湛江组结构性黏土中桩基竖向承载性状模型试验

The bearing behavior of pile foundations in the Zhanjiang Formation structured clay under vertical loads is studied by using in-situ model tests. Six groups of model piles with the same material and pile diameter but different penetration depths are selected. The single-pile in-situ vertical bearing model tests are carried out in the Zhanjiang Formation structured clay by using the slow maintained load method, and the single-pile load-settlement curve, the distribution curve of single-pile axial force along the pile body, and the distribution curve of single-pile side friction resistance along the penetration depth are obtained. The results show that: under the action of vertical loads, there is a significant steep drop in the load-settlement curves of the model single piles in the Zhanjiang Formation structured clay, and the inflection point in the ultimate state is obvious. The vertical ultimate bearing capacity increases with the increase of the length-diameter ratio; under the same load, with the increase of the length-diameter ratio, the settlement at the pile top gradually decreases and the decreasing trend gradually slows down. Under a relatively large load, the decreasing rate of the settlement at the pile top in the load-settlement curve of the super-long pile is almost zero, and there is an effective pile length; under the same pile top load, the proportion of the single-pile tip resistance to the total pile top load gradually decreases with the increase of the length-diameter ratio, from a maximum of 29.8% to 0.8%; the ultimate side friction resistance of single piles with different penetration depths under the ultimate load does not change much and is stable at about 40 kPa.

利用原位模型试验研究湛江组结构性黏土中桩基在竖向荷载作用下的承载性状。选取材质和桩径相同、入土深度不同的6 组模型桩，采用慢速维持荷载法，在湛江组结构性黏土中进行单桩原位竖向承载模型试验，得到了单桩荷载-沉降曲线、单桩轴力沿桩身分布曲线、单桩侧摩阻力沿入土深度分布曲线。结果表明: 在竖向荷载作用下，湛江组结构性黏土中模型单桩荷载-沉降曲线均存在显著陡降，极限状态拐点明显，竖向极限承载力随着长径比的增加而增大; 在相同荷载作用下，随着长径比的增加，桩顶沉降逐渐减小且减小趋势逐渐变缓，在较大荷载作用下超长桩荷载-沉降曲线中桩顶沉降的减小速率几乎为零，存在有效桩长; 在同级桩顶荷载作用下，单桩桩端阻力占总桩顶荷载的比例随着长径比的增加而逐渐变小，由最大29. 8%减小为0. 8%; 不同入土深度的单桩在极限荷载作用下的桩侧极限摩阻力变化不大，均稳定在40 kPa 左右。