煤矸石基质固化剂对非饱和膨胀土胀缩率的调控机制研究

In view of the applicants previous studies which were found that coal gangue could control the swelling shrinkage of expansive soil and improve the engineering properties of expansive soil, the project attempts to explore the mechanism of underlying and further optimize the parameters of coal gangue matrix curing agents and its mixture ratio with expansive soil. Coal gangue matrix curing agents, with good traits and external environmental sensitivity, are optimized and prepared for use in the test. With a certain proportion, the formulated coal gangue matrix curing agents are incorporated into the unsaturated expansive soil. The correlation model of swelling shrinkage ratio and the coal gangue matrix curing agents’ content and the engineering property index of mixture are determined. The engineering properties and swell-shrink of the mixture are evaluated. Dosage of curing agents and the reasonable proportion of mixture, satisfied expansive soil subgrade construction basic requirements, are determined. Spectrum analysis is used to discriminate and estimate the effect of fracture development regularity of unsaturated expansive soil and the wet bilge effect. Regulation mechanism of coal gangue matrix curing agents for unsaturated expansive soil expansion shrinkage is revealed. Dynamic characteristics and expansion contraction of unsaturated expansive soil subgrade, with coal gangue matrix curing agents, are tested to determine the effect of improving expansive soil by the roadbed model and field tests. Further optimize the parameters of coal gangue matrix curing agents and propose unsaturated expansive soil consolidate program for expansive soil subgrade improvement techniques establishing theoretical foundation and technical support.

针对申请人前期的研究发现煤矸石基质材料可以抑制膨胀土的胀缩性，探索煤矸石基质固化剂对膨胀土工程性质和胀缩率的调控机制这一科学问题。优化配制煤矸石基质固化剂，使其更增强膨胀土在外界环境变化下的稳定性；按照一定比例将配制的煤矸石基质固化剂掺入非饱和膨胀土中，建立煤矸石基质固化剂掺量及混合料的工程性质指标与胀缩率间的关系模型，评价其工程性质及胀缩性，确定满足膨胀土路基工程基本要求的固化剂掺量和混合料的合理配比；从微观结构角度，对掺煤矸石基质固化剂非饱和膨胀土合理配比条件下混合料进行图谱分析，判别和估计改良非饱和膨胀土的裂隙发育发展规律和湿胀效应，揭示煤矸石基质固化剂对非饱和膨胀土胀缩率的调控机制；通过路基模型和现场试验路对煤矸石基质固化剂膨胀土路基进行动力特性和胀缩性检测，验证其改良效果，进一步优化煤矸石基质固化剂参数，提出非饱和膨胀土的改良方案，为膨胀土路基改良技术奠定理论基础和提供技术支撑。

立足于内蒙古特有的资源现状，针对固体废弃物煤矸石循环利用的需求，借助膨胀土钝化煤矸石溶出的重金属特性，实现工程材料需求和解决环境污染问题，以探索煤矸石基质固化剂对膨胀土工程性质和胀缩率的调控机制这一科学问题。通过煤矸石性、改性膨胀土的胀缩性评价、裂隙发展规律及微观结构分析，优化煤矸石固化剂合理掺量，揭示煤矸石改性膨胀土的机制。结果表明：经过微观图谱吸收峰位置的变化推断煤矸石物相，获得试样表观形貌和元素变化，分析得到不同酸度溶液浸泡环境条件下，煤矸石的力学强度和密实程度得到增强。掺入煤矸石后，可有效降低膨胀土的胀缩特性，提高膨胀土的抗剪性能和抗压强度。通过压汞试验获得试样的孔隙特征，得到掺煤矸石后膨胀土的孔隙分布、孔隙类型的转变，得到试样的胀缩率、轴向变形能力得到抑制，强度发生改变的机理。因此推荐煤矸石较为合理的掺量范围在6%~8%。通过吸附性试验得到膨胀土可吸附煤矸石溶出的重金属离子，有效地控制对地下水的污染。基于云模型评价掺煤矸石固化剂膨胀土的胀缩等级，得到煤矸石可降低膨胀土胀缩性。基于海绵模型建立孔隙特征模型，确定了分形维数与孔隙特征参数的关系模型，得到分形维数与煤矸石掺量间的线性相关。通过干湿循环试验测得试样的裂隙特征参数，得到随着干湿循环次数的增加，煤矸石粉可延迟膨胀土的裂隙萌发时间，并制约膨胀土的裂隙裂缝的发展。由土样裂隙面三维断面计算所得粗糙度分析发现，裂隙越小其粗糙度越大，改良膨胀土的裂隙整体比素膨胀土小，主要原因是煤矸石改良膨胀土内部比素膨胀土内部粗糙度大，颗粒间啮合能力提高所致。通过PLAXIS软件建立煤矸石路基模型，计算路基的竖向位移、水平位移和超静孔隙水压力，利用SEM、EDS和LAMAN等微观检测手段分析得到引起路基位移及水压力变化的主要原因，确定碱激发煤矸石的活性产生凝胶物质，可提高煤矸石路基的稳定性的内在机理，为解决膨胀土路基病害和煤矸石污染环境问题具有重要的理论意义和实际价值。