Composite wedge failure using photogrammetric measurements and DFN-DEM modelling

Analysis and prediction of structural instabilities in open pit mines are an important design and operational consideration for ensuring safety and productivity of the operation. Unstable wedges and blocks occurring at the surface of the pit walls may be identified through three-dimensional(3D) image analysis combined with the discrete fracture network(DFN) approach. Kinematic analysis based on polyhedral modelling can be used for first pass analysis but cannot capture composite failure mechanisms involving both structurally controlled and rock mass progressive failures. A methodology is proposed in this paper to overcome such limitations by coupling DFN models with geomechanical simulations based on the discrete element method(DEM). Further, high resolution photogrammetric data are used to identify valid model scenarios. An identified wedge failure that occurred in an Australian coal mine is used to validate the methodology. In this particular case, the failure surface was induced as a result of the rock mass progressive failure that developed from the toe of the structure inside the intact rock matrix. Analysis has been undertaken to determine in what scenarios the measured and predicted failure surfaces can be used to calibrate strength parameters in the model.

Uncertain Modal Analysis of Unmanned Aircraft Composite Landing Gear

Through taking uncertain mechanical parameters of composites into consideration,this paper carries out uncertain modal analysis for an unmanned aircraft landing gear.By describing correlated multi-dimensional mechanical parameters as a convex polyhedral model,the modal analysis problem of a composite landing gear is transferred into a linear fractional programming(LFR)eigenvalue solution problem.As a consequent,the extreme-point algorithm is proposed to estimate lower and upper bounds of eigenvalues,namely the exact results of eigenvalues can be easily obtained at the extreme-point locations of the convex polyhedral model.The simulation results show that the proposed model and algorithm can play an important role in the eigenvalue solution problem and possess valuable engineering significance.It will be a powerful and effective tool for further vibration analysis for the landing gear.

Equilibrium points and orbits around asteroid with the full gravitational potential caused by the 3D irregular shape

We investigate the equilibrium points and orbits around asteroid 1333 Cevenola by considering the full gravitational potential caused by the 3D irregular shape.The gravitational potential and effective potential of asteroid 1333 Cevenola are calculated.The zero-velocity curves for a massless particle orbiting in the gravitational environment have been discussed.The linearized dynamic equation,the characteristic equation,and the conserved quantity of the equilibria for the large-size-ratio binary asteroid system have been derived.It is found that there are totally five equilibrium points close to 1333 Cevenola.The topological cases of the outside equilibrium points have a staggered distribution.The simulation of orbits in the full gravitational potential caused by the 3D irregular shape of 1333 Cevenola shows that the moonlet’s orbit is more likely to be stable if the orbit inclination is small.