Rock mass failure occurs either through slipping in the joints or rupture of intact rock between the discontinuities. Mode of failure can be predicted by knowing stress and strain level in the rock mass. In this paper, using the finite difference simulation of rock mass with parallel fractures under stripped foundation loads, the effects of the load direction are studied for different dip direction of joints in the rock mass. The stress and strain distribution are presented in some applicable graphs. The results are argued and compared with the other theoretical results.
Existence of joint, results in many alterations in mechanical behavior of a rock mass. This may even Increase the Poisson's ratio to 0.92 that is impossible in continuum media [1]. Kind and quantity of displacement is also extremely dependent on allocation of joints [2] and as the joint type and it's orientation change, the behavior of the rock mass may be completely different. Then specific investigation and simulation must be fulfilled to study existing condition in a media. In this article mechanical behavior of a rock mass containing parallel joints which bears load of a strip foundation is examined. As the angle of joints is assumed to be constant, the effect of loading angle on initiation of stress and strain is studied. Fast Lagrangian Analysis of Continua (FLAC). Studying this reaction helps to achieve a general pattern of joint behavior which could improve our understand of rock mass behavior which contains joints. There are other factors such as roughness of joint surface, stiffness, existence of fluid, surrounding temperature, etc that affects rock behavior but aren't included here.
Properties of the rock mass that are assumed in this analysis are: mass density ñ = 2.4 t /m3, bulk modulus K = 5.21 Gpa, shearing modulus G = 3.906 Gpa,Yuang modulus E = 9.376 Gpa. The following equations are presented by Goodman [3] and FLAC manual [4] to calculate shear stiffness () s K and Normal stiffness () n K of jointsen't included here. Geometry of joints is shown in Fig. 1 where T, s are joint dimensions. Width of model is 53 m and its height is 15 m, which joint distances (T) and the number of layers to be 1m and 53 m respectively. Fig. 1 shows geometry of joints. A 592 strip loading which has 3 m width with Infinite length is exerted on the middle layers. Layer direction's angle with vertical axis is called θ (positively measured clockwise) and loading direction angle with the vertical is called β that is measured counterclockwise too. Fig. 2 shows nine point that are selected in the system for standing deformation. B in this figure is equal to width of stripe foundation (i.e. B=3 m). Horizontal and vertical space between selected points are equal to B and 1.5B respectively.
