Sensitivity Analysis and 3 D-displacement Inversion of Rock Parameters for High Steep Slope in Open-pit Mining
Due to the complexity of multiple rocks and multiple parameters circumstance, various parameters are often reduced to only one parameter empirically to generalize geological conditions, ignoring the really influential parameters. A developed method was presented as a complement to 3D displacement inversion to obtain the relative important parameters under complex conditions with limited computational work. Furthermore, this method was applied to a high steep slope in open-pit mining to investigate field applicability of the developed system. Back analysis was conducted in the reality of the east open-pit working area of Daye Iron Mine and propositional steps were presented for parameters solving in complex circumstance. Firstly, multi-factor and single-factor sensitivity analysis were carried out to classify rock mass and mechanical parameters respectively according to the extent of their effects on deformations. Secondly, based on the results, main influence factors were selected as inversion parameters and taken into a 3D calculating model to get the displacement field and stress field, all of which would be the artificial network training samples together with inversion parameters. Thirdly, taking the real deformations as input for the trained back propagation (BP) neural network, the real material mechanical parameters could be obtained. Finally, the results of trained neural network have been confirmed by field monitoring data and provide a reference to obtain the matter parameters in complicated environment for other similar projects.
Intelligent Back Analysis of Geotechnical Parameters for Soft Rock Mass Surrounding Tunnel using Grey Verhulst Model
We present a new method of intelligent back analysis (IBA) using Grey Verhulst model (GVM) and Burger−creep viscoplastic (CVISC) model of FLAC3D to identify geotechnical parameters of time−dependent rock mass surrounding tunnel, and validate it via a test for a new excavated drift at −350m level in Gangdong, DPRK. The displacement components used for back analysis are the crown settlement and sidewalls convergence monitored at the end of the tunnel excavation, and the final closure displacements predicted by GVM with the maximum stable deformation rate of 0.05mm/d. The relative error between displacements calculated from numerical simulation with back analysis parameters and in situ monitored ones was less than 8%. Hence, we conclude that the proposed method could be successfully applied to determine design parameters and stability of mine openings and stopes.
Time and Heritage
As a historian studying what can be considered a form of intellectual history, I have slowly come to adopt Michel de Certeau’s observation made at the end of the 1980s that ‘objectifying the past, for the last three centuries, has undoubtedly left unconsidered time within a discipline that has continued to use it as a taxonomic instrument’. To a certain degree, time has become commonplace for the historian who has preserved or instrumentalized it. It is not considered because it is inconceivable, but because we do not think of it or, more simply, we do not think about it. As a historian attempting to pay attention to the time I’m living in, I have thus, like many others, noticed the swift development of the category of the present until it has become obvious that the present is omnipresent. This is what I refer to here as ‘presentism’.