Digital Image Processing Of Dynamic Photoelasticity Stripes

The effect of static stress field in the tunnel design at home and abroad is only considered at the present time. But in fact, the effect of the dynamic stress field due to blowing up is very obvious too, especially to the tunnel under the weak stratum. In our country, the rupture occurs to the concrete resistance or surface in the finished tunnels frequently, so it's harmful to the stability of tunnel, even it can cause the drop out or the local landslide, impossible to work normally. The long time static stress field is one reason of rupture, besides the instantaneous dynamic stress field caused by the blowing up in construction is also very important, when the method of as digging as supporting is very popular in tunnel digging, so study on effect of the stress wave caused by blowing up in tunnel to the resistance is quite important in the practical project.The methods of electromotive and indoor blowing up simulation are often used in tunnel blowing up, but we can't get the full-court information of the instantaneous blowing up, so the analysis of the dynamic stress propagation is very difficult. Dynamic photo elasticity experiment has many advantages, such as full-court, intuitionistic and instantaneous; it has been used in the study on plane stress wave, stress concentration and the stress wave propagation in plywood. But so far, its application in the practical projects of tunnel blowing up is still rare.Considering the problems, the effect of different interface on the stress wave propagation in structure was investigated by dynamic photo elastic method in this paper. The speed of wave propagation under different instances was also analyzed and compared .The experimental results prove that trough can slow the propagation of stress wave, but not too obvious. Meanwhile if the model is chopped up and then stuck together by two pieces of slice, it is found that the stress wave is limited in a narrow area, which can only spread to the lower layer from the slice, and in other places the wave has been held up. It is revealed by the experiment that the significant impact induced by the blasting under conditional exploitation can be considered as the proofs of tunnel design.In the photo elasticity digital image processing, a very important step is to extract the central line of the interferential fringe exactly, in order to analyze the stress, strain and displacement.In the basis of the experiment, the image processing of photo elasticity fringe and the calculation of stress are also referred to in this paper. At first, the edge detection is used to save the information in the image; second, we get the two value of the image to converseit into an image of two value; then median filter is used to clear up the noise in the two value picture; finally, the fringe skeleton is extracted in order to get the central line of the fringe. Besides, the stress value of every point in the image can be read out by the software in the paper.At last, the main achievements of this thesis are summed up and direction of further development in this field is pointed out.It proves that the contents and the method of study in the paper solves the problems in the practical projects of tunnel blowing up as well as the effect of dynamic stress wave on resistance, which can be considered as the proofs of tunnel design.