中文摘要：

采用拉格朗日有限差分数值计算方法，建立群桩数值模型，分析不同间距情况下桩侧摩阻力、中性点、以及土体变形规律。研究结果表明：桩侧负摩阻力沿桩身先增大后减小，并逐渐过度到正摩阻力；随着桩间距的增大，群桩效应逐渐减小，中心桩和角桩的正负摩阻力均逐渐增大；中性点位置以上土的位移大于桩的位移，桩受负摩阻力，在中性点位置桩土无相对位移，侧摩阻力为0kPa；中心桩中性点深度大约为0．39倍桩长，角桩中性点深度大约为0．44倍桩长；受到桩侧摩阻力的作用，土体沿中性点上下呈现被撑起的变化规律，桩侧土体受到桩体对其向上的摩擦力，当桩间距较小时，群桩效应显著。

英文摘要：

The Lagrange finite difference numerical method was used to build the numerical model for group piles. The variation discipline of pile skin friction, position of neutral point and deformation of soil were analyzed under the situations with different pile spacings. The results show that the negative skin friction of pile increases firstly and then decreases, and finally it changes to the positive skin friction. With the increase of the pile spacing, the effect of group piles reduces gradually, the positive skin frictions of both center and comer piles increase gradually. At the higher location, the displacement of soil is larger than that of piles at the neutral point, causing that piles resist negative skin friction. At the location of the neutral point, there is no relative displacement between piles and soil, so the negative skin friction is 0 kPa. The neutral point locates at about 0.39 times length of pile shaft for center piles, and 0.44 times length of pile shaft for comer piles. Due to the effect of pile skin friction, the soil is shored up to both side along the neutral point position. In the soil surrounding, the pile resists the friction force induced by pile-soil action. The effect of group pile is obvious with smaller pile spacing.