对称褶皱形成的三维构造物理模拟实验

依据褶皱形成和演化的三维构造物理模拟实验结果,得到以下认识:在双向挤压应力作用下,在作用应力与受力体边界相互垂直的状态下,且材料的性质为塑性和脆-塑性,各层大致为等厚度,形成的对称褶皱沿x坐标轴由模型中心向两侧近于对称展布,模型最终缩短了初始长度的27％,褶皱核部较两翼有增厚的趋势;但沿x、y、z坐标轴的构造变形是非一致的,浅部变形与深部变形有较大差异,模型下部发育对冲的逆断层,褶皱轴与应力作用边界有大约30°的水平夹角,这一特征与层面的非均匀滑动和材料质点的非均匀位移密切相关。在单向挤压应力作用下,应力由作用边界向无应力作用边界传播,产生反作用力,在作用力和反作用力作用下,形成的褶皱变形明显靠近应力作用边界,层的弯曲随着深度的增加由缓变陡,模型下部发育与应力传播方向一致的逆断层。图6表1参6

Three-dimensional physical experiments of symmetrical fold

On basis of the results from three-dimensional physical experiments of formation and evolution of fold,following knowledge is obtained: symmetrical fold may be formed under symmetrical compression stresses when direction of action stresses are perpendicular to boundary of deformational body with ductile and brittle-ductile material with the same layer thickness. The style of symmetrical fold spread over symmetrical model center along x-axis, but structural deformation of fold is characterized by nonuniform along x, y and z axis. The angle between axis of fold and loaded boundary is about 30°, this character is closely related to nonhomogeneous gliding of bedding and nonuniform displacement of material particle. The structural deformation is different in shallow and deep layer. Ramp fold-thrust may be developed on bottom of model. Core thickness of fold is larger than flank thickness of fold. Length of model shortened 27% than initial length in the end of experiment. Thickness of fold highest point in the model thickened 36% than initial thickness. The stresses propagate from loaded boundary to unloaded stresses boundary under unidirectional compress stresses. Fold may be formed by action and reaction force, but deformation is obviously near loaded boundary. Fold-thrust developed on the bottom of the model with uniform of stress propagation direction. Buckling of layer is characterized by low-angle to high-angle with increase of depth in the experiment.