膨胀土地基桩基承载特性模型试验研究

Model Experimental Study on Bearing Characteristics of Pile Foundation in Expansive Soil Foundation

输电杆塔基础的修建往往需要穿越复杂地质条件地区,膨胀土地基在遇水失水过程中剧烈的膨胀性和收缩性,不仅会引起土体强度改变,同时会引发膨胀变形,二者耦合作用使得膨胀土地基承载力的变化更为复杂。对此开展大尺寸模型试验,通过改变土体含水率,研究膨胀土地基中桩基在最优含水率和饱和含水率条件下的抗压承载力和抗拔承载力变化。研究表明:膨胀土含水率的变化,对抗压过程中的极限承载力影响更为明显,对抗拔过程中的极限位移影响更为明显。随着含水率的增加,桩身极限侧摩阻力和桩端阻力均在减小,但极限端阻力减小幅度大于极限侧摩阻力。同一含水率情况下,抗压试验桩身极限侧摩阻力呈抛物线形分布,而抗拔试验桩身极限侧摩阻力呈线性分布。

The construction of transmission tower foundation often needs to pass through the area of complex geological conditions. The swelling and shrinkage of expansive soil foundation in the process of water loss will not only cause the change of soil strength,but also cause expansion deformation. The interaction between them makes the change of the bearing capacity of expansive soil foundation more complicated. In this paper,a large-scale model test is carried out to study the change of compressive and pull-out bearing capacity of pile foundation in the condition of optimal moisture content and saturated water content. The results show that with the change of moisture content of expansive soil,the influence of ultimate compressive bearing capacity is more obvious and the influence of pull-out ultimate displacement is more obvious. With the increase of water content,both the ultimate side friction and end resistance decrease,but the limit end resistance decreases more than the limit side friction. Under the condition of the same moisture content,the lateral friction distribution of the compressive test pile is parabola,while that of the pull-out test pile is linear.