Browsing by Author "Rahman, Md. Mokhlesur"

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Disease and Health Condition of Tannery Workers, Fish Sellers, Mechanic Workers and Cleaners in Different Areas of Dhaka City
(East West University, 8/6/2015) Rahman, Md. Mokhlesur
The present study was designed to investigate the effect of chemical or metal on the physical health of the tannery workers, fish sellers, cleaners and mechanic workers in Dhaka city. Three hundred and fifty (100 tannery workers, 100 fish sellers, 51 cleaners and 100 mechanic workers) respondents were selected by purposive sampling method as samples for the present study The main objective of the present study was to investigate the effect of work environment on the physical health of workers. The specific objectives were: (i)To investigate overall physical health of the tannery workers, Fish sellers, Mechanic workers and Cleaners.(ii)To investigate which disease and symptom is most prominent among them. For Collecting data physical health questionnaires were applied on the respondents of the present research.
Effects of Sampling Disturbance on Mechanical Properties of Reconstituted Normally Consolidated And Overconsolidated Dhaka Clay
(Bangladesh University of Engineering & Technology (BUET), Dhaka, Bangladesh, 2010-09) Rahman, Md. Mokhlesur; Siddique, Prof. Dr. Abu
The present study has been carried out to investigate the effects of sampling disturbance on mechanical behaviour of reconstituted normally consolidated and overconsolidated Dhaka clay (OCR values of 2, 5, and 10). Disturbed Dhaka clay samples were collected from Rupnagar Housing Project, Mirpur-11, Dhaka. The clays were low to medium plasticity (LL = 47, PI= 26). Reconstituted normally consolidated samples of Dhaka clay were prepared in the laboratory by K0-consolidation of slurry in a large cylindrical consolidation cell using a consolidation pressure of 150 kN/m2 while overconsolidated samples having OCR values of 2, 5 and 10 were prepared by reducing the maximum pressure of 150 kN/m2 to 75 kNlm2, 30 kN/m2 and 15 kN/m2 respectively. "In situ" samples were prepared (by consolidating 38 mm diameter by 76 mm high specimens under K0-conditions in the triaxial cell) to its "in situ" stress state. "Tube" samples of various OCR values were prepared from the large diameter consolidated sample by inserting samplers of different area ratio, external diameter to thickness ratio (De/t) and outside cutting edge angle (OCA). The area ratio, D't ratio and OCA of the samplers varied from 16.4% to 73.1%, 27.3 to 8.3 and 5° to 20° respectively. Normally consolidated and overconsolidated "perfect" samples were prepared from respective "in situ" samples by undrained release of the total stress in the triaxial cell. Undrained triaxial compression tests were carried out on "in situ", "tube" and "perfect" samples. "Tube" and "perfect" samples having OCR values of 2 and 10 were also reconsolidated isotropically and anisotropically under K0-condition using Bjerrum (CKoU-1.0o'vc) and SHANSEP (-1.5' and -2.5o'vc) procedures. Disturbance due to perfect and tube sampling have significant influence on the mechanical properties of normally consolidated and overconsolidated Dhaka clay. Disturbance due to perfect sampling led to reduction in the values of s and Ap while Ei, E50 and €p increased caused due to total stress relief. Because of perfect sampling undrained strength (sn) reduced up to 8.2% while, axial strain at peak deviator stress (€p) increased up to 20.9% for samples of OCR value of 10. Due to perfect sampling pore pressure parameter at peak deviator stress (Ap) reduced up to 90% while, initial tangent modulus (E1) and secant stiffness at peak half deviator stress (E50) increased up to 14.0% and 19% respectively for normally consolidated sample. Due to total stress relief for perfect sampling disturbance, the reduction in su increases with increase in OCR while, the increase in E, E50 reduce with increase in OCR. The initial effective stress (ϐ'i) of "tube" samples reduced considerably because of disturbance caused by penetration of tubes. Compared with "in situ" samples, values of su, Ei, E50 and Ap of the "tube" samples reduced while εp increased. Changes in measured soil parameters between the "in situ" and "tube" samples have been found to depend significantly on the sampler characteristics (area ratio, De/t ratio and OCA) used for retrieving the "tube" samples. The values of ϐi, Su, and Ei were reduced up to 26.211/o, 43% and 62% respectively for normally consolidated sample due