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系统包括安装在软粘土中的坚固材料柱，以及覆盖在可能包括土工合成加筋的粗粒土层。覆盖“桥接层”的目的是将荷载从路堤或构筑物转移到柱中，从而减少差异沉降。现有的此类系统的设计方法对土工合成材料的加固提出了千差万别的要求，对于这些方法中的哪一种是准确的，如果有的话，还没有达成共识。此外，现有的方法都没有提供预测差异沉降量的方法。这项研究将包括(A)方柱和圆柱向上移动到土工合成材料加筋土层的中试试验；(B)从两个当代的全尺寸现场设备收集新的数据；(C)考虑各向异性、方向和应力集中的土工合成材料加筋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。将协调这些任务，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；柱顶部承台的大小和形状；土工合成材料层的材料特性、深度、方向和极限强度(S)；柱上桥接层的特性；柱之间软粘土的特性；桥接层的深度；每个土工合成材料层顶部和底部的界面行为；以及表面荷载。这项研究的更广泛影响包括开发工具，以更经济和可靠地设计交通路堤和结构的基础系统。研究人员将邀请少数族裔、女性和本科生参与他们的研究。他们将邀请来自美国和国际社会的感兴趣的个人、委员会和组织参与研究，并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.