STUDY ON MESO-MECHANICAL SIMULATION OF GROUTING FOR UNFAVORABLE GEOLOGICAL CONDITIONS

The numerical simulation program of PFC2D(Particle Flow Code in 2 Dimension)particle flow based on the flow-solid coupling principle and,on its built-in FISHTANK function library and FISH language,defines the flow equation and pressure equation of fluid domain respectively,and carries out numerical simulation calculations on the diffusion process and,on the morphology and particle displacement of slurry during the slurry injection process.By adjusting the parameters of hist,n_bond,s_bond and measure in the PFC command flow,the tracking of granular body displacement changes is achieved,and the mesoscopic mechanism such as the diffusion law of soil slurry at different depths and the change of formation porosity is revealed.The numerical calculations show that:the grouting pressure has a significant effect on the alteration and destruction of the formation structure,and the fracturing effect becomes gradually worse with increasing adhesive strength,while the porosity increases significantly with increasing grouting pressure.Based on the elastic-plastic theory of the Mohr-Colomb criterion to theoretically derive the stress field of the soil around the borehole,it is pointed out that the mechanical mechanism of annular tension and radial compression is the fundamental reason for the appearance of fracturing grouting action mode.The increase of slurry viscosity is beneficial to improve the grouting effect of fracturing-compacting grouting,while the increase of friction coefficient has little effect on the grouting effect.The comparative analysis of the laboratory tests shows that the PFC2D simulation of the grouting process is feasible.

The Inherent Law of the Unpredictability of Financial Asset Price Fluctuations: Multistability and Chaos

This paper aims at understanding the price dynamics generated by the interaction of traders relying on heterogeneous expectations in an asset pricing model.In the present work the authors analyze a financial market populated by five types of boundedly rational speculators-two types of fundamentalists,two types of chartists and trend followers which submit buying/selling orders according to different trading rules.The authors formulate a stock market model represented as a 2 dimensional piecewise linear discontinuous map.The proposed contribution to the existing financial literature is two aspects.First,the authors perform study of the model involving a 2 dimensional piecewise linear discontinuous map through a combination of qualitative and quantitative methods.The authors focus on the existence conditions of chaos and the multi-stability regions in parameter plane.Related border collision bifurcation curves and basins of multi-attractors are also given.The authors find that chaos or quasi-period exists only in the case of fixed point being a saddle(regular or flip)and that the coexistence of multiple attractors may exist when the fixed point is an attractor,but it is common for spiral and flip fixed points.