加筋高边坡中筋土作用规律及分析方法研究

The reinforced high slope has brought a great challenge to both fill technique and geosynthetic material itself. With bigger height of the slope, it is much more difficult to coordinate the deformation of reinforcement and the soil. The typical design and calculation theories on reinforced high slope nowadays are mainly following conventional experience, without realizing that the force and deformation characteristics of the slope have already changed. This project is aimed at dealing with the current critical issues involved in the design and construction of reinforced high slope, which focuses on the interaction relationship between the reinforcement and the soil material under the purpose of securing the slope stability. Great attention will be paid on the interaction and compliance mechanism between the reinforcement and the soil, the joint effects among the reinforced high slope, the foundation soil and other retaining structures, and the relationship between different computational methods. Through theoretical derivation, model tests, numerical simulation and analyses of typical engineering observation data, the project is intended to find the stress distribution pattern of the reinforcement, requirements of foundation soil for slopes with different slope angles, and the law of joint effects of geosynthetic-reinforced systems and other retaining structures. On the basis of revealing the multiscale variation mechanism of soil and geosynthetics properties, and theorem of different design and analysis methods, the investigation will be able to make clear the applicable conditions and matching relation of different methods, together with the deformation and stability mechanism of reinforced high slope and related control measures, which may lay a theoretical foundation for the optimal design, construction and monitoring of reinforced high slope as well as reinforced earthfill dam.

加筋高边坡对填方和土工合成材料本身都提出了挑战。由于填方高度较大，筋土变形协调更加困难。但目前关于加筋高边坡的设计计算理论只是常规经验的直接推广，没有认识到其受力变形性质已发生了变化。本项目针对加筋高边坡设计建造中涉及的关键问题，以保证边坡稳定为目的，以筋土作用关系为主线展开工作。重点研究加筋高边坡中筋材与土的相互作用和协调机制、加筋高边坡与地基、其它支挡结构的联合作用特点，以及不同计算方法之间的关系。通过理论推导、模型试验、数值模拟，以及结合典型工程观测资料的计算分析，给出加筋高边坡中筋材受力的分配关系，不同边坡坡度对地基土性质的要求，土工合成材料加筋与其它支挡结构的联合作用规律。在深入揭示土和筋材性质多尺度演化机理和不同计算分析方法原理的基础上，明确不同方法的适用条件和匹配关系、加筋高边坡的变形和稳定机制及其控制对策。为我国加筋高边坡和土石坝加筋的优化设计和施工监测奠定理论基础。

在基金的资助下，项目围绕加筋高边坡涉及的主要问题进行展开，重点研究加筋土边坡的变形破坏及筋材应力分布规律、平台分级、边坡地基、以及筋材与重力式挡土墙等结构物的联合作用。收集了土工合成材料加筋土边坡的设计方法，比较了中国与其它国家和地区的设计标准；用离心模型试验研究了加筋土边坡的变形破坏及与其它挡土结构物的关系，发现加筋使得挡土墙上部与土体有分离的趋势，因此边坡上部一定范围内可以不必修筑挡土墙。边坡底部由于挡土墙的约束，筋材难以发挥作用，但该位置筋材的存在能够增强填土的均匀性，且可以减小沉降变形，因此底部加筋还是有一定意义的；土压力计算时要考虑它的作用位置和方向，直接用最大惯性力或不平衡力是不合适的；编写了基于水平条分的极限平衡法和上限解法的程序，用于边坡安全系数和挡土墙土压力的计算分析；提出了基于加速度计算的边坡稳定分析方法，可以作为常规安全系数计算的补充；探讨了加筋土边坡强度折减法的失稳判据，认为采用筋材塑性区贯通是一个比较方便的判别方法，在此基础上研究了加筋高边坡的受力变形以及平台设置的影响。合适的平台位置和宽度能够充分发挥土的黏聚力和加筋的作用，对边坡安全有利；基于类比方法提出了边坡地基承载力和变形模量的确定方法。发现边坡的地基承载力很容易满足要求，地基性质主要影响边坡的变形。研究成果对于加筋高边坡的设计和方案优化具有指导意义。