红层软岩土石混填体变形力学特性及其高填地基承载变形机理研究

Red beds soft rock is widely distributed in southwest and central area of China which was usually filled as soil-rock aggregate for foundation or subgrade in practical engineering. However, the research object for most existing study was simply focused on the red beds soft rock itself which caused the research results cannot be fully fitted with the field situation, therefore, it’s necessary to study the deformation mechanical characteristics of red beds soil-rock aggregate and the loading-deformation mechanism of red beds soil-rock high filled foundation from a different perspective. Thus, this program is designed to carry out the laboratory disintegration-crusing tests, large-scale shear tests, triaxial tests and model tests of red beds soil-rock aggregate based on orthogonal tests and uniform tests to study the influence of stress state, water environment, gradation, rock content and compactness on deformation characteristics, bearing mechanism and failure mode. Secondly, supposing that red beds soil-rock aggregate consists of void and soil-rock particle skeleton, the porous media mechanical model is built on the base of experimental results. And then, the settlement deformation analysis method was set up by introducing an idea for step-loading and considering the influence of additional stress and initial stress on deformation and mechanical parameters of high filled foundation. Finally, via establish the reasonable failure mode under various conditions upon the results of model tests, the ultimate bearing capacity of red beds soil-rock high filled foundation can be computed based on limit analysis and slip line field theory.

红层软岩在我国西南及中部地区分布广泛，其在实际工程中基本上是以土石混填体的形式用于地基或路基填筑，而已有研究多是单独针对红层软岩进行的，从而造成有关研究成果与现场情况并不十分契合，故有必要对红层软岩土石混填体的变形力学特性及其高填地基承载变形机理进行研究。为此，本项目拟首先基于正交试验设计方法，对红层软岩土石混填体开展崩解破碎、大型直剪、大型三轴与模型试验，探讨应力状态、水作用环境、级配、含石量与压实度等因素对其变形力学特性、承载机理与破坏模式的影响；其次，将红层软岩土石混填体视为由孔隙和土石颗粒骨架构成，根据试验结果建立其孔隙介质力学模型，并在此基础上引入分级加载思想，考虑附加应力和初始地应力对高填地基变形力学参数的影响，提出相应的沉降变形分析方法；最后，引进极限分析和滑移线场理论，并结合模型试验结果探索红层软岩土石混填高填地基在不同条件下的破坏模式，建立其极限承载力计算方法。

在我国西南及中部地区，红层软岩土石混填体被广泛用于地基或路基填筑，而已有研究多是单独针对红层软岩进行的，造成有关研究成果与现场情况并不十分契合，故有必要对红层软岩土石混填体的变形力学特性及其高填地基承载变形机理进行研究。本项目首先对红层软岩土石混填体开展了大型直剪、大型三轴与模型试验，探讨了应力状态、水作用环境、级配、含石量等因素对其变形力学特性、承载机理与破坏模式的影响，即在一定范围内红层软岩土石混填体抗剪强度随含石量增大而增大，含石量越高，其低压剪胀性越明显，反之则高压剪缩性则更为明显；各种水的作用不仅会影响红层软岩土石混填体受力变形特征，还会使其强度发生明显弱化，但是当试样浸泡或干湿循环达到一定程度后，其强度将趋于稳定不再继续劣化；应力路径对红层软岩土石混填体的抗剪强度影响不大，但对其应力应变关系和体变特征存在显著影响,等应力比路径下试样的体积应变与轴向应变之间近似呈线性关系，其斜率随应力比的增加而减小；等p路径下试样则是以剪胀性为主，尤其在平均主应力较低时更为显著。然后，结合竖向均布荷载作用下红层软岩土石混填地基应力传递机理，首次推导了矩形、条形、圆形等均布荷载作用下的散体材料地基附加应力分布的解析解；将红层软岩土石混填体视为由孔隙和土石颗粒骨架构成，根据试验结果建立其孔隙介质力学模型，并在此基础上引入分级加载思想，并考虑附加应力和初始地应力对高填地基变形力学参数的影响，提出相应的沉降变形分析方法；推导了红层软岩土石混填地基压实度计算方法，结合地基实测p-s曲线，可用于现场压实度快速检测；最后，引入极限分析和滑移线场理论，并结合模型试验结果推导了红层软岩土石混填地基极限承载力计算方法。与此同时，课题组初步开展了水泥浆液对红黏土强度和渗透特性改良的试验研究，为红层软岩土石混填体改性研究奠定了基础。