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

一种重要的土工复合材料系统包括安装在软粘土中的坚固材料柱，上面覆盖一层可能包括土工合成加固的粗粒土。上覆“桥接”层的目的是将荷载从路堤或结构转移到柱上，从而减少不同的沉降。这种系统的现有设计方法对土工合成材料加固的要求各不相同，对于这些方法中哪一种是准确的，如果有的话，没有达成共识。此外，现有的方法都没有提供预测不同沉降幅度的手段。这项研究将包括(a)将方形柱和圆形柱向上移动到土工合成增强土层的中试规模试验；(b)从两个当代全尺寸现场装置收集的新数据，(c)考虑正交异性、方向和应力集中的土工合成增强层行为的三维数学分析，以及(d)整个土工复合系统的三维数值分析。这些任务将被协调以确定重要系统参数的影响，包括：柱的布局、间距、直径、刚度和强度；柱顶帽的大小和形状；土工合成层的材料特性、深度、方向和极限强度；柱上桥接层的性能；柱间软土的性能分析；桥接层的深度；各土工合成层顶部和底部的界面行为；表面载荷。这项研究的更广泛的影响包括开发更经济和可靠的交通路堤和结构基础系统设计工具。研究人员将邀请少数民族、女性和本科生参与他们的研究。他们将让美国和国际社会感兴趣的个人、委员会和组织参与研究，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交流、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.