地震作用下冻土路基随机热-动力破坏机理及可靠度研究

There are frequent earthquakes and extensive permafrost distributed on the Qinghai-Tibet Plateau, which makes the Qinghai-Tibet Plateau one region with complex engineering geology and environment. Moreover, its ecology and environment are very fragile. As a result, engineering constructions are great restricted on the Qinghai-Tibet Plateau, and some current engineering buildings are often very important lifelines. How to evaluate damage mechanism and reliability of frozen soil engineering under combined stochastic effect of frozen soil environment, soil parameters and seismic load is very important, which can not only evaluate and ensure dynamic stability of engineering but aso breach deterministic static evaluation theory of engineering, and further develops dynamic evaluation system on engineering with stochastic thermal-dynamic reliability analysis. In this proposal, firstly, a series of thermal and mechanical tests and dynamical experiments on typical frozen soils will be carried out to determine temperature-related statistical characteristics and dynamic cumulative damage models of these frozen soils. On the basis of these experimental studies, a stochastic thermal-dynamic reliability model on seismic responses of the embankment in frozen ground will be established and corresponding computer program will be developed. At last, some stochastic thermal-dynamic simulations on a typical permafrost embankment on the Qinghai-Tibet Plateau in different seasons will be done, and seismic damage mechanism, stochastic dynamic reliability, failure mode and their seasonal differences will also be thoroughly disclosed. The study can provide a scientific reference to earthquake resistance and disaster prevention of the embankment in permafrost regions.

青藏高原以地震频发、冻土广布而成为工程地质环境最为复杂的地域之一，加上其生态环境脆弱，工程建设受到极大的限制，而已有的工程大多数具有生命线意义，如何评价其在冻土环境、土性参数及地震荷载多个随机因素共同作用下的冻土工程破坏机理与可靠性，不仅对于评价和维护工程的动力稳定性具有指导意义，而且可突破已有以确定性静态评价为主的工程分析理论，进一步发展随机热-动力作用下的可靠度动态分析为主的工程评价体系。本申请项目先基于大量物理力学试验确定冻土土性参数的统计特征及其与温度的数学关系，并建立与温度相关的动力累积损伤破坏机制模型。在此基础上，构建冻土路基地震响应随机热－动力可靠度理论模型，研发数值计算程序；最后，开展不同季节下青藏高原典型多年冻土路基地震响应的随机热-动力模拟，揭示各个季节下冻土路基地震破坏机理、动力可靠度、失效模式及其季节差异性。项目研究成果可为冻土路基的防震减灾等工程问题提供科学依据。

青藏高原冻土分布广泛、地质构造复杂、地震活动剧烈，是世界上最复杂的地震工程地质环境之一。路基结构是青藏高原最主要、最广泛的工程型式，如何评价其在冻土环境和土性参数等随机因素共同作用下的动力响应过程和致灾机理，对于评价和维护冻土路基的动力稳定性具有指导意义。本项目采用现场试验、室内测试、理论建模和数值模拟相结合的研究方法，首先选择青藏高原典型路基断面多年冻土进行不同温度下的关键物理力学参数测试，确定各参数的均值、方差以及概率分布规律，并建立整个多年冻土温度分布范围内各指标与温度之间关系的数学表达式；考虑冻土水热参数、环境温度的随机性，基于多年冻土的水热耦合过程，建立多年冻土区路基随机水热耦合分析的理论模型，推导数值分析方程，研制随机温度场和水分场的计算程序模块；结合多年冻土路基的随机水热状态，考虑冻土力学参数的随机性及其温度相关性，建立多年冻土区路基地震响应随机热-动力可靠度数学力学模型，推导数值模拟方程，开发相应的计算机程序；选择典型路基断面进行数值模拟，研究路基结构在地震荷载作用下的破坏机理和失效模式，预测其动力响应随机演化过程，确定多年冻土路基极易地震失稳的季节。本项目执行过程中，项目组成员在国内外重要期刊上发表论文15篇，其中：SCI论文12篇、EI论文1篇；已录用待发表论文2篇。申请软件著作权2项；获省部级科技奖励2项；培养博士研究生3名、硕士研究生1名。