

Experimental and 3D numerical analysis of embankment on soft soil improved with cement bottom ash columns

Shear Strength of Soft Soil Reinforced with Singular Bottom Ash Column

Structures construct on soft clays are often affected by stability and settlement problems due to high compressibility, low shear strength and low permeability of soft clay which will lead to bearing capacity failure and excessive settlement. The soft clay samples had the dimensions of 50 mm diameter and 100 mm in height. The bottom ash column had two (2) different area replacement ratios which were 4% and 9% (10 mm and 15 mm diameters respectively) with the bottom ash column penetration ratio of 0.3, 0.7 and 1.0. The results of the unconfined compression test show that there is an improvement in shear strength of soft kaolin clay when reinforced with bottom ash column. For samples with area replacement ratio 4%, the results show the increment of 25%, 37.5% and 50% at height penetrating ratio of 0.3, 0.7 and 1.0, respectively in shear strength. Meanwhile, for samples of 9% area replacement ratio, the shear strength of the soft kaolin clay increased about 14.29, 28.57 and 57.14%, respectively. It can be concluded that by reinforcing the soft clay using singular bottom ash column, the shear strength of the soils increases and become more significant as the area replacement ratios and the column penetration ratios increase.

The Influence of Bottom Ash Column in the Geotechnical Properties Enhancement of Soft Clay Soil

The utilization of bottom ash in ground improvement studies can cut down the quantity of generated waste which is in response to environmental conservation and enhancing the soil properties. The bottom ash which plays the role of replacing the coarse aggregate like sand and gravel in upgrading the behaviour of soft clay soil can fulfill the sustainability concept in construction. For construction purposes, the soil and ground improvement activities are necessary to carry out by using the relevant techniques, including the vibro-replacement method. This method was applied which suits the limitation of this study as it was executed in the laboratory for the preparation of the bottom ash column. The properties examination of kaolin clay and bottom ash were first studied through its particle size, specific gravity, liquid and plastic limit, and compaction. The following procedure was about the column preparation process, where the column diameter was set to be constant at 20 mm throughout the study. The execution of the Unconfined Compression Test (UCT) on the Bottom Ash Column has shown its impact on the undrained shear strength upgrade and it was focused on the height of the bottom ash column built beneath the kaolin clay at 60mm, 80mm, and 100 mm. As observed from the trend, the height of the bottom ash column shows a direct proportional relationship by the undrained shear strength, ranging from 11.64% - 14.26% by using the control sample (with no bottom ash reinforcement) as reference. Conclusively, the use of bottom ash subsides the disposal waste and in no time provides support to the shear strength of soft clay soil which is sustainable and applicable.

Utilization of bottom ash waste as a granular column to enhance the lateral load capacity of soft kaolin clay soil.

Implementation of industrial wastes such as bottom ash in ground improvement can be cost-effective and environment-friendly. Ground improvement is an effective method of mitigation to improve problematic soils including soft kaolin clay soils as the problematic soils always expose to the severe settlements, low shear strength, immoderate plasticity, greater compressibility, dispersivity, bulging, erodibility, and susceptibility to climatic variables. Several studies conducted on the granular column using the bottom ash column. However, only a few studies have reported findings coherent with the statistical analysis. In this study, the lateral load capacity of bottom ash column-kaolin clay has been conducted. Coherently, the reinforced kaolin clay samples were tested via particle size distribution, Atterberg limit test, relative density, compaction test, permeability test, unconfined compression test, and unconsolidated undrained triaxial test with the single and group of encapsulated bottom ash columns with the geotextile encasement and a prediction model was developed. The effect of a number of columns, column diameter, column height, area replacement ratio, height penetration ratio, height-diameter column ratio, volume replacement ratio, and confining pressures on the shear strength of the single and group of encapsulated bottom ash columns have been investigated. The findings showed the effectiveness of using the bottom ash columns at various number of column, column diameter, column height, area replacement ratio, height penetration ratio, height-diameter column ratio, volume replacement ratio, and confining pressures can enhance the shear strength of the soil up to 77.00% at the optimal utilization of single encapsulated bottom ash column of 10-mm diameter and 80-mm height. Therefore, the study proved that the utilization of bottom ash waste as a granular column can significantly enhance the lateral load capacity of soft kaolin clay soil.

