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为研究一种底板周圈设置裙边、底板中部设置桩的新型沉箱复合基础的承载性能,尤其是裙边与桩对承载性能的影响机制,基于缩尺模型试验验证的FLAC3D接触面单元与桩结构单元数值分析方法,建立了琼州海峡跨海大桥西线实际地层中的沉箱复合基础三维数值模型,研究了裙边与桩的尺寸参数(裙边高度、桩长、桩径、桩数)和组合方式对沉箱复合基础竖向及水平向承载性能的影响。结果表明:裙边能约束箱底塑性区的开展与贯通,有效提高了沉箱的水平极限承载力,对底面尺寸125m×75m的沉箱基础,单独设置壁厚2m、高度6m的裙边后,设计荷载下裙边可分担47%的水平荷载和26%的竖向荷载;桩端落在相对较好持力层的桩可分担较多的竖向荷载,有效提高沉箱的竖向刚度、控制差异沉降,对底面尺寸125m×75m的沉箱基础,单独设置52根、直径2m、桩长72m、桩端进入4-2硬塑粉质黏土层的群桩基础后,设计荷载下群桩可分担67.8%的竖向荷载和37%的水平荷载;裙边与桩组合设置后,沉箱复合基础的竖向及水平向承载力得到进一步提高,设计荷载作用下,群桩承担64%的竖向荷载和31%的水平荷载,裙边承担14%的竖向荷载和52%的水平荷载。研究成果可为琼州海峡跨海大桥深水基础设计提供重要参考。
In order to study the bearing capacity of a new caisson composite foundation with skirts and piles in the middle of the bottom plate, especially the effect mechanism of the skirts and piles on the bearing capacity, the FLAC3D contact surface unit The three-dimensional numerical model of the caisson composite foundation in the actual strata on the west line of the Qiongzhou Strait Bridge was established. The relationship between the size parameters (skirt height, pile length, pile diameter, number of piles) and Effect of Combination Method on Vertical and Horizontal Bearing Capacity of Caisson Composite Foundation. The results show that the skirt can constrain the development and penetration of the plastic zone at the bottom of the box and effectively increase the horizontal ultimate bearing capacity of the caisson. After designing the caisson foundation with a floor size of 125m × 75m and separately setting a hem with a wall thickness of 2m and a height of 6m, Under the skirt can share 47% of the horizontal load and 26% of the vertical load; pile end of the pile is relatively good holding stratum can share more vertical load, effectively improve the vertical rigidity of caissons, differential settlement control For the caisson foundation with a floor size of 125m × 75m, 52 pile groups with a diameter of 2m and a pile length of 72m were set up separately. After the pile ends entered the group pile foundation of the 4-2 hard plastic silty clay layer, the pile groups under the design load could share 67.8% Vertical load and 37% horizontal load respectively. When the skirt and pile are set in combination, the vertical and horizontal bearing capacity of the caisson composite foundation is further improved. Under the designed load, the pile groups bear 64% vertical load and 31 % Of the horizontal load, 14% of the skirt to bear the vertical load and 52% of the horizontal load. The research results can provide important reference for deepwater foundation design of Qiongzhou Strait Bridge.