nCORETech-16

Abstract: The influence of position of water table and magnitude of hydraulic gradient on the behaviour of a strip footing resting on a cohesive soil is investigated by carrying out a series of finite element analyses using the software PLAXIS 2D. The results of finite element analyses are compared with those obtained from conventional mathematical models. It is observed that the effect of magnitude of hydraulic gradient is much more pronounced than the effect of position of water table. The results obtained from finite element analyses with respect to position of water table slightly differ from those obtained from conventional analyses. Keywords: Water Table, Hydraulic Gradient, Finite Element Analysis, Mathematical Model.

Abstract: Concrete is the most widely used construction material. To meet the growing infrastructure and industrial needs, huge quantities of concrete is required, which, in turn, means that large volumes of natural resources and raw materials are being used for concrete production around the world. To eliminate or minimize the negative environmental impact of the concrete industry and promote environmental sustainability of the industry, the use of waste from industries as materials for concrete making is considered as an alternative solution for preventing the excessive usage of raw materials. The wide availability of industrial wastes makes them a suitable and dependable alternative for aggregate in concrete, wherever available. In this paper, an attempt is made to present a state of the art review of papers on replacement of aggregates and fillers by industrial waste. This paper reviews the possible use of industrial wastes such as sludge wastes from marble cutting industries, sewage treatment plants, water treatment plants, paper industries etc as aggregate in the concrete industry. It aims to promote the idea of using these wastes by elaborating upon their mechanical properties. This summary of existing knowledge about the successful use of industrial wastes in the concrete industry helps to identify other existing waste products for use in concrete making. From this identification by industrial and civil engineers, significant achievements can be attained. Keywords: industrial waste, aggregate, cement, concrete.

Abstract: A briquette is a block of compressed coal, biomass or charcoal dust that is used as fuel to start and maintain fire. Briquetting is a mechanical compaction process for increasing the density of bulky materials. This process is used for forming fine particles into a designed shape. It can be regarded as a waste control measure in the case of production of briquettes from agricultural wastes. However, depending on the material of interest, briquetting can be used to provide fuel source as a preventive measure to many ecological problems. Briquetting is a high-pressure process which can be done at elevated temperature or at ambient temperature depending on the technology one wants to employ. Various briquetting machines have been designed, ranging from very simple types which are manually operated to more complex ones mechanically or electrically powered. Generally, briquetting operations have developed in two directions, mechanically compression (hydraulic or pistons) and worm screw pressing types. Currently available in Western India Plywood, produced sawdust briquettes have suboptimal densities, causing incomplete burn and excess smoke. Here I made Attempts to improve this technology, particularly by adjusting the screw length to diameter ratio, the screw rotation speed, feed pressure, and residence time in the extension chamber as a means of producing a higher-density, better quality briquette. Keywords: Briquette, Sawdust, Plywood, Redesign.

Abstract: This paper presents results of a series of finite element analyses carried out to determine the behaviour of a Reinforced Granular Bed (RGB) overlying clayey soil. The beneficial effects of prestressing the reinforcement is also studied. The interface shear parameters under various conditions were determined by carrying out large scale direct shear tests on Geogrid Reinforced Sand using a shear box of size 300 x 300 x 200mm. It is observed that the beneficial effects of prestressing the reinforcement also depends upon the geometric parameters of the RGB. Keywords: Finite element analyses, shear strength parameters, shear box, reinforced granular bed, strip footing.

Abstract: Construction and maintenance of embankments form an integral part of every highway or railway projects which are keystones of the economy of our nation. In many locations good soil will not be available for the foundation and also for the construction of embankment. In such cases reinforcing soil with geosynthetic is a very effective and economic option. This paper thoroughly reviews the improvements in load settlement behaviour of embankments attained by inclusion of various forms of natural and polymeric geosynthetics. It is seen from literature that natural geosynthetics made with coir or jute can also be effectively used for improving the durability and stability of embankments. Keywords: Embankments, Natural geosynthetics, Polymeric geosynthetics, Stability of embankments.