Experimental analysis of embankment on soft soil improved with bottom ash columns

Bottom ash is a byproduct formed during the combustion of coal and can be used as an alternative to aggregate and sand as a green material in columns to achieve sustainability in ground improvement. In this study, the bearing capacity performance of highway embankment models constructed on bottom ash columns reinforced soil was investigated. Model tests were carried out with various area replacement ratios (Ar) of 10.91 %, 16.37 % and 21.83 % and column length to diameter ratios (L/D) of 6 and 8. Load cell and three miniature pressure transducers were used for the measurement of vertical stress on the embankment surface, top and base of the column and adjacent soil surrounding the columns. A Pore pressure transducer was employed to record the excess-pore water pressure during the loading test. The stress concentration ratio and column failure modes were investigated for the stress transfer mechanism. The tests results revealed that bottom ash columns, whether floating or end bearing, was most effective in enhancing the ultimate bearing capacity (qult) of improved soil at almost 1.24, 1.39 and 1.63 times and 1.27, 1.42 and 1.83 times that of unreinforced soil for Ar of 10.91 %, 16.37 % and 21.83 % with L/D of 6 and 8, respectively. The stress concentration ratio (SCR) increased with higher Ar and L/D values. The highest improvement ratio was obtained for the model improved with bottom ash columns at Ar = 21.83 % and L/D = 8. The end-bearing bottom ash columns fail by bulging and floating bottom ash columns fail by bulging along with punching at the base. Furthermore, a mathematical expression with R2 = 0.9913 was developed for calculating the approximate qult. The approximate qult are in good agreement with actual qult. The findings of this study resulted in the utilization of bottom ash as a sustainable granular material in the column for the ground improvement underneath embankments.

Numerical analysis of embankment resting on floating bottom ash columns improved soft soil

The construction of embankment over soft clay is quite a challenging job for the geotechnical engineer, which may results in a large settlement, bearing failure and stability issues. Stone columns can be used to minimize the settlement and increase the bearing capacity in such conditions. This study was carried out to investigate the behaviour of bottom ash columns underneath embankments using numerical modelling. The soft soil improved with bottom ash columns under the embankment subjected to traffic-induced loading was simulated in Plaxis 3D foundation software. The study variables include three area replacement ratios (Ar) of 10%, 15% and 20% and two columns length of 5m and 7.5m. The results indicated that enlarging the Ar and length of columns significantly reduced the final settlement and consolidation time. The maximum settlement reduction of 58% was reported for the Ar of 20% with 7.5m column depth. The study suggests that bottom ash columns can be used to improve soft soil underneath the embankment.

Stabilization of Kaolin Clay Soil Reinforced with Single Encapsulated 20mm Diameter Bottom Ash Column

Ground improvement methods are used to reduce the weakness of soft clay, which is low strength and high compressibility. The stone column technique involves replacing any of the soil with crushed stone such as broken rocks or sand which is an efficient method of improving the strength parameters of soil. Bottom ash usage in materials of building will effectively decrease the buildup of the waste and hence protect the environment. This study is to determine the shear strength of kaolin soft clay reinforced with a 20 mm diameter single encapsulated bottom ash column with various lengths. The research will look into the physicomechanical qualities of the materials used, including subsoil and bottom ash. Three (3) batches of samples with each batch consists of five (5) samples were prepared by using compaction method. All kaolin samples with a diameter of 50mm and height of 100mm with single encapsulated bottom ash columns with various lengths which are 60mm, 80mm, and 100mm were tested under Unconfined Compression Test (UCT). The result illustrated that the strength of samples increases as the height and volume of encapsulated bottom ash column increases.

Settlement of soft soil treated with group of floating bottom ash columns

Settlement of soft soil treated with group of floating bottom ash columns

SHEAR STRENGTH OF SOFT CLAY REINFORCED WITH ENCASED LIME BOTTOM ASH COLUMN (ELBAC)

Soft clay soils are problematic soil that causes bearing capacity failure and excessive settlement, leading to severe damage to buildings and foundation. In this study, bottom ash is used to replace the natural aggregate while quicklime is used to increase the bonding between bottomash particles. This research is aimed to investigate the role of single encased lime bottom ash column (ELBAC) in improving the shear strength by using laboratory scale model. Kaolin is being used as soil sample while lime bottom ash as the reinforced column and the column is encased with non-woven geotextile. Laboratory tests are conducted to determine the physical properties of bottom ash, kaolin clay, and quicklime sample. Unconfined Compression Test (UCT) also used to test the shear strength of the reinforced kaolin samples. There are 21 kaolin samples being tested in this study and the dimension of the specimen used is 50mm in diameter and 100mm in height. However, there are two different types of the diameter of single lime bottom ash column being used which are 10mm and 16mm. The heights of the column are 60mm, 80mm and 100mm. The improvement of shear strength of single encapsulated lime bottom ash column with area replacement ratio of 4.00% (10mm column diameter) and 10.24% (16mm column diameter) are 43.58%, 50.00%, 49.17% and 38.08%, 42.67%, 32.75% at sample penetration ratio, Hc/Hs of 0.6, 0.8 and 1.0 respectively. It can be concluded that the shear strength of soft clay could be improved by the installation of the single encapsulated lime bottom ash column.

