M. Engg.

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Study on Pile Cap Design
(Bangladesh Institute of Technology (BIT), Khulna, Bangladesh., 2001-11) Masum, Mir Md. Al; Hossain, Prof. Dr. Md. Monjur
Piles are used to transfer the loads from the superstructure down to the soil stratum. where the required resistance is available. Unless a single pile is used, a pile cap is necessary to spread the vertical and horizontal loads and any overturning moment to all the piles in the group. Unlike footing the base reaction of pile cap Consists of a number of concentrated load. Different methods of designing pile caps are in practice. Those are Broadly classified as ACI Building Code and strut-and-lie model (STM). In this project the cost incurred by different design approaches are compared. The cost of pile caps according to different approaches is compared considering 4 pile -cap with constant pile diameter and column size but with varying pile spacing. The comparison reveals that the pile cap designed by STM costs 5% to 20% lower than AC Building Code for pile spacing 2 to 3 times pile diameter within a range of 75 to 625 kip of column load. The experimental ultimate strength of the pile caps is compared with that obtained by different design approaches. The behavior of pile cap at loading stage is also observed and is seen to agree with other investigators. It is seen that the experimental strength of pile caps is higher than the strength predicted by the STM in comparison to ACI Building Code. Within the limitation of pile spacing up to 3 times pile diameter, modified STM is more rational than ACI Building Code in terms of cost and integrity.
Determination of In Situ Soil Density by Sand Cone Method Using Locally Available Sands
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh., 2005-12) Rashid, A. B. M. Mamunur; Bashar, Prof. Dr. Md. Abul
In Bangladesh Ottawa sand is used to find out in situ soil density using Sand Cone Method. Ottawa sand is very expensive and it is always imported from abroad. Usually it requires much time to import this item. Instead of Ottawa sand, Sand Cone Method might use locally available sand as an alternative material for determining in situ soil density. In Bangladesh, local sand is available in abundance and compared with Ottawa sand it is also much cheaper in price. In this research the quality and suitability of locally available sand in and around Khulna district are assessed for determining in situ density using Sand Cone Method. Five samples of sand named by Sylhet sand, Kushtia sand, Fultala sand, Bogjhuri sand and Mongla sand were collected from nearby business centers. Original sand and some graded sands of each sample were under investigation to ascertain their suitability of use in lieu of Ottawa sand in determining in situ soil density. Four gradations were considered and those were (i) passing # 16 and retained in # 30, (ii) passing # 30 and retained in # 40, (iii) passing # 40 and retained in # 50 (iv) passing #30 and retained in # 50 sieve. Each of the original samples has been characterized by determining its index properties, Grain size distribution. Specific gravity and density are determined for each sample of original and graded sands. These properties are compared with those recommended by ASTM (1989) for selecting suitable sand in Sand Cone Method. From this study it was found that original sands of all selected places in Bangladesh did not satisfy the ASTM (1989) criteria for Ottawa sand. In case of graded sands, Sylhet sand satisfied all the required ASTM criteria for four gradations, while Kushtia and Fultala sands satisfied fully for three gradations except the gradation passing # 16 and retained in # 30 sieve. Bogjhuri and Mongla sands did not satisfy all the required criteria. So, the above graded sands that satisfy the criteria of Ottawa sand as mentioned in investigation can be used in sand cone method in lieu of costly Ottawa sand.
Study on Selection of Suitable Foundation for Khulna City Corporation Area
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh., 2006-11) Razzaque, Md. Abdur; Hossain, Prof. Or. Md. Monjur
The soil condition of Khulna City Corporation (KCC) area is different from other places due to its very soft nature up to a great depth and the existence of peat layer. As a result, the selection of suitable foundation type is a challenging job for the geotechnical engineer. In this region, even for a small project, a sub-soil condition is required to reveal completely for the safe design of structure. Since sub-soil exploration is expensive and time consuming, an evaluation of sub-soil condition in a comprehensive way may help designer in this context for the selection of suitable foundation for KCC area. In this study, samples were collected by auger boring from I 09 points within KCC. From test results of these samples and using correlation equations, the parameters are calculated. The samples from auger are disturbed sample from which moisture content, liquid limit, plastic limit and specific gravity are obtained. Unconfined compressive strength (qu) and compression index (Cc) are the important parameters for design purpose for which undisturbed samples are required. For these tests sample collection, preparation and testing need considerable amount of refinement, precaution and time, with the result that the procedure is costly. This situation calls for an alternative method by which this issue can be addressed. Correlation equation is available in literature verified in the context of Khulna soil. For this purpose available existing soil reports (202 nos.) were studied for where 617 nos. value· for qu and 2 IO nos. value for Cc were collected. Using existing correlation equations q0 and Cc were calculated from corresponding values of moisture content, liquid limit, plastic limit and specific gravity. Comparing the actual and calculated values, it was observed that the actual value of qu is approximately 1.98 times more than the correlation equations qu value and Cc is approximately 1.09 times more than the correlation equation Cc value, which means the q, and Cc from equation were much conservative and safe for structure. From the result of collected existing 112 nos. bore log and 109 nos. auger boring, the position and depth of peat layer are described. By combination auger boring and existing 202 nos. soil reports, the profile of q, and Cc are prepared. From this profile, q, and Cc may be measured from different places. The position of peat layer and instant observation water table are shown. The results accomplished in the study can be used by the practicing engineers as a background information for the selection of suitable foundation in KCC areas for the construction of relevant structures.
