Measurement of Suction for Fly Ashes

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Measurement of Suction for Fly Ashes

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Bilkeesa Jan1, Dr. Esar Ahmad2

1Post Graduate Scholar, Civil Engineering Dept., Mewar University, Chittorgarh

2Professor & HOD, Civil Engineering Dept., Mewar University, Chittorgarh Rajasthan

Abstract:- Fly ash has found wide application in agriculture, landfill liners and covers, etc. where its water retention relationship becomes important. Water retention relationship is defined by a graphical relationship between the water content (gravimetric or volumetric) and the negative pressure or suction existing in the geomaterial. Such a relationship is termed as water retention characteristic curve (WRCC) or in general water content suction relationship (WSR). In this study, WSR of Indian fly ashes and a pond ash has been developed based on spot measurement. The main objective of this study is to understand the variation in WSR of different fly ashes. Being a cohesionless material it is presumed that the suction range will be less in fly ash. Therefore, a tensiometer is used for measuring suction in fly ash. Volumetric water content of the compacted samples has been measured using electronic probes. Calibration of these probes is very important for getting correct values of volumetric water content and hence specific calibration equations has been determined for each of the fly ashes studied. The results were used to determine parameters for WSR, using different WSR fitting functions available in the literature. Based on these parameters and saturated hydraulic conductivity, unsaturated hydraulic conductivity function for different fly ashes has been established. Such functions are required for modeling unsaturated flow through compacted fly ash.

Keyword: Suction, water retention characteristic curve, gravimetric water content, Fly ash, compacted sample, tensiometer, electronic probes, parameter, unsaturated hydraulic conductivity.

1. INTRODUCTION

Some projects in geotechnical, hydrological and environmental engineering are associated with saturated and unsaturated flow through geomaterial . External factors such as rain infiltration cause variations in water content and consequently the pore water pressure, affecting not only the shear strength, but also the hydraulic conductivity. These days fly ash has found wide application in agriculture, landfill liners and covers, where its water retention characteristics become important. Water retention characteristics are generally defined as a graphical relationship between the water content (gravimetric or volumetric) and the negative pressure or suction existing in the geomaterial. Such a relationship is termed as water retention characteristic curve (WRCC) or in general water- content suction relationship (WSR). There are several methods for determining WSR in the laboratory and in the field.

2. TESTING METHODOLOGY

Measurement of suction and establishing water suction relationship (WSR) is important for the study of the unsaturated soil behaviour. This WSR relationship is required for determining different unsaturated property function and modelling the behaviour of unsaturated geomaterial. With

this in view this deals with an explanation of suction, WSR and the instruments used in present study for suction measurement. The description of volumetric water content probes, its principle of measurement for fly ash is discussed.

2.1 Measurement of Volumetric Water ContentMeasurement of suctionT5 Tensiometer

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