to increase in area ratio from 16.4% to 73.1% (or reduction in Delt ratio from 27.3 to 8.3). The respective reductions for normally consolidated sample due to increase in OCA from 4° to 15° are 21.9%, 38% and 60%. Values of εp for OCR values of 1 and 5, increased up to 57.7% and 52.6% due to increase in area ratio and OCA respectively. A quantitative increase in the degree of disturbance (Dd) has been obtained due to increase in area ratio and OCA. The results indicates that compared with normally consolidated reconstituted Dhaka Clay, tube sampling causes relatively little degree of disturbance in overconsolidated reconstituted Dhaka Clay. The reduction in initial effective stress due to tube sampling reduces with increase in OCR. The increase in value of c, due tube sampling reduces with increasing OCR. For tube sampling disturbance, trend of small decrease in the reduction of su/ ϐ'vc, Ei / ϐ'vc,, and E50 / ϐ'vc obtain with increasing OCR. However, significant increase in reduction of A with increasing OCR has been observed. It appeared that for good quality sampling, a sampler ought to have a well combination of area ratio and OCA. In order to reduce disturbance due to sampling in soft Dhaka clay, area ratio and OCA of sampler should be kept practically as low as possible. A connection curve has been provided from the plot of strength ratio versus overconsolidation ratio for samples of Dhaka clay. This correction curve can be used to find the perfectly undisturbed strength of the tube samples retrieved of Dhaka clay for use in analyses and designs. Isotropic reconsolidation (CIU-1.0c') has the effect of gross overestimation of "in situ" strength, c,,. and E1 for the "tube" and "perfect" samples. It has been found that compared with SI-IANSEP procedures reconsolidation using Bjerrum procedure (CKoU-1.0 ϐ') for both "tube" and "perfect" samples of overconsolidated Dhaka clay, produced the best overall estimate of the "in situ" properties in terms of undrained strength, stiffness, strain and pore pressure response.
Environmental Impacts of Entrepreneurial Fisheries in Barind Tract
(University of Rajshahi, Rajshahi, 2020) Rahman, Md. Mokhlesur; Islam, M. Nazrul
The gradual increase in fish production of Bangladesh is primarily attributed to the increased inland aquaculture especially from the entrepreneurial fisheries. Entrepreneurial fisheries in Barind Tract has also gained traction in the last several years like the few other top fish producing districts of Bangladesh. In four Barind districts (Bogura, Joypurhat, Naogoan, and Rajshahi), pond area and fish production have increased by 41.39% and 134.25% respectively in 2017-18 than that of 2007-08. In this process, thousands of hectares of the seasonal floodplain, paddy fields, and perennial wetlands have been purposely converted into large fishponds for entrepreneurial fisheries in Barind Tract. Since entrepreneurial fisheries are commercial ventures, these are also capital and input-intensive. Not only the intensity (quantity/unit area) of inputs but also the sheer volume (spread) of entrepreneurial fisheries has made it a new but significant farming system in Barind Tract hence deserves a closer look in terms of environmental impacts. Since a large number of paddy fields have been converted into entrepreneurial fishponds, input use was compared between entrepreneurial fisheries and paddy production in this study through a questionnaire-based survey. Additionally, the faunal diversity, especially aquatic invertebrates (aquatic insects, zooplankton and benthos) and water quality parameters, macro, and micro soil nutrients and heavy metal contents of the bottom sediments of entrepreneurial fishponds were compared with those of natural wetlands. Several experiments were conducted to know the impacts of various pesticides, hormones, and fish toxicants used in entrepreneurial fisheries on aquatic invertebrates and human health. To know the social impact of entrepreneurial fisheries, focus group the discussion was conducted. The current study revealed that the entrepreneurial fishponds were purposely built hence large (average size of more than an acre water area) in size with 5 to 10 feet water depth depending on the season and rearing of large-sized Indian major carps and Chinese carps. Of all the entrepreneurial fishponds, 61.5% of the ponds were located in areas that used to be seasonal floodplain, whereas 23.1% of the ponds were constructed by transforming paddy fields and 15.4% ponds were constructed through the transformation of perennial wetland.
