不同拉伸方式和速度下的伸展构造砂箱物理模拟实验研究

Sandbox Physical Simulation Experiment of Extensional Structure under Different Stretching Modes and Speeds

砂箱构造物理模拟实验是室内模拟自然界地质构造变形过程、成因机制以及动力学过程的一种高效方法。影响岩石变形的速度和力的作用方式等是影响伸展构造物理模拟实验的结果和构造形态的主要因素。基于此,为探究砂箱物理模拟实验中拉伸速度和拉伸方式(力的作用方式)对伸展构造变形特征的影响,笔者在已有研究基础上,将高(0.01 mm/s)、中(0.001 mm/s)、低(0.0005 mm/s)3种不同拉伸速度与单向拉伸、双向拉伸2种不同拉伸方式相结合,设计6组实验进行对比研究。结果表明:①拉伸速度对砂体的最终形态无显著影响,但对断层的发育过程有一定的影响,而拉伸方式对断层的发育过程和最终形态的影响均较为显著,且断层形成前砂体速度会增大到一定高值,并于断层形成后快速减小。②单向拉伸模型砂体最终均形成一个不对称的地堑,双向拉伸模型砂体最终均形成一个典型的地堑。③不对称地堑通常形成于相对拉伸或差异拉伸的环境中,相对拉伸侧发育形成一系列阶梯状正断层,而相对固定侧发育一条断距较大的正断层,且先存构造的位置往往决定了后期构造发育的初始位置。这一认识为伸展构造砂箱物理模拟实验中的模型设置和参数选取奠定了基础。

Sandbox structural physics simulation experiment is an efficient method to simulate the deformation process,genesis mechanism and dynamic process of natural structural deformation in laboratory.Factors affecting the rate of rock deformation and the mode of action of forces are the main factors affecting the results of physical simulation experiments of extensional tectonics and tectonic morphology.Based on this,in order to in-vestigate the effects of tensile speed and tensile mode(mode of the stress action)on extensional structural defor-mation characteristics in sandbox physical simulation experiment.This article is based on existing research,three different stretching speeds of high(0.01 mm/s),medium(0.001 mm/s)and low(0.0005 mm/s)are com-bined with two different stretching methods of unidirectional and bidirectional stretching,and six sets of experi-ments are designed for comparative study.The results show that:①Tensile velocity has no significant effect on the final morphology of the sand body,but has a certain influence on the development process of the fault,while the influence of the tensile mode on both the development process and the final morphology of the fault is more significant,and the velocity of the sand body increases to a certain high value before the formation of the fault and decreases rapidly after the formation of the fault.②The sand body of the unidirectional stretching model eventually forms an asymmetric graben tectonic feature.The sand bodies of the two-way stretching model even-tually form a typical graben tectonic feature.③Asymmetric graben structures are usually formed in a relatively stretched or differentially stretched environment,with a series of stepwise positive faults on the relatively stretched side and a large positive fault on the relatively fixed side,and the location of the pre-existing structure often determines the initial location of the later structure development.This understanding lays the foundation for the model setting and parameter selection in sandbox analogue modeling of the extensional structure.