大巴山前陆叠加构造力学特征的模拟研究

A numerical simulating study of mechanical characteristic of superposed deformation in Daba Mountain Foreland

采用非线性有限元数值模拟技术和方法,研究大巴山前陆构造带应力场、位移场和形变场的流变学特征,分析叠加褶皱的相干形式和联合弧的形态特征,展现了大巴山弧形构造的发育、演化过程,提供了一组与大巴山前陆叠加构造相适应的边界外力和约束条件。研究表明:(1)模型选用的蠕变材料在变形过程中,应力场的变化非常缓慢,使得我们有条件通过应力迹线去研究构造变形的形态特征。(2)大巴山弧形构造带早晚两期褶皱的干涉形式大致为构造横跨叠加、斜跨叠加和共轴叠加三种。(3)大巴山弧形构造带形成的关键条件是北东向区域应力的作用和东西两个基底构造结的存在;而与大巴山弧联合构成收敛双弧的川东弧形构造带主要为来自南东方向的动力作用所致。

In this paper, by using nonlinear finite element numerical method, we have studied the mechanical characteristics, the interference patterns of superposed folds and the feature of the united arc-shaped structures in Daba Mountain Foreland. The evolution of a series of arc-shaped structures has been demonstrated, and a group of boundary conditions adapted to the superposed deformation in this region has been obtained. The study shows that （1） the creep materials selected in our model were deformed greatly with time even under very small and slow variation of stress field, which made us possible to study the tectonic deformation through principal stress trajectory; that （2）the interference patterns of superposed folds in Daba Mountain Foreland are mostly perpendicular intersection, inclined intersection and in parallel roughly; that （3）the formation of Daba arc-shaped structures is thought due to the action of northeastern boundary forces with two tectonic convergences at east and west part, but another arc-shaped structure in Eastern Sichuan Basin assembled with Daba Mountain forming a convergent double arc is thought due to the action of the boundary forces from southeastern direction.