Laser Speckle Technique For Hydraulic Structure Model Test

Abstract

With the development of hydrostructural model test, it is necessary to find out a new measurement technique. Now the laser speckle technique is an effective non-touch measurement method, which can be used for both the Young's fringe analysis from point to point and the full-image analysis with high sensitivity but simple equipment in the laboratory. Since 1980, the authors of this paper have, repeatedly and systematically, applied the laser speckle photography method to the dam model materials and the linear and non-linear structural model tests of gravity dams. All the tests show that the relative error of displacement between the observation of laser and the dial guage is less than 4%. The data after observing the displacement of the triangular gravity dam from laser speckle method are considerably consistent with the results from finite element method. The error of them is less than 10%. The results of sliding model test of the simulating dam with the plaster block quite coinside with the calculation curves of the finite element method, in which the absolute error is 0.5-1.6 m. The results of the dam sliding model test of a given project made of geomechanical model materials by laser speckle method are approximately consistent with the data by the ordinary test method. The former final overloading coefficient of the dam is 17, and the latter is 20. Both the sandwich speckle method and the combined speckle method were presented here by the authors. All of the researches emphatically indicate that the laser speckle photography method for measuring two dimensional hydrostructural model test is full feasible and its precision is generally satisfied. Consequently, it is a non-touch measurement method, effective and useful, for the two dimensional geomechanical model test.