Simulation On The Multi-scale Spatial Distribution Of Fractures In Gaosong Field,Gejiu Tin Mine

In the geological research field, fracture is a basic structure form which is widely developed in the upper crust rock. Fractures provide favorable conditions for ore-forming fluid to rise, disperse, penetrate and aggregate during the formation of mineral resources. In order to make scientific predictions of the spatial distribution of fracture extension, how to make use of existing structural geology and rock mechanics test data is a difficult problem in geological prospecting. In this paper the fracture networks is modeled under different scales on the basis of the previous work, and finally their mutual relation is established. This paper conducts research in the following aspects.(1) Fracture characteristic’s measurement of Gaosong field in Gejiu tin deposit.A variety of fractures exists widely in nature, and contains a number of attributes (such as length, width, direction, position, filling). Fracture position can be considered to meet the Poisson distribution, but the fracture formed in the multiple phrases and by overprint of several geological processes, fracture distribution exhibit complicated characteristics as we see in the field; fracture size (size, diameter length, chord length) has a close relationship with stress intensity and rock properties; unit normal vector of crack surfaces can be used to represent the fracture direction, which is closely related to the stress direction which impacts the rock (body) in the research process; the actual fracture density can use total number fractures per unit to measure, and it is showen a strong nonuniformity in general; fracture width influences the permeability of rock significantly in general, and closely relates with the fracture length; fracture displacement reflects the migration direction and distance in the course of of fracture formation, and it has significance for simulation of fracture formation. Fracture properties, including length, displacement, size, density, width and other major obey power-law distribution, logarithmic normal distribution, exponential distribution, gamma distribution, while direction obeys Fisher distribution and Binghanm distribution. On the basis of previous study, the internal rules of multi-scale fracture attributes through the case study are analysised, and then the method of calculating across-scales law by box counting method and two-point correlation function is discussed, and then sample size, exponential expansion, estimation method, influence factors, the estimation accuracy in the process of estimating the scaling-exponent are detailed analysised. In view of the relationship between the observability of fractre length and other properties, the scale-index of fracture length estimation is especially discussed in detail. According to multi-scale contact law and the used method, the corresponding computer programs are compiled by Matlab.(2) In this paper GEOFRAC method are Constructed, which is concluding Ordinary Kriging (OK), Sequential Gauss Simulation (SGS), Principal Component Analysis (PCA) method. Specific content include:decomposition properties, fracture density estimation, fracture position generation, the principal component analysis and inversion of fracture direction (strike and dip), geostatistics estimation of fracture orientation distribution, fracture property valuation comprehension, basic fracture surface connection. Fracture multiple attribute, the same position and scale-invariant features can be considered through making full use of fractured samples data of different dimension and scale.(3) Fracture3D distribution in Gaosong ore field.By using acoustic emission, CT, surface, tunnel, remote sensing, the geological data and fracture sample data of different dimensions and different scales are collected. Taking this as the foundation, a3D strata model of Gaosong field by using geological data are constructed, and the relations between small-scale crack length, the density cross-dimension conversion and properties(direction, length, width) are established by using CT data, and then fracture spatial situation distributions, corresponding to the direction of the spatial distribution of fracture network in Gaosong field are simulated by using tunnel, surface data, and fracture elements in the spatial distribution is connected, and then linear structure in Gejiu deposit are extracted by using remote sensing DEM data, multi-scale contact of fracture density and length according to the established fracture network distribution analysis of different scales, the results of these studies are verified in the Gaosong ore field.(4) Through stereological analysis, fracture length distributions meet some laws in given certain assumptions. The relationships between the fracture density, one-dimensional, two-dimensional density, three-dimensional density, density, surface density, linear density, bulk density are concluded, then fracture length and chord length are statisticalized, and then fracture direction, the observation surface direction, the trace ray angle are built, and then the relationship between fracture density, length and direction across dimension conversion are established, and the then technique route of the fracture properties of cross dimension conversion are designed, and finally the idea of computer algorithms are conceived, and all of this implementation program was written by Matlab.(5) Through analyzing the remote sensing images of a375km2in Gejiu tin deposit and Gaosong ore field geological map, the spatial distribution characteristics of fracture system, and the fracture network distribution relationship with orebody are researched. According to the large scale fracture modeling results, orebody is closely associated with the first set of fracture, and with second, third groups of fracture distribution in mesoscale. The results show they have a good consistency.