Biaxial Response of Polymeric Structural Membranes

聚合物膜，通常被称为土工合成材料，用于许多土木工程项目中以加固土壤。它们通常用于挡土墙、已建造的斜坡、道路和加筋散体荷载传递平台。分析现有的，特别是涉及加筋土工合成材料的新应用的先进方法需要来自载荷试验的信息，这些载荷试验复制了现场应用中看到的载荷类型。现场应用通常涉及在材料的两个方向上同时施加载荷。到目前为止，实验室测试技术还没有充分发展到应用这些类型的负载。在该项目下进行的研究将涉及使用双向加载框架来评估一系列土工合成加筋材料的双向加载响应。这些数据将允许开发先进的材料模型，描述土工合成材料在两个方向上受载荷的机械响应。这些模型可以结合到针对上述应用类型的高级分析方法中。这项工作还可以导致制造技术的优化，从而产生优异的机械性能。聚合物薄膜或片材通常被称为土工合成材料，用于结构加固，包括挡土墙、已建造的斜坡、道路和加筋颗粒荷载传递平台。在这些应用中，土工合成材料在每个主要材料方向上同时承受载荷。与在单轴加载中观察到的材料响应相比，这些类型的载荷通常以有益的方式影响载荷-应变特性。土工合成材料的荷载-应变特性通常通过模拟平面应变加载的宽幅试件(ASTM、2011和2015)的单轴拉伸试验来确定。试件的自由面使得模拟效果很差，这意味着加载条件介于单轴加载和平面应变加载之间。这项测试通常被视为指数测试。需要一种更先进的测试来描述现场应用中预期载荷的材料行为。数值模型通常被用作研究工具，用于检查涉及加筋土工合成材料的新应用，并用于开发稳健的设计方法。这些模型还没有根据实际的现场负载进行校准。设计方法应使用与预期的现场载荷类型相关的载荷-应变材料特性。需要一种先进的测试设备来校准这些模型。双轴测试设备在材料的每个主要方向上同时施加载荷，并可以复制现场应用中看到的载荷类型。已经开发了用于织物建筑和屋顶系统的材料的双轴试验(Beccarelli，2015)，但只对土工合成材料进行了有限的研究。蒙大拿州立大学最近建造了一个用于土工合成材料双向加载的加载框架。这项研究将使用这个装置来检测一系列土工合成材料的双轴响应。需要这些数据来检验各种数值模型的适用性，以描述双向载荷响应并提供与现场载荷条件相关的线弹性材料特性。该项目的更广泛影响包括生成将通过以下方式影响工业、工程实践和教育的信息：i)推广可持续建筑材料的使用；ii)提供一种评估材料响应的方法，从而优化土工合成材料的制造工艺；以及iii)支持将负责测试项目的研究生。土工合成材料是一种可持续的建筑材料，因为它们减少了对自然资源的使用，可以用回收的材料制造，采用简单的施工技术，具有成本效益，并且由于它们与周围土壤材料的延展性兼容，提供了更高的强度和弹性。土工合成材料减少了自然资源的使用，减少了与资源开采和运输相关的能源，并延长了已建设施的寿命，从而减少了维护和更换作业，从而减少了建筑的碳足迹。

Polymeric membranes, commonly referred to as geosynthetics, are used for in a number of Civil Engineering projects to reinforce soils. They are commonly used in retaining walls, constructed slopes, roadways, and reinforced granular load transfer platforms. Advanced methods for the analysis of existing and especially new applications involving reinforcement geosynthetics require information from load tests that duplicate the type of loads seen in field applications. Field applications typically involve the simultaneous application of load in two directions of the material. To date, laboratory testing techniques have not been sufficiently developed to apply these types of loads. Research performed under this project will involve the use of a biaxial loading frame to evaulate the biaxial loading response of an array of geosynthetic reinforcement materials. These data will allow for the development of advanced material models describing the mechanical response of geosynthetics subject to load in two directions. These models can be incorporated into advanced analysis methods for the types of applications noted above. This work can also lead to optimization of manufacturing techniques that lead to superior mechanical properties.Polymeric membranes or sheets, commonly referred to as geosynthetics, are used for structural reinforcement in a number of applications including retaining walls, constructed slopes, roadways, and reinforced granular load transfer platforms. In these applications, geosynthetics experience load simultaneously in each principal material direction. These types of loads influence the load-strain properties typically in beneficial ways as compared to material response observed in uniaxial loading. Load-strain properties of geosynthetics are typically determined from uniaxial tension tests on wide-width samples (ASTM, 2011 and 2015), which simulate plane strain loading. The free sides of the sample make this simulation poor, meaning the loading condition is somewhere between uniaxial loading and plane strain loading. This test is typically regarded as an index test. A more advanced test is needed to describe material behavior for loads expected in field applications. Numerical models are commonly used as research tools for the examination of new applications involving reinforcement geosynthetics and for the development of robust design methods. These models have not been calibrated against realistic field loadings. Design methods should use load-strain material properties pertinent to the type of field loading expected. An advanced test device is needed to calibrate these models. Biaxial testing devices apply loads simultaneously in each principal direction of the material and can duplicate the types of loads seen in field applications. Biaxial tests have been developed for materials used for fabric buildings and roofing systems (Beccarelli, 2015), however only limited studies have been performed on geosynthetics. Montana State University has recently built a load frame for biaxial loading of geosynthetics. This research will use this device to examine the biaxial response of an array of geosynthetics. These data are needed to examine the suitability of various numerical models for describing biaxial load response and for providing linear elastic material properties pertinent to field loading conditions. The broader impacts of this project include generating information that will impact industry, engineering practice and education by: i) promoting the use of a sustainable construction material, ii) providing a means of assessing material response leading to optimization of geosynthetic manufacturing processes, and iii) supporting a graduate student who will take ownership of the testing program. Geosynthetics are a sustainable construction material in that they reduce the use of natural resources, may be manufactured from recycled content, lend themselves to simple construction techniques, are cost effective, and offer a higher degree of and resiliency due to their compatibility with the ductile behavior of surrounding soil materials. Geosynthetics reduce the carbon footprint of construction by the reduced use of natural resources and reduced energy associated with resource extraction and transport and by increasing the life of the constructed facility, thereby reducing maintenance and replacement operations.