基于机敏土工格栅变形自检测的加筋土破坏模式识别与状态诊断

Geosynthetic materials are widely used in earth reinforcement to improve the stability and the seismic performance of soil. But the understanding of the reinforcement mechanism is not very clear now. There is also not the effective detection means of geosynthetic materials deformation, and this limits the development of reinforced earth design methods and the safety diagnosis of reinforced earth structure. Based on the tension-sensitivity effect of conductive polymers, in this project, a carbon black/high density polyethylene geogrid will be developed. The deformation of this geogrid can be measured by itself. The conduction percolation phenomenon and tension-sensitivity effect of the geogrid will be studied to obtain the percolation threshold and the deformation-resistance model. The mechanical properties of the geogrid will be studied to obtain the creep model. Distributed deformation self-testing technology of geogrid network will be studied, and the characteristic information extraction method of geogrid deformation will be put forward. By tests, theoretical analyses and numerical simulations, the relation model of the characteristic information of geogrid deformation with the failure models of reinforced earth will be established. The geogrid has excellent durability and low cost, and high deformation testing precision because of avoiding the effect of exterior sensors installation on the geogrid-soil interface. It has a wide application prospect and is suited for monitoring the stability and diagnosing the safety state of the reinforced earth structure during total life cycle.

土工合成材料被广泛用于土体加固，以提高其稳定性和抗震性能。但目前对加筋机制的认识还不完善；也缺乏对全寿命周期内筋材变形等指标的有效检测手段，限制了人们对设计方法的完善及对加筋土体安全诊断方法的研究。本项目将基于导电聚合物的拉敏效应，研制一种炭黑/高密度聚乙烯机敏土工格栅，该格栅在保证其加筋作用的同时，能实现变形自检测。拟通过研究机敏格栅导电行为的渗滤现象和拉敏效应，给出其渗滤阈值，建立变形-电阻模型；研究机敏格栅力学性能，提出其蠕变模型。研究格栅网络变形的分布式自检测技术，并提出筋材变形、受力等特征信息的提取方法。通过试验、理论分析和数值模拟，构建筋材变形等特征信息与加筋土体破坏模式间的内在关系，提出加筋土破坏模式识别和破坏状态诊断方法。机敏格栅耐久性好、成本低，变形自检测技术避免了外部传感器植入对筋土界面的扰动，适于对加筋土结构全寿命周期内的稳定性和安全状态进行监测和诊断，应用前景广阔。

本项目基于导电聚合物的拉敏效应，以高密度聚乙烯为基体，超导电炭黑和碳纳米管为导电填料，在室内制备了两种传感型土工材料SEG。揭示了SEG导电行为的渗滤现象和拉敏效应，确定了其渗滤阈值，建立了变形-电阻模型；并研究了SEG的力学性能。将SEG在工厂进行了生产，确定了热缩管包裹和两布一膜包覆两种系列的产品，能够实现防水耐久的目的。提出了考虑土工材料塑性行为的土中变形分析模型，基于SEG的变形自检测性能和拉拔试验，验证了该模型的正确性，为加筋土工结构的安全预警提供了理论基础。传感型土工材料耐久性好、成本低，变形自检测技术避免了外部传感器植入对筋土界面的扰动，适于对加筋土结构全寿命周期内的稳定性和安全状态进行监测和诊断，应用前景广阔。