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在前人对褶皱冲断带的研究基础上,为进一步深入分析对比滑脱层数量、强度、深度等对褶皱冲断带的制约,设计了6组砂箱模拟实验,并运用粒子成像测速(PIV,Particle Image Velocimetry)技术的实时监测,计算出各阶段模型剖面上的速度场和涡度场,对褶皱冲断带的运动学过程和变形机制进行详细刻画和定量分析。实验结果表明,滑脱层的强度和深度均制约着褶皱断层的构造演化,滑脱层的强度越小,其上覆地层中的变形传播越远,滑脱层深度越深,对整个构造样式更具有控制作用,变形也就传播得更远。以微玻璃珠组成的滑脱层主要产生前展型逆冲叠瓦式构造,上部推覆体前缘水平位移较快;以硅胶组成的滑脱层上部形成叠瓦式构造,下部形成冲起构造,上、下两部分具有明显的分层变形特征。PIV监测结果显示,当上盘速度骤停,并且前缘涡度值骤降时,断坡形成并发展成断坪-断坡组合构造样式;下一条断层以相同方式在前缘形成,从而使褶皱冲断带向前陆方向扩展。将实验结果与龙门山南段褶皱冲断带进行了对比分析,得到了较好的印证。
Based on the previous studies on fold-thrust belts, six groups of sand box simulations were designed to further analyze and compare the control of fold-thrust belts with the number, strength and depth of the slipping layers. The particle image velocimetry (PIV) , Particle Image Velocimetry) technique, the velocity field and the vorticity field in each section of the model are calculated, and the kinematics and deformation mechanism of the fold-thrust belt are described in detail and quantitatively. The experimental results show that both the strength and depth of the slip layer constrain the tectonic evolution of the fold fault. The smaller the strength of the slip layer, the farther the deformation propagates in the overburden and the deeper the slip layer, which controls the whole tectonic pattern more Role, deformation also spread further. The front-edge of the upper nappe has a high level of displacement. The upper part of the skidding layer composed of silica gel forms a shingle-like structure, and the lower part forms an uplift structure. The upper and lower parts have distinct stratification characteristics. PIV monitoring results show that when the velocity of the hanging wall is stopped and the vorticity value of the leading edge plunges, the fault slope forms and develops into a faulted-fault combined structural pattern; the next fault is formed in the same way at the leading edge, Fold and thrust belt to the direction of the foreland expansion. The experimental results were compared with the fold-thrust belt in the southern segment of Longmen Shan, and a good proof was obtained.