碎石土湿陷性试验研究

采用不同工况的载荷试验、室内常规土工试验和易溶盐试验,分析了碎石土的荷载-沉降曲线特征,探讨了碎石土的湿陷性与湿陷机理。结果表明:碎石土在200 kPa稳定后浸水,再加荷到400 kPa,载荷试验荷载-沉降曲线呈折线型,明显分为三个阶段:压缩变形阶段,湿陷变形阶段,复合变形阶段。场地中4 m厚碎石土具有湿陷性,且湿陷性不均匀。碎石土湿陷的机理在于其结构是疏松的单粒架空结构。骨架颗粒间存在架空孔隙,且部分架空孔隙由砂质颗粒集合体充填;骨架颗粒间呈点与点接触,或者主要通过黏粒、黏土矿物、易溶盐组成的胶结物而联结在一起;在浸水加荷过程中,黏粒周围薄膜水增厚、粘土矿物自身产生膨胀、易溶盐溶解,导致胶结物的胶结强度丧失,结构失稳,发生湿陷。

Experimental study of collapsiblity of gravel soil

The characteristics of load–settlement curve of gravel soil and the collapsibility and collapsible mechanism of gravel soil were studied based on the results from plate loading tests under different work conditions, routine soil tests and soluble salt tests. The study shows that when the gravel soil stabilized under the load of 200 kPa, then immersed in the water and loaded to 400 kPa, the load-settlement curve is a broken curve, and can be obviously divided into three phases: compressive deformation phase，collapsible deformation phase and composite deformation phase. The gravel soil with 4m thick has collapsiblity and its collapsibility is uneven. The collapsible mechanism of gravel soil is due to its loose single-grain open structure. There is open pore in the frame grains and some of open pore is filled with sandy grain aggregation; frame grains are linked together with point-to-point contact or mainly connected with cement consisting of clay particle, clay minerals and soluble salt. During the process of ponding and loading, the film water around clay partvicle is becoming thicker, the clay minerals expands itself and soluble salt dissolves, so as to lead the loss of the cement strength and destabilization of the structure; and thus the gravel soil collapses.