Investigation of Strength and Deformation Characteristics of Cement and Lime Treated Soft Clays
(Bangladesh University of Engineering & Technology (BUET), Dhaka, Bangladesh, 2008-07) Rahman, Md. Mokhlesur; Siddique, Prof. Dr. Abu
This thesis presents experimental and numerical investigations for the effects of cement and lime treatment on compressibility, permeability, stress-strain, strength and stiffness behaviour of three soft clays. Effects of cement treatment on physiochemical and micro-structural properties have also been investigated. X-ray Diffraction, Scanning Electron Microscopy, particle size distribution, pH measurement, organic content, electrical conductivity, cation exchange capacity, exchangeable cation, water content, unit weight, specific gravity, and Atterberg limits tests were conducted to examine physiochemical and micro-structural properties. Compressibility and permeability properties of untreatcd and, cement and lime treated clays were investigated by performing one-dimensional consolidation tests. Stressstrain, strength and stiffness behaviour of untreated and, cement and lime treated clays were evaluated by performing unconfined compression (UC) tests. Consolidated drained direct shear (OS), unconsolidated undrained (UU), isotropically consolidated undrained (CIU) and isotropically consolidated drained (CID) triaxial compression tests were also carried out to assess the stress, deformation and strength properties of cement treated clays. Sets of variables considered in the testing program include a wide range for type of clay (PI = 13% to 47%), type of admixture, clay-water/cement ratio (2 to 30), curing time (1 to 104 weeks), mixing water content (120% to 250%) and effective confining pressure (50 kPa to 400 kPa). Finally, applicability of different constitutive models and Cap models were assessed for the predictions of drained and undrained behaviour. It has been observed that pH value, electrical conductivity (EC), cation exchange capacity (CEC), increases with decreasing clay-water/cement ratio. pH value, however, decreases while EC and CEC value increases with increasing curing time. Loss on ignition and organic matter decreases due to increasing cement content and with increasing curing time. The relative amount of cementitious product (CSH + CASH) was identified by the XRD analysis and found to increase with the increase of cement content and curing time. Due to the formation of cementitious product, the fabric of the treated clays changed to flocculated type, comprising of clay-cement clusters separated by large inter-cluster voids with smaller intracluster pores as seen from the SEM images of treated clays. These changes were more pronounced with higher cement content and longer curing time. The significant increase in yield stress and reduction in compression index (Ce) and swell index (Cs) were observed with increasing admixture (cement/lime) content and increasing curing time. Ce and Cs for lime treated clays were found to be greater than those of cement treated clays. Ce and Cs values increase significantly with the increase of mixing clay-water content. The lime-treated clays gained comparatively higher void ratio and volumetric strains and lower yield stress than those of cement-treated clays. The effect of cementation is to increase the values of coefficient of consolidation (cv) and coefficient of volume compressibility (mv). The higher the admixture content and curing time, the lower is the values of cv and mv. cv and mv values for lime treated clay were found to be higher than those of cement treated clay. A substantial increase in the value of cv and mv was found to have occurred within higher mixing water content. At higher stress level, progressive destructuration of the treated clay particles occurred, which has been verified from the SEM images of cement treated clay compressed at different consolidation pressure. Addition of admixture to the clay increases the permeability and void of the soils, due to flocculation of the soil particles, which has been seen from SEM images. The Intrinsic Compression Line (ICL) and Generalized Compression Line (GCL) have been proposed for the untreated and treated clays. Coefficient of permeability (k) and void ratio relationships have also been proposed for cement and lime treated clays. The values of k of cement and lime treated clays have been found to reduce with increasing cement or lime content and curing period. Values of k for lime treated clays were found to be higher than those of cement treated clays. Based on the rate of strength development with time, the unconfined compressive strength and cement content relationships have been divided into 3 zones: Inactive Zone, Active Zone and