Comparison of discrete element simulations to theoretical predictions of the elastic moduli of damaged rocks

损伤岩石弹性模量的离散元模拟与理论预测比较

International Journal of Rock Mechanics and Mining Sciences, Volume 88, October 2016, Pages 265-272

Steffen Abe

Abstract：The influence of damage, represented by a set of micro-cracks, on the elastic parameters of a solid is modeled using the Discrete Element Method (DEM). The results are compared with predictions from damage mechanics theory. In the simulated material, the observed dependence of the elastic parameters on the damage is qualitatively similar to the behavior theoretically predicted for a material containing a collection of micro-cracks which are frictionally sliding under compressive loading and opening under tension. Poisson's ratio of the DEM material is increasing with damage under compression and decreasing with damage under tension. Young's modulus decreases with increasing damage under compression and tension. Under compression the influence of the damage on Poisson's ratio and Young's modulus depends on the coefficient of friction on the crack surfaces, under tension it does not.

A damage plasticity model for different types of intact rock

不同种类完整岩石的损伤塑性模型

International Journal of Rock Mechanics and Mining Sciences, Volume 80, December 2015, Pages 402-411

D. Unteregger, B. Fuchs, G. Hofstetter

Abstract：A constitutive model for describing the nonlinear mechanical behavior of different types of intact rock subjected to complex 3D stress states is presented. It is formulated on the basis of a combination of plasticity theory and the theory of damage mechanics along the lines of a damage-plastic model for concrete. Irreversible deformations, associated with strain hardening and strain softening, as well as degradation of stiffness can be modeled. The material parameters and the model parameters are identified by means of an optimization procedure combining an evolutionary and gradient based optimization algorithm with niching strategy. The proposed model is validated by numerical simulations of laboratory experiments conducted on specimens of marble, granite and sandstone. The simulations are performed at integration point level. Thereby, the capability of capturing key features of the constitutive behavior of different types of intact rock is demonstrated. Finally, the application of the model to structural analyses is demonstrated by simulating a boundary value problem, including the formation of shear bands.

Analytical solutions for the stresses and deformations of deep tunnels in an elastic-brittle-plastic rock mass considering the damaged zone

弹脆塑岩体深部隧道损伤区应力与变形的解析解

Tunnelling and Underground Space Technology, Volume 58, September 2016, Pages 186-196

Mohammad Reza Zareifard, Ahmad Fahimifar

Abstract：The excavation impact (e.g. due to blasting, TBM drilling, etc.) induces an excavation damaged or disturbed zone around a tunnel. In this regard, in drill and blast method, the damage to the rock mass is more significant. In this zone, the stiffness and strength parameters of the surrounding rock mass are different. The real effect of a damage zone developed by an excavation impact around a tunnel, and its influence on the overall response of the tunnel is of interest to be quantified. In this paper, a fully analytical solution is proposed, for stresses and displacements around a tunnel, excavated in an elastic–brittle–plastic rock material compatible with linear Mohr–Coulomb criterion or a nonlinear Hoek–Brown failure criterion considering the effect of the damaged zone induced by the excavation impact. The initial stress state is assumed to be hydrostatic, and the damaged zone is assumed to have a cylindrical shape with varied parameters; thus, the problem is considered axial-symmetric. The proposed solution is used to explain the behavior of tunnels under different damage conditions. Illustrative examples are given to demonstrate the performance of the proposed method, and also to examine the effect of the damaged zone induced by the excavation impact. The results obtained by the proposed solution indicate that, the effects of the alteration of rock mass properties in the damaged zone may be considerable.

Rock damage assessment in a large unstable slope from microseismic monitoring - MMG Century mine (Queensland, Australia) case study

基于微震监测技术的不稳定大斜坡岩石损伤评估---澳大利亚昆士兰MMG世纪矿实例研究

Engineering Geology, Volume 210, 5 August 2016, Pages 45-56

M. Salvoni, P.M. Dight

Abstract：Movements, instability and failures in open pit mines can pose important geotechnical problems, leading to major impacts on the safety of personnel and the mining operations. In particular, large slope scale rockslides represent a significant challenge, as these types of instabilities require accurate observations and monitoring. However, in many cases engineers can only rely on surface displacements for their interpretation of the failure mechanism because there is no information on the extension of the deformation into the slope. More recently, several attempts have been made to monitor the volume of rock of unstable slope in open pit and natural slopes, using the microseismic technique. Nevertheless, the link between ground deformations, failure mechanism and microseismic data was rarely addressed in the details of these studies. In this paper, a case study of the SW Wall instability at Century mine (Queensland, Australia) is discussed. Since 2009, the pit wall has been affected by several multi-batter failures, associated with continuous bedding planes. Geotechnical investigations, supported by numerical modelling, have interpreted those instabilities as potential development of deep-seated failure. Consequently, in early 2013, the slope angle at the base of the slope was reduced and a buttress was left to avoid further progression of the instability into the lower section of the wall. Slope performance while mining has been primarily managed through surface monitoring (geodetic prisms and ground-based radar). However, as there were still concerns, a microseismic monitoring program was proposed by MMG geotechnical personnel and subsequently implemented. Our work integrated the approaches, analysing both ground deformation and microseismic data in order to reach a more complete understanding of rock damage at depth and mechanisms of instability.