正冻饱和路基土的结构损伤弹塑性模型与冻胀变形研究

The traffic constructions of China in cold regions has made significant progress with the constructing and running of important transportation infrastructures, such as Harbin-Dalian high-speed railway and Mohe-Beijicun highway. However, the durability of the engineering and safety of the traffic was constrained by the frost heave of subgrade. This research focuses on the requirements of theory and technology in the anti-frost design and frost damage prevention, especially the coupled stress, temperature and moisture in the freezing soil. Laboratory tests, theoretical analysis and numerical simulations are adopted to study the happening and developing mechanisms of the frost heave in the seasonal frozen regions. Based on frost heave tests of the saturated soil under the coupled stress and temperature, the evolution equations of the structural damage of freezing soil are obtained by choosing Pore Ice Ratio (PIR) as the damage variable. Then, an elastic-plastic constitutive models of the structural damage of freezing soil are obtained by constructing a series of reasonable yield functions and hardening rules, which are based on critical state soil mechanics. At last, a coupling hydro-thermo-mechanical frost heave model of the freezing soil is obtained through a constructed evolution function of the pore ice, and the model will be validated by the experiment results. This research is helpful for a better understanding on the happening mechanisms and deformation rules of the frost heave in subgrade soil, and provided a theory support for evaluating the stability of the frozen structures, which could improve the frozen soil mechanics, and also promote the developments of the infrastructure construction in cold regions.

随着哈尔滨-大连高速铁路与漠河-北极村高速公路等重大交通基础设施的建设与运营，我国在高寒季冻区的交通建设中取得了重大进展。然而路基的冻胀依然制约着工程的耐久性和行车安全。本课题瞄准寒区路基在抗冻设计和冻害防治方面的理论需求与技术欠缺，特别关注正冻土的应力、温度和水分的耦合效应，采用室内试验、理论分析和数值模拟相结合的方法，深入研究季节性冻土冻胀变形的发生与发展机制。首先，在应力－温度耦合作用下饱和土冻胀试验基础上，以孔隙冰比作为损伤变量，提出正冻土的结构损伤演化方程；据此，在临界状态土力学框架下，通过建立合理的屈服函数和硬化准则，构建正冻土的结构损伤弹塑性模型；基于此，改进孔隙冰发展函数，建立正冻土的水-热-力耦合冻胀模型，并验证该模型。本项目的研究，有利于深入理解路基冻胀的发生机制和变形规律，为冻土基础的稳定性评价提供理论支撑，促进寒区交通基础设施的建设和冻土力学的发展。

本项目瞄准寒区路基在抗冻设计和冻害防治方面的理论需求和技术欠缺，着眼于冻结过程中饱和路基土冻胀变形的发生与发展机制，特别关注正冻土的应力、温度和水分的三场耦合效应。以东北地区常见的粉质黏土为研究对象，采用室内试验、理论分析和数值模拟相结合的手段，深入研究季节性冻土冻胀变形机理。首先，总结并分析了国内外学者关于冻胀试验系统的研制进展，设计并研制了侧限条件下土体冻胀试验系统和复杂应力（三轴应力）状态下的土体冻胀试验系统，并提出了相应的试验方法。其次，以粉质黏土为研究对象，考虑应力水平、压实度、温度梯度等因素的影响，分别进行了侧限与复杂应力条件下饱和土的冻胀试验，分析了饱和粉质黏土的在冻结过程中的温度、水分分布规律，以及冻胀发展规律。再次，研究了正冻粉质黏土的冻结速率、冻胀速率、冻胀率的发生与发展机制，并考虑应力水平、压实度、温度梯度的综合影响，建立了冻胀率的经验预估模型。进而，以热传导、相变潜热、水分扩散等理论为基础，建立了饱和-非饱和压实粉质黏土水-热全耦合数值模型；基于COMSOL多物理场仿真软件，实现了饱和-非饱和压实粉质黏土的水-热全耦合数值模拟，并结合室内模型试验验证了模型的可靠性。最后，建立并验证了饱和-非饱和压实粉质黏土的冻胀预估模型。通过本项目的研究，有利于深入理解路基冻胀的发生机制和变形规律，为冻土路基的抗冻设计和稳定性评价提供理论支撑，并推动寒区交通基础设施的建设和冻土力学的发展。. 基于以上成果，项目组发表了学术论文18篇，其中SCI检索8篇，EI检索7篇；申请专利3项，授权1项；培养副教授1人，硕士生4名，博士生2名；完成专著2本；部分成果纳入我国行业标准《季节性冻土地区公路设计与施工技术规范》（JTG/TD31-06-2017）和辽宁省地方标准《公路路基弯沉验收标准》（DB21/T 2764-2017）。获得国家科技进步二等奖1项、中国公路学会科学技术一等奖1项、陕西省科技进步一等奖1项。