基于光固化链式反应的喷射土工膜：化学及岩土力学机理的研究

Geomembranes (GMs) have been widely used as a barrier for hazardous waste, solid waste, contaminants, mine tailings, and water canals. Frequent puncture and de-seaming failures of GMs result in leakage of hazardous or lethal materials into soil, water, and air, which poses a threat to human health and life. In view of these drawbacks, the PI (principal investigator) proposes using surficially initiated photocuring to create in-situ GMs to significantly improve their puncture resistance, and minimize de-seaming risk. Ultra-low viscosity liquid precursors (e.g., monomers) will be mixed with photoinitiators (Ph.) and carbon black to create a photocurable mixture. After this mixture is sprayed over subgrade soil, the photoinitiator on the surface of the mixture will absorb UV light irradiation to release radicals (R•) that trigger a chain reaction to form a continuous photocured in-situ geomembrane. This proposed method is particularly suitable for field applications, because it uses environment-friendly materials and safe light source, and is easy to control. The objective of this study is to develop the basic chemical and engineering principles to create and use such geomembrane. This study will: (1) establish the relationship between the chemical dynamics, molecular structure and properties of the formed geomembrane, (2) investigate the rheological behavior and spraying dynamics of the mixture, (3) study the mechanisms of interaction between soil and mixture droplets, as well as the interaction between soil and geomembrane, (4) examine the bonding between two layers of sprays, and (5) scrutinize the effect of wind during spray. Upon the completion of this research plan, a preliminary framework to apply the proposed method in the field will be developed. This study will build the fundamentals to utilize photocuring to form GMs in the field.

土工膜作为防渗材料，被广泛用于垃圾和废弃物填埋场、尾矿坝和输水渠道中。由于频繁发生穿透和接缝破坏，导致有害甚至致命的有毒物质泄露到土壤、地下水和空气中，给人民生活带来了极大的威胁。基于这些考虑，本项目提出利用表面激发光固化反应的原理，通过现场喷射形成连续的土工膜。具体操作是：将不饱和单体、光引发剂和碳黑粉混合，喷射于土层上。通过一定波长的紫外光激发化学聚合反应，从而生成连续的土工膜。这一设想是基于以自由基为基础的光固化聚合反应的链式性。本项目主要研究：(1)由表面激发的光固化链式反应的化学动力特性、分子结构、生成土工膜性质三者之间的关系；(2)在喷射过程中喷射液滴与土之间的碰撞作用，以及成膜以后，膜与土的相互作用；(3)在喷射以后，液膜与土之间的摩擦作用；(4) 两层喷射膜之间的结合强度；和(5)环境风速对喷射的影响。本项目为光固化喷射土工膜提供了化学、材料学和岩土力学的理论基础。

常规土工膜易发生接缝破坏并产生渗漏，使得防渗效果不理想，同时具有易造成固体废弃物大量堆积、降解后产生有毒有害物质问题。鉴于以上问题，本项目研发了施工简便，造价经济的新型光固化土工膜，以解决土工膜渗漏所带来的环境污染问题。目前，由于对土工膜的内部构造、化学反应、工作机制及研制技术等方面的研究探索不足，制约了该新型土工膜的开发和应用。本项目以丙烯酸族单体为基本原材料，1%-5%光引发剂作为反应引发剂，并添加1%-3%碳黑粉，通过光固化链式反应研发了具有优越岩土力学性能的新型防渗材料——光固化土工膜。通过开展土—膜界面剪切试验和拉拔试验并与传统土工合成材料的力学性能、作用机理和工程应用可行性等方面进行对比研究；通过比较不同光引发剂和碳黑粉含量作用下的光固化土工膜性能得出其最佳配比；开展拉伸试验、渗透试验和界面直剪试验，分析确定光固化土工膜的基本力学性能和成膜渗透系数；对比研究不同添加物对光固化土工膜生成时间、拉伸性、渗透性和界面剪切性能的影响；通过对光固化土工膜的拉伸、渗透和界面直剪试验数据分析并结合工程案例实际改进土工膜研发技术参数。本项目重点研发了一种新型光固化土工膜，并对其研制技术，工作机制，设计理论进行了系统研究，为光固化土工膜的设计、工程应用和相关规范的编制提供了科学依据，推进了新型土工膜的应用与发展。