Civil Engineering
http://repository.iitgn.ac.in/handle/123456789/387
2017-10-23T20:49:34ZFlow past a sand mining pit
http://repository.iitgn.ac.in/handle/123456789/3211
Flow past a sand mining pit
Joshi, Pariveeksha
In the present thesis, evolution of bed due to sand mining is studied by one dimensional flow and sediment modeling using HEC-RAS 5 (Hydrologic Engineering Centre � River Analysis) Software. HEC-RAS uses continuity and momentum equations for water flow and sediment continuity equation for sediment flow. The governing partial differential equations are solved using an implicit finite difference scheme. A numerical model is constructed in HEC RAS. The numerical model is validated using experimental data available in literature. In addition, the numerical model is also validated simulating by reproducing the experimental results obtained at Hydraulics Laboratory at IIT Gandhinagar. The numerical model is used to study the evolution of a hypothetical channel bed. Effects of flow characteristics, pit characteristics and sediment characteristics on bed evolution due to sand mining are studied. It is found that the sediment carrying capacity of water increases with discharge but this relationship is not linear. Also if the discharge is made fluctuating, rather than constant during the simulation time, the head cutting and pit migration increases. The pit migration and pit filling rate is found to be greatly affected by the shape of pit. The depth of the pit does not affect the upstream and downstream erosion but sediment deposition in the pit increases with the increase in pit depth up to a certain limit. Whereas, on doubling the pit width, the deposition in the pit is also doubled. The location of pit and number of mining pits is also found to be affecting the bed morphology.
2017-01-01T00:00:00ZDesign methodology of ash dyke using geosynthetics considering hydraulic conditions
http://repository.iitgn.ac.in/handle/123456789/3212
Design methodology of ash dyke using geosynthetics considering hydraulic conditions
Soni, Shubham
Ash dyke is an earthen embankment which is constructed at every thermal power plant for disposal of fly ash slurry. Seepage of water takes place into the dyke from the fly ash slurry. In order to control the seepage inside the dyke, conventionally ash dyke is provided with chimney and blanket drains, which required sand as a drainage material. Today sand is not often available at various sites in sufficient quantity and required quality. Hence, for dyke construction sand is transported from other locations. Transportation cost of such a huge quantity of sand from long distance can substantially increase the cost of construction. The deficit in availability of sand in dyke construction motivates to find an alternative solution. The various geosynthetics material like geotextile, geonet, geomembrane, geocomposite and perforated pipes are available. These materials are being used in various geotechnical structures like retaining wall, filter for rock toe, drainage trench for highway, liners for landfill and many more applications. In all the above structures functions performed by geosynthetics are similar to the function of chimney and blanket drain in ash dyke. The objective is to design ash dyke system such that, it does not require substantial amount of sand in dyke construction. Instead, it will use geosynthetics materials for proper functioning. Two alternative designs of ash dyke system have been proposed, and both of these have application of geosynthetics material to control the seepage in dyke body. These alternative designs are �ash dyke with vertical drainage composite� and �ash dyke with horizontal drainage composite�. The design of Ash dyke with vertical drainage composite is similar to the ash dyke with chimney drain. It consists of vertical drainage composite, drainage trench, horizontal drainage system and horizontal drainage composite. In this design a vertical drainage composite is placed at centre of the dyke to collect seepage water, which is connected to the drainage trench. A horizontal drainage system consisting of lateral pipes having initial portion perforated is connected to drainage trench, which collects seepage water from drainage trench and drain out from the dyke body. A drainage composite is also provided in downstream side of the dyke to collect seepage from foundation soil. Ash dyke with horizontal drainage composite consists of horizontal layers of drainage composite and down slope drainage system. Drainage composite in the dyke is installed in layers at different levels and top drainage composite is extended vertically up to height of fill slurry to collect seepage water. Arrangement of horizontal composite is depends upon the quantity of seepage. These drainage composites are connected to the downslope drainage system to drain out the seepage water. In both the alternate design raising of ash dyke is done by upstream method of raising. The methods proposed in this study have been developed to design each component of both the alternative ash dyke system by using the theories developed in the literature for the design of geosynthetics in above mentioned other structures. Also detailed specifications and various factors to be considered in the design of each component of ash dyke have been proposed. A step by step construction procedure for both the alternative designs has been proposed and a design example problem is solved for future reference.
2017-01-01T00:00:00ZEffect of in-plane boundary conditions on buckling and post buckling response of thin plates under uni-axial compression/in-plane shear
http://repository.iitgn.ac.in/handle/123456789/3208
Effect of in-plane boundary conditions on buckling and post buckling response of thin plates under uni-axial compression/in-plane shear
Botlapati, Sri Sahith
The present investigation comprises study on the buckling and the post buckling behaviour of thin plates with and without a cutout. The plate is subjected to a uniform uni-axial compression and/or in-plane shear. Both isotropic and laminated composite plates are considered. The instability behaviour of the plate is governed by its in-plane stress distribution which in turn is dependent on physical parameters like in-plane boundary conditions. In fact this aspect has not been covered effectively in earlier studies. That is why this is the main focus of the present investigation. The finite element analysis has been used to simulate the buckling and the post buckling response of plates with various in-plane boundary conditions using ANSYS v17.2. Results show that in-plane boundary conditions notably influence the buckling load and the post buckling response of plates. The investigation is carried out to obtain stress distribution plots, eigen values, mode shapes and load-displacement curves for a plate with different aspect ratios. The study is also extended to show the effect of in-plane boundary conditions on the buckling and the post buckling response of a [�300] angle-ply laminate and a cross-ply laminate plate under uni-axial compression. Effect of aspect ratio of the plate is also taken into consideration.
2017-01-01T00:00:00ZSimplified 1-D modeling of duo-pile system subjected to lateral loads
http://repository.iitgn.ac.in/handle/123456789/3210
Simplified 1-D modeling of duo-pile system subjected to lateral loads
Kolli, Mohan Krishna
Duo-pile (two piles connected by a beam) can be used as foundation system for elevated railways and highways. The design of foundation system for these types of structures is very critical with respect to lateral deflection which can affect serviceability and the stability of superstructure, as well. Duo-pile systems response can be estimated by three-dimensional (3-D) and as well one-dimensional (1-D) numerical (Finite element) modelling. Although 3-D models can simulate real scenario accurately but due to their sophisticated and time consuming nature 1-D models are very much in practice. In this study firstly, duo-pile behavior is studied from its 3-D response. Duo-pile system which can transfer moments in its longitudinal direction is much different from single pile response, hence, separate treatment for both transverse and longitudinal behavior of duo-pile system is to be given. Spring constants for beam and piles have been found out individually for using those in the combined duo-pile model. Spring constants for pile are proposed by considering the interactions prevailing in the system. A new type of interaction spring is introduced to capture couple effect. By integrating all the beam and pile springs, a simplified 1-D model for duo-pile system is proposed for both transverse and longitudinal response which can give approximate results with respect to 3-D modelling. By using the proposed model potential location of plastic hinges have been also found out.
2017-01-01T00:00:00Z