Enhancement of Soft Soil Behaviour by using Floating Bottom Ash Columns

The current disposition worldwide is for sustainable construction, and the application of by-products is one of the ways to achieve it. In this research, bottom ash was used as a substitute material in a granular column to decrease settlement and enhance the bearing capacity of soft soil. Bottom ash is a derivate of the coal burning process, it has similar engineering properties to sand and fine gravel. A set of reduced scale physical modelling tests were performed on floating bottom ash columns to assess the improvement in the bearing capacity of the composite ground. The results clearly showed that the bearing capacity of the model soil was greatly improved with the installation of bottom ash column sand. There was an obvious enhancement of the load capacity of the granular columns when they were encased. The usage of bottom ash instead of aggregate or sand for granular columns will reduce the project cost and it aligns with the goal of sustainable construction development.

THE UNDRAINED SHEAR STRENGTH OF SOFT CLAY REINFORCED WITH GROUP ENCAPSULATED LIME BOTTOM ASH COLUMNS

This research was aimed to investigate the role of group encapsulated lime bottom ash columns in improving the shear strength by using laboratory scale model. Kaolin was being used as soil sample and lime bottom ash as the reinforced columns. The reinforc ed kaolin samples were tested by using Unconfined Compression Test (UCT). A total 7 batches of kaolin sample had been tested and each batch consist of 3 specimens represent sample without lime bottom ash column, partially penetration and fully penetration for group lime bottom ash columns. The specimen used was 50 mm i n diameter and 100 mm in height . The height of the group columns was 60 mm, 80 mm and 100 mm with 10 mm and 16 mm column diameter . The group encapsulated lime bottom ash columns was installed in the triangular pattern, as it was much easier to maintain the location of installed columns and the spacing in between the columns. The improvement of shear strength of group encapsulated lime bottom ash columns with area replacement ratio of 12.00 % (1 0 mm column diameter) and 30.72 % (16 mm column diameter) was 29.00 %, 44.17 %, 29.75 % and 1.00 %, 3.92 %, 7.33 % at sample penetration ratio, H c /H s of 0.6, 0.8 and 1.0 respectively. It can be concluded that the shear strength of soft clay could be improv ed by the installation of group encapsulated lime bottom ash columns. However, the improvement of shear strength of 10 mm group encapsulated lime bottom ash columns was increased more significant compared to 16 mm group encapsulated lime bottom ash columns .

Bearing capacity of soft soil model treated with end-bearing bottom ash columns

Granular column technique is a soil improvement method used to increase the bearing capacity of a soft soil area by replacing the soil with a group of granular column materials. The by-product utilisation is a worldwide interest for sustainable infrastructure development. Bottom ash, which is a combustion deposit derived from coal burning, is a potential by-product that could be used alternatively to sand or aggregate as a green granular column material. This research is to study the potential use of the bottom ash column-improved soft clay by conducting a series of small-scale physical modelling test. The bearing capacity behaviour and failure mode of soft clay improved with end-bearing group of bottom ash columns with and without geotextile encasement are investigated. The bearing capacity of soft clay is significantly enhanced by the inclusion of bottom ash columns; that is, 239% of bearing capacity improvement is observed with only 13% of improvement area. The bulging of the bottom ash column is transferred to buckling failure with higher bearing capacity when the bottom ash column is encased by geotextile. The outcome of this research leads to the usage of bottom ash by-product as a granular column material in sustainable soil improvement technique.

