Analytical And Experimental Studies On Underreamed Pile As Anchor Foundation In Soft Clay

Vol. 4  Issue 3
Year: 2014
Issue: Jun-Aug
Title:Analytical And Experimental Studies On Underreamed Pile As Anchor Foundation In Soft Clay
Author Name:Y.S.Golait, Prasad Dahale and Jiwatode.R.N.
Synopsis:
Foundations of several civil engineering structures are required to be designed as anchor foundations. The analysis and design of deep anchors in clays are considered by very few researchers and investigators in the reported literature. Conspicuously this aspect appears to be inadequately investigated. The paper attempts to highlight the analysis of deep anchors in soft clays by proposing an idealized load transfer mechanism and the mode of failure of this soil-foundation system. The presently used foundation element for resting light structures on expansive soils, in the form of an underreamed pile, is proposed to be used as an effective deep anchor. With reference to this soil-under-reamed pile system, analytical as well as experimental studies are carried out. The analysis led to a simple and easy way to use equation for estimating the pullout load capacity of ground anchors, in clays of medium to soft consistency. In order to evaluate the validity of theoretical formulation, a detailed experimental program was undertaken. The model studies incorporated under-reamed pile models of three shaft diameters with under-reaming ratio of 2.5, four values of depth factors. The clay 2 soil used in studies had cu=0.24 kg/cm . The observed failure loads were compared with the computed values which revealed that, for under-reamed piles having length larger than 8 times the shaft diameter, there was very close agreement between the above two values.

Granular Pile Anchors For Soft Soils

Vol. 4  Issue 3
Year: 2014
Issue: Jun-Aug
Title:Granular Pile Anchors For Soft Soils
Author Name:Eswara Reddy.O, Madhav.M.R , Saibaba Reddy.E and Vidyaranya Bandi
Synopsis:
Soft soils need to be improved to make them suitable for construction. Granular Piles (GP) are effective and economical solutions to improve the behavior of the soft soil by increasing bearing capacity, reducing settlements due to reinforcement. Granular piles due to their inherent advantage are effective in countering swell pressures from expansive clays. Installation process of GPs densifies the ground adjacent to GPs inducing additional benefit. Advantages of GP to resist compressive and shear loads are well documented and attempts to extend its utility to resist tensile loads is being investigated. An anchor is placed at the base of granular pile and attached to the footing by a cable or rod which transfers applied pullout force to the bottom of GP. Such an assembly is termed as 'Granular Pile Anchor' (GPA). Experimental study on laboratory models of GPA in clayey sand for different compaction properties lead to different undrained shear strength and stress – strain characteristics. Pullout resistance derived from pile capacity is mainly affected due to the variation in undrained shear strength with depth. Results are presented as variations of load – displacement responses and failure patterns for three different undrained shear strength values.

An Experimental Investigation On CBR Improvement Of Sand-Flyash Mix Using Geogrid Layers

Vol. 4  Issue 3
Year: 2014
Issue: Jun-Aug
Title:An Experimental Investigation On CBR Improvement Of Sand-Flyash Mix Using Geogrid Layers
Author Name:Rajiv Chauhan and R.Sharma
Synopsis:
Development of an adequate network of roads, especially in remote rural areas is of vital importance for the socioeconomic development of a country. Search is being made to find alternative materials, for use in pavement construction. Fly ash, lime and cement are the commonly used materials for soil stabilization. Geosynthetics, Geotextiles and Geo-grids are also used nowadays in roads for subgrade improvement in road construction. This paper presents the laboratory CBR test results conducted on sandy soil mix with fly ash for unreinforced and reinforced cases. The reinforcement was done using geogrids in layers at different depths in CBR mould. The fly ash was varied from 15% to 35% in sand sample. All the tests were conducted at Optimum moisture content (OMC) and maximum dry density (MDD) of mixes. The results of California Bearing Ratio (CBR) tests have shown considerable improvement with the use of reinforcement. The maximum increase in CBR value with Geo- grid was observed with the 2 layers of Geo-grid use. The increase in value of CBR was from 6% for virgin soil to 13% with use of geogrids.

