不同工程环境下植物纤维秸秆加筋土强度劣化机制及其演化规律

Natural plant fiber（NPF）is an excellent soil improvement and reinforcement material. It is ecological and environmental friendly and has been used in the field of geotechnical engineering. Today, as research on fiber degradation and engineering properties deterioration is still in an experimental stage and the research goal on fiber degradation and engineering properties deterioration of fiber reinforced soil in different practical engineering environmental conditions cannot be realized, and the systematic degradation theory of NPF reinforced soil in different practical engineering environmental conditions cannot be presented, the promotion and application of natural plant fiber is seriously hampered. This project uses new degradation test methods to characterize the degree of fiber degradation in major engineering environments and illustrates the physical and chemical changes of fiber pyrolysis through comprehensive thermal analysis; reveals the micro mechanism of fiber degradation and strength deterioration of fiber reinforced soil with environmental scanning electron microscopy (ESEM) method; identifies the laws of change of mechanical parameters of reinforced soil under the coordination of fiber degradation and matrix in conjunction with macroscopic mechanical tests; builds the strength model of reinforced soil taking into account fiber degradation and strength deterioration. The research results have great value to and great significance in improving the applied basic theory of NPF reinforced soil, enhancing people's deep understanding of advantages and limitations on NPF reinforcement, eliminating environmental pollution caused by NPF waste, broadening the way to properly use NPF waste in geotechnical engineering, promoting their engineering application, and reducing the use of rebar and concrete curing agent.

天然植物纤维NPF是优良土质改良筋材，具有生态、环保显著优点，已在岩土工程得到一定应用。目前，关于植物纤维降解及其加筋土工程性质劣化研究仅处于初步试验阶段，没有实现实际应用工程环境下纤维加筋土工程性质劣化研究目标，工程环境下NPF加筋土劣化系统理论缺乏，严重制约了植物纤维在岩土工程中的应用推广。本项目采用降解试验新方法，通过综合热分析法进行主要几种工程环境下纤维降解程度表征及纤维热解物化过程阐释；用环境扫描电镜法揭示纤维降解及其加筋土强度劣化微观机制；结合宏观力学试验，阐明纤维降解与其加筋本体协调作用下加筋土力学参数变化规律；构建考虑纤维降解及强度劣化的加筋土强度模型。研究成果对完善NPF加筋土工程应用基础理论，促进人们对NPF加筋的深入认识，消减NPF废弃物对环境的污染，拓宽其在岩土工程中合理利用途径，推进其工程应用，减少钢筋和水泥固化剂使用，具有重要理论价值和实践指导意义。

天然植物纤维NPF是优良土质改良筋材，具有生态、环保显著优点，已在岩土工程得到一定应用。目前，关于天然植物纤维降解及其加筋土工程性质劣化研究仅处于初步试验阶段，相关研究成果多局限于饱和石灰溶剂或水泥砂浆环境或海水环境，水泥土、盐渍土及软黏土等实际工程应用环境下NPF加筋土强度劣化演化规律及其设计理论还不完善，工程环境下NPF加筋土劣化系统理论缺乏，严重制约了天然植物纤维在岩土工程中的应用推广。对此，本项目以棉花秸秆纤维作为NPF代表，分别对其在盐渍土、水泥土和淤泥土干湿循环和冻融循环下的六种工程环境下的纤维及其加筋土强度劣化机制及其演化规律进行了系统研究。具体而言，通过NPF降解室内测定方法，对这六种工程环境下棉花秸秆纤维降解程度进行了表征和定量化描述；通过综合热分析法，对工程环境下棉花秸秆纤维热解物化过程进行了阐释，结合扫描电镜法和宏观力学试验，揭示了工程环境对棉花秸秆纤维及其加筋土强度劣化的影响机制，阐明了这六种工程环境下棉花秸秆纤维及其加筋土强度劣化演化规律；构建了棉花秸秆纤维降解与纤维的抗拉强度、纤维降解与其加筋土抗压强度、抗折强度、抗剪强度以及筋土界面强度劣化之间的内在紧密关系式；进一步架构了考虑纤维降解所致加筋土强度劣化的加筋土强度强度模型，并通过了实验验证，从而为 NPF 加筋工程应用提供理论基础和技术支撑。研究成果对完善NPF加筋土工程应用基础理论，促进人们对NPF加筋的深入认识，消减NPF废弃物对环境的污染，拓宽其在岩土工程中合理利用途径，推进其工程应用，减少钢筋和水泥固化剂使用，具有重要理论价值和实践指导意义。