SHEAR STRENGTH OF CLAY REINFORCED WITH SQUARE AND TRIANGULAR ARRANGEMENT OF GROUP ENCAPSULATED BOTTOM ASH COLUMNS

Soft clay is known to be a problematic soil that consists of low shear strength, low permeability and high compressibility where the existing soil on the given site is low with load bearing capacity, and by that ground improvement is required. Granular column methods are being used extensively as ground improvement technique for supporting a wide variety of structures and infrastructures. In practice, the bearing capacity on soft clay increased by a layer of compacted sand or gravel. Bottom ash as by product of coal burning that has similar properties to granular material can be applied as one of the stabilizing method to the existing soil. Hence, by using bottom ash as substitute, the cost of construction can be reduced and make great progress of a growing awareness of the sustainable engineering. This research discusses the results of the improvement in the shear strength of soft clay after being reinforced with a group of square and triangular encapsulated bottom ash columns. The physical and mechanical properties of the materials used such as kaolin and bottom ash were determined. The results show that kaolin can be classified ad clayey soil and bottom ash has similarities of characteristic with granular material. A total of 52 unconfined compression tests had been conducted on kaolin specimens to determine the shear strength. The diameter for specimen is 50mm and 100mm in height. The diameter of bottom ash columns are 10mm and 16 mm respectively and the height of the column are 60mm, 80 mm and 100mm. The group columns have been arranged in square and triangular pattern. It can be concluded that the shear strength parameters were improved based on the different diameter and the height of the column.

BEARING CAPACITY OF SOFT CLAY INSTALLED WITH SINGULAR AND GROUP OF ENCASED BOTTOM ASH COLUMNS

Due to limited availability of construction site, many constructions are now carried out on site of poor ground condition, including on the soft soils. Vertical stone column technique has proven capable to increase the shear strength of soil and drain out water from the ground, decreasing the settlement of the structure. It is believed that the utilisation of coal ash as alternative material in constructing stone column can contribute to a more sustainable construction environment. This paper aims to investigate the improvement of bearing capacity of soft kaolin after installing with singular and group of encased bottom ash column using physical modelling. The white kaolin S-300 was used to represent the soft clay while bottom ash obtained from Tanjung Bin Power Plant, Johor was used in the construction of the stone column. The presence of bottom ash stone column has significantly increased the bearing capacity of kaolin clay. The increment of the bearing capacity in soft kaolin clay is higher when it is reinforced with group of bottom ash column and when the penetration ratio is larger. The penetration ratio showed more significant influences to the bearing capacity of soft kaolin clay as compared to the number of bottom ash column installed in soft kaolin clay.

Shear Strength Parameters and Consolidation of Clay Reinforced with Single and Group Bottom Ash Columns

Stone column could be used as a ground improvement technique where a portion of the soil is replaced with granular material such as crushed rocks or sand which is proven to increase bearing capacity and accelerate the dissipation of pore water pressure. Since “bottom ash”, as the waste of coal burning, possesses similar properties to sand, there is a potential of using bottom ash as stone columns. This paper discusses the results of the improvement in shear strength parameters of clay when reinforced with single and group bottom ash columns (BAC). A total of 39 specimens of kaolin samples were isotropically consolidated and sheared using Consolidated Undrained Triaxial Tests with pore pressure measurement to determine the shear strength parameters. Test variables include the diameter and height of columns and effective confining pressure. Results indicate that the installation of BAC in clay specimens increased the apparent cohesion but did not show any significant difference in the effective friction angle. Generally, the apparent cohesion of soft clay reinforced with partially penetrating columns is higher than that of fully penetrating columns. It is also found that during consolidation, the dissipation of pore water pressure was accelerated with the presence of BAC. Hence, it can be concluded that the consolidation and shear strength of soft clay could be improved by the installation of BAC.

Modeling of Crystal Violet Adsorption by Bottom Ash Column

The removal of crystal violet from wastewater, by means of bottom ash, was investigated in a packed bed down-flow column. The bed depth service time (BDST) model was used to analyze the experimental data up to breakthrough time (corresponding to C(t)/C(0) = 0.1). A mass transfer model was used to analyze the mass transfer zone. The breakthrough curve was analyzed by the Thomas, Yoon-Nelson, and Clark models. All models fit well with the experimental data. Results showed that as the flow rate increases, at a constant concentration and bed depth, the value of the adsorption capacity of bottom ash decreases. The adsorption capacity of bottom ash decreases with an increase in depth and initial crystal violet concentration. Error analyses were performed for the Thomas, Yoon-Nelson, and Clark models. Water

Adsorption and desorption characteristics of crystal violet in bottom ash column

This study described adsorption of Crystal Violet (CV) by bottom ash in fixed-bed column mode. Equilibrium of adsorption was studied in batch mode for finding adsorption capacity of bottom ash. In fixed bed column adsorption, the effects of bed height, feed flow rate, and initial concentration were studied by assessing breakthrough curve. The slope of the breakthrough curve decreased with increasing bed height. The breakthrough time and exhaustion time were decreased with increasing influent CV concentration and flow rates. The effect of bed depth, flow rate and CV concentration on the adsorption column design parameters were analyzed. Bed depth service time (BDST) model was applied for analysis of crystal violet adsorption in the column. The adsorption capacity of bottom ash was calculated at 10% breakthrough point for different flow rates and concentrations. Desorption studies reveals that recovery of CV from bottom ash was effective by using CH3COOH than H2SO4, NaOH, HCl and NaCl solutions.

