HYDRAULIC FRACTURING WITH PARTICULAR REFERENCE TO SOIL CYLINDERS

Abstract

Hydraulic fracturing is a live problem these days in the field of geotechnical engineering. The application of the concept of hydraulic fracturing to geotechnical problems, and in particular, to the development of cracks in the core of earth dams due to excessive hydraulic pressure is a matter of concern to researchers and design engineers. Cracks which develop in the impervious core of earth dams and cause leakage, have been observed in Hyttejuvet dam (Norway), Balderhead dam (England) and Teton dam (USA)• Hydraulic fracturing is also known to be one of the major causes of loss of drilling fluid through bore-holes in impervious cores of embankment dams. Hydraulic, fracturing is also important in other fields such as in oil exploration, determination of in-situ stresses, evaluation of allowable grout pressures and the pressure in piezometers for determination of in-situ permeability. The induced cracking in soil mass due to excessive hydrau-lic pressure is called 'Hydraulic Fracturing'. Hydraulic frac-turing would cause water to penetrate through very fine cracks and then would force them to open wider. The changes in the total stresses which occur in the core of embankment dams during construction, reservoir filling and subsequent drawdowns, test boreholes and grouting are extrem-ely complex and affect the safety against hydraulic fracturing. The contradictory opinions about the parameters involved indi-cate that a comprehensive investigation is necessary to have iv a clear insight into the mechanism of hydraulic fracturing. A detailed experimental. investigation has been carried out here, in order to study the effect of some of the para-meters involved in the mechanism of hydraulic fracturing under laboratory controlled conditions. The main factors investigat-ed are; moisture content, confining pressures, degree of satu-ration, type and rate of hydraulic pressure application, ten-sile strength of the soil, types of the soil, pattern of cracks and anisotropy of pressure application.....