约束固化土承载特性和机理初探
Bearing characteristics and mechanism of confined stabilized soils
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摘要: 将液性指数为0.26~1.19的土样与含不同比例膨胀组分的固化剂拌合制备固化土,并填充于约束刚度不同、外径11 cm、高20 cm的PVC筒中养护成型。测定固化土养护期间约束体的环向应变。分别对去除约束体的无约束固化土和带约束体的约束固化土进行轴压试验,测定试件的环向应变、竖向位移与荷载的关系。得出以下结论:①在固化剂掺量相等的条件下,约束固化土的极限承载力约为常规无约束固化土的5倍;根据约束固化土极限承载力和核芯固化土面积计算的视强度可达30 MPa以上。②将约束体和膨胀性固化剂结合,可提高膨胀组分的比例以提高AFt 的生成量、提高孔隙填充率,从而提高核芯固化土强度;AFt 的膨胀给核芯固化土施加预压应力,进一步提高约束体对核芯固化土的约束能力;这些效应的综合作用使约束固化土获得更高的承载力。③约束固化土荷载-位移曲线呈现斜率较大的线性阶段,近似线性、斜率较小的阶段2,斜率几乎为零的阶段3。④约束固化土在线性阶段,主要由结构保持整体性的核芯固化土承受荷载;阶段2,固化土结构逐步解体,约束体承受的荷载逐步增加;约束固化土破坏均因约束体失效。Abstract: The stabilized-soil cylinders are made by mixing the soil samples with the relative water content from 0.26 to 1.19 with the binders containing different contents of expansive components, and then they are put into PVC constraint tubes with length of 20 cm, external diameter of 11 cm and different confinement stiffnesses. The hoop expansion strains of the constraint pipes are measured during curing period. The compressive experiments on the cylinders are carried out, which are pressed respectively with and without the constraint pipes. The load-hoop strain curves of the cylinders, load-displacement curves and the failure modes of the cylinders are recorded. The conclusions are as follows: (1) The bearing capacities of the confined cylinders are 5 times those of the unconfined ones made of the ordinary binder with the same binder content. The equivalent strength of the confined stabilized soils can reach more than 30 MPa, which is calculated according to the data of its bearing capacity and cross-sectional area. (2) Combining the constraint with the binder containing expansive components results in unique effects: the binder expansion is confined to compact the core-stabilized soils so as to increase the strength obviously. The prestress upon the core-stabilized soils can be built, which with the hoop constraint the core-stabilized soils are made to be in triaxial compressive stress state under bearing load. (3) The load-displacement curve of the confined cylinders shows three stages: linear stage 1, approximately linear stage 2 with smaller slope and stage 3 with almost zero slope. (4) At the stage 1 the core-stabilized soils resist vertical load as a cemented entirety, at the stage 2 they are crushed gradually into pieces and resist further increasing load with help of hoop constraint force, and reach the ultimate bearing capacity because of the constraint losing its effectiveness.