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Rock Mechanics.pdf - Mining and Blasting

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PRINCIPLES OF CLASSICAL STRESS ANALYSIS<br />

functions <strong>and</strong> of a complex variable z, in the form<br />

U = R[z(z) + (z)]<br />

= 1<br />

[z(z) + z(z) + (z) + (z)] (6.9)<br />

2<br />

Expressions for the stress components may then be established from U (equation<br />

6.9) by successive differentiation. The displacements are obtained by setting up explicit<br />

expressions for the normal strain components εxx <strong>and</strong> εyy in terms of the stress<br />

components, <strong>and</strong> integrating. It is then found that stresses <strong>and</strong> displacements are given<br />

by<br />

where<br />

<strong>and</strong><br />

xx + yy = 4R[ ′ (z)]<br />

−xx + yy + 2ixy = 2[¯z ′′ (z) + ′ (z)] (6.10)<br />

2G(ux + iuy) =−[(z) − z ′ (z) − (z)]<br />

(z) = ′ (z)<br />

= 3 − 4 for plane strain<br />

In applying these results, it is often useful to invoke the transformation between the<br />

rectangular Cartesian <strong>and</strong> cylindrical polar co-ordinates, given in complex variable<br />

form by<br />

rr + = xx + yy<br />

−rr + + 2ir = [−xx + yy + 2ixy]e i2<br />

(6.11)<br />

The solution to particular problems in two dimensions involves selection of suitable<br />

forms of the analytic functions (z) <strong>and</strong> (z). Many useful solutions involve<br />

polynomials in z or z−1 . For example, one may take<br />

(z) = 2cz, (z) = d<br />

(6.12)<br />

z<br />

where c <strong>and</strong> d are real.<br />

Using the relations 6.9 <strong>and</strong> 6.10, equation 6.11 yields<br />

so that<br />

171<br />

rr + = 2c<br />

−rr + + 2ir =− 2d<br />

r 2<br />

rr = c + d<br />

r 2<br />

= c − d<br />

r 2<br />

r = 0<br />

(6.13)

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