Effects of Physical Properties Mechanical State on the Deformation of Porous Sediments

多孔沉积物的力学行为对于理解增生棱镜、沉降和扩张盆地以及其他“软”沉积物受到构造或重力应力作用的环境中的变形非常重要。不幸的是，人们对这些沉积物的物理性质、力学状态和结构结构之间的关系知之甚少，这阻碍了定量地质力学模型的发展。对中等孔隙（20-40%）粉质粘土（天然和人工固结）进行了一系列力学测试，这将使我们能够将这些沉积物的物理特性和力学状态与变形过程中产生的结构织物联系起来。我们研究了实验室固结沉积物的强度面，在三维空间中描述了有效平均应力、差应力和空隙比，以及在增生棱镜中典型地质条件下的平均应力。对盆地层序的天然沉积物进行了原位强度测量，并分析了层理平行缩短过程中产生的破坏组构。为了研究自然变形沉积物，我们从南开吸积棱镜的DSDP站点获得了几个样品。结构织物分析包括用于测量破坏区域整体和内部几何形状的光学显微镜，用于孔隙度变化的微探针研究，以及用于测量织物各向异性和应变的x射线极形几何。

The mechanical behavior of porous sediments is important for the understanding of deformation in accretionary prisms, subsiding and spreading basins, and other settings in which "soft" sediments are subjected to tectonic or gravitational stresses. Unfortunately the relationships among physical properties, mechanical state, and structural fabric for these sediments are very poorly known, which has impeded the development of quantitative geomechanical models. A series of mechanical tests have been made moderately porous (20-40%) silty clays (both natural and artificially consolidated) that will allow us to correlate the physical properties and mechanical state of these sediments with the structural fabrics produced during deformation. We investigated strength surface for laboratory consolidated sediments, as depicted in a 3-dimensional space of effective mean stress, differential stress, and void ratio, at mean stresses typical of geologic conditions in accretionary prisms. For natural sediments from basinal sequences we measured in-situ strength and analyze the failure fabrics produced during bedding parallel shortening. For the study of naturally deformed sediments we have several samples from DSDP sites in the Nankai accretionary prism. Structural fabric analyses included optical microscopy for measurement of the overall and internal geometries of the failure zones, microprobe studies for porosity variations, and x-ray pole figure goniometry for fabric anisotropy and strain.