逆断层活动引起湿砂沉积层破坏特征的模型试验研究

Experimental Study on the Movement of the Reverse Fault Causing Surface Rupture on Wet Sand Deposit

通过地质力学模型试验研究了逆断层活动在沉积层中的传播模式、以及引起沉积层变形和破裂的特征。试验中采用数字散斑相关方法计算沉积层表面变形的位移场,并采用高精度数码摄像系统捕捉和记录活动断层在沉积层中的破裂扩展过程。逆断层在沉积层中向上扩展时形成了一个剪切带,且断层倾角越小,沉积层中的剪切带就越宽;而基岩断层的抬升位移和滑移速度越大时,沉积层中的剪切带也越宽、变形越强烈。当断层抬升位移达到某一临界值时,沉积层表面的隆起将会出现拉张裂缝。在相同的沉积层厚度和断层抬升位移条件下,基岩断层抬升速度越大时,沉积层表面形变带的宽度越小,变形和破坏程度却更强烈。实验结果表明,断层倾角、滑移速率和沉积层厚度对于确定逆断层活动引起的地表变形和破坏特征具有重要意义。

Geomechanical model tests were performed on wet sand in a glass-walled fault rest box to investigate the relationship between the propagation of fault rupture and the shapes,and the locations of failure surface.Three CCD cameras were used to capture the process of the surface rupture development and to analyze the displacement field by using the digital speckle correlation method.Based on the experiment,it was observed that when the thrust fault moved upward,the sediment layers formed a shear zone.The smaller the angle of faults,the wider of shear zone was formed in the sediment layer.The vertical displacement and the movement velocity of the fault are greater,the deformation of sediment layer is wider,and the deformation of the soil layer is stronger.When the vertical displacement of the fault exceeds 40% of the soil thickness,the deformed soil will form tension crack at the surface of the sediment.For a fixed sediment thickness with a fixed vertical displacement,the width of the deformation bands decreased with the increased fault movement velocity.However,the degree of deformation and failure will become more intense under a faster fault movement.Experimental results of this study on fault angle,fault movement velocity and sediment thickness is an important issue in further studies on ground deformation and failure characteristics of a thrust fault.