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Given that FLAC3D (a geotechnical calculation software) is difficult to use for building large, complex, and three-dimensional mining models, the current study proposes a fast and a convenient modeling technique that combines the unique advantages of FLAC3D in numerical calculation and those of SURPAC (a mine design software) in three-dimensional modeling, and the interface program was compiled. First, the relationship between the FLAC3D and the SURPAC unit data was examined, and the transformation technique between the data was given. Then, the interface program that transforms the mine design model to calculate the model was compiled using FORTRAN, and the specific steps of the program implementation were described using a large iron and copper mine modeling example. The results show that the proposed transformation technique and its corresponding interface program transformed the SURPAC model into the FLAC3D model, which expedited FLAC3D modeling, verified the validity and feasibility of the transformation technique, and expanded the application spaces of FLAC3D and SURPAC.

Along with the rapid development of computer technology in recent years, the numerical method along with artificial intelligence technique has become an important mean of analyzing and calculating modern engineering technologies [

The numerical calculation of a large mining project often involves complicated three-dimensional geological models. The current study takes the mine design software SURPAC with its powerful modeling function as the platform, builds complex three-dimensional models of mines, and automatically generates a FLAC3D model through data transformation to expand the application of FLAC3D into the numerical simulation of mine projects to solve the difficulties of FLAC3D modeling and to build accurate three-dimensional mining models that can improve the reliability of simulation results and give play to the computational power of FLAC3D. Moreover, SURPAC could also expand its mechanical analytical ability based on its inherent functions such as data collection, storage, management, and inquiry to meet the requirements of an engineering model in prediction and decision support.

The SURPAC serial software is a set of megadigitized mining engineering software with domestic leading level in minefields, and it is extensively applied to resource appraisal, geological measurement, mine design plan, production plan management, and reclamation design after pit closure [

SURPAC adopts a polygon mesh to describe the physical borders of an orebody that forms during extraction, and block modeling is performed after the solid model is built. The solid model is a three-dimensional geometric model based on computer geometric shaping technologies, and it completely describes the spatial structure, geometric configuration, and spatial borderline of the lithology. A block, model includes a three-dimensional model consisting of common hexahedral blocks and it is the foundation for lithologic assignment and the subsequent numerical calculation. The basic idea is to divide the spatial geometric model of the orebody into a multitude of unit blocks and then to assign lithology values to the unit blocks that fill the entire orebody.

FLAC3D is a numerical modeling code for advanced geotechnical analysis of soil, rock, and structural support in three dimensions [

FLAC3D utilizes an explicit finite difference formulation that can model complex behaviors not readily suited to FEM codes, such as problems that consist of several stages, large displacements and strains, and nonlinear material behavior and unstable systems (even the cases of yield/failure over large areas or total collapse).

SURPAC provides hexahedral unit shapes for treating units of simulated objects and it changes the sizes of the hexahedral units based on the features of the geological body, precision requirements of calculation, and spatial layout features of the unit shapes. Compared with the unit shapes in FLAC3D, the hexahedra units in SURPAC are known to correspond to block units. The information in a FLAC3D unit includes the three-dimensional coordinates of eight nodes (

Data relationship between FLAC3D and SURPAC unit data.

The three-dimensional coordinates of points

Parts in the model that need special treatment are grouped together during FLAC3D calculation. Thus, the attributes of each unit is determined along with SURPAC modeling to transform the units with different attributes into different groups in the FLAC3D model. The specific implementation process is as follows: SURPAC builds a block model of the three-dimensional orebody during modeling, that is, three-dimensional dissection of the entity model of the orebody with squares or cuboids.

The blocks are assigned with different attributes. SURPAC adopts a series of three-dimensional arrays to store information, such as grade and lithology, among others. The subscripts of an array correspond to the row, line, and layer number of blocks to save storage space and calculation time. However, SURPAC is inflexible to use because its coordinates rotate quite often during modeling. SURPAC has sharp contradictions in accurately fitting the borderline and the division grain size (storage) of a mine. Thus, the octree method was introduced to solve this problem, that is, continuously dividing the three-dimensional entity space into eight three-dimensional networks of the same size, with one or several attributes, as shown in Figure

Header message.

Centroid coordinates, sizes, and attributes of the units.

Unit subdivision.

The geometric parameters and attributes of the SURPAC units are read during data transformation. Then, the three-dimensional coordinates of the FLAC3D unit are transformed in accordance with formulas (

The numerical model could be rebuilt through the “call” command in FLAC3D to transform the data, but it will consume many computer hours in building the model because it faces a large amount of unit data. However, the “impgrid” command embedded into FLAC3D could import all the data at one time, which omits the remodeling process of FLAC3D and shortens the computer hours; for instance, the “call” command needs about three hours to build a three-dimensional model with 10,000 units, whereas the “impgrid” command only needs less than a minute at the same computer. However, the “call” and “impgrid” commands have different call formats.

The format of the “impgrid” command is as follows.

Node information.

*GRIDPOINTS.

G Node No., Node Coordinate

Unit information.

Grouping information.

Based on the analysis of unit data relationship above, the current study uses FORTRAN to compile the interface program. First, the program transforms the data into the required data format. Then, the program calls in the data using the “impgrid” command of FLAC3D, and then it sums the boundary condition, initial condition, and dynamic parameters of the soil body for calculations. Refer to Figure

Model transformation flowchart.

Given a large iron/copper mine and the complicated properties distribution of rock mass the owner provides AUTOCAD plan view of the mine, as shown in Figure

AUTOCAD plan view.

AUTOCAD vertical view.

A three-dimensional model was then constructed using FLAC3D with the transformation technique proposed in this paper and the modeling of the worked out section as an example. The specific procedures are as follows.

Solid model of SURPAC.

The whole model

The model of stope

Block model of SURPAC.

FLAC3D model.

The whole model

The worked out area model

After calculation by FLAC3D, the displacement and state contours are shown in Figure

The results calculated by FLAC3D.

The vertical displacement contour after calculation

The state contour after calculation

(1) Considering the difficulty of using FLAC3D (geotechnical calculation software) for pretreatment modeling, the current study combined SURPAC (mine design software) and FLAC3D to utilize the advantage of SURPAC in simulating geological features and to provide a calculation model that conforms to the geological reality of FLAC3D.

(2) The differences between the information from the two types of unit information, that is, SURPAC and FLAC3D, were analyzed, the data relationship between units was built, the data transformation technique was proposed, and the FORTRAN was adopted to compile relevant transformation procedures.

(3) When the transformation technique proposed in the current paper was applied to the modeling of a given large iron/copper mine, it indicated that the proposed transformation technique and its corresponding interface program transformed the SURPAC model into the FLAC3D model, speeding up the FLAC3D modeling and verifying the feasibility and validity of the proposed transformation technique.

This paper gets its funding from Project no. 20120162120014 supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China; from Project no. 2013CB036004 supported by National Basic Research 973 Program of China; from Project no. 201201 supported by Open Fund of Key Laboratory of Mechanics on Disaster and Environment in Western China (Lanzhou University), Ministry of Education; Project no. 12KF01 funded by the Open Projects of State Key Laboratory of Coal Resources and Safe Mining, CUMT. The authors wish to acknowledge these supports.