Inert Zone. Since the behaviour of cement treated clays was remarkably governed by we/e, the strength prediction in terms of we/e as well as the interrelationship involving strength, curing time and clay-water content/cement content ratio (we/e) have been proposed. From stress-strain relationships, the overall behaviour has been categorized into brittle, quasi-brittle and ductile. Comparatively, brittle, quasi-brittle and ductile types for the cement treated clays, while quasi-brittle and ductile types for the lime treated clays have been found. The correlation between yield stress, (σy') and unconfined compressive strength (qu), τf0 and qu axial strain at failure (εf) and qu, and stiffness (Ei and E50) and qu have also been proposed. In direct shear test, for cement treated clays, vertical expansion (dilation) was observed at low normal stress and experienced vertical contractions or settlement throughout the shearing stage at higher normal stress. The cohesion and friction angle have been increased with increasing cement content and curing time. The undrained effective stress paths of the cement treated clays obtained from CIU triaxial compression tests indicate that the stress paths belong to different category of states such as normally consolidated, lightly, moderately and heavily over-consolidated state. The degree of alteration have been found different for different samples depending on the amount of cement content, curing time and pre-shear effective consolidation pressure. Upon reaching the peak deviator stress in CIU triaxial test, the progressive destructuration takes place and thus the stress path tends to move either on the I-Ivorslev envelope or envelope of strain softening behaviour. SEM results have been suggested that complete destructuration takes place only on the shear plane at which the clay-cement cluster crushes. The prevalent role of pre-shear effective consolidation pressure was manifested to annihilate the cementation effect attributing ductility to the treated matrix. The main effect of cement treatment was to modify the behaviour of the soft clay form normally consolidated to over-consolidated state. Similar natures of deviator stress-axial strain and volumetric strain-axial sirain relationships were observed for all samples having the identical wclc ratio in cm triaxial tests. So, the wclc is a prime parameter governing the engineering behaviour of cement treated samples having different mixing water content. For cement treated clays, peak deviator stress (qmax) criterion of failure envelopes can be used as obtained from CIU and CID triaxial compression tests. The degree of overall curvature of the failure envelope for each type of clay depends on the range of consolidation stresses and hence increases with increasing cement content and curing time. The values of soil constants λ and κ for the treated clays have been found to be less than those for the untreated clays while the values of the constant N and M are greater for the cement treated clays than those of untreated clays. At a particular curing time, the soil constants λ and κ decreased, while the constant N and M increased with increasing cement content. Correlations between the soil constants λ, κ and N with plasticity index have been proposed. Hvorslev surface was established for the cemented clays. No definite Roscoe surface could be found for cemented clays. For the untreated clay, it has been observed that the predicted stress paths, deviator stresses, volumetric strains and excess pore pressure responses at small strain levels using the MCC model appear to be significantly close to experimental curves. It appears from the present study that MCC, MMCC, EMMCC and Cap models (Plane Cap and Elliptic Cap) cannot be applied for predictions of drained and undrained behaviour of cemented clays at high water content.
Use of Smokeless Tobacco by Low Socio-Economic Populations and Risk Factors Associated with it
(2015-03-04) Shahjahan, Dr. Md.; Rahman, Prof. Dr. M. Mizanur; Kabir, Prof. Dr. M.; Rahman, Md. Mokhlesur; Chowdhury, Dr. ABM Alauddin
Despite the national and international collaborative efforts and commitment of World Health Organization through Framework Convention on Tobacco Control (FCTC), prevalence of tobacco consumption is facing an increasing trend. If disaggregated analysis on smokeless forms and smoked forms are reviewed prevalence of smokeless tobacco remain static. Cost, social acceptability and non-stringent rule in smokeless product sales have made people to choose and continue on smokeless tobacco use. This study is aimed to investigate the use of smokeless tobacco among low socio-economic populations around Dhaka city to investigate in-depth situation in this context.