寒区渠床冻胀与浮石混凝土衬砌冻融耦合的耐久性机理研究

Aiming at the special circumstances for farmland water delivery canals in cold regions, the characteristics of pumice lightweight concrete and the fact of water delivery canals under a cold environment are closely combined to make full use of natural pumice resources enriched in Inner Mongolia region. Through the indoor and outdoor experiments of pumice lightweight concrete, the pumice lightweight concrete with favorable frost resistance properties is developed as a new lining material for water delivery canals in cold regions, so as to reveal the deformation law and durability mechanism under the coupling between canal-bed soil frost heave and lining freeze-thaw of pumice lightweight concrete. Comprehensively utilizing field in-situ experimental observation data and indoor freeze-thaw test data, a quantitative coupling relationship is established between canal concrete block and deformation as well as temperature of canal-bed soil system. The actual desert environment of Hetao Irrigation District is simulated to discuss the damage mechanism of pumice lightweight concrete under the coupled action of sand erosion and freeze-thaw. Through the macroscopic mechanics test of pumice lightweight concrete, a determination of microstructure characteristic parameters is carried out with the help of modern imaging technologies to analyze the destruction features of internal microstructures in the freeze-thaw adverse environment. The related damage mechanics theory is used to analyze the damage evolution process of pumice lightweight concrete and establish the freeze-thaw damage prediction model, providing a theoretical basis and related design parameters for the lining durability design of pumice lightweight concrete in canals of cold regions.

针对严寒地区农田输水渠道面临的特殊环境，密切结合浮石轻骨料混凝土的特性及严寒环境下输水渠道的实际，充分利用内蒙古地区富集的天然浮石资源，通过对浮石轻骨料混凝土进行室内外试验，研制具有优良抗冻特性的浮石轻骨料混凝土作为寒区渠道的新型衬砌材料；揭示寒区渠床土体冻胀与浮石轻骨料混凝土衬砌冻融耦合作用下的形变规律及耐久性机理。综合利用野外原位试验观测资料和室内的冻融试验数据，建立定量的渠道混凝土砌块和渠床土层系统中形变、温度的耦合关系。模拟河套灌区实际风沙环境，探讨风沙侵蚀与冻融耦合作用下浮石轻骨料混凝土的损伤机理；通过对浮石轻骨料混凝土的宏观力学试验并借助现代影像技术进行微结构特征参数测定，分析其在冻融不良环境中内部微结构破坏特征；利用损伤力学相关理论对浮石轻骨料混凝土力学损伤演化过程进行分析并建立冻融损伤预测模型，为寒区渠道浮石轻骨料混凝土衬砌耐久性设计提供理论基础及相关设计参数。

我国北方的西北部地区，该地区冬春季节寒冷多风沙，混凝土结构长期处于冻融循环和风沙吹蚀等不利自然环境下，容易影响结构的耐久性和安全性，导致结构的服役寿命降低，产生安全隐患。充分利用丰富的浮石资源，研制开发水泥、浮石、砂子、粉煤灰等混合的浮石轻骨料混凝土，作为寒区渠道的新型衬砌材料。依据北方环境特点模拟浮石混凝土结构服役的实际自然环境，分析破坏机理并建立耐久性的预测模型。同时结合室内冻结试验和内蒙古河套灌区的室外冻结试验，对比分析浮石混凝土的衬砌结构在冻结环境下对渠床基土的保温能力，得出渠道冻胀规律。.利用风沙吹蚀系统模拟实际沙尘环境，通过改变吹蚀时间、吹蚀角度、吹蚀风速和下沙率探讨浮石混凝土的损伤情况。通过超景深三维显微系统对试验现象进行观测，分析了浮石混凝土风沙吹蚀的破坏形态和劣化规律。利用气流携沙法和快冻法研究浮石混凝土在风沙吹蚀与冻融耦合破坏中的耐久性，分析质量损失及相对动弹性模量的变化规律，并进行核磁共振和扫描电镜试验，测试内部孔隙和微观结构的发展变化，得出浮石混凝土风沙吹蚀与冻融耦合的劣化机理。.通过室内开放系统中分别对普通混凝土、浮石混凝土、不同含水率渠床基土、不同含水率基土对应的衬砌结构进行冻结试验，在冻结过程中监测各试件的温度变化及冻胀量变化，得出混凝土衬砌渠道冻胀变化规律及破坏形式。通过野外现场观测巴彦淖尔市磴口县的灌区实际建设无混凝土和浮石混凝土衬砌板的渠道，于全部监测时段内定时分别为各工况的渠道进行温度、冻胀量两个变化量的测量，结合室内室外试验数据对比，得出衬砌渠道的冻胀规律。