ENGINEERING GEOLOGICAL CHARACTERISTICS OF DENSE SAND AND ITS INFLUENCE ON SHIELD TUNNELLING

Shield tunnelling is more and more popular in the modern underground projects because of its high efficiency, and its geological condition is more and more complicated. As a special geological environment, dense sand has a direct impact on shield tunnelling. But so far, the study on the characteristics of dense sand has not yet reached the mature stage. In this paper, portable digital microscope was employed to capture images of undisturbed sand which comes from Sutong GIL Utility Tunnel Engineering; Adobe Photoshop splicing, the spliced image were subsequently converted into binary picture to produce contour boundary for particle shape; finally image-Pro plus was used to count and analyze particle shape parameters; the test results and the Sutong GIL Utility Tunnel Engineering survey results were compared. It is concluded that the method can be used as an effective means to accomplish the dense sand particle shape quantification and the dense sand has a long axis distribution in the space, which has a good correlation with the shape parameters of the particles. The results of the study have reference value for the study of particle shape, and have guiding significance for the construction of shield tunnel.