Numerical Simulations Of Structural Deformations Under Compressive Stress

Fold structure is one of the most typical structures under compressive stress. Firstly, We studied the maximum principal stress and horizontal strain during the deformation of single fold and multi-layer fold and the effect of strain velocity on fold deformation under compressive stress. The results show that the strain velocity mainly affects maximum principal stress.Furthermore, for the forecast of volcanic-type U-deposits in Xiangshan basin, the ore-controlling problem in this region need to be further studied. On the basis of known geological data, the numerical simulation software FLAC is used in this paper to establish structure-fluid coupling section model and plane model respectively, using the structural movement and ore-forming fluid transportation as a coupling system to study the distributing rules of ore bodies.Through the simulations, the section model represents the process of strata deformations and fluid transportation under compressive stress before mineralization. The results show that, (1) the fault and fold have certainly effects on the mixing locations of ore-forming fluid under compressive stress. And (2) some tensile areas appear under compressive stress. Moreover, the tensile areas move upward with the increasing deformation and a great deal of tensile fractures combined to provide favorable spaces for mineralization. And (3) some rhombic shear zones are formed near the Zou-Shi fault, which is consistent with the distribution of secondary faults in the real region. Because the secondary faults are also ore-hosting structures, it shows that compressive stress field is important precondition and shearing deformation is good ore-controlling factor.In the plane model, the main ore-controlling factors and dynamic mechanism are studied, discussing the variation process of regional structural stress field, (including the shear strain and volumetric strain that is closely related with mineralization), and the variation of pore pressure in adjacent regions of Zou-Shi fault. The results show that, (1) The NE and SW sections of Zou-Shi fault in the west of Xiangshan basin are transitional structural locations between maximum values to minimum values of shear strain and volumetric strain, where is easy to produce dilatancy phenomena and form ore bodies. And (2) the pore pressure is mainly controlled by volumetric strain. Stress can directly make the pore volume change, and indirectly control the variation of pore pressure changed by the pore volume.Finally, through the general analysis and comparison with other dada, it shows that the model can instruct the exploration of uranium deposits in west of Xiangshan basin and provide clues for further exploration.