极限荷载下平顶楔体破坏机理的非线性能耗分析方法与试验研究

The ultimate load of flat wedge is the basic problem in geotechnical plasticity theory, including the soil pressure, bearing capacity of foundations and slope. Although the weightness and nonlinear feature of geomaterials is a well-known fact, the traditional methods have neglected it due to the complexity of theoretical solution. This design way is the main reason lead to the unmatched in features between calculation results with the engineering practice, hence the traditional methods could not guarantee a satisfactory design. The limit analysis approach has the characteristics of clear physical meaning, strict and effective solutions and easy to introduce the geotechnical nonlinear material properties. In addition, it can directly apply the nonlinear programming method to obtain the critical failure state of the rock mass in instability region without gradation loading. Therefore, this topic adopts this method to study several basic problems of the nonlinear failure mechanism for flat wedge under the ultimate load. Through the research, the complete 2d upper limit velocity field building method is put forward based on the theory of slip line field. According to the general nonlinear failure criteria of the geotechnical material, the nonlinear energy dissipation model of geotechnical ultimate load is established, and thus gets the failure mode of flat wedge and internal energy dissipation distribution, thereby reveals the failure mechanism of flat wedge under the common action of internal and external nonlinear energy dissipation. Finally, adopting model test and finite element simulation to compare with the theoretical results, and then carrying out expanding research on the basis of this study. This project will broaden the geotechnical plastic mechanics research field and content from theoretical system, and provide solid theoretical basis for geotechnical structure disaster assessment and prevention in practical engineering.

平顶楔体极限荷载问题是岩土塑性理论中的基本问题，地基承载力、土压力和边坡承载力均可归结为该问题。传统的不考虑土体重度、界面摩擦和材料非线性特点的分析方法，为避免数学求解的困难而忽视了材料的"有重和非线性"自然本质，导致计算结果与实际偏差较大，是土工构筑物设计面临的主要困境之一。本课题充分利用能量法物理意义明确、解答严格有效、便于引入材料非线性特性获得直观破坏模式的特点，深入研究极限荷载下平顶楔体非线性失稳机理的几个基础性问题：提出基于滑移线场理论的有重土二维完整上限速度场构建方法；建立通用非线性破坏准则条件下平顶楔体极限荷载问题的非线性能量耗散模型，揭示内外非线性能耗效应共同作用下平顶楔体破坏的演化机理；同时采用模型试验和数值仿真与理论结果对比验证；最后开展拓展应用研究，开发便于工程应用的可视化程序包。项目研究可以完善岩土塑性理论的研究内容，为工程实际中土工构筑物灾变评估提供理论依据。

本课题利用能量法物理意义明确、解答严格有效、便于引入材料非线性特性获得直观破坏模式的特点，深入研究极限荷载下平顶楔体非线性失稳机理的基础性问题；同时采用模型试验和数值仿真与理论结果对比验证，并开展拓展应用研究。项目取得了预期的阶段性研究成果，已基本完成了预期考核目标。取得的主要研究成果如下所示：.（1）基于刚体极限分析上限法，构建了一种基于滑移线场的极限荷载下平顶楔体二维上限速度场构建方法；基于虚功率原理，建立起平顶楔体极限承载力的半解析计算表达式，实现了编制程序与优化运算；.（2）建立起基于非线性规划模型的刚体平动运动单元上限有限元法基本理论，实现了程序编制以及结果后处理全流程。进一步，提出了提高运动单元上限有限元理论求解效率和精度的网格合并与剔除、网格加密以及网格继承与修正的网格更新技术；.（3）利用编制的相关程序开展了平顶楔体极限承载力基本问题和地基承载力、刚性挡墙土压力、太沙基活动门塌落拱、边坡稳定性、隧道围岩和掌子面稳定性等多类岩土构筑物稳定性极限状态研究，获得了不同岩土构筑物失稳临界极限状态条件下的精细滑移线网图谱、破坏模式与上限解答；.（4）提出了通用非线性破坏准则的“单、多外切线”法引入抗剪强度参数的计算策略。以概化通用非线性抗剪强度特性为计算指标，结合非线性破坏准则外切线引入技术，提出基于刚体上限分析法和上限运动单元法的均质化概化平顶楔体及其特例问题的稳定性分析方法；.（5）以土石混合材料典型平顶楔体极限承载特性为例开展了室内模型实验与数值分析研究。建立了与室内模型实验对应的土石混合材料平顶楔体数值分析模型，进一步揭示了极限荷载作用下土石混合平顶楔体非线性失稳机理和破坏模式的初步规律；.（6）基于刚体极限分析上限法和极限上限运动单元法，初步开发了平顶楔体极限承载力基本问题的可视化软件界面，实现了极限承载量值与失稳破坏图形的可视化输出；.（7）在项目执行期内（2014.09.01-2018.12.31），项目资助发表学术论文30余篇，其中SCI/EI检索论文30余篇，CSCD源刊论文3篇；另外，投稿SCI 期刊论文4篇，EI期刊论文2篇；.（8）在项目执行期内（2014.09.01-2018.12.31），在本项目主要内容或拓展性研究内容方面累计培养博士后1名，硕士5名；另外，目前仍有在站博士后2名，在读研究生8人持续开展项目及关联性相关研究工作。