Correlation Between Penetrometer Test Value and Bearing Capacity for Granular Soil
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh., 2007-01) Quader, Md. Golam; Bashar, Prof. Dr. Md. Abul
In the present study, an attempt to investigate the correlation between hand penetrometer test value and bearing capacity of granular soil especially sand, was under consideration. To achieve this goal artificial sand beds of thirteen samples were prepared in an open test bed above the ground surface, and on these samples, direct shear test and field density test were carried out to find out the friction angle and the field density of each sample. Bearing capacity of sandy soil were predicted from Terzaghi's bearing capacity equation for strip footing. Three penetrometers of different diameters (18.75 mm, 25 mm and 31.25 mm) were especially fabricated and used to find out penetrometer test value. The test procedure of these penetrometers is similar to standard penetration test (SPT) by split spoon sampler, but diameter of penetrometers, weight of hammer and height of fall were different. To correlate between hand penetrometer test value, friction angle and bearing capacity, seven equations have been established for hand penetrometer of three different diameters. It has been found that there established better correlations between friction angle and hand penetrometer test value for three penetrometers with high coefficient of correlations. In the investigation it has observed that there exists a best correlation between friction angle and bearing capacity of granular soil (sand). Finally it has been found that there are good correlations between hand penetrometer test value and bearing capacity of granular soil for any diameter of penetrometer with coefficient of correlation from 0.79 to 0.96.
Study on the Performance of Rice Husk Ash as a Cementing Material
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh., 2007-05) Khan, Md. Azad Hossain; Hossain, Prof. Dr. Md. Monjur
Utilization of rice husk has become subject of growing interest. The possibilities of its utilization of rice husk in various ways have evoked much interest due to its high silica content. Particularly in the developing countries of South-east Asia where the production of rice is more than half of the production of entire world. Most important among various methods suggested for the utilization, is the development of construction materials from rice husk as such and from its ash. For every 1000 kg of paddy milled, about 220 kg (22%) of husk is produced, and when this husk is burnt in the boilers, about 55 kg (25%) of rice husk ash (RHA) is obtained. Rice husk ash is a great threat to environment causing damage to the land and surrounding area in which it is dumped. Rice husk burnt at 450CC have been found to produce a pozzolana conforming to the requirements of the ASTM standard C618-72. Therefore, valuable product from this rice hush ash (RHA) is possible. The rice husk For the study was collected from rice husking mill and was burnt in muffle furnace in laboratory (at 450°C) for 60 minutes. Rice husk is found to contain about 76.53 % organic volatile matter and the balance 23.47 % as ash (Table 3.7). The rice husk ash was grounded in laboratory by using Industrial Ball Mill to the form of powder. The particles finer than 200 meshes was collected for further test. The new product of RHA cement sample was tested for properties like Ordinary Portland Cement. RAH cement made in this study contains ash, lime and clay in different ratio. For this purpose a typical samples at the beginning was made with RHA (60%) mixed with finely grounded lime (30%) and un-burnt clay (10%). Similar samples were made with burnt (800 °C) clay. The result between two are found to agree. Rest of the cement samples were made with Un-burnt clay and burnt clay. Results of these samples are shown in table no. 4.1, 4.2, 4.3, 4.4, 4.5. By discussion the test results we find that, (a) in case of un-burnt clay, average water-cement ratio required for cement paste of normal consistency (CPNC) was found to be 0.56, initial setting time was found to be 96 minutes, final setting time was found to be 6 hrs. 58 minutes. and 3 days compressive strength for cement mortar cube was found to be 171 psi. respectively. (b) in case of burnt clay, average water- cement ratio required for cement paste of normal consistency (CJNC) was found to be 0.56, initial setting time was found to be 96 minutes. final setting time was found to be 7 hrs.13 minutes and 3 days compressive strength for cement mortar cube was found to be175 psi respectively. These values when compared with those of Ordinary Portland Cement, it was found that in case of un-burnt clay, CPNC varied only 7%, initial setting time was double than OPC, final setting time was increased by one hour than OPC. (b) in case of burnt clay, CPNC was found to be 0.56, initial setting time was found to be more than double than OPC, final setting time was increased by one and half hour than OPC and 3 days compressive strength was found to be 175 psi. It is clear from the study that RHA can be attributed cementing property when combined with lime and clay. The properties of this cement resembles with those of OPC with compromise of' higher setting time and lower strength. However this may be recommended for the cases where lower strength can be used (e.g., boundary walls, normal load bearing residential buildings, partition walls, surface drains etc.)