Abstract: Voids may be natural or manmade .The calcareous sediment rocks contain voids as they are susceptible to water dissolution. The voids could also be the result of activities like mining, tunnelling etc .These voids either continuous or discrete, impose a hitch in the smooth designing of foundations. The problem is further aggravated as the foundation is to be designed to withstand seismic forces. The systematic scientific study of the effect of underground voids on the stability of foundation began by mid eighties of the last Century as some laboratory level investigations were initiated in conjunction with numerical studies using Finite Element Method. A series of investigations led to the conclusion that the depth and eccentricity of voids play a vital role in the analysis of stability of foundation. There exists a critical depth and a critical eccentricity beyond which the effect of a void becomes insignificant. Efforts were on to reduce the magnitude of the critical depth and eccentricity. A certain depth of top weak soil can be replaced by a layer of granular fill and the footing made to rest on this prepared layer. The performance can be further improved by reinforcing the granular fill with geo-synthetics .The geo-synthetic reinforcement possess the inherent drawback of excessive settlement during the initial stages of loading which adversely affects the performance of footing over voids. Recent developments in laboratory investigations reveal that this issue can be overcome by using pre-stressed reinforced granular beds, which reduces the initial settlement considerably. The challenge in the present scenario is the economical application of laboratory findings in in-situ activities giving due share to the durability aspects of the Pre-stressed Reinforced Granular Bed. Keywords: Underground Void , Critical depth , Critical Eccentricity , Multiple Voids , Granular Bed , Prestressed Reinforced Granular Bed.

Abstract: In this paper the results of a series of finite element analyses carried out to investigate the improvement in bearing capacity of a strip footing resting on a weak clayey soil with voids due to the addition of a Reinforced Foundation Bed are presented. The results of finite element analyses are validated by carrying out laboratory scale load tests. From the results of finite element analyses it is seen that the effect of void is considerable only when it is located within a critical depth and critical eccentricity. The critical eccentricity is found to reduce with depth of void from the base of footing. It is observed that the addition of Foundation Bed (FB) and Reinforced Foundation Bed (RFB) significantly improves the load-settlement behaviour. It is also observed that there is considerable stress concentration near the underground void. Keywords: Underground void, Reinforced Foundation Bed, Finite Element Analyses, Stress Concentration.

Abstract: Civil infrastructure systems such as highways, bridges, buildings represent the skeleton of any nation. The deterioration of bridges in many countries in the last few decades calls for effective methods for condition evaluation and maintenance. Since there is increasing dependency of the society on infrastructure systems such as bridges, proper design and timely monitoring and maintenance is essential. However, various factors such as neglect, overuse and lack of proper inspection and monitoring has led to accelerated deterioration of bridges, Often, unsatisfactory inspection and monitoring leads to detection of damage only at the critical state where repair cost becomes comparable with replacement cost. Assessing the extent of damage and its speedy restoration essentially requires information about the current and previous states of health of the structure. Hence there is a need for continuous monitoring of the health of the structure. This has resulted in the development of several non-destructive testing (NDT) techniques for monitoring their performance. The concept of non destructive testing (NDT) is to obtain material properties of in place specimens without the destruction of the specimen or the structure from which it is taken. It can provide knowledge that may not be possible to deduce from visual observation alone. Successful NDT tests allow locating and characterizing material conditions which might not be visible on the surface but which affects the structural durability or performance. This paper reviews various NDT methods that are currently being used in conjunction with the condition assessment of bridge component when subject to cracking, fracture and other unseen damage cases, specifically focusing on Rebound hammer Test and ultrasonic pulse velocity Test. Also this paper reviews three case studies conducted in India, Malaysia and Turkey. The case study from India determines the quality and strength of a T-beam girder bridge. 75 concrete bridges under the supervision of Public Works Department, Malaysia and 10 out of 200 reinforced concrete bridges (i.e. 10 most deficient bridges) in Turkey were selected to determine the strength and to establish a correlation between visual inspection rating and the non-destructive testing results. The investigation shows that the use of non-destructive testing methods can help reduce the backlog of deficient bridges in two ways. First, these techniques will allow inspectors to get a more accurate view of the condition of a bridge. The second way is by allowing inspectors to locate damages earlier. The studies also show that Ultrasonic pulse velocity Test is the ideal NDT method to predict the deterioration in the structures and to determine the service life of the structures. And there exists a correlation between results of non-destructive tests and condition states based on visual inspections. Keywords: non-destructive testing, rebound hammer test, Ultrasonic Pulse velocity method, Case Studies.

Abstract: Reinforced soil is being extensively used for various Ground Improvement applications due to its effectiveness and durability. The load-settlement behaviour of Reinforced Soil depends upon the interaction between the reinforcement and surrounding granular soil. This paper investigates the effect of gradation of surrounding soil on the interface shear parameters, by carrying out a series of large scale direct shear tests using a shear box of dimensions 300 x 300 x 200mm.Tests were conducted on five no coarse aggregate (CA) and sand (S) with varying mix ratio of 1:0.5, 1:1, 1:1.5 and 1:2and separately for coarse aggregate and sand also. It is observed that gradation of soil, shear parameters and aperture of Geogrid considerably influences the interface shear parameters between the Geogrid and surrounding soil. Keywords: Reinforced Soil, Load-Settlement Behaviour, Gradation, Interface Shear Parameters.