Test Research On Structure Characteristics And Mechanical Characteristics Of Xiyu Conglomerate

ABSTRACT:Xiyu conglomerate belongs to quaternary latest diagenetic stratum, which is widely distributed in the margin of the Tarim Basin, the south of Tianshan mountains and the Kunlun mountains in the north piedmont basin. Its engineering characteristics are mainly manifested by:difference in the structure composition, uneven grain composition; high variation in indoor and outdoor test results; unstable cementation performance and difficult to determine mechanical parameters. With the Xinjiang area carrying out large-scale water conservancy and hydropower project construction, studying on engineering properties of Xiyu conglomerate seems necessary and urgent. In this paper, on the basis of research method of similar conglomerate rock mass and taking advantage of indoor physical mechanics test, by comprehensive utilization of phase analysis method, fractal geometry theory, digital image processing technology and discrete element numerical simulation method, this paper aims at studying the deformation-destruction behavior and teterioration mechanisms, revealing the characteristics of microstructure and the law of grain size fractal, analysising of the meso failure characteristics and influencing factors of shear strength of Xiyu conglomerate.(1) Based on sieving tests, gradation characteristic curves were abtained, around its microstructure self similarity, fractal dimension calculation model were established. Through which relationship between the stone content and the average fractal dimension was explored. The results indicates that fractal dimension of grain size presents the characteristics of double fractal dimension and Xiyu conglomerate has a good self-organizing characteristic. XRD and XRF tests were used to study the difference of the composition of the grain size distribution of cement, which contributes to reveal the distribution of the Xiyu conglomerate.(2) In order to investigates structure characteristics of Xiyu conglomerate, based on digital image processing technology, using image segmentation to eliminate irrelevant information, two-dimensional structure moded of Xiyu conglomerate was obtained. Using edge detection and feature measurement method, the geometric shape parameters of closed image were acquired quickly and accurately. The distribution, angularity and orientation of gravel were analyzed on the base of fractal geometry theory.(3) For revealing the complex mechanical properties of Xiyu conglomerate. Indoor shear tests were conducted in this pater. So shear strength parameters were gained, three kinds of typica shear stress-shear displacement curves were also demonstrated and analyzed based on the morphology of the specimen after failure.(4) By the particle flow code numerical simulation of direct shear tests, study the meso-structure failure process, which helps to deepen insight into mechanical behavior of Xiyu conglomerate. Finally, the influence of the stone content and cement strength on the shear strength was analyzed.