Characterization of Khulan Subsoil and Settlement Response of This Soil Improved by Granular Fills
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh., 2012-12) Alam, Md. Shamsul; Bashar, Prof. Dr. Md. Abul
The study area, Khulna City Corporation (KCC) is one of the important urban areas in the South-West part of Bangladesh. In the present study the whole KCC area was subdivided into three zones: North, Middle and South. In the North Zone (Afilgate, Shiromoni, Fulbarigate, Mohesshorpasha, etc) it is found that the soil layers between 0 12 m from EGL are mostly clayey silt. In this stratum there exists an organic clay layer with the variation of 3 m to 6 m depth in most of the locations. The soil layers between the depth of 12 in to 18 m at the northeast part of the North zone, which is near Bhairab river, contain predominantly sand, while in the areas namely Fulbarigate, KUET campus the soil at this depth contains predominantly silt. In the middle zone (Khalishpur, Daulatpur, Boyra, Mujgunni, etc.) it is found that the sub-soil in the western side contains an organic layer of 3m to 4.5 m thickness starting from about 1.5m to 3m depth to downward. Below this depth the soil consists of predominantly silt up to about 18 in depth. In the eastern side of this zone the soil contains predominantly silt up to about 6m to 7.5m depth. Below this depth the soil contains mainly fine sand. In the South zone (Sonadanga, Nirala, Gollamari, Sheikhpara, West side of Rupsha, Khulna University, etc) the sub-soil contains organic clay up to about 3m to 4.5m depth from EGL. Below this level the soil mainly consists of silt with small portion of clay and organic matters up to about 18 m depth from EGL. From the model test it was found that the load carrying capacity of soft soil can be increased significantly by adopting ground improvement technique with filling sand under foundations. The rate of settlement of the test footing on untreated ground increased substantially after the settlement of the ground exceeds 20mm. It is also evident that the load bearing capacity of treated grounds do not depend on the depth of filling only but also on the width of granular fills. From the experiment, it was seen that the load bearing capacity was increased by replacement of soft soil with granular materials (sand) at the bottom of the foundation up to 1.95 times than that of untreated soil. The load bearing capacity of treated soil was significantly increased with the increase of depth of sand filling under foundation. The bearing capacity was increased by 30%, 72% and 85% with the increase of filling depth by 1.0, 1.5 and 2 times the width of foundation respectively when area of foundation is equal to area of sand filling. For the granular fills of depth 150 mm(D1Bf , the degrees of improvement were found as 30%, 56% and 59% higher than that of untreated condition when width of filling were 1 Bf, 21 Bf, and 313f respectively. So, it was exhibited that for constant depth ((Ds= 1 Bf) of compacted sand, bearing capacity was increased significantly up to the width of sand filling equal to twice the width of foundation. In case of sand fills of depth 225 mm (Ds=1 .5Bf), the degrees of improvement were found as 72%, 79% and 8 1 % higher than that of untreated condition when width of filling were 1Bf, 2.51Bf, and 4Bf respectively. From this it is observed that for constant depth (Ds=1.5Bf) of compacted sand, bearing capacity was increased significantly up to the width of sand filling equal to 2.5 times the width of foundation. When the depth of granular fills was increased up to 300 mm (Ds=2Bf , the degrees of improvement were observed as 85%, 92% and 95% higher than that of untreated condition when width of filling were 1 Bf, 3 Bf and 5Bf respectively, it is observed from this result that for constant depth ((Ds=2Bf) of compacted sand, bearing capacity was increased significantly up to the width of sand filling equal to 3 times the width of foundation.