Zonal disintegration mechanism of deep crack-weakened rock masses under dynamic unloading

Size and quantity of fractured zone and non-fractured zone are controlled by cracks contained in deep rock masses. Zonal disintegration mechanism is strongly dependent on the interaction among cracks. The strong interaction among cracks is investigated using stress superposition principle and the Chebyshev polynomials expansion of the pseudo-traction. It is found from numerical results that crack nucleation, growth and coalescence lead to failure of deep crack-weakened rock masses. The stress redistribution around the surrounding rock mass induced by unloading excavation is studied. The effect of the excavation time on nucleation, growth, interaction and coalescence of cracks was analyzed. Moreover, the influence of the excavation time on the size and quantity of fractured zone and non-fractured zone was given. When the excavation time is short, zonal disintegration phenomenon may occur in deep rock masses. It is shown from numerical results that the size and quantity of fractured zone increase with decreasing excavation time, and the size and quantity of fractured zone increase with the increasing value of in-situ geostress.

[1]  John W. Hutchinson,et al.  Dynamic Fracture Mechanics , 1990 .

[2]  Yang Haiqing,et al.  STRENGTH CRITERIA OF DEEP ROCK MASS , 2008 .

[3]  É. A. Tropp,et al.  Zonal disintegration of rocks around underground workings. Part II: Rock fracture simulated in equivalent materials , 1986 .

[4]  W. C. Cooley,et al.  Mechanics of Brittle Fracture , 1982 .

[5]  Ming Cai,et al.  Generalized crack initiation and crack damage stress thresholds of brittle rock masses near underground excavations , 2004 .

[6]  S. Nemat-Nasser,et al.  Brittle failure in compression: splitting faulting and brittle-ductile transition , 1986, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[7]  Hideyuki Horii,et al.  A constitutive model and FEM analysis of jointed rock masses , 1993 .

[8]  É. A. Tropp,et al.  Zonal disintegration of rocks around underground workings, Part 1: Data of in situ observations , 1986 .

[9]  Qian Qihu.  ZONAL FRACTURING MECHANISM IN DEEP TUNNEL , 2007 .

[10]  A. Gerasoulis.  The use of piecewise quadratic polynomials for the solution of singular integral equations of Cauchy type , 1982 .

[11]  Xiaoping Zhou,et al.  Zonal fracturing mechanism in deep crack-weakened rock masses , 2008 .

[12]  Xiaoping Zhou,et al.  The Constitutive Relation of Crack-Weakened Rock Masses under Axial-Dimensional Unloading , 2008 .

[13]  Jian Niu,et al.  Analysis of Asymmetric Kinked Cracks of Arbitrary Size, Location and Orientation – Part I. Remote Compression , 1998 .

[14]  Kevin K. Lo,et al.  Analysis of Branched Cracks , 1978 .

[15]  É. A. Tropp,et al.  Zonal disintegration of rocks around underground mines, part III: Theoretical concepts , 1987 .