Batch and bulk removal of hazardous colouring agent Rose Bengal by adsorption techniques using bottom ash as adsorbent

Rose Bengal is a halogen-containing fluorescein water soluble dye, which is widely used for medical purposes. The dye, however, is highly toxic and can cause irritation, itching etc. to the human skin and eyes. It is therefore considered worthwhile to develop a systematic method for the removal of Rose Bengal by adsorption processes. The present investigation is devoted to batch as well as bulk removal of Rose Bengal. Under preliminary batch studies, adsorption isotherm measurements and kinetic studies were carried out, while for the bulk removal, a glass column was used as a fixed bed adsorber made up of Bottom Ash. Attempts were also made for the recovery of the dye from the exhausted Bottom Ash column by eluting dilute NaOH. The paper also presents a detailed procedure for activating Bottom Ash and its chemical and physical analysis. Rose Bengal showed a decrease in adsorption with increasing pH and conversely, increases in concentration, temperature, amount of adsorbent and sieve size increased the adsorption. Langmuir, Freundlich, Tempkin and D–R adsorption isotherm models were also verified, and on the basis of Langmuir constants thermodynamic parameters such as the Gibb's free energy, enthalpy and entropy of the adsorption were also calculated. A pseudo-second order process was found to operate during the adsorption. During column operations various parameters like fractional capacity of the column, mass flow rate, percentage saturation of column etc. were calculated. Desorption from the exhausted column gave almost 91% of dye recovery.

Process development for the batch and bulk removal and recovery of a hazardous, water-soluble azo dye (Metanil Yellow) by adsorption over waste materials (Bottom Ash and De-Oiled Soya)

Bottom Ash and De-Oiled Soya have been used as adsorbents for the removal of a hazardous azo dye—Metanil Yellow from its aqueous solutions. Adsorption of Metanil Yellow on these adsorbents has been studied as function of time, temperature, concentration and pH. Batch adsorption studies, kinetic studies and column operations enabled extraction of lethal dye from wastewaters. Adsorption equilibrium data confirms both Langmuir and Freundlich isotherm models and monolayer coverage of dye over adsorbents. Kinetic data have been employed to calculate specific rate constants, indicating thereby involvement of first order kinetics in the on-going adsorption and activation energy was determined as 0.813 and 1.060 kJ mol −1 for Bottom Ash and De-Oiled Soya, respectively. For both adsorbents, the adsorption process has been found governing by film diffusion, over the entire concentration range. Column operations have also been performed for the bulk removal of the dye and also to examine the practical utilization of fixed bed adsorption technique in elimination of dangerous effluent. Saturation factors for Bottom Ash and De-Oiled Soya columns have been calculated as 99.15 and 99.38%, respectively. Attempts have also been made to regenerate the dye from the exhausted columns using aqueous sodium hydroxide as eluent.

Process development for the removal and recovery of hazardous dye erythrosine from wastewater by waste materials—Bottom Ash and De-Oiled Soya as adsorbents

Erythrosine is a water-soluble xanthene class of dye. It is widely used as colorant in foods, textiles, drugs and cosmetics. It is highly toxic, causes various types of allergies, thyroid activities, carcinogenicity, DNA damage behaviour, neurotoxicity and xenoestrogen nature in the humans and animals. The photochemical and biochemical degradation of the erythrosine is not recommended due to formation of toxic by-products. The present paper is an attempt to remove erythrosine from wastewater using adsorption over Bottom Ash—a power plant waste and De-Oiled Soya—an agricultural waste. Under the batch studies, effect of concentration of dye, temperature, pH of the solution, dosage of adsorbents, sieve size of adsorbents, etc., have been studied for the uptake of the dye over both adsorbents. The adsorption process verifies Langmuir and Freundlich adsorption isotherms in both the cases and based on the data different thermodynamic parameters have been evaluated. Batch studies also include kinetic measurements, rate constant study, mass transfer behaviour and establishment of mechanistic pathway for both the cases. For the bulk removal of the dye column operations have been carried out and breakthrough capacities of the Bottom Ash and De-Oiled Soya columns have been calculated. Attempts have also been made for the recovery of the adsorbed dye from exhausted columns by eluting dilute NaOH and more than 90% of the dye was recovered.