3D Design for hydraulic tunnel and its space distance analysis

For large-scale hydraulic and hydroelectric project, it has complex underground tunnel group. Traditional design for tunnel was usually based on the method of CAD in 2D which could not embody the geological features where the tunnel was passed, and also could not describe the space relations of the tunnel networks. With the development of graphics and GIS, 3D Design for hydraulic tunnel is to be possible. This paper proposes one method for modeling hydraulic tunnel in 3D and analyzing its space distance in 3D based on distance analysis of GIS. The space distance is important for construction safety protection. The design of tunnel can be divided into two parts: the section and the axis. The design of section is based on its function of tunnel, such as non-pressure tunnel and pressure tunnel. The design of axis is based on space distribution. The main procedure of modeling the tunnel: determining the axis, and then choosing the corresponding section. The section needs to be performed the translated and rotated matrix to the proper position along the axis. The next step is to extrude the section along the axis, so the entity model of one tunnel is created. Two entities are the outer one and the inner one. The tunnel model can be acquired through the outer tunnel subtracting the inner one by Boolean operations. The tunnel model is one entity by complex geometric transformations and Boolean operations. Performing the space distance analysis directly is quite difficult, and it needs find an indirect mean. The axis of tunnel has relatively simple expression, so, the link between the tunnel model and its corresponding axis and section is established. Here, the C++ as the program design language, the map class is used to implement the link. Thus, it can find the axis and section equation from the tunnel. In virtue of such method, analyzing the space distance of complex solid model becomes easy. The calculating model is created and discussed how to calculate the minimum dist- - ance between tunnels. At first, the minimum distance between axes is calculated, which formed a minimum distance Vector. Second, the parts between the axes and sidewall of tunnel are subtracted. Finally, this method is applied to one large-scale hydraulic and hydroelectric project.