DEFORMATION-BASED DESIGN OF GEOTECHNICAL COMPOSITE FOUNDATION SYSTEMS INCORPORATING COLUMNAR SUPPORT WITH OR WITHOUT GEOSYNTHETIC REINFORCEMENT

一种重要类型的土工复合系统包括安装在软粘土中的坚固材料柱，其上覆层为粗粒土壤，可能包括土工合成材料加固。 上覆的“桥接”层的目的是将荷载从填料或结构转移到柱子上，从而减少不均匀沉降。 这种系统的现有设计方法对土工合成加固提供了广泛变化的要求，并且对于这些方法中的哪一种（如果有的话）是准确的没有共识。 此外，没有一个现有的方法提供用于预测差异沉降幅度的手段。 这项研究将包括（a）方形和圆形柱移动到土工合成材料加固土层中的中试规模试验;（B）从两个当代、全尺寸现场装置收集的新数据，（c）考虑正交各向异性、取向和应力集中的土工合成加固层的行为的三维数学分析，以及（d）整个岩土复合系统的三维数值分析。 将协调这些任务，以确定重要系统参数的影响，包括：立柱的布局、间距、直径、刚度和强度;立柱顶部帽的尺寸和形状;土工合成层的材料特性、深度、方向和极限强度;立柱上方桥接层的特性;立柱之间软粘土的特性;桥接层的深度;每个土工合成层顶部和底部的界面特性;以及表面载荷。 这项研究的更广泛的影响包括工具的开发，更经济和可靠的设计基础系统的运输设施和结构。 研究人员将让少数民族、妇女和本科生参与他们的研究。 他们将涉及来自美国和国际社会的感兴趣的个人，委员会和组织的研究，他们将促进与包含柱状支撑和土工合成加固的土工复合地基系统相关的沟通，网络和伙伴关系。

An important type of geotechnical composite system incorporates columns of strong material installed in soft clay, with an overlying layer of coarse-grained soil that may include geosynthetic reinforcement. The purpose of the overlying "bridging" layer is to transfer loads from embankments or structures into the columns, thereby reduceing differential settlements. Existing design methods for such systems provide widely-varying requirements for geosynthetic reinforcement, and there is no consensus regarding which of these methods, if any, is accurate. Furthermore, none of the existing methods provide means for predicting differential settlement magnitudes. This research will include (a) pilot-scale tests of square and round columns moving up into a geosynthetic-reinforced soil layer; (b) new data collection from two contemporary, full-scale field installations, (c) three-dimensional mathematical analysis of the behavior of geosynthetic reinforcement layers considering orthotropy, orientation, and stress concentrations, and (d) three-dimensional numerical analysis of the entire geotechnical composite system. These tasks will be coordinated to determine the effects of the important system parameters, including: the layout, spacing, diameter, stiffness, and strength of the columns; the size and shape of caps on top of the columns; the material properties, depth, orientation, and ultimate strength of the geosynthetic layer(s); the properties of the bridging layer above the columns; the properties of the soft clay between the columns; the depth of the bridging layer; the interface behavior at the top and bottom of each geosynthetic layer; and the surface loading. The broader impacts of this research include the development of tools for more economical and reliable design of foundation systems for transportation embankments and structures. The investigators will engage minorities, women, and undergraduates in their research. They will involve interested individuals, committees, and organizations from the U.S. and international community in the research, and they will promote communication, networking, and partnerships related to geotechnical composite foundation systems incorporating columnar support and geosynthetic reinforcement.