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长棱柱、下沉和扩张盆地以及“软”沉积物受构造应力或重力作用的其他环境中的变形很重要。不幸的是，这些沉积物的物理性质、力学状态和结构组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。对中等孔隙度(20-40%)的粉质粘土(天然和人工固结)进行了一系列力学测试，使我们能够将这些沉积物的物理性质和力学状态与变形过程中产生的结构组构联系起来。我们研究了实验室固结沉积物的强度表面，如有效平均应力、差异应力和孔隙率的三维空间所描绘的，在平均应力下的典型地质条件下的增长棱柱。对盆地层序中的天然沉积物进行了现场强度测量，分析了层理平行缩短过程中产生的破坏组构。为了研究自然变形的沉积物，我们从南开增生棱柱中的DSDP遗址采集了几个样品。结构组构分析包括用于测量破碎区整体和内部几何形状的光学显微镜、用于孔隙率变化的微探针研究、以及用于织物各向异性和应变的X射线极图测角。

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.