Reducing The Life Cycle Cost of Reinforced Concrete Structures by using Fiber in Concrete

Vol. 4  Issue 3
Year: 2014
Issue: Jun-Aug
Title:Reducing The Life Cycle Cost of Reinforced Concrete Structures by using Fiber in Concrete
Author Name:Badrinarayan Rath, Shirish Deo and Gangadhar Ramtekkar
Synopsis:
A major challenge for concrete in today’s engineering is to build structures with lowest possible life cycle cost for sustainability. One of the major problems with reinforced concrete structures is the corrosion of steel reinforcement. It is one of the primary causes of premature deterioration of RCC (Reinforced Cement concrete) structures. The damage caused by corrosion seriously limits the service life of many concrete structures. The cost to rehabilitate these deteriorated concrete structures is expensive. As a result, over the past two decades, extensive research has been conducted to improve the durability of existing and new concrete reinforced structures. Plain concrete is a brittle material, with low tensile strength and strain capacities. To help overcome these problems, there has been a steady increase over the past years in the use of fibre reinforced cements and concretes (FRC). In general, the most important advantage of adopting Steel Fiber Reinforced Concrete (SFRC) is the increase of tensile strength, enhancement of toughness and increased resistance to crack propagation with the help of stress transfer from the matrix to the fibres. Addition of fibres has also shown modest increase in compressive strength. FRC thus exhibits strain hardening behaviour after first cracking as well as improvement in energy absorption capacity. Reduction of cracks shall increase initiation period of corrosion of reinforcement in RCC by many years, thereby increasing durability and reducing service life cost of the structure

Hydraulics of Fluid Flow in a Single Cohesive Crack: A Review of Some Basic Concepts

Vol. 4  Issue 2
Year: 2014
Issue: Mar-May
Title:Hydraulics of Fluid Flow in a Single Cohesive Crack: A Review of Some Basic Concepts
Author Name:K. K. Pandey and V. Kumar
Synopsis:
Present review discusses the scope and limitations of basic equations of continuity and momentum used in the study of flow behavior in single crack. The continuity equation for liquid flow used in the literature does not account for source and sink which occurs during crack wall leakages. In two-phase continuity equation, inter-phase transfer terms have been identified to be used as source or sink terms. Navier-Stokes momentum equation and its simplifications under various assumptions, leading to derivations of Stokes and Reynolds equations, and their limitations along with computational difficulty in crack flow problems is discussed. Emergence of Local Cubic Law (LCL) equation and its limitations has been indicated. Validity of LCL equation has been tested in the literatures under the influence of various factors. The relative importance of inertial and viscous forces show that LCL equation is valid for Reynolds number of 10 and a non-linear relation between pressure gradient and volumetric flow rate need to be used when Reynolds number is between 10 and 100. The use of scaling law used in the fracture mechanics shows that in smooth walled fracture, the volumetric flow rate vary with fifth power of crack aperture and so this law is termed as 'quintic' law. There are few published works in literature to study the effect of slip boundary condition in deriving the correction factor in hydraulic conductivity of fracture using Beaver-Joseph slip boundary conditions in case of smooth permeable fracture walls. Some works have shown that formulation of momentum equation for different flow regimes of two phase flow in cracks is a difficult task.

Relationship Between The Optimum Usage Of Copper Slag As Fine Aggregate And Compressive Strength In Copper Slag Admixed Concrete

Vol. 4  Issue 2
Year: 2014
Issue: Mar-May
Title:Relationship Between The Optimum Usage Of Copper Slag As Fine Aggregate And Compressive Strength In Copper Slag Admixed Concrete
Author Name:Binaya Patnaik, Seshadri Sekhar. T and Srinivasa Rao
Synopsis:
The rapid urbanization and natural resources scarcity had created a huge demand for non-conventional resources in the construction industry. Copper slag, which is a by-product obtained during the refining and metal smelting process of Copper Ore having Silica (SiO ) as a major composition, could potentially be used as a partial replacement of Sand in 2 the manufacturing of Concrete. In the present Experimental Investigation, for M30 grade of Concrete, fine aggregate (River Sand) was partially replaced with Copper Slag from 0% to 50% and compressive strength at the ages of 28 & 90 days were investigated. Finally, mathematical equations were derived for compressive strength at 28 & 90 days with percentage of Copper Slag used as partial replacement of Fine aggregate in copper slag admixed concrete.

Plastic Optic Fiber (POF) Based Phase Difference Measurement Method For Estimation Of Crack Mouth Opening Displacement (CMOD) In Concrete

Vol. 4  Issue 2
Year: 2014
Issue: Mar-May
Title:Plastic Optic Fiber (POF) Based Phase Difference Measurement Method For Estimation Of Crack Mouth Opening Displacement (CMOD) In Concrete
Author Name:K. Samrajyam, B. Sobha, T. D. Gunneswara Rao and R.L.N. Sai Prasad
Synopsis:
Crack detection and measurement of crack width in concrete are important for structural health monitoring of structures. In this paper, we report on a technique for estimation of crack mouth opening displacement ((CMOD) in concrete specimens of M20 composition. It is based on the principle of using Plastic Optical Fiber(POF) based strain displacement sensor employing phase difference measurement technique. The motivation for the method has been to improve on the sensitivity of detection of crack width measurement and propagation by looking at the phase changes rather than amplitude changes as attempted earlier by the authors.