EFFECT OF RATE OF LOADING ON STRENGTH OF ROCK

Abstract

The static, rapid and shock loading response of rock is of interest to many in field of rock mechanics. Drilling, mining and blasting of rock like materials, insitu fracturing, rock fragmentation size and permeability are strongly affected by rates of loading. The influence of rate of loadihg on the mechanical response of rocks are also important because these data are needed in calculations of ground motion and gas containment in explosively formed underground cavities, and for prediction of fragment sizes and distributions formed by percussive rock fragmentation. it is therefore very essential to understand the strengh and deformation behaviour of rock under varying rates of loading so as to assess the realistic rock engineering parameters for the design purpose. With this objective in mind, samples of micaceous sand stone and lime stone are brought from Hardwar and Rishikesh respectively and tested in the laboratory in order to know the "Effect of rate of loading on strength of rock". The samples of red sand stone are obtained from Geotechnical laboraory. The effect of rate of loading on stress strain characteristics, strength, failure strain and tangent modulus have been studied. The samples are tested at natural moisture content. This study comprises of preparation and testing of rock cores of 38 mm diameter with length to diameter ratio 2.0, confirming to IS: 9179-1979 and IS: 9143-1979 besides detailed analysis of test data. The statistical analysis of data are carried out by the least square method and correlation coefficient and standard error in estimation is also computed. The analysis of data indicate that strength is a weak and chaotic function of rate of loading, because no fixed pattern of variation in strength and modulus of elasticity is obtained with rate of loading. Failure strain is found to decrease or remain constant with increase in rate of loading. (